Reduced brain perfusion and cognitive performance due to constitutional hypotension This review article includes a systematic evaluation of the empirical data concerning deficits in mental ability , brain perfusion , and cerebral functioning due to chronically low blood pressure . A number of studies have provided strong evidence for reduced cognitive performance in hypotension , particularly in the domains of attention and memory . EEG studies have demonstrated that the hypotension-related poorer mental ability is also reflected in diminished cortical activity . Contrary to convention , more recent research has suggested a deficient regulation of cerebral blood flow in persons with low blood pressure . In addition to reduced tonic brain perfusion , studies demonstrated insufficient adjustment of blood flow to cognitive requirements . Altogether , these findings suggest that more attention should be allocated to chronic hypotension in both research and clinical practice . Introduction Chronically low blood pressure is accompanied by a variety of complaints including fatigue , reduced drive , faintness , dizziness , headaches , palpitations , and increased pain sensitivity -LSB- 1 -- 4 -RSB- . In addition , hypotensive individuals report cognitive impairment , above all deficits in attention and memory . Nevertheless , it is generally the case that in research , as well as in clinical practice , relatively little importance is ascribed to hypotension . One reason for this is that , despite mental symptoms , cerebral dysfunction generally is not taken into account -LSB- 1 -RSB- . This is a consequence of the current doctrine that low systemic blood pressure is compensated by autoregulatory processes which prevent reduced blood perfusion of the brain -LSB- 5 , 6 -RSB- . Some recent findings challenge this doctrine : reduced cognitive performance in hypotension has been demonstrated by neuropsychological testing , and EEG studies have revealed diminished cortical activity . Moreover , the assumption of unimpaired brain perfusion in hypotension no longer holds . In the present review the necessity of a reappraisal concerning hypotension is discussed in light of the relationship between blood pressure and cerebral functioning . Constitutional hypotension Hypotension has been defined by the World Health Organization -LRB- WHO -RRB- -LSB- 4 -RSB- as a low blood pressure with a systolic reading below 110 mmHg in males and below 100 mmHg in females , regardless of diastolic blood pressure . The concept of constitutional hypotension refers to a chronic condition of inappropriately reduced blood pressure independent of the presence of further pathological factors . Both secondary hypotension -LRB- e.g. due to blood loss or medication -RRB- and orthostatic hypotension -LRB- caused by circulatory problems when assuming an upright position -RRB- are distinguished from the constitutional form -LSB- 1 , 6 -RSB- . Constitutional hypotension is relatively widespread in the general population . In a representative German sample of more than 7,000 subjects approximately 3 % fulfilled the criteria of the WHO -LSB- c.f. 1 -RSB- . In contrast to elevated blood pressure , which constitutes a significant risk factor for cardiovascular disease , hypotension is commonly not regarded as a severe condition . Nevertheless , its impact on personal well-being and quality of life has been shown in several epidemiological studies . For instance , Wessely et al. -LSB- 7 -RSB- , as well as Pilgrim et al. -LSB- 3 -RSB- demonstrated impaired physical and mental health in the case of low blood pressure . Reduced health-related quality of life -LSB- 8 -RSB- and a heightened degree of depressiveness -LSB- 9 -RSB- were also reported by hypotensive individuals . Chronic hypotension has been identified as a major risk factor in pregnancy -LSB- 10 -RSB- . Moreover , several studies focusing on the elderly population have reported associations between low blood pressure and the prevalence and incidence of Alzheimer 's and vascular dementia -LSB- c.f. 11 -- 14 -RSB- . Whilst a few longitudinal studies examining this relationship have been published -LSB- 15 , 16 -RSB- , the causal role of low blood pressure in degenerative brain disorders has thus far not been proven -LSB- e.g. 13 -RSB- .1 Concerning the etiology of hypotension , reduced liquid intake and low body weight may be considered -LSB- c.f. 1 , 17 -RSB- . A dysregulation of the autonomous nervous system may additionally be of significance . Various findings on reduced electrodermal activity -LSB- 18 -RSB- and increased heart rate variability -LSB- 19 -RSB- reflect diminished sympathetic tone and habitually heightened parasympathetic activity in persons with low blood pressure values . This is corroborated by findings on the effects of sympathomimetic drugs -LSB- 20 , 21 -RSB- . In mixed samples of persons with constitutional and orthostatic hypotension , α and β adrenergic substances were shown to lead to blood pressure elevation accompanied by a reduction of subjective symptoms . A malfunction of the arterial baroreceptor system was postulated as a further etiological factor -LSB- 22 -RSB- . Responding to mechanical stretch of the vessel walls , the baroreceptors form part of a negative feedback loop -LRB- `` baroreflex '' -RRB- compensating phasic blood pressure fluctuations -LSB- 23 -RSB- . Increased sensitivity of the baroreceptor system may result in stabilizing blood pressure at a lower level . In addition to findings in animals -LSB- 24 -RSB- , this hypothesis is supported by a still unpublished study of our own group which yielded increased baroreflex sensitivity in the case of low blood pressure . Cognitive deficits in constitutional hypotension Table 1 presents the most relevant studies devoted to cognitive functioning in hypotension . In addition to the main results , the table includes information concerning the respective samples and assessment instruments . Table 1Studies on cognitive performance in hypotension -LRB- SBP , systolic blood pressure ; DBP , diastolic blood pressure -RRB- AuthorsMain focusSamplesAssessment instrumentsMain resultsRichter-Heinrich