bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regional Cerebral Plasma Volume Response to Carbon Dioxide Using Magnetic Resonance Imaging
Authors: Payen Jean-Francois , Vath Albert , Koenigsberg Blanche , Bourlier Virginie , Decorps Michel 
Published: November 2003

Background
Noninvasive techniques used to determine the changes in cerebral blood volume in response to carbon dioxide are hampered by their limited spatial or temporal resolution or both. Using steady state contrast-enhanced magnetic resonance imaging, the authors determined regional changes in cerebral plasma volume (CPV) induced by hypercapnia in halothane-anesthetized rats.

Methods
Cerebral plasma volume was determined during normocapnia, hypercapnia and recovery in the dorsoparietal neocortex and striatum of each hemisphere, in cerebellum, and in extracerebral tissue of rats with either intact carotid arteries (group 1) or unilateral common carotid ligation (group 2). Another group was studied without injection of a contrast agent (group 3).

Results
Hypercapnia (partial pressure of carbon dioxide in arterial blood [PaCO2] approximately 65 mmHg) resulted in a significant increase in CPV in the striatum (+42 +/- 8%), neocortex (+34 +/- 6%), and cerebellum (+49 +/- 12%) compared with normocapnic CPV values (group 1). Carotid ligation (group 2) led to a marked reduction of the CPV response to hypercapnia in the ipsilateral striatum (+23 +/- 14%) and neocortex (+27 +/- 17%) compared with the unclamped side (+34 +/- 15% and +38 +/- 16%, respectively). No significant changes in CPV were found in extracerebral tissue. In both groups, the CPV changes were reversed by the carbon dioxide washout period. Negligible changes in contrast imaging were detected during hypercapnia without administration of the contrast agent (group 3).

Conclusions
The contrast-enhanced magnetic resonance imaging technique is sensitive to detect noninvasively regional CPV changes induced by hypercapnia in rat brain. This could be of clinical interest for determining the cerebrovascular reactivity among different brain regions.
Effects of Volatile Anesthetic Agents on In Situ Vascular Smooth Muscle Transmembrane Potential in Resistance- and Capacitance-regulating Blood Vessels
Authors: Yamazaki Mitsuaki , Stekiel Thomas A. , Bosnjak Zeljko J. , Kampine John P. , Stekiel William J. 
Published: November 2003

Introduction
This study was designed to compare the inhibitory effect of inhaled volatile anesthetic agents on in situ sympathetic neural versus nonneural regulation of vascular smooth muscle transmembrane potentials as correlates of vascular smooth muscle tone in resistance- and capacitance-regulating blood vessels.

Methods
Vascular smooth muscle transmembrane potentials were measured in situ with glass microelectrodes in neurally intact, small (200-300 m OD) mesenteric arteries and veins of rats before, during, and after inhaled halothane, isoflurane, or sevoflurane (0.5 or 1.0 minimum alveolar concentration [MAC]). Such transmembrane potentials and their anesthetically induced changes were compared, respectively, with those measured in similar vessel preparations after local sympathetic neural denervation with 6-hydroxydopamine.

Results
In neurally intact vessels, transmembrane potentials (in millivolts, mean +/- SD) before inhalation of the anesthetic agent were -39 +/- 2.8 (artery) and -43 +/- 4.6 (vein). At 1.0 MAC, halothane, isoflurane, and sevoflurane induced respective hyperpolarizations (in millivolts, mean +/- SD) of 9 +/- 3.1, 6 +/- 2.7, and 9 +/- 4.0 in arteries and 6 +/- 4.4, 2.8 +/- 3.0, and 8.7 +/- 5.6 in veins. Sympathetic denervation significantly attenuated these hyperpolarizations (except for venous response to isoflurane). At 0.5 MAC, transmembrane potential responses to all three volatile anesthetic agents were small and not consistently significant in either the intact or denervated vessels.

