Women with Depression—“You Can't Tell by Looking”™

Introduction
Perinatal depression, a mood disorder that occurs during pregnancy or the first year postpartum, affects 10–15% of women and up to 28% of women living in poverty. A previous history of depression, either preconceptionally or during the interconception period, is the strongest predictor that a woman will suffer from perinatal depression. Perinatal depression can adversely affect not only the woman, but also her fetus or infant, and has been linked with prematurity, difficulties with maternal-infant bonding and infant behavior problems later in life. If a woman has a known history of depression, she can be counseled preconceptionally about her increased risk of experiencing a subsequent episode during the perinatal years and thus take an active role in recognizing signs and symptoms of depression and accessing treatment as early as possible should an episode occur. The earlier treatment is sought for perinatal depression, the greater the chance for improved outcomes.
Background
Depression is currently the leading cause of disease-related disability among women worldwide [1]. Depression can cause moodiness, irritability, changes in sleep patterns, sexual interest or appetite, and an inability to carry on with daily activities. In the most severe cases depression can cause thoughts of harming others or oneself or suicide. Prevalence rates of perinatal depression, which occurs during pregnancy or at some point within the first postpartum year, are similar to those in the general population, affecting 10–15% of women and up to 28% of women living in poverty [2, 3]. Some studies suggest that a woman's risk of becoming depressed during the early postpartum period is approximately three times that of women in the general population [4]. Depression may affect how a woman is able to relate and respond to her infant and if untreated, may lead to thoughts of harming the infant or infanticide. In addition, depression can have significant effects on prenatal care-seeking behavior [5], substance abuse [6], and infant/child mental health [7–9] and nutrition [10]. Depression has also been associated with low birthweight [11] and premature delivery [12].
Approximately 50% of women with perinatal depression remain undiagnosed when they are screened based on clinical observations alone [13]. Perhaps the strongest argument for routine screening of all pregnant and postpartum women is the fact that you can't tell simply by looking that a woman is depressed. However, there are some women who may be at increased risk for perinatal depression, including women living in poverty, those in abusive relationships, and women with a prior history of depression [14]. In fact, it is thought that having a history of depression is the strongest predictor that a woman will suffer from an episode of major depression during pregnancy or the postpartum period [15, 16]. Women with other mental disorders are at risk as well. For example, women with bipolar disorder also have an increased risk of experiencing postpartum depression, and some studies suggest an increased risk for a much more serious illness, postpartum psychosis [17]. Due to the predictive value of a history of depression, it is vital that women with a history of depression be counseled about the relationship between pregnancy and depression prior to conception.
One method to incorporate depression screening & counseling into preconception care
Counseling about depression should become a routine part of preconception care. Health care providers who have contact with women during the preconception period can assist women in becoming aware of how pregnancy and depression can affect one another. By controlling depression prior to conception, just as one would with an illness such as diabetes or epilepsy, a woman's chances for healthy perinatal outcomes may improve [18].
The Wisconsin Association for Perinatal Care (WAPC) is a 35-year-old statewide, non-profit organization dedicated to the improvement of healthy outcomes for women, infants and their families. Since 1989, WAPC has been working toward infusing depression screening and counseling into preconception care by encouraging health care providers to ask women and their partners about their histories with depression and other mental illnesses prior to conception. One tool that has been developed by WAPC is an information sheet entitled Women with Depression that answers four basic questions: How does depression affect pregnancy? How does pregnancy affect depression? How could medications for depression affect the pregnancy? What can you do before pregnancy?
Case examples
The following are two case examples illustrating the impact of depression on pregnancy and the positive effects of being educated prior to a subsequent depressive episode. Although these women were not educated about perinatal depression prior to their first pregnancies, these examples illustrate the importance of depression counseling in the interconception period as well. These cases demonstrate that addressing the questions in Women with Depression can provide an anticipatory contextual framework on which to develop a plan of care.
Case example #1
Sara began experiencing symptoms of depression six months after giving birth to her first child. She had no prior history of depression and had received no counseling prior to conception about the symptoms and presentation of perinatal depression. Sara waited approximately six months before seeking help, but encountered numerous barriers to accessing care. She did eventually get into treatment and attended 15 sessions of interpersonal therapy.
Through both her therapy and additional self-education, Sara became quite informed about the effects and consequences of postpartum depression. Approximately six months after giving birth to her second child, Sara began experiencing depression again. This time, Sara sought treatment within one week of the presentation of symptoms. In addition to being able to recognize the signs of depression earlier, as reported by both her and her husband, Sara also remarked on how much easier it was to access treatment, as she knew how to “navigate the system.” She knew what type of therapy worked for her and was able to resolve her depression in only seven sessions.
Case example #2
Melanie had a history of anxiety and depression prior to conception, but was never diagnosed or treated. Melanie experienced extreme continuous sleep disturbances almost immediately after the birth of her first child. When this problem had not resolved itself within two months, Melanie sought treatment. She was initially reticent about taking medications because she was breastfeeding her infant, but at nine months postpartum, Melanie began a regimen of paroxetine, which finally resolved the depression.
After Melanie's second birth, she felt slight anxiety about the possibility of suffering from postpartum depression again, but this time had a plan of action in place. When she began having trouble sleeping at two months postpartum, she immediately contacted her therapist and began treatment. She was once again hesitant about taking medication, but at nine months postpartum, began taking paroxetine on the recommendation of her care provider. Although she waited to begin medications with the second depressive episode, Melanie reported having “a kind of comfort knowing I was on paroxetine before and it didn't hurt my baby.”
Benefits of preconception counseling for women with a history of depression
The benefits of counseling women about depression prior to conception are numerous. By treating depression as a chronic condition and by actively managing depression prior to conception, a woman's chances of being prepared for a depressive episode during the perinatal period greatly increase. In a recent meta-analysis of psychosocial and psychological interventions to reduce the risk of postpartum depression there was no statistically significant effect on the prevention of postpartum depression [19]. In the absence of preventive treatment, then, understanding postpartum depression could allow families to anticipate possible consequences of maternal depression so they could take steps to help assure healthy outcomes [20]. By fully disclosing the increased risk of depression if she chooses to become pregnant, a woman can make informed decisions about planning for a family [21]. If the woman is taking antidepressant medication, she can discuss the impact of those medications on her future pregnancy and breastfeeding. By working with her health care provider, steps can be taken to change the medication or dose if necessary.
One of the most devastating effects of perinatal depression is that it occurs at a time when most women feel they should be experiencing joy. By educating women prior to pregnancy or birth about the high prevalence of perinatal depression, they may be better prepared for an episode, should it occur. Women with a history of depression especially should have a plan of action in place in the event of perinatal depression.
Women who have suffered from depression once may be more likely to recognize the signs and symptoms of a subsequent episode whether or not the first episode occurred preconceptionally or postpartum. This may be especially true if they are counseled about the possibility of a subsequent episode occurring. Women are not the only ones who can be counseled about the interaction between pregnancy and depression. Loved ones often do not know how to help women suffering from perinatal depression and cannot understand why the woman is depressed. By counseling significant others and family members, they, too, can become better prepared and in addition, can help recognize signs of severe depression and assist with accessing treatment.
Seeking treatment may present fewer challenges to women who have been successfully treated and counseled about depression as well. Women with a history of depression can be counseled about seeking treatment at the earliest possible sign of depression, rather than waiting, as so often happens in primary episodes. The earlier treatment can be sought, the better the outcomes [22]. Stigma may be reduced as well if women are counseled ahead of time, making them more open to seeking treatment and more comfortable with their treatment decisions.
Conclusions
Testimonials from affected women suggest that counseling women with a history of depression leads to improved outcomes should they suffer from a subsequent episode during the perinatal period. Women may be more likely to recognize the signs of depression, more likely to seek treatment earlier and will know what treatment options work for them. Due to an earlier recognition of depression, treatment may have a shorter duration as well. In addition, by counseling women about depression prior to conception, they and their families will have time to develop a plan of action should a depressive episode occur and will be equipped to make informed decisions about family planning. Tools such as Women with Depression may be beneficial in both educating consumers and assisting providers with consultations about depression prior to pregnancy or during the interconception period.
The major challenge currently lies in convincing health care providers to address women's mental health and to screen and counsel for depression during the preconception period. Intervention strategies using medication or counseling have not been significantly effective in preventing postpartum depression. Anticipating the potential interplay between depression and pregnancy may be an intervention that can lead to better mental health and perinatal outcomes.
Future research should address the content and timing of preconception counseling, including what information is needed and when and how it should be disseminated. Treatment algorithms and strategies could then be developed for practitioners and families to help prepare for the postpartum period. Finally, well-controlled intervention studies utilizing the materials developed could focus on maternal mental health, perinatal, and infant outcomes to answer questions about efficacy and effectiveness.

depression
perinatal
mood disorder
preconception


Social cognitive determinants of ecstasy use to target in evidence-based interventions: a meta-analytical review

Aims The health hazards and prevalence of ecstasy use have been documented in two decades of research, but no review reporting on potentially modifiable antecedents of use is available. The aim of this study was to integrate systematically research identifying cognitive correlates of ecstasy use. Such research has the potential to identify targets for evidence-based interventions designed to discourage use.
INTRODUCTION
Ecstasy use is potentially damaging to health [1–3] yet prevalent [4,5]. Legislative changes have not been effective in discouraging ecstasy use, and the development of theory-based behavioural interventions is warranted because these have been successful in generating behaviour change in other areas [6,7].