et al. -LSB- 18 -RSB- Attentional performance in hypotension and hypertension30 hypotensives -LRB- SBP < 106 mmHg -RRB- ; 40 hypertensives -LRB- SBP > 140 mmHg -RRB- ; 31 normotensive controls ; age 16 -- 40 yearsKonzentrations-Verlaufs-Test -LRB- course of concentration test -RRB- -LSB- 25 -RSB- Reduced attentional performance in the case of both lowered and elevated blood pressureStegagno et al. -LSB- 26 -RSB- Attentional , memory and arithmetic performance in hypotension17 female hypotensives -LRB- SBP < 100 mmHg -RRB- ; 19 normotensive controls ; mean age 23 yearsReaction times to acoustic stimuli ; digit span -LSB- 27 -RSB- ; recall of word lists -LSB- 28 -RSB- ; serial subtractionsProlonged reaction times , poorer performance on the verbal memory and arithmetic tasks in hypotension , no effect for digit spanCosta et al. -LSB- 29 -RSB- Attentional and memory performance in hypotension26 female hypotensives -LRB- SBP < 105 , DBP < 65 mmHg -RRB- , 22 normotensive controls ; mean age 29 yearsAufmerksamkeits-Belastungs-Test -LRB- attentional strain test -RRB- -LSB- 30 -RSB- ; Zahlen-Verbindungs-Test -LRB- trail making test -RRB- -LSB- 31 -RSB- ; recall of word lists -LSB- 28 -RSB- Poorer attentional and memory performance on each of the three tests in hypotensionMorris et al. -LSB- 32 -RSB- Relationship between blood pressure and cognitive performance in elderly personsRepresentative population sample covering the total spectrum of blood pressure -LRB- n = 5,816 ; age over 64 years -RRB- East Boston Memory Test -LSB- 33 -RSB- ; Symbol Digit Modalities Test -LSB- 34 -RSB- ; Mini-Mental State Examination -LSB- 35 -RSB- Weak U-shaped relationship between blood pressure and cognitive performanceWeisz et al. -LSB- 22 -RSB- Attentional performance in hypotension25 female hypotensives -LRB- mean SBP = 102 mmHg -RRB- ; 25 normotensive controls ; age 19 -- 44 yearsAttentional and Cognitive Efficiency Battery -LSB- 36 -RSB- Reduced performance on a subtest assessing cognitive flexibility in hypotensionDuschek et al. -LSB- 37 -RSB- Attentional performance in moderate hypotension26 borderline hypotensives -LRB- mean SBP = 112 mmHg -RRB- ; 29 normotensive controls ; mean age 26 yearsReaction times to acoustic stimuli ; Aufmerksamkeits-Belastungs-Test -LRB- attentional strain test -RRB- -LSB- 30 -RSB- ; Zahlen-Verbindungs-Test -LRB- trail making test -RRB- -LSB- 31 -RSB- Prolonged reaction times and poorer performance on the `` Aufmerksamkeits-Belastungs-Test '' in moderate hypotension , no effects for the `` Zahlen-Verbindungs-Test '' Duschek et al. -LSB- 38 -RSB- Attentional and working memory performance in hypotension with motor performance and mood controlled40 hypotensives -LRB- SBP < 105 mmHg in women , SBP < 110 mmHg in men -RRB- ; 40 normotensive controls ; age 19 -- 45 yearsTestbatterie zur Aufmerksamkeitsprüfung -LRB- battery for the assessment of attention -RRB- -LSB- 39 -RSB- ; Motorische Leistungsserie -LRB- motor performance series -RRB- -LSB- 40 -RSB- ; Befindlichkeitsskala -LRB- mood scale -RRB- -LSB- 41 -RSB- Poorer performance on six tests assessing tonic and phasic alertness , selective , divided and sustained attention as well as working memory in hypotensives with fine motor performance and mood controlled A pioneering study investigating the relationship between blood pressure and cognitive abilities was conducted by Richter-Heinrich et al. -LSB- 18 -RSB- . They showed reduced performance of individuals with both lowered and elevated blood pressure on a test of concentration . A more comprehensive assessment was carried out by Stegagno et al. -LSB- 26 -RSB- , in which poorer performances of hypotensive subjects on a verbal memory test and on an arithmetic task , as well as prolonged reaction times to acoustic stimuli were observed . Costa et al. -LSB- 29 -RSB- found reduced scores on two standard German paper -- pencil tests assessing selective attention and cognitive speed . Moreover , as in the Stegagno et al. -LSB- 26 -RSB- study , impaired verbal memory performance was documented . Weisz et al. -LSB- 22 -RSB- reported that female hypotensive subjects performed significantly worse than controls on a computer-based test measuring attentional flexibility -LSB- 36 -RSB- . Subjects with only a moderately decreased blood pressure were assessed by Duschek et al. -LSB- 37 -RSB- . In this sample , reduced attentional performance and prolonged reaction times were again found as compared to normotensive controls . Duschek et al. -LSB- 38 -RSB- investigated the relationship between low blood pressure and attentional abilities through the application of a multidimensional diagnostic approach . They presented their subjects with a battery of six computer-based tasks -LSB- 39 -RSB- focusing on tonic and phasic alertness , selective , divided and sustained attention , as well as working memory . Additionally , in order to control for possible confounders , a test battery examining fine motor abilities -LSB- 40 -RSB- and a mood questionnaire -LSB- 41 -RSB- were presented . Reduced performance of hypotensives was evident in each of the six cognitive tests . The significant differences between hypotensive and control subjects persisted even when the effects of motor performance and mood were controlled . Altogether , the existing data provide strong evidence for cognitive deficits related to constitutional hypotension , especially in the domains of attention and memory . The reduced performance seems to be a direct consequence of low blood pressure rather than an effect of impaired well-being related to this state . Up to now there have been no empirical data concerning specific effects of hypotension-related deficits on everyday life . Nonetheless , these findings raise concern regarding the impact of the deficits on attention-demanding activities -LRB- e.g. professional or academic -RRB- , including public health-related functions -LRB- e.g. traffic safety -RRB- -LSB- 42 -RSB- . It would appear that both extremes of the blood pressure spectrum are accompanied by a decrease in cognitive ability . A number of studies concerned with elevated blood pressure showed reduced