bluuebunny/crossref_metadata_2025_split huggingface dataset:
Renal Nerves Are Not Involved in Sodium and Water Retention during Mechanical Ventilation in Awake Dogs
Authors: Boemke Willehad , Krebs Martin O. , Djalali Kourosh , Bunger Harald , Kaczmarczyk Gabriele 
Published: November 2003

Background
The role of renal nerves during positive end-expiratory pressure ventilation (PEEP) has only been investigated in surgically stressed, anesthetized, unilaterally denervated dogs. Anesthesia, sedation, and surgical stress, however, decrease urine volume and sodium excretion and increase renal sympathetic nerve activity independent of PEEP. This study investigated in awake dogs the participation of renal nerves in mediating volume and water retention during PEEP.

Methods
Eight tracheotomized, trained, awake dogs were used. The protocol consisted of 60 min of spontaneous breathing at a continuous positive airway pressure of 4 cm H2O, followed by 120 min of controlled mechanical ventilation with a mean PEEP of 15-17 cm H2O (PEEP), and 60 min of continuous positive airway pressure. Two protocols were performed on intact dogs, in which volume expansion had (hypervolemic; electrolyte solution, 0.5 ml x kg(-1) x min(-1)) and had not (normovolemic) been instituted. This was repeated on the same dogs 2 or 3 weeks after bilateral renal denervation.

Results
Hypervolemic dogs excreted more sodium and water than did normovolemic dogs. There was no difference between intact and renal-denervated dogs. Arterial pressure did not decrease when continuous positive airway pressure was switched to PEEP. Plasma renin activity, aldosterone, and antidiuretic hormone concentrations were greater in normovolemic dogs. The PEEP increased aldosterone and antidiuretic hormone concentrations only in normovolemic dogs.

Conclusions
In conscious dogs, renal nerves have no appreciable contribution to sodium and water retention during PEEP. Retention in normovolemic dogs seems to be primarily caused by an activation of the renin-angiotensin system and an increase in the antidiuretic hormone. Excretion rates depended on the volume status of the dogs.
Parental Presence during Induction of Anesthesia versus Sedative Premedication
Authors: Kain Zeev N. , Mayes Linda C. , Wang Shu-Ming , Caramico Lisa A. , Hofstadter Maura B. 
Published: November 2003

Background
Both midazolam and parental presence during induction of anesthesia are routinely used to treat preoperative anxiety in children. The purpose of this investigation was to determine which of these two interventions is more effective.

Methods
Anxiety of the child during the perioperative period was the primary end point. Secondary end points included anxiety of the parent and compliance of the child during induction. Children (n = 88) were randomly assigned to one of three groups: (1) 0.5 mg/kg oral midazolam; (2) parental presence during induction of anesthesia; or (3) control (no parental presence or premedication). Using multiple behavioral measures of anxiety, the effect of the intervention on the children and their parents was assessed.

Results
Observed anxiety in the holding area (T1), entrance to the operating room (T2), and introduction of the anesthesia mask (T3) differed significantly among the three groups (P = 0.032). Post hoc analysis indicated that children in the midazolam group exhibited significantly less anxiety compared with the children in the parental-presence group or control group (P = 0.0171). Similarly, parental anxiety scores after separation were significantly less in the midazolam group compared with the parental-presence or control groups (P = 0.048). The percentage of inductions in which compliance of the child was poor was significantly greater in the control group compared with the parental-presence and midazolam groups (25% vs. 17% vs. 0%, P = 0.013).

Conclusions
Under the conditions of this study, oral midazolam is more effective than either parental presence or no intervention for managing a child's and parent's anxiety during the preoperative period.
Myocardial Effects of Desflurane in Hamsters with Hypertrophic Cardiomyopathy
Authors: Vivien Benoit , Hanouz Jean-Luc , Gueugniaud Pierre-Yves , Lecarpentier Yves , Pierre MD , Riou Bruno 
Published: November 2003

Background
The effects of desflurane on myocardial contraction and relaxation in diseased myocardium have not been completely understood.

Methods
The effects of desflurane (1.8 to 9.4 vol%) in left ventricular papillary muscles of healthy hamsters and those with genetically induced cardiomyopathy (strain BIO 14.6) were investigated in vitro (29 degrees C, pH 7.40, Ca2+ 2.5 mM; stimulation frequency, 3/min) under low (isotony) and high (isometry) load. Data are mean percentages of baseline +/- SD.