Behaviour change interventions are more likely to be effective if they target modifiable antecedents of the target behaviour. For example, if expected positive outcomes of a target behaviour differentiate between those who do and do not engage in that behaviour, it is prudent to target outcome expectancies in behaviour change interventions [8]. Which potentially modifiable cognitive antecedents of ecstasy use should interventions target? Unfortunately, although ecstasy was synthesized in 1912 [9], and ecstasy use has been studied for 20 years (e.g. [10,11]), there is no systematic review of this research identifying potentially modifiable cognitive antecedents of use. We aimed to summarize research to date, synthesizing quantitatively all published, quantitative studies of psychological determinants of ecstasy use among young people living in western society.
METHOD
The search strategy comprised three iterative steps. First, the databases PsycINFO, MedLine and ERIC (Education Resources Information Center) were searched using several combinations of keywords (see Appendix I). The results of the final query were then scanned manually for relevant entries by examining the paper titles and abstracts (see Appendix II). Four inclusion criteria were used. Firstly, a study should investigate the target population of young recreative ecstasy users in western society, as factors influencing behaviour can be population-specific [12–14]. Secondly, a study should measure one or more potentially modifiable determinants of ecstasy use-related behaviour; that is, an antecedent that could be influenced potentially by health promotional interventions (excluding for example demographics, personality, etc.); for a list, see chapter 7 of Bartholomew et al. [8]. Thirdly, the study should measure either actual behaviour or intention. Finally, it should assess quantitatively the relationship between determinants and behaviour or intention. Publications selected by this process were examined in detail. Second, reference lists of these papers were scanned for relevant publications (the ancestry approach). Third, texts citing the relevant papers were located using the Web of Science database (the descendancy approach).
Potentially modifiable determinants were extracted from the studies using a recommended published list [8], on the basis of which two authors selected determinants from each paper and perfect agreement was observed. Associations between determinants and behaviour or intention across studies were integrated by converting all statistics to the correlation coefficient r. These coefficients were then transformed to Fisher's Z and weighed by sample size −3 (cf. [15]). The mean Fisher's Z was then transformed back to the correlation coefficient r+. When a study tested a variable several times (e.g. frequency of use and intensity of use), the resulting effect sizes were averaged before being included in the calculations.
RESULTS
The search yielded 367 hits, from which 15 publications were included (see Appendix II). Many excluded studies had a biological focus (e.g. [3]), examined determinants not feasibly changed by health promoting interventions (e.g. [16]) or used qualitative methods (e.g. [17]). All included publications studied the behaviour ‘using ecstasy’ (or the intention to use); none examined determinants of trying out ecstasy, ceasing use, changing use patterns or applying harm reduction practices. Of these 15 publications, six were discarded after thorough examination, as they were then discovered to yield no quantitative information on the relevance of potentially modifiable determinants of behaviour in the target population ([18–23]; see also Appendix II). Application of the ancestry approach yielded no additional publications (365 citations scanned), but the descendancy approach yielded one additional publication (of 85 unique citing publications; [24]). Of the final set of 10 publications [24–33], one publication described two studies ([26]; 26a and 26b refer to studies 1 and 2, respectively). Table 1 describes the 11 included studies, listing the sample details, the extracted potentially modifiable antecedents and how they were measured in the original studies.
Table 1
Quantitative studies into the determinants of using ecstasy and measures used.
No.
Sample details
n
Age
% ♀
Relevant variables
I
R
[24]
UK, before July 2002 Polydrug users
364
19
44%
Negative mood function scale
3
5
Social function scale
5
5
Negative effects
4
5
Other functions (9 functions)
1
5
Extent of peer use
1
4
Partner/best friend use
1
2
Intensity of use
1
–
[25]
UK, before March 1998 Alcohol and drug users
100
19
45%
Mood function scale
3
5
Social/contextual function scale
5
5
Negative effects/events scale
3
5
Extent of peer use
1
5
Intention
1
7
Intensity of use
1
–
Frequency of use
1
–
[26a]
UK, March 1992 Students
186
19–25
58%
Attitudes
6
7
Subjective norms
1
7
Perceived behavioural control
6
7
Behavioural beliefs (17)
2
19
Normative beliefs (5)
2
19
Control beliefs (8)
2
19
Intention to use ecstasy
4
7
[26b]*
UK, mid-1996 Club members
t1: 203 t2: 123
23
41%
Attitudes
8
7
Normative influences
13
7
Perceived behavioural control
1
7
Self-efficacy
1
7
Behavioural beliefs
13
7
Control beliefs
6
7
Intention
3
7
Behaviour (longitudinal)
4
–
[27]
Netherlands, 2000, 2001 Party attendants
844
22
33%
Negative outcome expectancies
11
2
Enhancement outcome expectancies
3
2
Euphoria outcome expectancies
4
2
Sex outcome expectancies
4
2
Dancing outcome expectancies
3
2
Insight outcome expectancies
4
2
Communication outcome expectancies
4
2
Whether ecstasy was currently used
1
2
[28]
*
UK t1: October 1994–1995 t2: May1995–1996 Students
t1: 461 t2: 136
19–22 19–22
55% 65%
Attitude
2
7
Injunctive norms
6
7
Perceived behavioural control
8
7
Descriptive norms
2
6
Moral norm
1
7
Intention
1
8
Behaviour (longitudinal)
1
8
[29]
UK, before 2003 College students
657
19
55%
Frequency of past use
1
7
Intentions to use
1
9
Normative influence (friends’ use)
1
6
Beliefs about ecstasy use (7 beliefs)
1
5
[30]
*
UK
t1: 84 t2: 32
20
74%
Attitude
10
8
Subjective norm
2
8
Perceived behavioural control over obtaining ecstasy
3
8
Perceived behavioural control over taking ecstasy
4
8
Intention
5
8
Habit
2
8
Specific attitudinal beliefs (13 beliefs)
1
5
Behaviour (longitudinal)
1
2
[31]
the Netherlands, 2001–2002
490
22
34%
Energy motives
4
5
Euphoria motives
3
5
Self-insight motives
2
5
Sociability/flirtatiousness motives
8
5
Sexiness motives
4
5
Coping motives
3
5
Conformism motives
4
5
Perceived positive effects
24
2
Perceived negative effects
11
2
Perceived friends’ use
1
5
Frequency of ecstasy use
1
5
[32]
UK
200
21
66%
Attitude
5
?
Subjective norm
5
5
Perceived behavioural control over obtaining ecstasy
3
7
Perceived behavioural control over taking ecstasy
11
?
Intention
6
7
Habit
2
7
[33]
USA Club rave attendees
70
20
47%
Risk associated with using ecstasy once or twice
1
4
Risk associated with using ecstasy regularly
1
4
Harmful short-term physical effects
1
4
Harmful long-term physical effects
1
4
Harmful short-term psychological effects
1
4
Harmful long-term psychological effects
1
4
Positive physical effects
1
4
Positive psychological effects
1
4
Ecstasy use within the past 12 months
1
2
No. = number in reference list, I = number of items used to measure variable, R = number of scale points on response scale of each item.
*
Longitudinal design.
All 11 studies can be viewed as tests of two theoretical frameworks which are applied frequently in drug use research [34]. Six studies [26a,26b,28–30,32] tested the theory of planned behaviour (TPB; [35]). The TPB proposes that the most proximal cognitive determinant of behaviour is intention which, in turn, is predicted by attitude (i.e. evaluation of probable consequences of that behaviour), subjective norm (i.e. perception of others' approval of the behaviour) and perceived behavioural control (PBC; i.e. perception of control based on perception of skills and external obstacles/facilitators). Each of these constructs is based on underlying beliefs. Several extensions of the TPB have been proposed [36]; for example, personal norm (personal moral evaluation of the behaviour), descriptive norm (perception of others' performance of the behaviour [37]), habit [38] and anticipated regret (the regret one experiences when prospectively imagining having—or not having—performed a behaviour [39,40]).
Five studies [24,25,27,31,33] tested expectancy models (e.g. [41]), which propose that behaviour is determined by expectations people have of the behaviours' consequences. Two studies [24,25] assessed how often participants used ecstasy for particular reasons (e.g. ‘in the past year, how often have you used ecstasy to help you to let go of inhibitions?’), implying germane expectations (such as ‘taking ecstasy helps me let go of inhibitions’). Three studies [27,31,33] used more traditional measures (e.g. ‘I have experienced/would expect that ecstasy makes it easier to communicate’). Note that these expectations are viewed as underlying beliefs in the TPB, particularly in relation to the structure of attitudes [12,35].
In both the TPB and outcome expectancy models, higher-level constructs, such as attitudes, are based on lower-level beliefs. Most studies tested models involving this hierarchical cognitive structure. For the purposes of this review, higher-level constructs are referred to as ‘compound constructs’ and lower-order cognitions as ‘expectancies’ (e.g. beliefs about probable consequences of ecstasy use). Details of the particular theoretical models explored in the original studies are not provided here.
Only bivariate analyses were synthesized because multivariate analyses were incommensurable over studies as they tested different models. [In order to resolve this by conducting uniform regression analyses, all authors were asked to provide matrices of covariance. However, due to lost data sets, missing data and non-response, not enough data could be retrieved to render this feasible. The authors are grateful to M. Conner and T. ter Bogt, who did supply additional data.] It is worth noting none the less that in the two TPB-based studiesin which ecstasy use was regressed onto compound constructs, the average (weighed) R2 was 0.51 [26b,28], and in the five TPB-based studies in which intention to use was regressed onto compound constructs the average R2 was 0.67 [26a,26b,28,30,32]. The average R2 for the three expectancy studies in which ecstasy use was regressed onto expectancies was 0.35 [24,27,31], and in the expectancy study where intention to use was regressed onto expectancies was 0.64 [25]. In three prospective studies ecstasy use was found to be related strongly to prior intention to use with an average (weighed) r of 0.71 [26b,28,30].