performance on various cognitive tests -LSB- 43 , 44 -RSB- . This is in line with epidemiological studies reporting an inverted U-shaped relationship between blood pressure and cognitive performance in elderly persons -LSB- c.f. 11 , 13 , 32 , 45 , 46 -RSB- . Therefore , it may further be hypothesized that there is a relatively small range of normal blood pressure in which the brain exerts its optimal function . Neuroelectrophysiological correlates of hypotension-related cognitive deficits Cognitive deficits in low blood pressure states are also reflected in decreased cortical activity . In accordance with earlier results -LSB- 22 , 29 -RSB- , Duschek et al. -LSB- 47 -RSB- found the amplitude of the contingent negative variation -LRB- CNV -RRB- to be reduced in a hypotensive sample defined according to the WHO criteria -LSB- 4 -RSB- -LRB- c.f. Fig. 1 -RRB- . Fig. 1The CNV occurs during the period between a warning signal -LRB- S1 -RRB- and a second stimulus -LRB- S2 -RRB- demanding a motor , verbal or cognitive response . As can be seen in the figure , its amplitude was found to be reduced in hypotensive subjects -LRB- N = 40 -RRB- as compared to normotensive controls -LRB- N = 40 -RRB- ; modified from -LSB- 47 -RSB- The CNV is an evoked potential which is generally viewed as a neuroelectrophysiological correlative of attentional processing -LSB- 48 -RSB- . This is supported by pharmacological studies showing that the effects of various stimulant and sedative drugs on attention involve an increase or decrease , respectively , of the CNV amplitude -LSB- 49 , 50 -RSB- . Moreover , attentional deficits due to brain lesions and psychiatric diseases are associated with a reduced CNV -LSB- 51 , 52 -RSB- . In the Duschek et al. -LSB- 47 -RSB- study , the amplitude of the CNV proved to be negatively correlated with reaction time , which in turn was prolonged in the hypotensive group . This highlights that the CNV constitutes a brain electrical correlate of an aspect of cognitive functioning which is affected in hypotension . The relationship between blood pressure and cortical activity is also reflected in a negative correlation between blood pressure and α wave activity in the spontaneous EEG -LSB- 47 -RSB- . This suggests that low blood pressure is associated with a reduced tonic cortical arousal -LSB- 53 -RSB- . On the behavioral level , higher degrees of α activity are known to be associated with generally diminished vigilance and preparedness to react -LSB- 54 -RSB- . Considering the physiological processes mediating the relationship between blood pressure and brain function , it must be taken into account that blood pressure can influence cortical activation processes via afferent projections -LSB- 47 , 55 -- 57 -RSB- . The brain continuously receives information about the state of the cardiovascular system by means of viscero-afferent fibers -LSB- 23 -RSB- . These afferent signals enter the brain via brainstem nuclei . From there , ascending pathways continue via hypothalamic and thalamic regions to cortical areas such as the anterior cingulate , the insula and the prefrontal lobe -LSB- 58 -RSB- . The latter areas , in particular the prefrontal cortex and the anterior cingulate are of crucial importance in the regulation of cortical arousal , as well as for attentional processes -LSB- 59 , 60 -RSB- . Thus , these brain structures may represent functional interfaces between cardiovascular activity and attention -LSB- 42 -RSB- . Also neurochemical mediators should be regarded in the relationship between blood pressure and cortical activity . Noradrenaline is involved in the control of cortical arousal and attentional processes , as well as in the genesis of the CNV -LSB- 59 , 61 -RSB- . Catecholamines are also of great influence in the regulation of blood pressure -LSB- 62 -RSB- . Bearing this in mind , one could speculate on the neurochemical level about a specific role of noradrenaline linking cardiovascular and cortical activation . Cerebral blood perfusion in constitutional hypotension It is generally assumed that in healthy individuals processes of autoregulation keep the cerebral blood flow constant within a wide range of arterial pressure . In order to ensure stable perfusion , cerebral resistance vessels constrict during increases and dilate during reductions in systemic blood pressure -LSB- 5 -RSB- . Autoregulation is considered to be a protective mechanism which prevents brain ischemia during blood pressure decrease , and guards against capillary damage and edema formation during periods of elevated blood pressure . Under normal conditions the limits within which cerebral blood flow is assumed to be constant are approximately between a mean arterial pressure -LRB- MAP -RRB- of 60 and 150 mmHg -LSB- 5 , 63 , 64 -RSB- . If blood pressure is outside of this range , cerebral blood flow rises or falls with respective increases or decreases in blood pressure . Slight reductions of blood pressure below the lower limit of autoregulation can be compensated by an increase of the extraction coefficient of oxygen from the blood . Further reductions are accompanied by symptoms such as pallor and dizziness and ultimately lead to irreversible brain damage -LSB- 5 -RSB- . MAP in individuals with constitutional hypotension usually does not decrease beyond the assumed lower MAP limit of autoregulation -LRB- 60 mmHg -RRB- . In light of this , low blood pressure in these subjects should be compensated , and cerebral blood flow should not be affected . This assumption was challenged by Duschek and Schandry -LSB- 65 -RSB- . They recorded blood flow velocities by means of transcranial Doppler sonography in both middle cerebral arteries -LRB- MCA -RRB- in hypotensive individuals , defined according to the WHO -LSB- 4 -RSB- , and in normotensive control subjects . Contrary to the current doctrine , MCA blood flow at rest was found to be substantially bilaterally reduced in hypotensives -LRB- c.f. Fig. 2 -RRB- . Fig. 2Mean flow velocities in the left and right middle cerebral arteries under resting conditions in hypotensive -LRB- N = 40 -RRB- and control subjects -LRB- N = 40 -RRB- ; bars represent