Results
Desflurane induced no significant inotropic effect in healthy muscles (maximum unloaded shortening velocity and isometric active force at 9.4 vol%: 97 +/- 9% and 92 +/- 20%, respectively). In contrast, in cardiomyopathic muscles, desflurane induced a moderate negative inotropic effect (maximum unloaded shortening velocity and active force at 9.4 vol%: 84 +/- 19% and 75 +/- 25%, respectively). The negative inotropic effect was more pronounced than that in healthy muscles under low (P < 0.05) but not high load, and even when concentrations were corrected for minimum alveolar concentrations in each strain. Adrenoceptor blockade or pretreatment with reserpine did not modify the inotropic effect of desflurane, suggesting the absence of intramyocardial catecholamine release. However, tyramine also did not induce any significant catecholamine release in hamster myocardium. In both strains, desflurane induced no significant lusitropic effect under low or high load.

Conclusions
Desflurane had no inotropic effect in healthy muscles and a moderate negative inotropic effect in cardiomyopathic muscles. The absence of desflurane-induced intramyocardial catecholamine release was related to hamster myocardium characteristics.
Sciatic Nerve Blockade in Infant, Adolescent, and Adult Rats
Authors: Kohane Daniel S. , Sankar Wudbhav N. , Shubina Maria , Hu Delphine , Nader Rifai , Berde Charles B. 
Published: November 2003

Background
Ropivacaine is a newly introduced local anesthetic. No data are available regarding its safety, efficacy, or sensory-selectivity in children. The sciatic block duration and systemic toxicity of bupivacaine and ropivacaine were compared among infant, adolescent, and adult rats.

Methods
Infant, adolescent, and adult rats received blocks with ropivacaine or bupivacaine. Nociceptive, proprioceptive, and motor blockade were assessed. Systemic effects (contralateral leg analgesia, seizures, respiratory distress, apnea) were quantified. Plasma local anesthetic concentrations were measured at terminal apnea.

Results
Nerve blockade for a given absolute dose lasted longer in infants than in older rats for both drugs. Block duration from ropivacaine generally was the same as or slightly shorter than bupivacaine. There was no difference in sensory-selectivity between the drugs. Doses required to induce all systemic toxicity indices were inversely related to age (e.g., the lethal dose in 50% of animals [LD50] of ropivacaine in infants is 155 mg/kg; in adults it is 54 mg/kg). All indices of toxicity occurred at higher doses per kilogram for ropivacaine than bupivacaine, at all ages (e.g., the LD50 of bupivacaine in infants is 92 mg/kg; in adults it is 30 mg/kg). Plasma concentrations at terminal apnea were higher for ropivacaine than for bupivacaine at all ages, and were higher in infants than in older rats.

Conclusions
Ropivacaine resembles bupivacaine in its local anesthetic effects but has a greater margin of safety. For a given absolute dose, sciatic blockade in infant rats lasts longer than in adolescents or adults. Although the doses (in milligrams per kilogram) causing toxicity were much higher in infants than in adults, this probably does not correspond to a wider therapeutic index.
Efficacy and Costs of Patient-controlled Analgesia versus Regularly Administered Intramuscular Opioid Therapy
Authors: Choiniere Manon , Rittenhouse Brian E. , Perreault Sylvie , Chartrand Daniel , Rousseau Pierre , Smith Bruce , Pepler Carolyn 
Published: November 2003

Background
Many studies have shown the efficacy of patient-controlled analgesia (PCA). However, it is not clear whether PCA has clinical or economic benefits in addition to efficient analgesia. The current study was designed to evaluate these issues by comparing PCA with regularly administered intramuscular injections of opioids after hysterectomy.

Methods
This prospective study included 126 patients who underwent abdominal hysterectomy and were randomly assigned to receive PCA or regularly timed intramuscular injections of morphine during a period of 48 h. Doses were adjusted to provide satisfactory analgesia in both treatment groups. Pain at rest and with movement, functional recovery, drug side effects, and patient satisfaction were measured using rating scales and questionnaires. The costs of PCA and intramuscular therapy were calculated based on personnel time and drug and material requirements.