Table 2 shows the strength of association between predictor variables and measures of ecstasy use and intention to use. The strongest predictor of intention and use was the TPB-specified attitude measure. Attitudes are thought to be based on more specific expectancies [12,35] and these are shown separately in Table 2, grouped into ‘positive’ and ‘negative’ expectancies. In addition to these perceived advantages and disadvantages of ecstasy use, normative measures have been used, especially subjective and descriptive norms, as well as perceived behavioural control over ecstasy use. Variables proposed as extensions to the TPB have been categorized as ‘miscellaneous’.
Table 2
Effect sizes of predictors of ecstasy use and intention to use.
Association with behaviour
Association with intention
Variable type
Compound or expectancy
k
r+
k
r+
Attitude
Attitude [C]
5
0.53 (L)
5
0.63 (L)
Positive expectancies
Social function [C]
4
0.09
2
0.30 (M)
Produces a positive mood state
3
0.12 (S)
2
0.28 (M)
Mood function [C]
4
0.20 (S)
1
0.41 (L)
Helps lose weight
2
0.09
1
0.08
Enhances sex
3
0.11 (S)
Helps stay awake
3
0.08
Helps keep fit
1
0.14 (S)
1
0.22 (S)
Enhances insight/openness
2
0.18 (S)
Helps to relax/helps coping
2
0.08
Produces excitement
1
0.31 (M)
Produces intoxication
1
0.19 (S)
Eases after-effects
1
0.15 (S)
Improves other drugs' effects
1
0.11 (S)
Is conforming to peers
1
0.05
Helps work
1
0.05
Negative expectancies
Short-term negative effects [C]
4
−0.47 (L)
Produces mood swings
1
−0.34 (M)
2
−0.31 (M)
Leads on to more frequent use
1
−0.30 (M)
2
−0.39 (L)
Produces mental side-effects
1
−0.24 (M)
2
−0.40 (L)
Leads on to ‘worse’ drugs
1
−0.23 (S)
2
−0.31 (M)
Produces physical side-effects
1
−0.18 (S)
2
−0.39 (L)
Makes one unhealthy
1
−0.18 (S)
2
−0.30 (M)
Produces depression
1
−0.18 (S)
2
−0.28 (M)
Produces lethargy
1
−0.05
2
−0.20 (S)
Produces addiction
1
−0.32 (M)
1
−0.12 (S)
Leads to death
1
−0.30 (M)
1
−0.32 (M)
Produces paranoia
1
−0.27 (M)
1
−0.26 (M)
Makes one feel run down
1
−0.17 (S)
1
−0.25 (M)
Subjective injunctive norm
Subjective norms (approval) [C]
5
0.39 (L)
5
0.52 (L)
Best friends' approval
1
0.36 (M)
1
0.25 (M)
Partners approval
1
0.15 (S)
1
0.30 (M)
Parents' approval
1
0.10 (S)
1
0.01
Health experts' approval
1
0.09
1
0.00
Other ecstasy users' approval
1
0.07
1
0.08
Subjective descriptive norm
Subjective norms (descriptive) [C]
1
0.52 (L)
1
0.63 (L)
Perceived peer use
2
0.39 (L)
1
0.43 (L)
Perceived use in close relatives
2
0.21 (S)
Perceived best friend/partner use
1
0.37 (L)
Perceived behavioural control
PBC [C]
3
0.33 (M)
3
0.52 (L)
PBC (over obtaining ecstasy)
2
0.20 (M)
2
0.25 (M)
PBC (over taking ecstasy)
2
0.01
2
−0.03
Being with friends who use
1
0.45 (L)
2
0.62 (L)
Going out dancing
1
0.41 (L)
2
0.67 (L)
Being offered ecstasy
1
0.40 (L)
2
0.59 (L)
Ecstasy being available
1
0.40 (L)
2
0.57 (L)
Cheap ecstasy
1
0.19 (M)
2
0.54 (L)
Having alcohol
1
−0.02
2
0.10 (S)
PBC (over not taking ecstasy)
1
−0.06
1
0.07
Needing to lose weight
1
−0.05
1
0.00
Needing to exercise
1
−0.01
1
0.05
Miscellaneous
Habit [C]
2
0.45 (L)
2
0.46 (L)
Moral norm [C]
2
−0.28 (M)
2
−0.31 (M)
Denial of negative consequences
1
0.17 (S)
1
0.18 (S)
Anticipated regret
1
−0.11 (S)
1
−0.22 (S)
[C] = compound construct, k = no. of samples, r+ = weighed average correlation, (S) = small, (M) = medium, (L) = large effect size magnitude according to Cohen [42]. PBC: perceived behavioural control.
Table 2 is based on the Pearson correlations reported in five studies [24,25,28,30,32] and correlation matrices received from the authors of two publications [26,31]. One study [27] reported t-values, which were converted into effect size correlations using r = √[t2/(t2 + df)]. The results from two studies [29,33] could not be converted and will be provided later. Only associations found in at least two samples, of magnitudes corresponding to a medium (Cohen's d = 0.5 [42], r = 0.24) or large effect size (d = 0.8 and r = 0.37), are considered.
All significant associations were in the expected direction and some large effect sizes were observed, suggesting that both the theory of planned behaviour and the expectancy approach can help to explain ecstasy use and intentions to use. In the TPB studies, intention and behaviour are associated most strongly with TPB's attitude, with a large effect size (r+ = 0.53 with behaviour, r+ = 0.63 with intention). Specifically, this compound construct appears to be associated mainly with positive outcomes regarding mood control and social facilitation, and negative expectations regarding short-term negative effects, escalating use and physical and mental side effects.
Normative influences are also important covariates of use and intention to use with stronger associations observed for descriptive (r+ = 0.52 with behaviour, r+ = 0.63 with intention) than injunctive norms (r+ = 0.39 with behaviour, r+ = 0.52 with intention). The strongest effect sizes for expectancies underpinning these compound constructs were observed for perceived ecstasy use by peers and approval of use by one's best friend and partner. The results also indicate that whether parents, health experts and ‘other ecstasy users’ approve is inconsequential.
Perceived behavioural control was related to use with a medium (near large) effect size (r+ = 0.33) and also related strongly to intention (r+ = 0.52). Underlying beliefs showed a medium effect regarding control over obtaining ecstasy and large effects of control in relation to being with friends who use, going out dancing, being offered ecstasy and ecstasy being available. Two proposed extensions to TPB appear relevant: habit, with a large effect size (r+ = 0.45 with behaviour, r+ = 0.46 with intention) and moral norm, with a medium effect size (r+ = −0.28 with behaviour, r+ = −0.31 with intention).
Two studies reported results using statistics that could not be transformed to an effect size measure. One study [29] conducted a polynomial logistic regression predicting user group (six levels: rejectors, at-risk non-users, ex-users, and light, moderate and heavy users; for details, see [29]), testing whether a number of variables contributed significantly to model fit when predicting user group. Another study [33] conducted t-tests on beliefs (also predicting user group, with two levels: non-user and user), but did not report t-values, exact P-values, or variance information. The variables tested in these studies are shown in Table 3. Effect sizes were estimated (conservatively) on the basis of sample size and significance.
Table 3
Significant and non-significant predictors of user group (user group had six levels in study [29] and two levels in study [33]).
Variable
Study
Significance
Association
Effect size
Perceived use by friends
[29]
< 0.001
Positive
M
Anticipated regret (‘use would induce guilt’)
[29]
< 0.001
Negative
M
Is hard to resist
[29]
< 0.001
Positive
M
Moral norm (‘ecstasy use is immoral’)
[29]
< 0.05
Negative
S
Perceived availability of ecstasy
[29]
< 0.05
Positive
S
Is bad for one's physical health
[29]
None
–
–
Is bad for one's mental health
[29]
None
–
–
Subjective norm (approval)
[29]
None
–
–
Harmful long-term physical effects
[33]
< 0.01
Negative
M
Risk associated with using regularly
[33]
< 0.01
Negative
M
Risk association with using once or twice
[33]
< 0.05
Negative
M
Harmful long-term psychological effects
[33]
< 0.05
Negative
M
Harmful short-term physical effects
[33]
None
–
–
Harmful short-term psychological effects
[33]
None
–
–
Positive physical effects
[33]
None
–
–
Positive psychological effects
[33]
None
–
–
S = small, M = medium, effect size magnitude according to Cohen [42].
These additional results confirm the relevance of descriptive norm, negative expectancies (particularly long-term effects) and perceived control, and add anticipated regret, with at least a medium effect size, to the list.
DISCUSSION
Synthesis of the included studies shows the main predictors of intention to use and actual ecstasy use to be attitude (specifically positive outcomes regarding mood control and social facilitation and negative outcomes regarding escalating use and physical and mental side-effects); subjective and descriptive norms regarding one's friends, partner and peers; perceived control regarding obtaining ecstasy and control in relation to being with friends who use, going out dancing, being offered ecstasy and ecstasy being available; and habit, moral norm and anticipated regret. In addition to lending support to both the TPB and expectancy models, these findings show that some expectancies underlying attitude are irrelevant (e.g. ecstasy enhances sex), as are norms relating to some social referents (e.g. parents), and perceived control regarding some ecstasy-related behaviours (e.g. taking ecstasy).