standard errors -LSB- 65 -RSB- The perfusion territory of the MCA includes subcortical areas , large fractions of the frontal and parietal lobes , as well as the temporal lobes -LSB- 66 -RSB- . Thus , the latter finding demonstrated that , despite autoregulation , blood pressure in subjects with constitutional hypotension is not sufficient in maintaining the perfusion of a large part of the brain at the level of normotensive individuals -LSB- see also 67 -RSB- . In explaining this unexpected result , it must be noted that the determination of the lower limit of autoregulation was exclusively based on the experimental manipulation of blood pressure employing pharmacological methods , as well as head up-tilt -LSB- 68 -- 71 -RSB- . However , such a transient reduction of blood pressure is most certainly not comparable to conditions of chronic hypotension . Additionally , in all of these studies global cerebral blood flow was assessed by means of the oxygen difference method according to Lennox and Gibbs -LSB- 72 -RSB- , which may be less sensitive to perfusion changes than Doppler sonography . Nevertheless , more recent findings suggest values for the lower MAP limit of autoregulation to be considerably higher than 60 mmHg -LSB- 73 -- 75 -RSB- . In a critical review of the literature , Drummond -LSB- 76 -RSB- postulated an average lower limit of no less than 70 mmHg . Moreover , the limit seems to vary strongly across individuals . Waldemar et al. -LSB- 77 -RSB- , for instance , reported an inter-individual range between 53 and 103 mmHg . In accordance with Duschek and Schandry 's -LSB- 65 -RSB- data , the doctrine of stable cerebral perfusion down to the limit of a MAP of 60 mmHg can no longer be supported by the current state of research . A further important aspect of cerebral hemodynamics concerns the continuous adjustment of brain perfusion to current requirements . Due to the close coupling of neural activity and brain metabolism , cerebral activation processes are accompanied by changes in cerebral blood flow -LSB- 78 -RSB- . Neurovascular coupling is based on the contraction and dilation of small resistance vessels , resulting from the changing metabolic demands of neuron populations in the vicinity -LSB- 64 -RSB- . With regards to hypotension-related cognitive deficits , the extent of blood flow adjustment to mental activity was also tested in the Duschek and Schandry -LSB- 65 -RSB- study . Subjects were presented with a simple attentional task -LRB- motor reactions to visual stimuli cued by acoustic signals -RRB- . During task execution blood flow velocities in the MCA of both hemispheres were recorded by means of functional transcranial Doppler sonography -LRB- for technical details see -LSB- 66 -RSB- -RRB- . As expected , mental activity was accompanied by a substantial increase of MCA perfusion . In control subjects , however , this increase was approximately 70 % stronger than in hypotensives -LRB- c.f. Fig. 3 -RRB- . It would seem that blood pressure in the latter group was not sufficient to enable adjustment of brain perfusion to cognitive demands , as seen in normotensives . Moreover , hypotensive participants showed prolonged reaction times , and a positive correlation was found between reaction speed and the extent of blood flow increase . This finding corroborates the significance of hemodynamic adjustment for optimal cognitive functioning . Fig. 3Changes of blood flow velocities in the left and right MCA during the execution of an attentional task in hypotensives -LRB- N = 40 -RRB- and controls -LRB- N = 40 -RRB- . The subjects had to press a key in response to a visual imperative stimulus which was announced by a cuing tone . In both MCA the rise in flow velocity which occurred during the anticipation of the imperative stimulus was substantially less pronounced in hypotensives . A second flow velocity maximum visible after the motor reaction was also slightly reduced in hypotensives -LSB- 65 -RSB- Final comments There is strong evidence suggesting that chronically low blood pressure is accompanied by diminished cognitive performance , primarily involving attention and memory -LSB- 26 , 29 , 38 -RSB- . Recent research has provided an insight into the psychophysiological mechanisms of action underlying these deficits : EEG studies have demonstrated that the weaker cognitive performance is associated with reduced cortical activity -LSB- 22 , 29 , 47 -RSB- . Furthermore , deficient regulation of cerebral blood flow must be assumed in hypotension . In addition to diminished tonic brain perfusion , reduced adjustment of brain perfusion to cognitive demands was documented -LSB- 65 -RSB- . It stands to reason that , as a consequence of this situation , a diminished metabolic supply of the brain tissue accounts for the cognitive deficits . The cognitive deficits can widely affect the every day life of hypotensive persons , and more attention should therefore be allocated to this topic within basic and clinical research , as well as in clinical practice -LSB- 1 , 17 -RSB- . This finally leads to the issue of the treatment of hypotension . Empirical knowledge concerning the effectiveness of antihypotensive therapy continues to be scant . A variety of treatment strategies such as physical training , increase of liquid intake and pharmacological measures have been suggested -LSB- 1 -RSB- . In two clinical trials the administration of sympathomimetics was found to result in a reduction of subjective hypotensive symptoms -LSB- 20 , 21 -RSB- . Recent data of our own group suggest that cognitive performance may also be enhanced by pharmacological blood pressure elevation -LSB- 79 -RSB- . Based on a placebo controlled design , the vasopressor agent midodrine was shown to raise cerebral blood perfusion as well as performance on a test assessing selective attention -LSB- 30 -RSB- in hypotensive subjects , defined according to the WHO -LSB- 4 -RSB- . The results of these pioneering studies are promising . Further research would appear worthwhile and should aim to establish precise guidelines which enable chronic hypotension to be efficiently and effectively dealt with in practice .