Results
Comparable analgesia was observed with the two treatment methods, with no significant differences in the incidence of side effects or patient satisfaction. The medication dosage had to be adjusted significantly more frequently in the intramuscular group than in the PCA patients. The PCA did not favor a faster recuperation time compared with intramuscular therapy in terms of times to ambulation, resumption of liquid and solid diet, passage of bowel gas, or hospital discharge. The results of the economic evaluation, which used a cost-minimization model and sensitivity analyses, showed that PCA was more costly than regular intramuscular injections despite the fact that no costs for the pump were included in the analyses. Cost differences in nursing time favoring PCA were offset by drug and material costs associated with this type of treatment.

Conclusions
Compared with regularly scheduled intramuscular dosing, PCA is more costly and does not have clinical advantages for pain management after hysterectomy. Because of the comparable outcomes, the general use of PCA in similar patients should be questioned.
Effects of Hyperventilation and Hypocapnic/Normocapnic Hypoxemia on Renal Function and Lithium Clearance in Humans
Authors: Olsen Niels Vidiendal , Christensen Henrik , Klausen Tom , Fogh-Andersen Niels , Plum Inger , Kanstrup Inge-Lis , Hansen Jesper Melchior 
Published: November 2003

Background
Using the renal clearance of lithium as an index of proximal tubular outflow, this study tested the hypothesis that acute hypocapnic hypoxemia decreases proximal tubular reabsorption to the same extent as hypocapnic normoxemia (hyperventilation) and that this response is blunted during normocapnic hypoxemia.

Methods
Eight persons were studied on five occasions: (1) during inhalation of 10% oxygen (hypocapnic hypoxemia), (2) during hyperventilation of room air leading to carbon dioxide values similar to those with hypocapnic hypoxemia, (3) during inhalation of 10% oxygen with the addition of carbon dioxide to produce normocapnia, (4) during normal breathing of room air through the same tight-fitting face mask as used on the other study days, and (5) during breathing of room air without the face mask.

Results
Hypocapnic and normocapnic hypoxemia and hyperventilation increased cardiac output, respiratory minute volume, and effective renal plasma flow. Glomerular filtration rate remained unchanged on all study days. Calculated proximal tubular reabsorption decreased during hypocapnic hypoxemia and hyperventilation but remained unchanged with normocapnic hypoxemia. Sodium clearance increased slightly during hypocapnic and normocapnic hypoxemia, hyperventilation, and normocapnic normoxemia with but not without the face mask.

Conclusions
The results indicate that (1) respiratory alkalosis with or without hypoxemia decreases proximal tubular reabsorption and that this effect, but not renal vasodilation or natriuresis, can be abolished by adding carbon dioxide to the hypoxic gas; (2) the increases in the effective renal plasma flow were caused by increased ventilation rather than by changes in arterial oxygen and carbon dioxide levels; and (3) the natriuresis may be secondary to increased renal perfusion, but application of a face mask also may increase sodium excretion.
Population Pharmacodynamics of Midazolam Administered by Target Controlled Infusion in SICU Patients after CABG Surgery
Authors: Somma Jacques , Donner Andrew , Zomorodi Katayoun , Sladen Robert , Ramsay James , Geller Eran , Shafer Steven L. 
Published: November 2003

Background
Midazolam is used commonly for sedation in the surgical intensive care unit. A suboptimal dosing regimen may lead to relative overdosing, which could result in delayed extubation and increased cost. This multicenter trial characterized midazolam pharmacodynamics in patients recovering from coronary artery bypass grafting.

Methods
Three centers enrolled 90 patients undergoing coronary artery bypass grafting. All patients received sufentanil and midazolam via target-controlled infusion. After surgery, midazolam was titrated to a Ramsay sedation score of 5 for 2 h and then decreased to maintain a sedation score of 3 or 4 for at least another 4 h. Pharmacodynamic parameters were derived using NONMEM. The model was cross-validated to test performance.

Results
The probability of a given level of sedation was related to the midazolam concentration by this equation: P(Sedation > or = ss) = Cn/(Cn + C(50,ss)n), where ss is the sedation score, C is the sum of the midazolam concentration and a term reflecting the dissipating effect of anesthesia: C = [midazolam] + theta x e(-Kt), where theta = 256 ng/ml and K = 0.19 h(-1). C(50,ss) values for Ramsay scores of 2 to 6 were 5.7, 71, 171, 260, and 659 ng/ml, respectively. The model predicted 57% of the data points correctly and 88% within one sedation score.