Conclusions
In resistance-regulating arteries in situ, inhaled halothane, isoflurane, and sevoflurane (1.0 MAC) attenuate both sympathetic neural and nonneural regulation of vascular smooth muscle transmembrane potentials (and tone). In capacitance-regulating veins in situ, sevoflurane (1.0 MAC) also attenuates both regulatory mechanisms, whereas halothane and isoflurane primarily attenuate nonneural mechanisms. At 0.5 MAC, none of these agents significantly affected either mode of regulation of vascular smooth muscle transmembrane potentials in arteries or veins.
Exposure to Environmental Tobacco Smoke and the Risk of Adverse Respiratory Events in Children Receiving General Anesthesia
Authors: Skolnick Eric T. , Vomvolakis Maria A. , Buck Karen A. , Mannino Salvatore F. , Sun Lena S. 
Published: November 2003

Background
Exposure to environmental tobacco smoke is associated with detrimental effects on pulmonary function in children. The authors investigated the relation between airway complications in children receiving general anesthesia and the passive inhalation of tobacco smoke.

Methods
Six hundred two children scheduled to receive general anesthesia were enrolled in this prospective study. The anesthesiologist and the recovery room nurse, unaware of the smoke exposure history, recorded the occurrence of airway complications. A history of passive smoking was assessed by measuring the urinary concentration of the major nicotine metabolite cotinine and by questionnaire.

Results
Airway complications occurred in 42% of the patients with urinary concentrations of cotinine > or =40 ng/ml, in 33% of the patients with concentrations of cotinine between 10.0 and 39.9 ng/ml, and in 24% of the patients with concentrations of cotinine < 10 ng/ml (P = 0.01 for the trend among the three groups). The gender of the child (P = 0.001) and the educational level of the child's mother (P = 0.0008) significantly modified the effect of the concentration of cotinine on the incidence of adverse respiratory events.

Conclusions
There is a strong association between passive inhalation of tobacco smoke and airway complications in children receiving general anesthesia. The relationship is greatest for girls and for those whose mothers have a lower level of education. Passive smoking should be regarded as a risk factor in children undergoing general anesthesia.
The Influence of Method of Administration and Covariates on the Pharmacokinetics of Propofol in Adult Volunteers
Authors: Schnider Thomas W. , Minto Charles F. , Gambus Pedro L. , Andresen Corina , Goodale David B. , Shafer Steven L. , Youngs Elizabeth J. 
Published: November 2003

Background
Unresolved issues with propofol include whether the pharmacokinetics are linear with dose, are influenced by method of administration (bolus vs. infusion), or are influenced by age. Recently, a new formulation of propofol emulsion, containing disodium edetate (EDTA), was introduced in the United States. Addition of EDTA was found by the manufacturer to significantly reduce bacterial growth. This study investigated the influences of method of administration, infusion rate, patient covariates, and EDTA on the pharmacokinetics of propofol.

Methods
Twenty-four healthy volunteers aged 26-81 yr were given a bolus dose of propofol, followed 1 h later by a 60-min infusion. Each volunteer was randomly assigned to an infusion rate of 25, 50, 100, or 200 microg x kg(-1) x min(-1). Each volunteer was studied twice under otherwise identical circumstances: once receiving propofol without EDTA and once receiving propofol with EDTA. The influence of the method of administration and of the volunteer covariates was explored by fitting a three-compartment mamillary model to the data. The influence of EDTA was investigated by direct comparison of the measured concentrations in both sessions.

Results
The concentrations of propofol with and without EDTA were not significantly different. The concentration measurements after the bolus dose were significantly underpredicted by the parameters obtained just from the infusion data. The kinetics of propofol were linear within the infusion range of 25-200 microg x kg(-1) x min(-1). Age was a significant covariate for Volume2 and Clearance2, as were weight, height, and lean body mass for the metabolic clearance.

Conclusions
These results demonstrate that method of administration (bolus vs. infusion), but not EDTA, influences the pharmacokinetics of propofol. Within the clinically relevant range, the kinetics of propofol during infusions are linear regarding infusion rate.
Pulsed Doppler Ultrasonography Guidance for Catheterization of the Subclavian Vein
Authors: Lefrant Jean-Yves , Cuvillon Philippe , Benezet Jean-Francois , Dauzat Michel , Peray Pascale , Saissi Gilbert , de La Coussaye Jean-Emmanuel , Eledjam Jean-Jacques 
Published: November 2003

Background
Catheterization of the subclavian vein may lead to severe complications. The current randomized study compared a technique of pulsed Doppler ultrasonography guidance and the standard method for subclavian vein catheterization.

