bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Fentanyl on the Minimum Alveolar Concentration of Isoflurane in Swine
Authors: Moon Paula F. , Scarlett Janet M. , Ludders John W. , Conway Teresea A. , Lamb Steven V. 
Published: November 2003

Background
Fentanyl is used in anesthetic protocols for swine, but there are no reports on its potency in this species. This study measured the extent to which fentanyl reduces the minimum alveolar concentration of isoflurane (MACISO) in swine.

Methods
Sixteen swine were randomly assigned to four groups. For each group, baseline MACISO was determined, and three groups received two of three fentanyl infusions as follows: 50 micrograms.kg-1.h-1 intravenously followed by 100 micrograms.kg-1.h-1, 50 micrograms.kg-1.h-1 followed by 200 micrograms.kg-1.h-1, or 100 micrograms.kg-1.h-1 followed by 200 micrograms.kg-1.h-1 (n = 8 for each dosage). A loading dose of fentanyl preceded each infusion. Each infusion was maintained for 60 min before initiating minimum alveolar concentration determination. The infusions were maintained throughout the period of minimum alveolar concentration determination. Plasma fentanyl samples were obtained after 30 min of each infusion, and plasma fentanyl and hemodynamic parameters were obtained immediately before stimulating swine for the final isoflurane concentration used in determining minimum alveolar concentration. A fourth group, control animals, received saline infusions. After each infusion, the MACISO was redetermined. Minimum alveolar concentration was determined using incremental changes in isoflurane concentrations until gross purposeful movement resulted when using a hemostat stimulus applied for 1 min to a rear dewclaw.

Results
MACISO for controls was 2.19 +/- 0.17% (mean +/- SEM) and changed minimally over time (-0.13 +/- 4.77%). MACISO decreased significantly (P < or = 0.01) 24.5 +/- 3.2%, 29.9 +/- 4.8%, and 45.9 +/- 5.5% with fentanyl dosages of 50, 100, and 200 micrograms.kg-1.h-1, respectively. Corresponding plasma fentanyl concentrations were 14 +/- 1 ng/ml, 26 +/- 3 ng/ml, and 59 +/- 5 ng/ml, respectively. A ceiling effect on reduction of MACISO was not observed. Changes over time or between groups were not observed for arterial blood gas tensions, blood pressure, heart and respiratory rate, or body temperature.

Conclusions
These fentanyl dosages are larger than those commonly used in humans and other species. Anesthetic protocols using fentanyl for swine should be designed with the knowledge that a fentanyl infusion of 200 micrograms.kg-1.h-1 contributes approximately a 50% MACISO equivalent.
Region of Epidural Blockade Determines Sympathetic and Mesenteric Capacitance Effects in Rabbits
Authors: Hogan Quinn H. , Stekiel Thomas A. , Stadnicka Anna , Bosnjak Zeljko J. , Kampine John P. 
Published: November 2003

Background
The mechanisms producing hemodynamic changes during epidural anesthesia are incompletely understood. The role of capacitance changes in the splanchnic venous bed can be clarified by comparing blocks of differing segmental distributions. Specifically, we speculated that blocks that include the innervation to the mesenteric circulation alter hemodynamics, sympathetic activity, and venous capacitance to a greater extent than blocks without blockade of sympathetic nerves to this critical vascular bed.

Methods
Rabbits were studied during alpha-chloralose anesthesia and mechanical ventilation. Sympathetic efferent nerve activity to the mesenteric vessels was measured by surgically placed electrodes, and mesenteric vein diameter was measured by videomicroscopy. Heart rate and mean arterial pressure were monitored by intraarterial cannulation. Responses were compared after administration of epidural lidocaine using a dose and catheter level that limited anesthetic to lumbar levels (lumbar group) or thoracic levels (thoracic group). In addition, hemodynamic responses were recorded after thoracolumbar block in animals receiving alpha-chloralose but breathing spontaneously (spontaneous ventilation group) and in awake animals (awake group).

Results
Mean arterial pressure decreased 38.3 +/- 5.8% in the thoracic group but only 16.5 +/- 2.8 in the lumbar group. Sympathetic efferent nerve activity decreased in the thoracic group but increased in the lumbar group. An increase in vein diameter followed thoracic epidural anesthesia, but venoconstriction was observed after lumbar epidural block. The addition of intravenous sedation with alpha-chloralose did not increase the hypotensive effect of epidural anesthesia in this model.