Conclusions
Despite previous reports of high interindividual variability in midazolam pharmacodynamics in patients in the surgical intensive care unit, these cross-validation results suggest that, when midazolam is administered using a target-controlled infusion device, the level of sedation can be predicted within 1 sedation score in 88% of patients based on the target midazolam concentration and the time since the conclusion of the anesthetic.
Isobolographic Analysis of the Interactions between Midazolam and Propofol at GABAAReceptors in Embryonic Mouse Neurons
Authors: McAdam Laura C. , MacDonald John F. , Orser Beverley A. 
Published: November 2003

Background
Clinical studies suggest that midazolam and propofol interact synergistically to induce hypnosis, but these drugs do not interact synergistically to prevent movement in response to noxious stimuli. The mechanisms underlying these interactions are not certain but may occur at the level of the gamma-aminobutyric acid A (GABA(A)) receptor.

Methods
The authors evaluated the interactions between propofol and midazolam in modulating GABA(A) receptor activity in embryonic hippocampal neurons. The effects of midazolam and propofol on peak current evoked by submaximal concentrations of GABA were studied using the patch clamp method. Isobolographic analysis was undertaken by constructing concentration-response curves for midazolam and propofol alone and then evaluating the potency of combinations of midazolam and propofol. In other experiments, the concentration of GABA was increased and flurazepam was substituted for midazolam.

Results
Isobolographic analysis confirmed that midazolam and propofol interact synergistically to enhance currents evoked by low concentrations of GABA (1 microM). However, when the concentration of GABA was increased to 3 microM, the interaction was additive. The interaction between flurazepam and propofol was also additive for enhancement of currents evoked by 3 microM GABA.

Conclusions
The interaction between midazolam and propofol was critically dependent on the concentration of GABA: Synergism was evident at low concentrations of GABA, but an additive interaction was apparent when the concentration of GABA was increased. Changes in GABA(A) receptor function may underlie the synergistic interaction between propofol and midazolam for clinical effects such as hypnosis. The clinical implication of the results is that the benefits of synergism observed at one concentration ratio of these drugs may not be apparent at another.
Carotid Body Chemoreceptor Function Is Impaired by Vecuronium during Hypoxia
Authors: Wyon Nicholas , Joensen Henning , Yamamoto Yuji , Lindahl Sten G. E. , Eriksson Lars I. 
Published: November 2003

Background
Neuromuscular blocking agents reduce the human ventilatory response to hypoxia at partial neuromuscular block. It was hypothesized that vecuronium impairs carotid body chemoreceptor function during hypoxia.

Method
The effect of systemic administration of vecuronium on single chemoreceptor activity during hypoxia, as recorded from a single nerve fiber preparation of the carotid sinus nerve, was studied in seven mechanically ventilated New Zealand White rabbits during continuous thiopental anesthesia. During normoventilation, the isocapnic hypoxic chemosensitivity of the single carotid body chemoreceptor was measured at four levels of oxygenation; these measurements were repeated at six separate occasions: control recording before injection, after intravenous administrations of 0.1 mg and 0.5 mg of vecuronium, and then at three occasions during a 90-min recovery period. Chemoreceptor chemosensitivity during isocapnic hypoxia was expressed as a hyperbolic function: Chemoreceptor output (Hz) = a + b x PaO2(-1) (mmHg).

Results
Chemosensitivity was reduced after both 0.1 mg and 0.5 mg vecuronium intravenous administration compared with control measurements; the hypoxic response curve was significantly depressed after both doses (P < 0.05). Notably, there was variation in the effect of vecuronium; some chemoreceptor preparations showed only minimal impairment, whereas some showed an almost abolished response to hypoxia. The chemosensitivity remained significantly depressed at 30 and 60 min but had recovered spontaneously at 90 min after 0.5 mg vecuronium.

Discussion
It is concluded that vecuronium depresses carotid body chemoreceptor function to a varying extent during hypoxia and that the depression recovers spontaneously.
Propofol-induced Increase in Vascular Capacitance Is Due to Inhibition of Sympathetic Vasoconstrictive Activity
Authors: Hoka Sumio , Yamaura Ken , Takenaka Tomoaki , Takahashi Shosuke 
Published: November 2003

Background
Venodilation is thought to be one of the mechanisms underlying propofol-induced hypotension. The purpose of this study is to test two hypotheses: (1) propofol increases systemic vascular capacitance, and (2) the capacitance change produced by propofol is a result of an inhibition of sympathetic vasoconstrictor activity.