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blood pressure
hypotension
cerebral blood flow
cognitive


Clinical

review

Complications

and

risk

factors

of

peripheral

arterial

catheters

used

for

haemodynamic

monitoring

in

anaesthesia

and

intensive

care

medicine

In

order

to

evaluate

the

complications

and

risk

factors

associated

with

peripheral

arterial

catheters

used

for

haemodynamic

monitoring

we

reviewed

the

literature

published

from

to

We

closely

examined

the

three

most

commonly

used

arterial

cannulation

sites

The

reviewed

papers

included

a

total

of

radial

femoral

and

axillary

artery

catheterizations

Factors

that

contribute

to

higher

complication

rates

were

investigated

Major

complications

occurred

in

fewer

than

of

the

cases

and

rates

were

similar

for

the

radial

femoral

and

axillary

arteries

We

conclude

that

arterial

cannulation

is

a

safe

procedure

Introduction

Indwelling

arterial

catheters

are

used

routinely

for

continuous

haemodynamic

monitoring

in

the

operating

room

during

major

surgery

and

in

critically

ill

patients

Arterial

cannulation

provides

easy

and

convenient

access

allowing

multiple

blood

samplings

and

blood

gas

analysis

Arterial

cannulation

has

generally

been

found

to

be

a

safe

procedure

with

few

serious

complications

-LSB-

-RSB-

Approximately

million

and

million

arterial

catheters

are

placed

yearly

in

the

USA

and

Europe

respectively

-LSB-

-RSB-

Despite

the

frequency

with

which

arterial

catheters

are

employed

there

is

little

information

on

the

impact

of

cannulation

site

on

risk

for

complications

-LSB-

-RSB-

We

reviewed

reports

concerning

arterial

cannulation

sites

such

as

the

radial

femoral

axillary

brachial

ulnar

dorsal

pedis

tibial

posterior

and

temporal

arteries

with

regard

to

thrombotic

infectious

and

vascular

complications

Material

and

methods

The

PubMed

Medline

Express

and

Winspirs

databases

-LRB-

publication

years

-RRB-

were

searched

to

identify

pertinent

articles

The

keywords

artery

catheter

radial

artery

catheter

femoral

artery

catheter

axillary

artery

catheter

catheter

complication

hemodynamic

monitoring

and

peripheral

methods

were

used

We

reviewed

the

papers

and

identified

further

articles

from

the

references

of

the

papers

found

in

the

initial

search

We

reviewed

all

studies

concerning

the

use

of

radial

femoral

axillary

brachial

ulnar

dorsal

pedis

tibial

posterior

and

temporal

artery

catheters

for

haemodynamic

monitoring

that

dealt

with

complications

and

risk

factors

in

adults

We

excluded

studies

conducted

in

the

paediatric

patient

population

We

opted

not

to

perform

statistical

analyses

because

the

data

selection

of

the

published

reports

do

not

follow

the

same

criteria

and

most

of

them

give

no

specific

information

regarding

patient

population

catheter

material

cannulation

technique

and

times

Therefore

comparison

between

studies

and

statistical

analyses

are

unlikely

to

be

valid

Results

We

identified

studies

that

met

our

criteria

Radial

artery

The

radial

artery

is

the

most

common

site

for

arterial

cannulation

and

the

studies

that

reported

complication

rates

are

listed

in

Table

-LSB-

9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32

-RSB-

The

most

common

complication

was

temporary

occlusion

of

the

artery

the

incidence

of

which

ranged

from

-LSB-

-RSB-

to

-LSB-

-RSB-

-LRB-

mean

-RRB-

the

variability

being

due

to

the

different

methods

employed

and

the

degree

of

effort

invested

in

detecting

this

complication

Table

Complications

following

radial

artery

cannulation

Reference

Cases

Permanent

ischaemic

damage

-LRB-

n

-RRB-

Temporary

occlusion

-LRB-

n

-RRB-

Sepsis

-LRB-

n

-RRB-

Local

infection

-LRB-

n

-RRB-

Pseudoaneurysm

-LRB-

n

-RRB-

Haematoma

-LRB-

n

-RRB-

Bleeding

-LRB-

n

-RRB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

Mean

incidence

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

The

total

number

of

cannulations

was

One

study

examining

two

different

populations

Not

investigated

Generally

temporary

occlusion

of

the

artery

has

no

serious

sequelae

Permanent

occlusion

of

the

radial

artery

appears

to

be

rare

because

it

was

reported

in

only

four

patients

-LRB-

mean

incidence

-RRB-

Another

serious

complication

is

pseudoaneurysm

which

was

reported

in

patients

-LRB-

mean

incidence

-RRB-

Pseudoaneurysm

poses

a

risk

for

infection

sepsis

rupture

-LSB-

-RSB-

and

formation

of

an

extracorporeal

pseudoaneurysm

-LSB-

-RSB-

Radial

catheterization

was

associated

with

sepsis

in

eight

patients

-LRB-

mean

incidence

-RRB-

whereas

local

infection

at

the

cannulation

site

was

identified

in

patients

-LRB-

mean

incidence

-RRB-

Minor

complications

such

as

haematoma

formation

or

bleeding

at

the

puncture

site

are

also

shown

in

Table

Other

complications

include

abscess

cellulitis

paralysis

of

the

median

nerve

-LSB-

-RSB-

suppurative

thrombarteritis

-LSB-

-RSB-

air

embolism

-LSB-

-RSB-

compartment

syndrome

and

carpal

tunnel

syndrome

-LSB-

-RSB-

Other

rarely

reported

complications

include

catheter

failure

as

result