Conclusions
Block of sympathetic fibers to the splanchnic circulation with thoracic epidural lidocaine produces mesenteric venodilatation that contributes to hypotension in rabbits. A lesser decrease in blood pressure follows blocks limited to lower segments, because baroreceptor stimulation produces increased splanchnic sympathetic activity and mesenteric venoconstriction. Responses in this model are comparable with and without general anesthesia and mechanical ventilation. To minimize hemodynamic consequences, epidural blockade should ideally be confined to the fewest necessary segments, avoiding splanchnic innervation if possible.
Cardiovascular Effects of Sevoflurane Compared with Those of Isoflurane in Volunteers
Authors: Malan Jr. Philip T. , DiNardo James A. , Isner Joseph R. , Frink Jr. Edward J. , Goldberg Mark , Fenster Paul E. , Brown Elizabeth A. , Depa Raymond , Hammond Leslie C. , Mata Heriberto 
Published: November 2003

Abstract

Background
Sevoflurane is a new inhalational anesthetic with desirable clinical properties. In some clinical situations, an understanding of the detailed cardiovascular properties of an anesthetic is important, so the authors evaluated the hemodynamic effects of sevoflurane in healthy volunteers not undergoing surgery.
Dose-Response Curves of Inhaled Nitric Oxide with and without Intravenous Almitrine in Nitric Oxide-responding Patients with Acute Respiratory Distress Syndrome
Authors: Lu Qin , Mourgeon Eric , Law-Koune Jean Dominique , Roche Sabine , Vezinet Corinne , Abdennour Lamine , Vicaut Eric , Puybasset Louis , Diaby Mohamed , Coriat Pierre , Rouby Jean-Jacques 
Published: November 2003

Abstract

Background
Inhaled nitric oxide, a selective pulmonary vasodilator, in combination with intravenous almitrine, a selective pulmonary vasoconstrictor, markedly improves arterial oxygenation in 50–60% of patients with acute lung injury. The goal of this study was to assess dose response of inhaled nitric oxide with and without almitrine in patients with acute respiratory distress syndrome responding to nitric oxide.
Analysis of Halothane Effects on Myocardial Force-Interval Relationships at Anesthetic Concentrations Depressing Twitches but Not Tetanic Contractions
Authors: Vogel Stephen M. , Weinberg Guy L. , Djokovic Andreja , Miletich David J. , Albrecht Ronald F. 
Published: November 2003

Abstract

Background
Tetanic contractions in rat myocardium depend solely on cellular Calcium2+ uptake, whereas twitches depend on Calcium2+ release from the sarcoplasmic reticulum. Because halothane may cause loss of sequestered Calcium2+, the anesthetic was tested for its differential effects on twitch and tetanic forces. The in vitro effects of halothane on the twitch force-interval relationship were then evaluated, using a mathematical model that relates twitch contractile force to the Calcium2+ content of intracellular compartments.
Evaluation of a Double-lumen Multiorifice Catheter for Resuscitation of Swine from Lethal Venous Air Embolism
Authors: Mongan Paul D. , Hinman Jon A. 
Published: November 2003

Abstract

Background
A double-lumen multiorifice catheter has been developed to potentially enhance accurate electrocardiographic central venous localization and resuscitation from a massive venous air embolism (VAE). This double-lumen multiorifice catheter was compared to a Bunegin-Albin multiorifice catheter for flow characteristics, air aspiration efficiency, and efficacy in resuscitating swine from a lethal VAE.
Premedication with Famotidine Augments Core Hypothermia during General Anesthesia
Authors: Hirose Munetaka , Hara Yumi , Matsusaki Masahiko 
Published: November 2003

Abstract

Background
Animal studies have provided considerable evidence to support a role of histamine in the central nervous system in thermoregulation, and premedication with a histamine Hydrogen2receptor antagonist before general anesthesia is used to reduce the risk of acid aspiration. The authors investigated whether premedication with famotidine had an effect on thermoregulation during general anesthesia.
Volatile and Intravenous Anesthetics Decrease Glutamate Release from Cortical Brain Slices during Anoxia
Authors: Bickler Philip E. , Buck Leslie T. , Feiner John R. 
Published: November 2003