As it is now clear which determinants best predict intention to use and ecstasy use according to the research so far, these determinants seem advisable intervention targets. However, not all determinants are equally easy to modify. As attitude encompasses several specific expectancies, it may be easier to target these more concrete expectancies than the abstract attitude construct. Also, not all expectancies are influenced equally easily. Because most users have experienced positive mood shifts, it may be difficult to develop persuasive messages that undermine this expectancy among users [43]. Negative variables are also associated strongly, and changed more easily. However, simply presenting information about negative outcomes (‘fear appeals’) has been shown not to work, or even work inversely, unless a number of critical conditions are met, such as efficacy enhancement (see [6,44]; also see [45]). Similarly, it may be difficult to change a subjective norm if it reflects reality. As ecstasy use is social [46] and most users take ecstasy at a dance event [47] where ecstasy use is high (in the Netherlands, about two-thirds of the visitors use ecstasy; [48]), it might be hard to reduce descriptive norms, especially if participants' friends use ecstasy. Similarly, it may be challenging to establish a disapproving norm (see [49]).
Similarly, it may be difficult to reduce perceived control over obtaining ecstasy among users, as they probably have repeatedly performed this behaviour successfully. However, the large effects of specific control beliefs suggest that users who wish to stop may well be aided by adopting a stimulus control strategy avoiding the social contexts of use. In addition, enhancing refusal skills would influence perceived behavioural control, while also diminishing the effect of undesirable subjective norms (by decreasing users' motivation to comply, see [35]). Thus, among those with intentions not to use, refusal skills training and stimulus control are recommended [50]. Finally, habit and moral norm are useful predictors but may be difficult to change ([8], but also see [51]). Although anticipated regret has a smaller association with use and intention to use, it can be changed more easily (e.g. [39]). A list of methods and strategies to change these determinants, and the theoretical parameters prerequisite to success, is provided in chapter 7 of Bartholemew et al. [8].
This review is limited mainly by the fact that only bivariate associations could be synthesized and by two consequences of the paucity of research into ecstasy use thus far. First, the small number of studies into determinants of ecstasy use limit the robustness of the current findings. Second, many theories and models have not yet been studied and are therefore not included in this review. Only social cognitive theories have been tested; no studies have investigated, for example, the predictive value of implicit cognitions. However, recent research implies that implicit processes may be changeable [52]. Moreover, within social cognitive research, recently developed constructs such as consideration of future consequences [53] have not yet been applied to ecstasy use, but may aid in intervention development.
Regarding the theories that have been studied, in order to gain a more comprehensive understanding of motives for ecstasy use future research should combine the two theoretical perspectives studied thus far, so that relative overlap can be determined. It would be interesting to see whether, and to what degree, particular expectancies account for the predictive utility of the TPB attitude measures. Also, the list of expectancies that has been studied so far may omit a number of consequences (such as ‘suicide Tuesday’, a term for a period following use when low serotonin levels can induce depressive feelings).
Another important gap in the literature concerns behaviours other than ‘using ecstasy’. Not only can the determinants of trying ecstasy out, starting use, ceasing use and maintaining cessation differ from the determinants of using ecstasy [12], little is known about the determinants of harm reduction practices, such as having one's ecstasy tested by a test service, ensuring sufficient hydration and maintaining a low body temperature (although studies such as [54] are a step in the right direction). Intervening to promote these behaviours could prove to be more beneficial to the health of party visitors, given the difficulty of intervening on most variables determining ecstasy use.
In conclusion, this review suggests that there is sufficient evidence to guide intervention development so that evidence-based practice is established. These interventions could then be evaluated to test the utility of particular theoretical frameworks. The priorities for interventions should be negative expectancies, perceived behavioural control and anticipated regret. Tailored interventions can offer refusal skills training and strategies to avoid risky situations to participants not intending to use ecstasy.
Appendix I
Search terms used in PsycINFO (equivalent terms used in corresponding fields in MedLine and ERIC) [query in words, as corresponding to ‘concepts’ column, in brackets].No.ConceptOperationalizationFields1Language(English) or (Dutch)Language2Publication type(journal*) or (peer-reviewed-journal)Publication type3Publication date> 1980Publication year4Ecstasy(clubdrug*) or (club near drug*) or (dance near drug*) or (dancedrug*) or (party near drug*) or (partydrug*) or (xtc) or (mdma) or (methylenedioxymethamphetamine) or (‘3,4-methylenedioxymethamphetamine’) or (ecstasy)Title, abstract, keywords5Theoretical(theor*) or (attitud*) or (motivat* near functio*) or (mode*) or (norm*) or (perceived near control) or (pbc) or ('social cognitive’) or (self adj efficacy) or (stages near change) or (perceived adj (harm or risk or functions)) or (functional) or (outcome adj (expectancies or expectations)) or (sct) or (tpb) or (patter*) or (psychosoc*) or (health adj belief adj model) or (hbm)Title, abstract, keywords6Determinants(determin*) or (facto*) or (variabl*) or (parameter*) or (reason*) or (caus*) or (motiv*) or (incentive*) or (correlat*) or (antecedent*) or (character*)Title, abstract, keywords7Initiation(start*) or (commenc*) or (originat*) or (onset) or (initiat*) or (instigat*) or ((use) not (user)) or (using) or (usage) or (establish*)Title, abstract, keywords8Maintenance(maint*) or (sustain*) or (continu*) or (uphold*) or (persist*) or (further*) or (prolong*)Title, abstract, keywords9Cessation(end*) or (stop*) or (discontinu*) or (terminat*) or (ceas*) or (cessat*) or (abstain*) or (abstin*) or (quit*) or (remiss*) or (resolut*) or (recover*)Title, abstract, keywords10Harm reduction(harm or risk or damage or casualt*) and (reduc* or manag* or limit* or minimi*)Title, abstract, keywords11Excluded((treatment not (‘not in treatment’ or ‘non-treatment’ or ‘non- treatment’ or ‘no treatment’)) or rat or rats or mouse or mice or animal or monkey* or pigeon* or spectro* or cardio* or seroton* or dopamin* or neurotransm* or receptor* or psychiatr* or psychopath* or cell* or diagnos*)Anywhere12Inclusion#1 and #2 and #3 [Language and Publication Type and Publication Date]–13Behaviour#7 or #8 or #9 or #10 [Initiation or Maintenance or Cessation or Harm reduction]–14Empirical*#6 near #13 [Determinants near Behaviour]–15Final query*#12 and #4 near (#5 or #14) not #11 [Inclusion and Ecstasy near (Theoretical or Empirical) not Excluded]–When executed, the query consisted of one command; therefore the use of the ‘near’-operator was valid here.
Appendix II
Search procedure, number of resulting hits, and results of each step.
Step
Activity
Number of resulting publications
1
Input of query at 20 August 2007 in PsycINFO (162), MedLine (194) and ERIC (11)
367
2
Removal of duplicate records (83)
284
3
Removal of records about publications that (entries were removed in this order):
3.1
studied biological variables (e.g. sequelae of ecstasy use; 75)
209
3.2
did not study ecstasy use or a related behaviour (such as trying out ecstasy, ceasing use, changing use patterns, or applying harm reduction practices; 32)
177
3.3
studied variables that cannot be changed using a health promotion intervention (e.g. sex, ethnicity or religion; 68)
109
3.4
studied ecstasy use as an independent variable in a multivariate or longitudinal analysis (22)
87
3.5
did not employ quantitative methods (e.g. qualitative studies; 30)
57
3.6
did not study behaviour or cognitions (25)
32
3.7
studied a ‘non-normal’ subpopulation or gathering data from samples inseparably encompassing these subpopulations (e.g. dependent participants, patients or delinquents)*, studying generic drug categories (e.g. ‘hard drugs’)†, or not explicitly stating which drugs were studied (14)
18
3.8
were not published in a peer-reviewed journal (3)
15
*
inclusion of these subpopulations would restrict generalization of the results to the target population of the current study (i.e. the average adolescent; see [12,55]).
†
this demand of drug specificity is necessary because previous research has shown that beliefs about drugs can vary between different drugs [56], rendering aggregation questionable.

determinants
ecstasy
review
expectancies
drugs
theory of planned behaviour


Incidence of late vitamin K deficiency bleeding in newborns in the Netherlands in 2005: evaluation of the current guideline

Vitamin K prophylaxis is recommended to prevent the hazard of haemorrhage caused by vitamin K deficiency in newborns. The present Dutch guideline recommends 1 mg of vitamin K1 orally at birth, followed by a daily dose of 25 μg of vitamin K1 from 1 to 13 weeks of age for breastfed infants. Since the introduction of this prophylaxis, the incidence of vitamin K deficiency bleeding (VKDB) has decreased; however, late VKDB is still reported. From 1 January to 31 December 2005, a nationwide active surveillance was performed by the Netherlands Paediatric Surveillance Unit (NSCK) to study the current incidence and aetiology of late VKDB in infants. Six cases could be validated as late VKDB: all were breastfed, one fatal idiopathic intracranial haemorrhage at the age of 5 weeks and five bleedings secondary to an underlying cholestatic liver disease between the age of 3 and 7 weeks. The total incidence of late VKDB and idiopathic late VKDB was calculated to be 3.2 (95% CI: 1.2–6.9) and 0.5 (95% CI: 0–2.9) per 100,000 live births, respectively. With the current Dutch guideline, idiopathic late VKDB is rare but late VKDB secondary to cholestasis still occurs in breastfed infants. Doubling the daily dose of vitamin K1 to 50 μg, as is comparable to formula-feeding, may possibly prevent VKDB in this group. Further research, however, is needed to prove this hypothesis.