of

manufacturing

defect

or

incorrect

use

with

resultant

catheter

replacement

-LSB-

-RSB-

Femoral

artery

We

identified

studies

that

used

the

femoral

artery

for

haemodynamic

monitoring

which

are

listed

in

Table

-LSB-

-RSB-

Temporary

occlusion

was

reported

in

patients

-LRB-

mean

incidence

-RRB-

and

serious

ischaemic

complications

requiring

extremity

amputation

was

reported

in

three

patients

-LRB-

mean

incidence

-RRB-

-LSB-

-RSB-

Table

Complications

following

femoral

artery

cannulation

Reference

Cases

Permanent

ischaemic

damage

-LRB-

n

-RRB-

Temporary

occlusion

-LRB-

n

-RRB-

Sepsis

-LRB-

n

-RRB-

Local

infection

-LRB-

n

-RRB-

Pseudoaneurysm

-LRB-

n

-RRB-

Haematoma

-LRB-

n

-RRB-

Bleeding

-LRB-

n

-RRB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

Mean

incidence

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

The

total

number

of

cannulations

was

Not

investigated

Pseudoaneurysm

formation

occurred

in

six

patients

-LRB-

mean

incidence

-RRB-

sepsis

was

observed

in

patients

-LRB-

mean

incidence

-RRB-

and

local

infection

was

reported

in

five

patients

-LRB-

mean

incidence

-RRB-

Bleeding

-LRB-

generally

minor

-RRB-

was

observed

in

five

patients

-LRB-

mean

incidence

-RRB-

and

haematoma

formation

was

reported

in

-LRB-

mean

incidence

-RRB-

One

patient

developed

an

infected

haematoma

and

needed

blood

transfusion

-LSB-

-RSB-

and

another

patient

eventually

died

from

massive

retroperitoneal

bleeding

-LSB-

-RSB-

Axillary

artery

The

axillary

artery

was

cannulated

in

a

total

of

reported

cases

The

complication

rates

at

this

site

are

summarized

in

Table

-LSB-

-RSB-

Serious

complications

included

permanent

ischaemic

damage

in

two

patients

-LRB-

mean

incidence

-RRB-

pseudoaneurysm

formation

in

one

patient

-LRB-

mean

incidence

-RRB-

and

sepsis

in

five

patients

-LRB-

mean

incidence

-RRB-

Paresthesia

of

the

hand

due

to

pressure

on

the

brachial

nerve

plexus

was

also

described

-LSB-

-RSB-

Table

Complications

following

axillary

artery

cannulation

Reference

Cases

Permanent

ischaemic

damage

-LRB-

n

-RRB-

Temporary

occlusion

-LRB-

n

-RRB-

Sepsis

-LRB-

n

-RRB-

Local

infection

-LRB-

n

-RRB-

Pseudoaneurysm

-LRB-

n

-RRB-

Haematoma

-LRB-

n

-RRB-

Bleeding

-LRB-

n

-RRB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

Mean

incidence

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

The

total

number

of

cannulations

was

One

study

examining

two

different

populations

Not

investigated

Other

sites

for

arterial

cannulation

Other

less

frequently

reported

cannulation

sites

are

the

brachial

dorsal

pedis

ulnar

tibial

posterior

and

temporal

arteries

Only

one

serious

complication

was

found

in

a

study

of

patients

-LSB-

-RSB-

in

which

the

brachial

artery

was

used

for

invasive

monitoring

in

ambulatory

patients

This

complication

was

an

infected

haematoma

arising

from

a

pseudoaneurysm

Another

study

that

employed

the

brachial

artery

for

arterial

blood

sampling

in

patients

-LSB-

-RSB-

also

showed

a

small

number

of

complications

-LRB-

incidence

-RRB-

mainly

paresthesias

The

dorsal

pedis

artery

has

also

been

cannulated

without

any

major

complications

-LSB-

-RSB-

However

because

of

its

distance

from

the

central

circulation

and

associated

difficulties

in

hypotensive

patients

it

is

generally

avoided

-LSB-

-RSB-

The

ulnar

artery

has

been

used

without

serious

complications

and

in

a

direct

comparison

-LSB-

-RSB-

this

site

exhibited

similar

complication

rates

to

those

encountered

with

the

radial

artery

The

tibial

posterior

artery

has

been

used

in

paediatric

patients

without

major

complications

-LSB-

-RSB-

However

there

also

exists

a

case

report

of

limb

amputation

secondary

to

a

tibial

artery

catheterization

-LSB-

-RSB-

The

temporal

artery

is

an

end

artery

of

the

external

carotid

artery

and

is

usually

avoided

for

fear

of

serious

complications

There

is

a

report

of

three

cases

of

cerebral

embolization

in

paediatric

patients

-LSB-

-RSB-

Further

studies

Other

studies

that

examined

arterial

catheter

complications

but

that

did

not

specifically

attribute

their

occurrence

to

one

specific

site

are

listed

in

Table

-LSB-

-RSB-

One

study

-LSB-

-RSB-

used

mainly

the

radial

-LRB-

n

-RRB-

ulnar

-LRB-

n

-RRB-

and

dorsalis

pedis

arteries

-LRB-

n

-RRB-

whereas

another

-LSB-

-RSB-

used

mainly

the

femoral

-LRB-

n

-RRB-

brachial

-LRB-

n

-RRB-

axillary

-LRB-

n

-RRB-

and

radial

arteries

-LRB-

n

-RRB-

One

serious

complication

was

found

at

the

femoral

site

with

compromised

circulation

to

the

leg

-LSB-

-RSB-

eventually

thrombectomy

was

required

Another

reported

serious

complication

is

air

embolism

caused

by

improper

use

of

the

flushing

device

-LSB-

-RSB-

Table

Studies

examining

arterial

catheter

complications

without

specifically

attributing

them

to

any

specific

site

Reference

Cases

Air

embolism

-LRB-

-RRB-

Permanent

occlusion

-LRB-

-RRB-

Temporary

occlusion

-LRB-

-RRB-

Haematoma

-LRB-

-RRB-

Bleeding

-LRB-

-RRB-

Sepsis

-LRB-

-RRB-

Abscess

-LRB-

-RRB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