Abstract

Background
Extracellular accumulation of the excitatory neurotransmitter L-glutamate during cerebral hypoxia or ischemia contributes to neuronal death. Anesthetics inhibit release of synaptic neurotransmitters but it is unknown if they alter net extrasynaptic glutamate release, which accounts for most of the glutamate released during hypoxia or ischemia. The purpose of this study was to determine if different types of anesthetics decrease hypoxia-induced glutamate release from rat brain slices.
Diaspirin Cross-linked Hemoglobin Does Not Increase Brain Oxygen Consumption during Hypothermic Cardiopulmonary Bypass in Rabbits
Authors: Hindman Bradley J. , Dexter Franklin , Cutkomp Johann , Smith Tom 
Published: November 2003

Abstract

Background
Decreased erythrocyte deformability due to cardiopulmonary bypass (CPB) and/or hypothermia, may result in brain capillary beds that have decreased erythrocyte transit, resulting in a generalized impairment of brain oxygenation during CPB. Because brain capillary plasma flow continues even when erythrocyte flow is absent, the authors' hypothesized augmentation of plasma oxygen content with a non-erythrocyte-associated oxygen transport molecule would increase brain oxygen uptake during hypothermic CPB.
Vasomotor Responses of Rat Coronary Arteries to Isoflurane and Halothane Depend on Preexposure Tone and Vessel Size
Authors: Park K. W. , Dai H. B. , Lowenstein E. , Sellke F. W. 
Published: November 2003

Abstract

Background
The authors previously reported that in rabbits, isoflurane exhibited a heterogeneous vasomotor effect, constricting small resistance coronary arteries and dilating larger conductance arteries. The novelty of isoflurane-induced constriction of small coronary arteries raised the question of whether the finding depended on the unique experimental setup or species used. The purpose of this study was to address these questions. Therefore, a second species was studied, namely rats, as well as a second volatile anesthetic, halothane. In addition, the dependence of the vasomotor effect on the preexisting tone of the vessels was examined.
Cardiac Outcome after Peripheral Vascular Surgery
Authors: Bode Robert H. , Lewis Keith P. , Zarich Stuart W. , Pierce Eric T. , Roberts Mark , Kowalchuk Glen J. , Satwicz Paul R. , Gibbons Gary W. , Hunter Jennifer A. , Espanola Cynthia C. , Nesto Richard W. 
Published: November 2003

Background
Despite evidence that regional anesthesia may be associated with fewer perioperative complications than general anesthesia, most studies that have compared cardiac outcome after general or regional anesthesia alone have not shown major differences. This study examines the impact of anesthetic choice on cardiac outcome in patients undergoing peripheral vascular surgery who have a high likelihood of associated coronary artery disease.

Methods
Four hundred twenty-three patients, between 1988 and 1991, were randomly assigned to receive general (n = 138), epidural (n = 149), or spinal anesthesia (n = 136) for femoral to distal artery bypass surgery. All patients were monitored with radial artery and pulmonary artery catheters. Postoperatively, patients were in a monitored setting for 48-72 h and had daily electrocardiograms for 4-5 days and creatine phosphokinase/isoenzymes every 8 h x 3, then daily for 4 days. Cardiac outcomes recorded were myocardial infarction, angina, and congestive heart failure.

Results
Baseline clinical characteristics were not different between anesthetic groups. Overall, the patient population included 86% who were diabetic, 69% with hypertension, 36% with a history of a prior myocardial infarction, and 41% with a history of smoking. Cardiovascular morbidity and overall mortality were not significantly different between groups when analyzed by either intention to treat or type of anesthesia received. In the intention to treat analysis, incidences of cardiac event or death for general, spinal, and epidural groups were 16.7%, 21.3%, and 15.4%, respectively. The absolute risk difference observed between general and all regional anesthesia groups for cardiac event or death was -1.6% (95% confidence interval -9.2%, 6.1%) This reflected a nonsignificant trend for lower risk of postoperative events with general anesthesia.