Introduction
Vitamin K deficiency can cause severe haemorrhage in the newborn. The term “haemorrhagic disease of the newborn” (HDN) was coined by Charles Townsend in 1894 to describe an acquired bleeding disorder in the newborn due to vitamin K deficiency [26]. Nowadays, the term HDN is replaced by vitamin K deficiency bleeding (VKDB), as neonatal bleeding is often not due to vitamin K deficiency and VKDB often occurs after the 4-week neonatal period [23].
VKDB can be classified according to the time of presentation after birth into early (0–24 h), classical (1–7 days) and late (2–12 weeks) VKDB. Late VKDB occurs primarily in exclusively breastfed infants who have received no or inadequate vitamin K prophylaxis. In addition, intestinal malabsorption defects (cholestatic jaundice, cystic fibrosis, α-1-antitrypsin deficiency etc.) are a well known frequent cause of late VKDB [13]. In some children, “warning bleeds” such as mild bruises, nose bleeds or umbilical oozing are the first manifestation of VKDB. In about 50% of the cases in late VKDB, intracranial haemorrhage occurs, accounting for death and serious neurological and mental handicaps [22]. The efficacy of neonatal vitamin K prophylaxis (oral or parenteral) in the prevention of classic VKDB is firmly established [16]. It has been the standard of care since the Committee on Nutrition of the American Academy of Paediatrics recommended to administer vitamin K prophylaxis to all newborn infants in 1961 [1]. Since then, many countries adopted this recommendation, although controversies concerning the best dose, route and frequency of administration still exist.
In 1990, the Dutch Paediatric Association recommended the administration of a single oral dose of 1 mg of vitamin K1 at birth to all healthy infants. Parenteral administration of vitamin K1 at birth was recommended for newborns especially at risk (preterm babies, babies born with instrumental help or caesarean section, asphyxia or if maternal medication was interfering with coagulation). For infants who are largely or fully breastfed, a daily dose of 25 μg of vitamin K1 orally was recommended from 1 to 13 weeks of age. In case of additional risk factors like a known malabsorption, this dose should be increased to 50 μg per day [29].
After the introduction of this guideline, the incidence of late VKDB, which was studied by a nationwide active surveillance performed by the Netherlands Paediatric Surveillance Unit (NSCK) in 1992 to 1994, decreased from about 7.0 to 1.1/100,000 live births [2]. However, still, some cases of late VKDB have been reported in the Netherlands, merely due to an underlying cholestatic liver disease [7, 10, 11].
Therefore, a one-year surveillance was started again to study the current incidence and the aetiology of late VKDB in the Netherlands. Discussion will rise about the efficacy of the current guideline in order to completely prevent late VKDB.
Methods
From 1 January to 31 December 2005, an active surveillance programme for VKDB was in operation in the Netherlands, using methods developed by the British Paediatric Association Surveillance Unit [8]. Surveillance was based on monthly report cards sent to paediatricians responsible for in- and outpatient care in all hospitals by the NSCK. A “nothing to report” option was included. The return rate of these report cards was 94.7% in 2004 [17].
The paediatricians were asked to report all infants in whom bleeding may have resulted from VKDB. The reported cases were validated with a questionnaire asking for information about the infant, type of feeding, clinical presentation, dose of vitamin K prophylaxis, route of vitamin K prophylaxis, associated diseases and laboratory data. For all reported cases, we asked for an anonymous hospital discharge letter to verify the diagnosis of late-onset VKDB.
The case definition of late-onset VKDB was as internationally defined: any infant between 8 days to 26 weeks of age, with spontaneous bruising, bleeding or intracranial haemorrhage associated with a grossly prolonged prothrombin assay, not due to an inherited coagulopathy or disseminated intravascular coagulation [23].
Confirmed VKDB was diagnosed when the prothrombin assay results were grossly abnormal compared with the standards for age: international normalized ratio (INR) ≥4 control value, prothrombin time (PT) ≥4 control value and at least one of the following was present:
Platelet count normal or raised and normal fibrinogenProthrombin assay returned to normal after vitamin K administrationConcentration of proteins induced by vitamin K absence (PIVKA) exceeded normal controls
PIVKA is a sensitive indicator of vitamin K status, allowing the detection of subclinical deficiency states which would not be detected by conventional coagulation assays [20].
Idiopathic cases were defined as cases in whom no factor predisposing to vitamin K deficiency was identified. Secondary cases were those in whom an underlying condition such as cholestasis or other causes of malabsorption of vitamin K could be identified.
Vitamin K prophylaxis was considered to be “as recommended” if the Dutch guideline was followed at the time of bleeding: 1 mg of vitamin K1 (oral, intravenous, intramuscular) directly after birth, followed by a daily dose of 25 μg of vitamin K1 from 1 to 13 weeks of age for all breastfed babies.
The Konakion mixed micellar preparate (Phytomenadion 10 mg/ml, Hoffmann-La Roche, Basel, Switzerland), which can be used for both oral, intramuscular and intravenous administration, an oral preparate called Davitamon K (marketed by Chefaro, Rotterdam, the Netherlands, 25 μg/5gtt) and an oral preparate, Phytomenadion, which is made by the Dutch pharmacist Mixtura (Phytomenadion 10 mg/ml FNA) were the only vitamin K preparations licensed in the Netherlands.
The 95% confidence intervals (CI) were calculated according to a binomial distribution and the chi-squared test was used for the comparison of incidences between different periods, with a value of P < 0.05 being considered as significant.
Results
The response rate to the surveillance amounted to 93.4% and the response to our questionnaires was 100%. In total, seven cases of late VKDB were reported: four reports from academic paediatric centres and three from general district hospitals. A hospital discharge letter was obtained in six cases. In all cases, the diagnosis could be verified by the completed questionnaire or the additional discharge letter.
One case did not fulfil the criteria of the case definition because there were no clinical signs of bleeding, only biochemical clotting disorders due to a vitamin K deficiency.
Six cases fulfilled the criteria of the case definition and could be validated as late VKDB. The surveillance data are shown in Table 1. The mean age of presentation was 5 weeks and 2 days, and all of the cases were exclusively breastfed. In all cases, the PT time or INR was at least four times greater than normal and vitamin K deficiency was confirmed by a documented PT or INR normalisation after the administration of vitamin K. Five of the cases also received fresh frozen plasma.
Table 1Confirmed cases of late vitamin K deficiency bleeding (VKDB) in the Netherlands from 1 January to 31 December 2005Patient; sex; age (weeks)PresentationFeedingVitamin K prophylaxisProthrombin assay (after vitamin K administration) Additional morbidityOutcome of bleedingA; female; 5 + 1/7Intracranial bleedingBreastfeedingBirth: 1 mg p.o.→25 μg/dayPT>120 s (13.3); APTT>120 s (37)NoDiedB; female; 6 + 6/7Intracranial bleedingBreastfeedingBirth: 1 mg p.o.→25 μg/dayINR>8 (INR<2); APTT>240 s (49)Biliary atresiaHemipareses rightC; male; 4 + 4/7Intracranial bleedingBreastfeedingBirth: 1 mg p.o.→25 μg/dayPT>90 s (30); APTT>120 s (38); Vitamin K: 0.1 nmol/lBiliary atresiaHemipareses rightD; male; 5 + 2/7Nasal bleedingBreastfeedingBirth: 1 mg p.o.→25 μg/dayPT>75 s (normal); APTT: 118 s (normal)Biliary atresiaNo sequelaeE; male; 6 + 2/7Nasal bleedingBreastfeedingBirth: 1 mg p.o.→25 μg/dayPT>165 s (normal); APTT>240 s (normal)Biliary atresiaNo sequelaeF; male; 3 + 6/7Nasal bleedingBreastfeedingBirth: 1 mg p.o.→25 μg/dayPT>71 s (12.7); APTT: 128 s (39.1)CholestasisNo sequelae
Concerning the cause of VKDB, there was one case of idiopathic VKDB, who presented with signs of bleeding at the age of 5 weeks. She was breastfed and died due to the consequence of an intracranial bleeding. She received exactly the recommended prophylaxis. Unfortunately, no post-mortem obduction was performed but, biochemically, there were no signs of cholestasis. Five out of six cases could be validated as secondary late VKDB. The age of presentation in this group was between 3 and 7 weeks of age. All of these bleedings were due to an underlying cholestasis which was diagnosed after the first presentation of bleeding. In two cases, an intracranial bleeding was the first presenting sign. Four cases were diagnosed as having a bile duct atresia. All infants had been exclusively breastfed and all had received exactly the recommended prophylaxis.
In the study period, the number of live births amounted to 187,910 [21]. Therefore, the total incidence of late VKDB and idiopathic late VKDB was calculated to be 3.2 (95% CI: 1.2–6.9) and 0.5 (95% CI: 0–2.9) per 100,000 live births, respectively.
Discussion
Data from the United Kingdom, Germany and Switzerland prove that intramuscular vitamin K1 prophylaxis (1 mg) is highly effective in the prevention of late VKDB. This is supported by data from Australia, which demonstrate a higher incidence of late VKDB in babies who received oral vitamin K compared to those with parenteral vitamin K at birth. However, most of these failures of oral vitamin K were in cases reported with an underlying cholestatic liver disease [3, 12, 14, 25, 32, 33].