Methods
In 33 Wistar rats previously anesthetized with urethane and ketamine, vascular capacitance was examined before and after propofol infusion by measuring mean circulatory filling pressure (Pmcf). The Pmcf was measured during a brief period of circulatory arrest produced by inflating an indwelling balloon in the right atrium. Rats were assigned into four groups: an intact group, a sympathetic nervous system (SNS)-block group produced by hexamethonium infusion, a SNS-block + noradrenaline (NA) group, and a hypovolemic group. The Pmcf was measured at a control state and 2 min after a bolus administration of 2, 10, and 20 mg/kg of propofol.

Results
The mean arterial pressure (MAP) was decreased by propofol dose-dependently in intact, hypovolemic, and SNS-block groups, but the decrease in MAP was less in the SNS-block group (-25%) than in the intact (-50%) and hypovolemic (-61%) groups. In the SNS-block + NA group, MAP decreased only at 20 mg/kg of propofol (-18%). The Pmcf decreased in intact and hypovolemic groups in a dose-dependent fashion but was unchanged in the SNS-block and SNS-block + NA groups.

Conclusions
The results have provided two principal findings: (1) propofol decreases Pmcf dose-dependently, and (2) the decrease in Pmcf by propofol is elicited only when the sympathetic nervous system is intact, suggesting that propofol increases systemic vascular capacitance as a result of an inhibition of sympathetic nervous system.
Ulnar Neuropathy in Surgical Patients
Authors: Warner Mark A. , Warner David O. , Matsumoto Joseph Y. , Harper Michel C. , Schroeder Darrell R. , Maxson Pamela M. 
Published: November 2003

Background
The goal of this project was to study the frequency and natural history of perioperative ulnar neuropathy.

Methods
A prospective evaluation of ulnar neuropathy in 1,502 adult patients undergoing noncardiac surgical procedures was performed. Patients were assessed with a standard questionnaire and neurologic examination before surgery, daily during hospitalization in the first week after surgery, and by telephone if they were discharged before 1 postoperative week. Patients in whom ulnar neuropathy developed were followed for 2 yr.

Results
Ulnar neuropathy developed in seven patients (0.5%; 95% confidence interval, 0.2% to 1.0%). Six of the seven patients were men. Symptoms of ulnar neuropathy began 2-7 days after surgery. Manifestations were mild and confined to sensory deficits in six patients. Symptoms resolved in four patients within 6 weeks. The remaining three patients had residual symptoms 2 yr later.

Conclusions
In this surgical population, ulnar neuropathy was an infrequent complication. It occurred primarily in men who were 50-75 yr old and was not symptomatic until several days after surgery. Gender-dependent differences in the anatomy of the ulnar nerve and related structures at the elbow may serve as risk factors for ulnar neuropathy in patients having surgery.
Effect of Nonsedative Doses of Propofol on an Innate Anxiogenic Situation in Rats
Authors: Pain Laure , Oberling Philippe , Launoy Anne , Di Scala Georges 
Published: November 2003

Background
The effect of propofol on anxiety has not been well studied. In humans, such investigations are confused by the fact that sedation often coexists with anxiolysis. Therefore, the authors evaluated the effects of minimal sedation with propofol in rats placed in an innate anxiogenic situation, the elevated plus-shaped maze.

Methods
In experiment 1, spontaneous locomotor activity was determined in rats as a measure of sedative effect induced by propofol (0-9 mg/kg administered intraperitoneally). In experiment 2, groups of rats received propofol (0-9 mg/kg) or diazepam (0-2 mg/kg) and then were placed on a plus-shaped maze elevated above the ground that was composed of two opposite closed arms and two opposite open arms. On an initial exposure to the maze, undrugged rats avoid the open arms, with the number of entries into and time spent within the open arms constituting approximately 20% of their total activity. This reflects normal anxiety in a rodent for any elevated open platform.

Results
In experiment 1, 0-9 mg/kg propofol did not alter spontaneous activity in rats. In experiment 2, propofol and diazepam significantly increased the number of entries into and the time spent within the open arms. Propofol at a dose of 9 mg/kg significantly increased the rats' level of exploration of the open arms to about 50% of all exploratory activity, and a similar observation was made with 2 mg/kg diazepam.

Conclusions
In a standard animal model, propofol has anxiolytic properties at doses that do not produce sedation.