Conclusions
The choice of anesthesia, when delivered as described, does not significantly influence cardiac morbidity and overall mortality in patients undergoing peripheral vascular surgery.
Effects of Combining Propofol and Alfentanil on Ventilation, Analgesia, Sedation, and Emesis in Human Volunteers
Authors: Pavlin D. J. , Coda B. , Shen D. D. , Tschanz J. , Nguyen Q. , Schaffer R. , Donaldson G. , Jacobson R. C. , Chapman C. R. 
Published: November 2003

Background
Propofol and alfentanil frequently are administered together for intravenous sedation. This study investigated pharmacokinetic and pharmacodynamic interactions between propofol and alfentanil, at sedative concentrations, with specific regard to effects on ventilation, analgesia, sedation, and nausea.

Methods
Ten male volunteers underwent steady-state infusions on 3 separate days consisting of propofol alone, alfentanil alone, or a combination of the two. Target plasma concentrations for propofol were 150, 300, and 600 ng/ml for 1 h at each concentration; for alfentanil it was 40 ng/ml for 3 h. Assessment included serial measurements of (1) ventilatory function (minute ventilation, carbon dioxide production, end-tidal carbon dioxide, ventilatory response to rebreathing 7% CO2); (2) analgesia (subjective pain report in response to graded finger shock and evoked potential amplitude); (3) sedation (subjective rating, observer scores, and digit symbol substitution test); (4) nausea (visual analog scale, 0-100 mm).

Results
During combination treatment, propofol plasma concentration was 22% greater than during propofol alone using replicate infusion schemes (P < 0.009). End-tidal carbon dioxide was unchanged by propofol, and increased equally by alfentanil and alfentanil/propofol combined (delta end-tidal carbon dioxide 7.5 and 6.2 mmHg, respectively). Analgesia with propofol/alfentanil combined was greater than with alfentanil alone. (Pain report decreased 50% by PA vs. 28% for alfentanil, P < 0.05). Sedation was greater with propofol/alfentanil combined than with alfentanil or propofol alone (digit symbol substitution test 30 for propofol/alfentanil combined vs. 57 for alfentanil, and 46 for propofol, P < 0.05). Nausea occurred in 50% of subjects during alfentanil, but in none during propofol/alfentanil combination treatment.

Conclusions
The combination of propofol and alfentanil produced greater sedation and analgesia than that with either drug alone. Propofol offset the emetic effects of alfentanil. Equivalent depression of the carbon dioxide response curve, and elevation of end-tidal carbon dioxide occurred with propofol/alfentanil combined and alfentanil.
Measuring the Performance of Anesthetic Depth Indicators
Authors: Smith Warren D. , Dutton Robert C. , Smith Ty N. 
Published: November 2003

Background
An appropriate measure of performance is needed to identify anesthetic depth indicators that are promising for use in clinical monitoring. To avoid misleading results, the measure must take into account both desired indicator performance and the nature of available performance data. Ideally, anesthetic depth indicator value should correlate perfectly with anesthetic depth along a lighter-deeper anesthesia continuum. Experimentally, however, a candidate anesthetic depth indicator is judged against a "gold standard" indicator that provides only quantal observations of anesthetic depth. The standard anesthetic depth indicator is the patient's response to a specified stimulus. The resulting observed anesthetic depth scale may consist only of patient "response" versus "no response," or it may have multiple levels. The measurement scales for both the candidate anesthetic depth indicator and observed anesthetic depth are no more than ordinal; that is, only the relative rankings of values on these scales are meaningful.

Methods
Criteria were established for a measure of anesthetic depth indicator performance and the performance measure that best met these criteria was found.

Results
The performance measure recommended by the authors is prediction probability PK, a rescaled variant of Kim's dy.x measure of association. This performance measure shows the correlation between anesthetic depth indicator value and observed anesthetic depth, taking into account both desired performance and the limitations of the data. Prediction probability has a value of 1 when the indicator predicts observed anesthetic depth perfectly, and a value of 0.5 when the indicator predicts no better than a 50:50 chance. Prediction probability avoids the shortcomings of other measures. For example, as a nonparametric measure, PK is independent of scale units and does not require knowledge of underlying distributions or efforts to linearize or to otherwise transform scales. Furthermore, PK can be computed for any degree of coarseness or fineness of the scales for anesthetic depth indicator value and observed anesthetic depth; thus, PK fully uses the available data without imposing additional arbitrary constraints, such as the dichotomization of either scale. And finally, PK can be used to perform both grouped- and paired-data statistical comparisons of anesthetic depth indicator performance. Data for comparing depth indicators, however, must be gathered via the same response-to-stimulus test procedure and over the same distribution of anesthetic depths.