In 1992, Golding et al. [5] reported an increased risk of developing childhood cancer after parenteral vitamin K1 prophylaxis. Recent studies, however, show that solid tumours are no commoner in children who had parenteral vitamin K. Although no convincing evidence between parenteral vitamin K and childhood leukaemia was found in these studies, it cannot be fully excluded that there is no risk [4, 18].
Since the report of Golding et al., there has been an increasing trend towards oral vitamin K administration and many oral prophylaxis regimes have been developed.
In 1997, we summarised the results of surveillance studies of over 2 million infants in four different countries using different multiple oral dose schedules and parenteral administration of vitamin K. A daily low oral dose of 25 μg of vitamin K1 following an initial oral dose of 1 mg vitamin K1 directly after birth for exclusively breastfed infants, as was used in the Netherlands since 1990, seemed to be as effective as parenteral vitamin K1 prophylaxis [3].
The present surveillance study shows that the current Dutch guideline still seems quite effective in preventing idiopathic late VKDB, but it is insufficient against secondary late VKDB. In our surveillance, the incidence of all late VKDB and idiopathic late VKDB was 3.2 (95% CI: 1.2–6.9) and 0.5 (95% CI: 0–2.9) per 100,000 live births, respectively. The incidence of the latter is comparable to 0.5 (95% CI: 0.1–1.6) per 100,000 live births reported in our surveillance study performed by the same Netherlands Paediatric Surveillance Unit (NSCK) in 1992–1994 [2]. The incidence of late VKDB secondary to an underlying cholestatic liver disease is, however, significantly higher (P < 0.05); 2.7 (95% CI: 0.9–6.2) compared to 0.7 (95% CI: 0.1–2.0) in 1992–1994. A higher incidence of cholestatic liver diseases in general or a delayed recognition of symptoms can be explanations for this difference. Unfortunately, data about the incidence or recognition of cholestatic liver diseases in the Netherlands are not available.
In this surveillance, there were no reports of late VKDB after parenteral administration of vitamin K1. This can be explained by the assumption of the higher efficacy of parenteral vitamin K1 or the low use of intramuscular and intravenous vitamin K1 these days.
Since 1994, a new preparate, Konakion mixed micellar, has been available. This mixed micellar formulation is prepared with the phospholipids lecithin and the bile salt glycocholic acid, and it was presumed that this preparate would reduce the incidence of late VKDB due to a better absorption of oral vitamin K. However, a recent randomised controlled trial shows that the mixed micellar vitamin K gives unreliable and still severely impaired intestinal absorption in infants with cholestasis [15]. Furthermore, von Kries et al. [31] reported no significant reduction in the incidence of late VKDB in healthy infants and infants with an underlying cholestatic liver disease with this preparate compared to the use of the original Konakion (Cremophor EL) and Kanavit (Polysorbat 80).
In view of the fact that vitamin K has limited tissue reserves and is rapidly catabolised, with 60–70% of a single dose being excreted via the urine and bile in about 3 days, it seems reasonable that repeated doses rather than a higher single dose is more effective in preventing late VKDB [15].
An important study from Denmark has established that 1 mg of oral vitamin K1 given weekly during the first 3 months of life, following an initial oral dose of 2 mg of vitamin K1 directly after birth, is as effective as 1 mg of vitamin K1 given intramuscularly at birth [9]. Therefore, we hypothesise that the dosage of 25 μg of vitamin K1 daily is not enough to prevent the secondary cases of late VKDB, as we encountered in this study.
In most co-operative studies, the upper age limit for inclusion was set arbitrarily at the end of 12 weeks of age [32]. In our study, we included infants presenting with VKDB up to the age of 26 weeks of age, as suggested by Tripp et al. [27]. However, no infant between 12 and 26 weeks of age was reported.
The mean age of all infants with late VKDB was 5 weeks, which is comparable to other reports [22].
In our study, the boy:girl ratio was 2.5:1. Why late VKDB occurs more in boys than girls is unknown, but this is consistent with other European reports [22, 24].
Unfortunately, this study has some limitations. First, this surveillance was based on one data source only: the Netherlands Paediatric Surveillance Unit. In spite of the high return rate of the report cards (93.4%), it is plausible that dramatic conditions, such as intracranial bleedings, are more likely to be reported, as also noted by von Kries et al. [31]. For this reason, our data could give an under-reporting of the true incidence of late VKDB in the Netherlands. However, the fact that 50% of late VKDB cases were intracranial bleedings is comparable to other, larger reports [3, 13, 14, 19, 22, 30, 31, 33].
Secondly, the surveillance lasted only 1 year. In all probability, the confidence interval would be smaller when the length of the surveillance was prolonged. Third, the proportion of infants that is breastfed is unknown, and, additionally, we lack data about compliance to the prophylaxis. It is likely, however, that less than 100% of the eligible cases received the recommended prophylaxis. Prophylaxis failure, therefore, is likely to be underestimated due to a greater denominator than the true numbers exposed.
We would suggest to double the daily dose of vitamin K1 to 50 μg for all breastfed babies from 1 to 13 weeks of age to prevent bleedings in infants with an underlying cholestatic liver disease as well. This amount is comparable to the ingested dose of vitamin K1 by formula-feeding [6]. Formula is supplemented with vitamin K1 to a minimal concentration of 50 μg/l. VKDB are not reported in formula-fed babies and there is no evidence that they are at an increased risk of childhood cancer [28]. Studies with such a concentration of vitamin K1 have never been performed and further research is necessary to study the efficacy of this prophylaxis in infants with underlying cholestatic liver disease. Due to the low incidence of late VKDB, it would be difficult to perform a randomised trial of 25 μg versus 50 μg of vitamin K1 daily. Alternatively, a new surveillance for 1 or 2 years after implementing 50 μg of vitamin K1 as the prophylaxis could give an indication of the efficacy of this dose.
Furthermore, an earlier recognition of symptoms associated with cholestatic liver disease and immediate investigation and treatment of “warning bleeds” helps to prevent the severe consequences of secondary late VKDB.
In conclusion, with the current guideline of vitamin K prophylaxis in the Netherlands, idiopathic late VKDB is rare, but late VKDB secondary to an underlying cholestatic liver disease still occurs. We suggest to double the daily maintenance dose of vitamin K1 to 50 μg per day for all breastfed infants from 1 to 13 weeks of age in order to prevent bleedings in children with an underlying cholestatic liver disease as well. Further research, however, is recommended.

vitamin k
vitamin k deficiency
newborn
prophylaxis
infant


Molecular mechanism of edema formation in nephrotic syndrome: therapeutic implications

Sodium retention and edema are common features of nephrotic syndrome that are classically attributed to hypovolemia and activation of the renin–angiotensin–aldosterone system. However, numbers of clinical and experimental findings argue against this underfill theory. In this review we analyze data from the literature in both nephrotic patients and experimental models of nephrotic syndrome that converge to demonstrate that sodium retention is not related to the renin–angiotensin–aldosterone status and that fluid leakage from capillary to the interstitium does not result from an imbalance of Starling forces, but from changes of the intrinsic properties of the capillary endothelial filtration barrier. We also discuss how most recent findings on the cellular and molecular mechanisms of sodium retention has allowed the development of an efficient treatment of edema in nephrotic patients.
Introduction
Interstitial edema is a common clinical feature of nephrotic syndrome (NS). It is often massive (up to 30% of body weight) and constitutes a functional constraint, owing to locomotive restriction and eyelid shutting. Expansion of the interstitial compartment volume results from the combination of abnormal renal sodium retention and alterations of fluid transfer across capillary walls.
Renal retention of sodium in nephrotic syndrome
Site of sodium retention Most of our current knowledge on the site and mechanism of renal sodium retention in NS comes from experimental models of the disease, in particular the puromycin aminonucleoside (PAN) rat model. Following a single injection of PAN, rats develop massive proteinuria within 4–5 days and sodium retention within 2–3 days. Sodium excretion resumes after 9–10 days, while proteinuria lasts for 2–3 weeks [1, 2]. Unilateral NS can be induced by the injection of PAN into one of the renal arteries [3]. Early in vivo micropuncture studies in rats with unilateral PAN nephrosis demonstrated that sodium retention in the nephrotic kidney originates beyond the last nephron segment accessible to micropuncture, i.e., between the late distal convoluted tubule and the tip of the collecting duct [3]. This part of the nephron encompasses the connecting tubule and the cortical and outer medullary collecting ducts, which reabsorb sodium and are the major sites of the adjustment of sodium balance under the homeostatic control of aldosterone, and the inner medullary collecting duct, which is able to secrete an overload of sodium in response to atrial natriuretic peptide [4]. Methods allowing in vitro analysis of isolated sub-segments of the distal nephron demonstrated a marked stimulation of sodium reabsorption in the cortical collecting duct (CCD) of PAN nephrotic rats [1, 5]. This stimulation of sodium transport likely extends upstream to the connecting duct but not downstream to the outer medullary collecting duct. In addition, in NS, the inner medullary collecting duct becomes insensitive to the natriuretic action of atrial natriuretic peptide [6–8], thereby preventing any compensation of sodium retention in upstream nephron segments.