Medical

intensive

care

unit

-LRB-

radial

artery

femoral

artery

-RRB-

Surgical

intensive

care

unit

-LRB-

radial

artery

femoral

artery

-RRB-

Not

investigated

A

recent

study

-LSB-

-RSB-

examined

complication

rates

comparing

medical

with

surgical

intensive

care

units

It

also

directly

compared

radial

and

femoral

artery

catheters

There

were

no

significant

differences

in

terms

of

sepsis

and

local

infection

rates

between

the

femoral

and

radial

arteries

and

no

significant

difference

between

the

medical

and

surgical

intensive

care

units

Another

nine

studies

specifically

looked

for

septic

complications

associated

with

arterial

catheter

placement

and

included

a

total

number

of

patients

-LRB-

Table

-RRB-

-LSB-

-RSB-

No

septic

complications

were

identified

in

seven

of

those

studies

-LSB-

-RSB-

and

nine

cases

of

sepsis

were

reported

in

the

remaining

two

studies

-LSB-

-RSB-

All

of

the

cases

of

sepsis

were

identified

after

the

line

had

been

in

place

for

longer

than

days

The

studies

in

which

sepsis

was

reported

predominately

used

the

radial

artery

Table

Incidence

of

sepsis

following

arterial

cannulation

Reference

Cases

Sepsis

-LRB-

-RRB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

-LSB-

-RSB-

Risk

factors

A

further

objective

of

the

present

review

was

to

consider

risk

factors

that

might

have

impacted

on

complication

rates

Thrombotic

complications

Thrombus

formation

and

occlusion

of

the

artery

appear

to

be

caused

by

changes

in

the

integrity

of

the

vessel

wall

induced

by

the

presence

of

the

catheter

-LSB-

-RSB-

Recannulation

of

the

occluded

artery

generally

occurs

but

this

may

take

up

to

days

-LSB-

-RSB-

The

incidence

of

thrombus

appears

to

be

related

to

the

degree

to

which

the

catheter

fills

the

arterial

lumen

-LSB-

-RSB-

It

has

been

shown

that

the

incidence

of

radial

obstruction

increases

linearly

with

the

ratio

of

outer

diameter

to

vessel

lumen

diameter

-LSB-

-RSB-

This

might

explain

the

higher

incidence

of

radial

occlusion

in

female

patients

who

generally

have

vessels

of

smaller

diameter

-LSB-

-RSB-

This

has

led

to

a

preference

for

catheters

for

radial

artery

cannulation

-LSB-

-RSB-

Teflon

catheters

also

appear

to

be

associated

with

a

lower

incidence

of

occlusion

-LSB-

-RSB-

but

in

another

study

-LSB-

-RSB-

this

could

not

be

confirmed

Patients

with

a

low

cardiac

output

have

a

higher

incidence

of

radial

artery

occlusion

-LSB-

-RSB-

but

no

difference

was

found

among

patients

with

episodes

of

hypotension

-LSB-

-RSB-

Multiple

punctures

for

catheter

insertion

was

shown

to

be

a

risk

factor

for

complications

in

one

study

-LSB-

-RSB-

but

this

could

not

be

confirmed

in

another

-LSB-

-RSB-

A

higher

incidence

of

occlusion

is

found

in

the

presence

of

a

haematoma

-LSB-

-RSB-

Patients

who

are

treated

with

aspirin

or

low-dose

heparin

have

fewer

vessel

occlusions

-LSB-

-RSB-

The

age

of

adult

patients

does

not

appear

to

be

a

risk

factor

-LSB-

-RSB-

An

important

factor

with

regard

to

arterial

occlusion

is

the

duration

of

cannulation

A

higher

incidence

of

occlusion

was

reported

when

the

cannula

was

left

in

place

longer

than

or

hours

-LSB-

-RSB-

Infectious

complications

Important

factors

in

decreasing

the

incidence

of

catheter-related

infections

are

aseptic

insertion

technique

and

adequate

disinfection

of

the

insertion

site

-LSB-

-RSB-

The

risk

for

infectious

complications

and

sepsis

increases

with

the

duration

of

cannulation

especially

if

the

catheter

is

left

in

place

for

longer

than

hours

-LSB-

-RSB-

The

catheter

material

also

appears

to

be

of

importance

because

Teflon

has

a

greater

resistance

to

Escherichia

coli

and

Pseudomonas

aeruginosa

-LSB-

-RSB-

and

a

lower

affinity

for

stapylococci

-LSB-

-RSB-

Prophylactic

treatment

with

antibiotics

does

not

appear

to

reduce

the

risk

for

catheter-related

infections

-LSB-

-RSB-

but

antibiotic

bonding

of

the

catheter

may

confer

a

degree

of

protection

-LSB-

-RSB-

Arterial

catheter

placement

via

the

cut-down

technique

is

associated

with

a

higher

risk

for

infection

-LSB-

-RSB-

Furthermore

sepsis

occurs

more

frequently

in

the

presence

of

local

site

inflammation

-LSB-

-RSB-

Infection

may

also

occur

through

contamination

by

caregivers

of

the

monitoring

system

the

flushing

device

and

the

infusion

system

-LSB-

-RSB-

Discussion

The

use

of

peripheral

arterial

catheters

for

haemodynamic

monitoring

is

widespread

The

most

frequently

used

site

is

the

radial

artery

because

of

its

well

documented

low

complication

rates

and

easy

access

-LSB-

-RSB-

In

the

present

review

we

report

on

radial

artery

cannulations

and

the

main

complication

was

temporary

occlusion

of

the

artery

-LRB-

incidence

-RRB-

This

complication

rate

is

close

to

the

finding

of

Wilkins

-LSB-

-RSB-

who

reviewed

reports

of

catheterization

of

the

radial

artery

with

regard

to

ischaemic

complications

published

between

He

reported

a

temporary

occlusion

rate

of

In

an

extensive

study