Methods
Standard and Doppler ultrasonography guidance methods were performed by the same physician in 286 patients, 143 in each group. Primary end points were immediate complications (arterial puncture, pneumothorax, wrong position of catheter tip), failures, the number of subclavian vein catheterizations with immediate complication or failure, the number of skin punctures per catheterization, and the time to placement of the guide wire. The secondary end points were the determination of predicting factors of successful cannulation in each group.

Results
Both groups were similar according to morphologic parameters of the patients. A greater number of subclavian vein catheterizations were performed on the right side using Doppler guidance (105 vs. 73, P < 0.01). Doppler guidance decreased complications (5.6% vs. 16.8%, P < 0.01), largely because of a smaller number of catheters for which the tip was defined to be in incorrect position (0.7% vs. 7.7%, P < 0.01). The time to catheterization was longer with Doppler guidance (300 vs. 27 s, P < 0.001). Failures, catheterizations of the subclavian vein with immediate complications or failure, and the total number of skin punctures per catheterization were similar in both groups. Using Doppler guidance, the presence of a good Doppler signal (124 of 143) was predictive of successful catheterization (123 successful cannulations, P < 0.001).

Conclusions
Doppler guidance reduces the incidence of inappropriately positioned subclavian catheters.
Metabolic Changes during Recovery in Normothermic versus Hypothermic Patients Undergoing Surgery and Receiving General Anesthesia and Epidural Local Anesthetic Agents
Authors: Motamed Syrusse , Klubien Kristine , Edwardes Michael , Mazza Louise , Carli Franco 
Published: November 2003

Background
Mild hypothermia is accompanied by metabolic changes. Epidural local anesthetic agents attenuate the surgical stress response, but it is not known whether they modulate thermal stress.

Methods
Thirty patients undergoing colorectal surgery, performed by one surgical team, received epidural 0.5% bupivacaine to achieve T3-S5 sensory block. They were then assigned randomly to two groups of 15 patients each. The control or unwarmed group was left to cool during surgery, whereas active warming was used in the warmed group. General anesthesia was induced by thiopentone, vecuronium, fentanyl, nitrous oxide in oxygen, and enflurane. At the end of surgery, both groups received epidural 0.25% bupivacaine to maintain a T5-L3 sensory block. Aural canal (core) and skin surface (15 sites) temperatures; oxygen consumption; pain visual analogue score; and concentrations of epinephrine, norepinephrine, glucose, cortisol, lactate, and free fatty acids in plasma were measured before epidural blockade, 30 min after epidural blockade, at the end of surgery, and for 4 h after surgery. Patients and those measuring the outcomes were unaware of group allocation.

Results
Core and mean skin temperatures decreased significantly in the control group (P < 0.001) but not in the warmed group. Catecholamine concentrations in plasma decreased significantly after epidural block, and although concentration of epinephrine in plasma increased from baseline sharply in the control group at the end of surgery (P = 0.004), it decreased in the warmed group (P = 0.007). During recovery, there was no difference between the two groups for norepinephrine concentrations in plasma, body weight-adjusted oxygen consumption, pain visual analogue score, and metabolites.

Conclusions
The postoperative metabolic changes obtained with epidural block were similar except for an attenuated concentration of epinephrine in normothermic patients compared with those who were mildly hypothermic.
Desflurane-mediated Sympathetic Activation Occurs in Humans Despite Preventing Hypotension and Baroreceptor Unloading
Authors: Ebert Thomas J. , Perez Francisco , Uhrich Toni D. , Deshur Mark A. 
Published: November 2003

Background
Increasing concentrations of desflurane result in progressive decreases in blood pressure (BP) and, unlike other currently marketed, potent volatile anesthetics, heightened sympathetic nervous system activity. This study aimed to determine whether baroreflex mechanisms are involved in desflurane-mediated sympathetic excitation.

Methods
Healthy volunteers were anesthetized with desflurane (n = 8) or isoflurane (n = 9). Heart rate (HR; measured by electrocardiograph), blood pressure (BP; measured by arterial catheter), and efferent sympathetic nerve activity (SNA; obtained from percutaneous recordings from the peroneal nerve) were monitored. Baroreflex sensitivity was evaluated at baseline while volunteers were conscious and during 0.5, 1, and 1.5 minimum alveolar concentration (MAC) anesthesia via bolus injections of nitroprusside (100 microg) and phenylephrine (150 microg) to decrease and increase BP. To prevent the BP decline with increasing depths of anesthesia, phenylephrine was infused to maintain mean BP at the 0.5 MAC level.