Cellular mechanism of sodium retention in the collecting duct In vitro microperfusion of isolated CCDs confirmed that the rate of sodium reabsorption and the trans-epithelial voltage are negligible in CCDs from control rats, whereas both are high in CCDs from PAN nephrotic rats [5]. CCDs are made of principal and intercalated cells, which account for sodium and water reabsorption and potassium secretion for principal cells, and proton, bicarbonate and likely chloride transport for intercalated cells [4]. In principal cells, sodium reabsorption proceeds along a two-step mechanism (Fig. 1): Na,K-ATPase, exclusively present in the basolateral membrane, energizes the active extrusion of sodium at the expense of ATP hydrolysis. The electrochemical gradient for sodium generated by this primary process drives passive entry of sodium through the apical membrane, which contains selective sodium channels (epithelial sodium channels, ENaCs). Both Na,K-ATPase and ENaCs are targets for multiple, and often coordinated, regulations in CCDs [4].Increased sodium reabsorption along the CCDs of PAN nephrotic rats, as well as sodium retention and edema formation, are associated with stimulation of both basolateral Na,K-ATPase [1, 9, 10] and apical ENaC [11–13] (Fig. 1), but the latter is dispensable (see below). Stimulation of Na,KATPase is fully accounted for by transcriptional induction of its α and β subunits and targeting of newly synthesized pumps to the basolateral membrane of principal cells [14]. In contrast, stimulation of ENaC mainly results from the targeting of a pre-existing pool of latent intracellular channels to the apical membrane of principal cells and slightly from transcriptional induction of the α and β subunits [11–13]. The patch-clamp technique shows that the intrinsic properties of ENaC (open probability and unitary conductance) are not altered in the CCD of nephrotic animals [13].
Fig. 1Cellular mechanism of sodium reabsorption in principal cells of collecting ducts from normal rats and nephrotic rats. Sodium reabsorption in principal cells proceeds along a two-step mechanism that includes active extrusion of intracellular sodium ions by the basolateral Na,K-ATPase and passive apical entry of sodium via the amiloride-sensitive epithelial sodium channel (ENaC). In CCDs from normal rats (top panels), most ENaCs are sequestered in the intracellular compartment of principal cells (left panel), and basolateral expression of Na,K-ATPase in collecting ducts (asterisk) principal cells is very weak, in comparison with that in thick ascending limbs (T) and even proximal tubules (P) (right panel). Accordingly, the rate of sodium reabsorption is very low. In CCDs from PAN nephrotic rats (bottom panels), ENaC is expressed at the apical border of principal cells (left panel), and expression of basolateral Na,K-ATPase is drastically increased in collecting ducts (asterisk). Polarized increases in expression of ENaC and Na,K-ATPase in principal cells account for increased sodium reabsorption in CCDs. In both normal and nephrotic rats expression of Na,K-ATPase is undetectable in the glomerulus (G); in CCDs, unlabeled cells for both ENaC and Na,K-ATPase are intercalated cells (redrawn from [13, 14])
Aldosterone and activation of mineralo-corticoid receptors are not involved in sodium retention in nephrotic syndrome Historically, it is acknowledged that sodium retention and edema formation result from hypovolemia-induced stimulation of the renin–angiotensin–aldosterone system. Hypovolemia is supposed to proceed as follows: proteinuria induces hypoalbuminemia and reduces plasma oncotic pressure, which generates an imbalance of Starling’s forces across capillary walls, leading to interstitial leakage of fluid and decreased efficient volume [15]. Although this mechanism is consistent with the renal site of sodium retention, with the activation of ENaC and the induction of Na,K-ATPase in the collecting duct, and with the hyperaldosteronemia observed in PAN nephrotic rats [13], a large body of clinical evidence argues against this theory.
Analbuminemic patients display no sodium retention and no, or only modest, edema, despite low plasma oncotic pressure [16].In children with steroid-sensitive minimal change disease, natriuresis resumes at the same time as proteinuria stops, before normalization of albuminemia [17].Blood volume is not correlated with plasma oncotic pressure in nephrotic patients [18].Among children with relapse idiopathic nephrotic syndrome, (a) 21% display hypertension but only 4% exhibit collapse [19], and (b) only 1% display low blood volume, whereas 17% present hypervolemia [20].Intravenous injection of albumin induces volume expansion but promotes only mild natriuresis (reviewed in [21]).Blockade of mineralo-corticoid receptor or inhibition of angiotensin-converting enzyme has no effect on natriuresis in most patients [22, 23].The lack of a role for hyperaldosteronemia in sodium retention in NS was directly demonstrated in PAN nephrotic rats. In this model it is possible to blunt PAN-induced hyperaldosteronemia through bilateral adrenalectomy and corticosteroid replacement through implanted mini-pumps delivering constant physiological level of aldosterone and glucocorticoids. Administration of PAN to these corticosteroid-clamped rats reduces sodium excretion, establishes sodium balance and promotes ascites formation with similar time course and intensity as in adrenal-intact rats [11, 13].These findings also exclude a possible role in sodium retention of promiscuous activation of the mineralo-corticoid receptor (MR) by glucocorticoid brought about by decreased 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2). Indeed, use of dexamethasone instead of corticosterone for glucocorticoid replacement prevents MR activation, even in the presence of 11β-HSD2 inhibition. The lack of involvement of MR activation in sodium retention in nephrotic syndrome is consistent with the fact that nephrotic syndrome does not induce potassium secretion.
None of the known factors that control sodium reabsorption in the collecting duct accounts for sodium retention in PAN-nephrotic rats Since aldosterone, the major factor that controls sodium reabsorption in collecting ducts, is not involved in sodium retention, several hormones or paracrine factors that modulate this process have been considered as putative candidates:
Vasopressin (AVP), through activation of its V2 receptors coupled to the cAMP pathway, increases sodium reabsorption in the collecting duct synergistically with aldosterone [24, 25].Angiotensin II (AII) increases sodium reabsorption directly through activation of AT1 receptors coupled to phospholipase C, independently of the induction of aldosterone release [26].Insulin-like growth factor I (IGF-1) used in the treatment of insulin resistance in type 2 diabetes can induce sodium retention and edema [27], likely through its stimulatory action on sodium transport along the collecting duct [28].In mouse collecting duct cells, tumor necrosis factor alpha (TNFα) increases membrane expression of Na,K-ATPase [29], and administration of etanercept, a TNFα receptor antagonist, to diabetic rats induces natriuresis [30].More recently, the thiazolidinedione agonists of peroxisome proliferator-activated receptor γ (PPARγ) were reported to induce sodium retention [31] through a stimulatory effect on the collecting duct [32].Quite unexpectedly, inhibition of nitric oxide synthase promotes sodium excretion in cirrhotic rats with ascites [33].Except for AII, all maneuvers aimed at blocking these different pathways had no effect on sodium retention in nephrotic syndrome (Fig. 2). Only the AT1 blocker irbesartan was able to improve sodium excretion, although not up to normal level. However, this effect was limited to the initial sodium retention observed 2–4 days after PAN administration and did not alter the main effect observed at days 5 and 6. This suggests that AII, independently of aldosterone, may be involved in the early retention of sodium observed after the peak of sodium excretion at day 1.
Fig. 2Profile of sodium excretion in PAN nephrotic rats. Daily urinary sodium excretion, expressed as a function of urinary creatinine excretion, following administration of puromycin aminonucleoside (150 mg/kg body wt, intravenously) in normal rats (dotted lines) or genetically modified or pharmacologically treated rats (solid lines). Arrows or grey boxes show the time of treatment. Brattleboro rats genetically lack vasopressin secretion. JB1, an inhibitor of IGF-1 receptors, was continuously administered via subcutaneous mini-pumps at a dose of 12 μg/100 g body wt per day, starting on day 3. The antagonist of AT1 receptor, irbesartan, was administered per os at a dose of 2 mg/100g body wt per day. Etanercept, a chimeric antibody directed against TNF receptor, was administered twice (days −1 and 2) at a dose of 0.2 mg/100g body wt. The inhibitor of nitric oxide synthase, L-NAME, was administered twice daily by gavage (0.5 mg/100 g body wt per 12 h) throughout the study. The antagonist of PPARγ, SR202, was given per os at a dose of 20 mg/100 g body wt. All controls were treated in parallel with the vehicle. Values are means ± SE from 4–5 ratsAs a matter of fact, sodium retention in PAN nephrosis unlikely results from the presence of an abnormal blood concentration of any factor, since only the treated kidney displays increased sodium reabsorption in unilateral PAN-nephrotic rats. Rather, alterations in collecting duct function may be accounted for either by a direct effect of PAN on CCD or by the abnormal presence of an unidentified stimulatory factor in the luminal fluid that reaches the distal nephron. The presence of this factor may result from its abnormal filtration secondarily to the alteration of the glomerular filtration barrier (e.g., a high molecular weight protein), or from its generation in the proximal tubule secondarily to alteration of protein/peptide handling.
Na,K-ATPase is the primary target of sodium retention in PAN nephrosis Analysis of corticosteroid-clamped rats not only demonstrated that hyperaldosteronemia is not involved in the etiology of edemas in NS, but it also provided insights into the primary molecular target of sodium retention in the CCD. Indeed, in CCDs from corticosteroid-clamped PAN rats, Na,K-ATPase is induced as in adrenal-intact nephrotic rats [13]. In contrast, targeting of ENaC to the apical membrane is fully blunted [11, 13], and the residual channels expressed at the apical membrane are drastically inhibited, as their open probability is reduced >10-fold [13].Thus, induction of Na,K-ATPase is primarily responsible for sodium retention in PAN nephrotic syndrome. This conclusion likely applies to all experimental models of nephrotic syndrome and, possibly, to the disease in humans, since there is a significant reverse correlation between Na,K-ATPase activity in collecting duct and urinary sodium excretion during the phase of sodium retention in rats with nephrotic syndrome induced by PAN, Adriamycin or mercury chloride [1].