of

patients

Slogoff

and

coworkers

-LSB-

-RSB-

reported

a

rate

of

temporary

occlusion

Although

temporary

occlusion

is

reported

quite

frequently

serious

ischaemic

damage

was

reported

in

only

two

studies

-LSB-

-RSB-

with

a

mean

complication

rate

of

Nevertheless

there

have

been

reports

of

serious

ischaemic

damage

after

radial

artery

cannulation

that

led

to

necrosis

and

amputation

of

fingers

or

the

whole

hand

-LSB-

-RSB-

Other

major

complications

such

as

pseudoaneurysm

and

sepsis

were

reported

to

occur

in

a

mean

of

and

of

cases

respectively

The

second

most

cannulated

artery

for

haemodynamic

monitoring

is

the

femoral

artery

and

we

reviewed

cases

Temporary

occlusion

was

reported

in

only

of

the

reviewed

cases

The

incidence

of

this

complication

in

the

femoral

artery

is

much

lower

than

that

in

the

radial

artery

We

attributed

this

to

the

larger

vessel

diameter

of

the

femoral

artery

Serious

ischaemic

complications

were

reported

in

only

one

study

-LSB-

-RSB-

and

the

mean

complication

rate

was

The

incidence

rates

for

other

major

complications

such

as

pseudoaneurysm

and

sepsis

-LRB-

and

respectively

-RRB-

were

similar

to

our

findings

in

the

radial

artery

Some

authors

caution

against

use

of

the

femoral

artery

for

cannulation

for

fear

of

higher

sepsis

rates

because

of

the

close

proximity

to

the

perianal

region

-LSB-

-RSB-

We

are

unable

to

corroborate

this

on

the

basis

of

the

reviewed

literature

and

recent

studies

that

directly

compared

the

radial

and

femoral

arteries

with

regard

to

septic

complications

identified

similar

rates

of

sepsis

-LSB-

-RSB-

In

particular

in

an

extensive

study

of

patients

Frezza

and

Mezghebe

-LSB-

-RSB-

were

unable

to

identify

a

difference

in

complication

rates

between

the

radial

and

femoral

arteries

In

that

study

the

femoral

artery

was

actually

the

preferred

site

in

the

medical

intensive

care

unit

Other

authors

prefer

the

femoral

artery

over

the

radial

artery

because

the

femoral

artery

is

usually

palpable

even

in

hypotensive

patients

and

may

be

the

only

accessible

route

for

haemodynamic

monitoring

-LSB-

-RSB-

The

blood

pressure

curve

that

is

obtained

from

this

larger

artery

is

generally

more

accurate

and

gives

a

closer

estimation

of

the

aortic

blood

pressure

-LSB-

-RSB-

The

third

most

cannulated

artery

in

the

present

review

of

the

literature

was

the

axillary

artery

with

almost

reported

cases

Some

authors

prefer

not

to

cannulate

the

axillary

artery

because

of

its

close

location

to

the

carotid

artery

and

because

of

fear

of

embolism

to

the

brain

-LSB-

-RSB-

On

the

basis

of

the

data

summarized

here

we

can

not

confirm

this

and

no

case

of

embolism

to

the

brain

was

reported

Sometimes

the

axillary

artery

is

avoided

because

of

the

more

difficult

approach

required

although

-LRB-

particularly

in

anaesthesia

-RRB-

it

is

a

well

known

route

because

it

requires

the

same

approach

as

that

for

axillary

nerve

block

-LSB-

-RSB-

The

major

complications

encountered

with

the

axillary

artery

were

similar

to

those

for

the

radial

and

femoral

arteries

and

we

conclude

that

it

is

a

safe

route

for

arterial

cannulation

Other

reviewed

arteries

employed

for

catheterization

such

as

the

brachial

dorsal

pedis

ulnar

tibial

and

temporal

arteries

have

been

used

without

serious

complications

but

published

reports

of

their

use

are

limited

Conclusion

Incidence

rates

for

major

complications

such

as

permanent

ischaemic

damage

sepsis

and

pseudoaneurysm

formation

are

low

and

similar

for

the

radial

femoral

and

axillary

arteries

They

occur

in

fewer

than

of

cases

On

the

basis

of

the

present

systematic

review

we

can

conclude

that

serious

complications

of

the

radial

femoral

and

axillary

artery

are

rare

and

that

arterial

cannulation

is

a

relatively

safe

procedure

Nevertheless

one

must

be

aware

of

the

possible

serious

complications

that

might

arise

Therefore

it

is

important

to

use

an

arterial

catheter

only

when

it

is

indicated

and

to

select

carefully

the

best

cannulation

site

individually

for

each

patient

because

the

different

cannulation

sites

have

their

specific

advantages

and

attendant

risks

Competing

interests

UJP

is

President

of

Pulsion

Medical

Systems

AG

and

AP

is

on

the

medical

advisory

board

of

Pulsion

Medical

Systems

AG

whose

PiCCO

product

uses

a

femoral

arterial

line

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O O O O O O O O O O O O O O O O B I O B I O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O B I O O O O O O O O O B I O O O B I O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O B I O O O O O O O O O O B I O O O O O O B O O O O O O O O O O O O O O O O B I O O O O O B O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O B I O O O O O O O O O O O O O O O O O O O O O O O O B O O B I O O O O O O O B I O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O B I O O B I O O B I O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O

axillary artery
catheter
complication
femoral artery
haemodynamic monitoring
peripheral
radial artery