Conclusions
Prediction probability PK is an appropriate measure for evaluating and comparing the performance of anesthetic depth indicators.
Prospective Examination of Epidural Catheter Insertion
Authors: D'Angelo Robert , Berkebile Brenda L. , Gerancher J. C. 
Published: November 2003

Background
Although it is generally accepted that inserting epidural catheters 3-4 cm into the epidural space minimizes complications, no prospective randomized examination of epidural catheter insertion length has been published.

Methods
Eight hundred healthy parturients requesting epidural analgesia were randomized to have open-tip epidural catheters inserted 2, 4, 6, or 8 cm within the epidural space. The incidences of intravenous cannulation, unilateral sensory analgesia, and subsequent catheter dislodgment were recorded. Catheter insertions that resulted in intravenous cannulation or unilateral analgesia were incrementally withdrawn and retested with additional local anesthetic to determine the effectiveness of epidural catheter manipulation.

Results
Epidural catheters inserted 8 cm within the epidural space were more likely to result in intravenous cannulation. Epidural catheters inserted 2 cm within the epidural space were less likely to result in unilateral sensory analgesia but were more likely to become dislodged. Twenty-three percent of epidural catheters inserted > 2 cm within the epidural space required manipulation. Epidural catheters inserted 2 or 4 cm required replacement more often than epidural catheters inserted 6 or 8 cm. Ninety-one percent and 50% of epidural catheters that resulted in unilateral sensory analgesia and intravenous cannulation, respectively, provided analgesia for labor and delivery after incremental withdrawal.

Conclusions
Epidural catheters should be inserted either 2 cm when rapid labor is anticipated or 6 cm when prolonged labor or cesarean delivery is likely. Additionally, epidural catheters that result in intravenous cannulation or unilateral sensory analgesia can be manipulated effectively to provide analgesia for labor and delivery.
Effect of Volatile Anesthetics on Hydrogen Peroxide-induced Injury in Aortic and Pulmonary Arterial Endothelial Cells
Authors: Johnson Michael E. , Sill Christopher J. , Uhl Cindy B. , Halsey Teresa J. , Gores Gregory J. 
Published: November 2003

Background
Oxidant damage to endothelial cells occurs during inflammation and reperfusion after ischemia, mediated in part by endogenously produced hydrogen peroxide (H2O2). Previous studies have established a role for increased cytosolic calcium in the mechanism of endothelial oxidant injury, and have suggested that volatile anesthetics may exacerbate oxidant injury in pulmonary endothelium. However, the effect of volatile anesthetics on oxidant injury to systemic arterial endothelial cells, and their effect on oxidant-related changes in cytosolic calcium homeostasis, have not been reported previously.

Methods
Primary cultures of human aortic and pulmonary arterial endothelial cells were studied. The rate of cell death after H2O2 exposure was determined in cell suspension by propidium iodide fluorimetry and lactate dehydrogenase release. The final extent of cell death 24 h after H2O2 exposure was determined in monolayer cultures by methyl thiazolyl tetrazolium reduction. Cytosolic calcium and cell death were determined in single cells using fura-2 and propidium iodide imaging with digitized, multiparameter, fluorescent video microscopy.

Results
In aortic endothelial cells, clinical concentrations of halothane (1.0%) and isoflurane (1.5%) decreased both the rate of cell death and the final extent of cell death after H2O2 exposure, with halothane being more protective. Supraclinical concentrations of halothane (2.7%) and isoflurane (4.0%) were less protective. In pulmonary arterial endothelial cells, halothane and isoflurane had essentially no effect on H2O2-mediated cell death. The protective effect of anesthetic in aortic endothelial cells was not due to an enhanced removal of H2O2 by endogenous enzymes. Hydrogen peroxide exposure caused a large increase in cytosolic calcium well before cell death, and this was moderated by anesthetic treatment.

Conclusions
The effect of volatile anesthetics on oxidant injury to endothelial cells may differ between cells derived from systemic and pulmonary vascular beds. Halothane, and to a lesser extent, isoflurane, protects against oxidant injury in aortic endothelial cells. The mechanism of protection may involve modulation of the interaction of H2O2 with vital cellular constituents, and/or amelioration of the toxic increase in cytosolic calcium that follows such interaction.