Edema formation in nephrotic syndrome
Most sodium-retaining states are associated with high blood pressure but not with development of edema or ascites. Edema formation in NS results from the asymmetry of extracellular volume expansion brought about by sodium retention: the vascular volume is not, or only slightly, modified, whereas water and solutes accumulate in the interstitium. Distribution of fluid between vascular and interstitium compartments is governed by fluid exchanges across the capillary wall and by lymphatic draining. Capillary filtration capacity is increased almost twofold in nephrotic patients [34]. This fluid leakage is governed by several parameters according to Starling’s law:
where Jv is the trans-capillary flux of fluid, Lp the hydraulic conductivity of capillaries, S the exchange surface, Pc and Pi the hydrostatic pressure of the capillary and interstitium, respectively, σ the reflection coefficient of proteins across the capillary wall, and Πc and Πi the oncotic pressure in the capillaries and interstitium, respectively.
Unexpectedly, data from the literature indicate that the increase in Jv in NS is not accounted for by change in the oncotic pressure gradients, as intuitively thought, but by changes in the intrinsic properties of the capillary walls that govern their hydraulic conductance and reflexion coefficient for proteins. This means that the capillary wall is a direct target in NS, to the same right as the glomerular filtration barrier.
The trans-capillary gradient of oncotic pressure (Πc–Πi) is unchanged in NS The lack of edema and ascites in analbuminemic rats and patients [16, 35] has questioned the importance of low plasma oncotic pressure in the genesis of edema in NS. As a matter of fact, the trans-capillary gradient of oncotic pressure is unchanged in analbuminemic rats, owing to a parallel decrease in plasma and interstitium oncotic pressure [35]. Experiments in dogs, in which plasma oncotic pressure was progressively decreased by 50% through plasmapheresis, showed that the interstitium oncotic pressure decreased in parallel and that the trans-capillary gradient remained unaffected. Extracellular volume increased transiently during the phase of variation of plasma oncotic pressure, in response to hyperaldosteronemia and renal sodium retention, but returned to normal level during the period of stabilized low plasma oncotic pressure [36].Essentially similar observations were made in humans. During NS, it was also observed that the oncotic pressure of the interstitium decreases in parallel with that of the vascular compartment, so that the trans-capillary gradient is only slightly reduced [37]. In addition, diuretic treatments [37] or extracorporeal ultrafiltration [38] allow the withdrawal of significant amounts of edema without significant change in the trans-capillary gradient of oncotic pressure.Thus, decrease in plasma oncotic pressure in animal models as well as in nephrotic patients does not alter significantly the trans-capillary gradient of oncotic pressure and is neither a determinant parameter in the genesis of edema nor a resistance factor to edema withdrawal.
The trans-capillary gradient of hydrostatic pressure (Pc–Pi) is unchanged in NS Capillary pressure is unchanged in nephrotic patients [34]. Because soft tissues display an almost infinite compliance, their interstitium pressure increases by only 2 mmHg with their fluid filling [39]. In nephrotic patients interstitial pressure in edematous and non-edematous sectors differs by <4 mmHg [40]. Thus, it can be admitted that the trans-capillary gradient of hydrostatic pressure is not significantly altered in soft edematous tissues during NS.
The capillary hydraulic conductivity Lp is increased in NS The threshold of venous pressure triggering fluid transfer across capillaries is significantly reduced in NS [34], suggesting that endothelial Lp is decreased. The main determinants of the hydraulic conductivity of capillaries are the occlusive junctions (constituted by occludin, claudins and proteins ZO) and adhesive junctions (made of cadherins, catenins and actinin) between endothelial cells. These proteins are direct targets for intracellular signaling cascades, in particular protein kinase C (PKC), which phosphorylates occludin [41] and alters the endothelial permeability [42]. In NS this pathway may be activated through two mechanisms. Firstly, hypoalbuminemia increases Lp via an increase in intracellular calcium [43]. Secondly, high plasma levels of TNFα observed in patients with minimal change disease [44] activate PKC and increase Lp [45].
The reflexion coefficient of proteins (σ) is increased in NS Increased coefficient of reflexion of macromolecules in NS is evidenced by the higher rate of leakage of technetium-labeled albumin towards the interstitium in nephrotic patients than in controls [46]. Because this change in reflexion coefficient is observed in patients with NS of different origin, it is likely not accounted for by the circulating permeability factor of lymphocyte origin responsible for glomerular hyperfiltration in minimal change disease. Increased σ was also reported in blood–peritoneal barrier permeability in PAN-nephrotic rats [47].
Therapeutic implications
Nephrotic edema results from the combination of renal sodium retention and increased capillary permeability. Although treatment of either of these two alterations would prevent edema, treatment of capillary permeability alone would lead to hypertension. Thus, treatments of edema must primarily target renal sodium retention.
Different therapeutic strategies are needed to prevent edema formation in children with chronic proteinuria and to treat massive edema. In the first case it is sufficient to prevent sodium accumulation, either through limiting dietary sodium uptake or by natriuretic drugs that target the collecting duct, e.g., amiloride. In clinical practice the daily uptake of sodium is usually limited to 0.5 mmol/kg. In PAN-nephrotic rats administration of amiloride starting before the onset of sodium retention fully prevents sodium retention and formation of ascites [5].
More classically, clinicians are confronted with patients who already display massive edema. Treatment aims both at limiting further sodium retention and at promoting the excretion of the mass of sodium and water sequestered in edema. While amiloride is well suited to block further sodium retention, it is inefficient in promoting massive sodium excretion, because, under normal conditions, sodium reabsorption along the collecting duct is quantitatively low. Recourse to more potent diuretics, such as loop diuretics, is restricted by the functional resistance of nephrotic patients to the natriuretic effect of furosemide. Several explanations have been proposed to account for this resistance, but none has been confirmed:
The pharmacokinetics of furosemide urinary elimination is not significantly altered in nephrotic children [48]Binding of furosemide to albumin in the tubular fluid does not account for furosemide resistance, since, despite controversial data [49, 50], inhibitors of furosemide–albumin binding do not improve sodium excretion significantly.The intrinsic sensitivity of the Na/K/2Cl transporter of the loop of Henle, the molecular target of furosemide, is not altered in nephrotic rats [5].
Based on our present knowledge of the site and cellular mechanism of sodium retention in NS, another explanation of furosemide resistance, and a therapeutic strategy to circumvent it, can be proposed. In non-nephrotic patients, furosemide decreases sodium reabsorption along the thick ascending limb of the loop of Henle, which increases sodium delivery to the distal nephron. Because the sodium reabsorption capacity of the distal nephron is rather limited, only a small fraction of the overload of sodium is reabsorbed, and the major fraction is excreted in the urine, accounting for the natriuretic effect of loop diuretics. Note that following long-term treatment with furosemide, there are adaptations of the distal nephron which increase its sodium reabsorption capacity and, thereby, reduce the natriuretic effect of furosemide. Because nephrotic patients display a huge sodium reabsorption capacity along their connecting and cortical collecting tubules, most of the overload of sodium brought about by furosemide-induced inhibition of transport in the thick ascending limb is reabsorbed, thereby blunting the natriuretic effect. Thus, the apparent resistance of nephrotic patients to loop diuretics can be circumvented by the inhibition of distal sodium reabsorption with amiloride. As a matter of fact, co-administration of furosemide and amiloride to nephrotic children increases urinary sodium excretion, induces a negative sodium balance and promotes complete edema withdrawal within 1 week [21].
Conclusion
Whatever their etiology, nephrotic syndromes are always associated with renal retention of sodium. Renal sodium retention results from enhanced sodium reabsorption along the connecting and cortical collecting ducts and from blunted responsiveness of medullary collecting ducts to the natriuretic response to atrial natriuretic peptide. Induction of de novo synthesis of Na,K-ATPase is the primary effector of increased sodium reabsorption. It is not accounted for by any circulating factor, in particular aldosterone, known to stimulate sodium reabsorption along the distal nephron. New research strategies will be required to identify the unknown regulatory pathway that is dysregulated in NS.
Sodium retention in NS does not lead to high blood pressure but leads to an asymmetric expansion of the interstitium, while the vascular volume remains unchanged in most patients. This asymmetry of extracellular volume expansion is accounted for by changes in the intrinsic properties of the endothelial capillary barriers, i.e., an increase in its hydraulic conductivity and permeability to proteins, rather than to an imbalance of Starling’s forces.
Thus, the pathophysiology of nephrotic syndrome relies on at least three disorders: a major alteration of the glomerular filtration barrier responsible for proteinuria and hypoalbuminemia, an induction of distal nephron Na,K-ATPase responsible for sodium retention, and alterations in the capillary permeability accounting for the asymmetry of volume expansion. Although causal relationships between these three events have not been formally established, it is assumed that the glomerular defect engenders both the tubular and the capillary alterations. This conclusion is based on the facts that: (a) whatever its origin, alteration of the glomerular filtration barrier always leads to sodium retention and edema formation, i.e., to the tubular and capillary defects, and (b) loss of function mutations of nephrin, which is expressed in the glomerular slit diaphragm but in neither the collecting duct nor capillary endothelial cells, is sufficient to promote proteinuria, sodium retention and edema [51]. Curiously, in PAN-induced nephrosis, sodium retention precedes proteinuria, suggesting that it is not secondary to the glomerular dysfunction. It should be stressed, however, that microproteinuria may appear sooner and concomitantly with sodium retention.

sodium retention
aldosterone
collecting duct
na,k-atpase
epithelial sodium channels (enacs)
diuretics
capillary hydraulic conductivity