Results
The HR, BP, and SNA were similar between the groups at the conscious baseline measurement. Efferent SNA did not change during higher MAC of isoflurane, but it increased progressively as desflurane concentrations were increased beyond 0.5 MAC, despite maintaining BP at the 0.5 MAC value with phenylephrine infusions (P < 0.05). Cardiac baroslopes (based on changes in HR) were progressively and similarly decreased with increasing concentrations of isoflurane and desflurane (P < 0.05). Sympathetic baroslopes (based on SNA) decreased with increasing isoflurane concentrations but were maintained with increasing concentrations of desflurane; the response was significantly different between groups.

Conclusions
The increase in basal levels of SNA with increasing concentrations of desflurane persisted despite "fixing" BP and thus is probably not due to hypotension and unloading of the baroreceptors. Further, the preservation of reflex increases in SNA to nitroprusside during desflurane indicates that desflurane preserves one component of the baroreflex in humans when BP is "fixed."
Dobutamine Stress Echocardiography to Detect Inducible Demand Ischemia in Anesthetized Patients with Coronary Artery Disease
Authors: Seeberger Manfred D. , Skarvan Karl , Buser Peter , Brett Wolfgang , Rohlfs Reinhard , Erne Jean-Jacques , Rosenthaler Cyril , Pfisterer Matthias , Atar Dan 
Published: November 2003

Background
A cardiac risk stratification test that can be performed during operation would be expected to give valuable information for the therapeutic management of patients who need urgent noncardiac surgery. This study was designed to evaluate the feasibility and safety of a dobutamine-atropine stress protocol to detect inducible demand ischemia in anesthetized patients.

Methods
A standard dobutamine-atropine stress protocol was performed in 80 patients with severe coronary artery disease during fentanyl-isoflurane anesthesia. Biplane transesophageal echocardiography and 12-lead electrocardiography were used to detect induced ischemia. After dobutamine testing, esmolol, nitroglycerin, or both were used to revert ischemia and any hemodynamic changes, as appropriate.

Results
The protocol detected inducible ischemia or achieved the target heart rate in 75 of the 80 (94%) patients. None of the prospectively defined adverse outcomes, such as cardiovascular collapse, severe ventricular arrhythmia, persistent (> or =5 min) ischemia, or hemodynamic instability, occurred in any of the patients. Ischemia was induced and detected in 73 of the 80 (91%) patients.

Conclusion
Dobutamine stress echocardiography is feasible in anesthetized patients with severe coronary artery disease. The lack of serious complications and the high sensitivity to detect inducible ischemia in this patient population provide the basis for further evaluation of the safety and diagnostic value of dobutamine stress echocardiography during general anesthesia in larger studies of patients at risk for coronary artery disease undergoing noncardiac surgery.
Pulmonary Blood Flow Redistribution with Low Levels of Positive End-expiratory Pressure
Authors: Kallas Harry J. , Domino Karen B. , Glenny Robb W. , Anderson Emily A. , Hlastala Michael P. 
Published: November 2003

Background
Recent studies have questioned the importance of the gravitational model of pulmonary perfusion. Because low levels of positive end-expiratory pressure (PEEP) are commonly used during anesthesia, the authors studied the distribution of pulmonary blood flow with low levels of PEEP using a high spatial resolution technique. They hypothesized that if hydrostatic factors were important in the distribution of pulmonary blood flow, PEEP would redistribute flow to more dependent lung regions.

Methods
The effects of zero cm H2O PEEP and 5 cm H2O PEEP on pulmonary gas exchange were studied using the multiple inert gas elimination technique; the distribution of pulmonary blood flow, using fluorescent-labeled microspheres, was also investigated in mechanically ventilated, pentobarbital-anesthetized dogs. The lungs were removed, cleared of blood, dried at total lung capacity, and then cubed to obtain approximately 1,000 small pieces of lung (approximately 1.7 cm3).

Results
Positive end-expiratory pressure increased the partial pressure of oxygen by 6 +/- 2 mmHg (P < 0.05) and reduced all measures of ventilation and perfusion heterogeneity (P < 0.05). By reducing flow to nondependent ventral lung regions and increasing flow to dependent dorsal lung regions, PEEP increased (P < 0.05) the dorsal-to-ventral gradient. Redistribution of blood flow with PEEP accounted for 7 +/- 3%, whereas structural factors accounted for 93 +/- 3% of the total variance in blood flow.

Conclusions
The increase in dependent-to-nondependent gradient with PEEP is partially consistent with the gravitationally based lung zone model. However, the results emphasize the greater importance of anatomic factors in determining the distribution of pulmonary blood flow.
Comparison of the Effects of Bupivacaine and Ropivacaine on Heart Cell Mitochondrial Bioenergetics
Authors: Sztark Francois , Malgat Monique , Dabadie Philippe , Mazat Jean-Pierre 
Published: November 2003

Background
High lipophilic local anesthetics interfere with mitochondrial energy metabolism. These metabolic effects could in part explain some of the toxic effects of local anesthetics, such as bupivacaine-induced myocardial depression. The aim of this study was to compare the bioenergetic effects of the local anesthetics bupivacaine and ropivacaine.

Methods
The effects of both local anesthetics on mitochondrial energy metabolism were studied in rat heart isolated mitochondria and in saponin-skinned left ventricle fibers. Oxygen consumption, adenosine triphosphate synthesis, and enzymatic activities of the complexes of the respiratory chain were measured.

Results
Bupivacaine and ropivacaine acted, in isolated mitochondria, as uncouplers between oxygen consumption and phosphorylation of adenosine diphosphate. Further, an inhibitory effect of mitochondrial respiration was evidenced with both anesthetics during maximal respiration and was assigned to a direct inhibition of complex I of the respiratory chain. Mitochondrial adenosine triphosphate synthesis was decreased by both mechanisms. However, both in isolated mitochondria and in permeabilized heart fibers, ropivacaine was less potent than bupivacaine. Adenosine triphosphate synthesis was completely suppressed at 3 mM (approximately 0.1%) bupivacaine, whereas 3 mM ropivacaine induced only about a 40% inhibition.

Conclusions
Ropivacaine disturbs mitochondrial energy metabolism less than bupivacaine does. The lower lipid solubility of ropivacaine may be responsible for the lesser dose-dependent effects of this drug on mitochondrial bioenergetics.
Upper Airway Reflexes during a Combination of Propofol and Fentanyl Anesthesia
Authors: Tagaito Yugo , Isono Shiroh , Nishino Takashi 
Published: November 2003

Background
The effects of intravenous anesthetics on airway protective reflexes have not been fully explored. The purpose of the present study was to characterize respiratory and laryngeal responses to laryngeal irritation during increasing doses of fentanyl under propofol anesthesia.

Methods
Twenty-two female patients anesthetized with propofol and breathing through the laryngeal mask airway were randomly allocated to three groups: (1) eight patients who received cumulative total doses of 200 microg fentanyl given in the form of two doses of 50 microg and one dose of 100 microg spaced 6 min under mechanical controlled ventilation while end-tidal carbon dioxide tension (PCO2) was maintained at 38 mmHg (fentanyl-controlled ventilation group), (2) eight patients who received cumulative total doses of 200 microg fentanyl while breathing spontaneously while end-tidal PCO2 was allowed to increase spontaneously (fentanyl-spontaneous ventilation group), and (3) six spontaneously breathing patients who were anesthetized with propofol alone (propofol group). The laryngeal mucosa of each patient was stimulated by spraying the cord with distilled water, and the evoked responses were assessed by analyzing the respiratory variables and endoscopic images.

Results
Before administration of fentanyl, laryngeal stimulation caused vigorous reflex responses, such as expiration reflex spasmodic panting, cough reflex, and apnea with laryngospasm. Increasing doses of fentanyl reduced the incidences of all these responses, except for apnea with laryngospasm, in a dose-related manner in both the fentanyl-controlled ventilation and the fentanyl-spontaneous ventilation groups. Detailed analysis of endoscopic images revealed several characteristics of laryngeal behavior during the airway reflex responses.

Conclusion
Incremental doses of fentanyl depress airway reflex responses in a dose-related manner, except for apnea with laryngospasm.