bluuebunny/crossref_metadata_2025_split huggingface dataset:
Human Chest Wall Function while Awake and during Halothane Anesthesia
Authors: Warner David O. , Warner Mark A. , Ritman Erik L. 
Published: November 2003

Background
Data concerning chest wall configuration and the activities of the major respiratory muscles that determine this configuration during anesthesia in humans are limited. The aim of this study was to determine the effects of halothane anesthesia on respiratory muscle activity and chest wall shape and motion during spontaneous breathing.

Methods
Six human subjects were studied while awake and during 1 MAC halothane anesthesia. Respiratory muscle activity was measured using fine-wire electromyography electrodes. Chest wall configuration was determined using images of the thorax obtained by three-dimensional fast computed tomography. Tidal changes in gas volume were measured by integrating respiratory gas flow, and the functional residual capacity was measured by a nitrogen dilution technique.

Results
While awake, ribcage expansion was responsible for 25 +/- 4% (mean +/- SE) of the total change in thoracic volume (delta Vth) during inspiration. Phasic inspiratory activity was regularly present in the diaphragm and parasternal intercostal muscles. Halothane anesthesia (1 MAC) abolished activity in the parasternal intercostal muscles and increased phasic expiratory activity in the abdominal muscles and lateral ribcage muscles. However, halothane did not significantly change the ribcage contribution to delta Vth (18 +/- 4%). Intrathoracic blood volume, measured by comparing changes in total thoracic volume and gas volume, increased significantly during inspiration both while awake and while anesthetized (by approximately 20% of delta Vth, P < 0.05). Halothane anesthesia significantly reduced the functional residual capacity (by 258 +/- 78 ml), primarily via an inward motion of the end-expiratory position of the ribcage. Although the diaphragm consistently changed shape, with a cephalad displacement of posterior regions and a caudad displacement of anterior regions, the diaphragm did not consistently contribute to the reduction in the functional residual capacity. Halothane anesthesia consistently increased the curvature of the thoracic spine measured in the saggital plane.

Conclusions
The authors conclude that (1) ribcage expansion is relatively well preserved during halothane anesthesia despite the loss of parasternal intercostal muscle activity; (2) an inward displacement of the ribcage accounts for most of the decrease in functional residual capacity caused by halothane anesthesia, accompanied by changes in diaphragm shape that may be related to motion of its insertions on the thoracoabdominal wall; and (3) changes in intrathoracic blood volume constitute a significant fraction of delta Vth during tidal breathing.
The Dose-Response Relationship of Ondansetron in Preventing Postoperative Emesis in Pediatric Patients Undergoing Ambulatory Surgery
Authors: Watcha Mehernoor F. , Bras Paul J. , Cieslak Gary D. , Pennant John H. 
Published: November 2003

Background
Postoperative nausea and vomiting is a distressing anesthetic complication that may delay discharge after ambulatory surgery. Effective prophylaxis for postoperative nausea and vomiting can be achieved in adults with lower doses of ondansetron, a 5-hydroxytryptamine subtype 3 receptor antagonist, compared with chemotherapy-induced emesis. However, the doses of ondansetron used in preventing postoperative nausea and vomiting in children are based on data from chemotherapy-induced emesis. The dose-related efficacy of intravenous ondansetron in the prophylaxis of postoperative emesis in the pediatric outpatient population was determined.

Methods
In a double-blind, randomized placebo-controlled study, 130 patients (mean age 5.7 +/- 3.4 yr) received placebo, 10, 50, or 100 micrograms/kg ondansetron during a standardized anesthetic. Episodes of postoperative vomiting or retching were recorded.

Results
Intravenous ondansetron in a dose of 50 micrograms/kg was more effective than placebo or a dose of 10 micrograms/kg in controlling the incidence and frequency of emesis in the hospital and during the first 24 postoperative hours. Increasing the dose of ondansetron to 100 micrograms/kg intravenously did not significantly reduce the incidence or frequency of emesis compared to 50 micrograms/kg intravenously.

Conclusions
Intravenous ondansetron in a dose of 50 micrograms/kg is as effective as larger doses for the prophylaxis of emesis in children undergoing surgical procedures known to be associated with an increased risk for postoperative nausea and vomiting.
Using Alcohol as a Standard to Assess the Degree of Impairment Induced by Sedative and Analgesic Drugs Used in Ambulatory Surgery
Authors: Thapar Pankaj , Zacny James P. , Thompson Wesley , Apfelbaum Jeffrey L. 
Published: November 2003

Background
There is a need for a standard by which to compare the degree of subjective and behavioral impairment caused by anesthetic drugs, because anesthesiologists may not be able to gauge how extreme or important a statistically significant change in psychomotor functioning is. This study examined the psychomotor and subjective effects of alcohol at blood concentrations equal or greater than 0.10% as a standard with which to compare those effects caused by sedative and analgesic agents commonly used in ambulatory surgery.

Methods
Twelve healthy human volunteers (11 men and 1 nonpregnant woman), with an average age of 28 yr (range 24-34 yr) and an average alcohol consumption of four drinks per week, were selected in this institutional review board-approved study. Each subject was exposed to five drug conditions (70 mg/70 kg propofol intravenously, 2 mg/70 kg midazolam intravenously, 50 micrograms/70 kg fentanyl intravenously, 0.8 g/kg alcohol orally, and placebo orally and intravenously) in a double-blind randomized fashion over five weekly sessions. Testing was done at baseline and at different intervals until 240 min after drug administration. Testing included psychomotor performance (Maddox Wing, eye-hand coordination, auditory reaction time test, and digit symbol substitution test), subjective effects (strength of drug effect scale, drug liking scale, and visual analog scale), and short-term memory. Psychomotor performance was used as an index of objective impairment, and mood was used as an index of subjective impairment.

Results
After consumption of the alcoholic beverage, a blood alcohol level of 0.11 +/- 0.003% (mean +/- SE) was obtained at 15 min after injection. The study drugs not only produced statistically significant impairment (i.e., impairment greater than that seen with placebo) but also, at one or more times after injection, produced impairment similar to that observed with alcohol at a blood alcohol concentration of 0.11%. Midazolam produced a similar degree of impairment to that of alcohol for a longer duration than did fentanyl and propofol.

Conclusions
This study provides evidence that degree of impairment caused by sedative and analgesic drugs used in ambulatory surgery is similar to that obtained with a dose of alcohol that produces a blood alcohol concentration of 0.11%. We suggest that anesthesiologists can use alcohol as a standard by which to assess degree of impairment produced by drugs used for sedation/analgesia.
The Catecholamine, Cortisol, and Hemodynamic Responses to Mild Perioperative Hypothermia
Authors: Frank Steven M. , Higgins Michael S. , Breslow Michael J. , Fleisher Lee A. , Gorman Randolph B. , Sitzmann James V. , Raff Hershel , Beattle Charles 
Published: November 2003

Background
Unintended hypothermia occurs frequently during surgery and may have adverse effects on the cardiovascular system. Although the mechanisms responsible for the cardiovascular manifestations of hypothermia are unclear, it is possible that they are sympathetically mediated. In this prospective study, relationships between body temperature, the neuroendocrine response, and hemodynamic changes in the perioperative period were examined.

Methods
Seventy-four elderly patients, undergoing abdominal, thoracic, or lower extremity vascular surgical procedures, were randomly assigned to either "routine care" (n = 37) or "forced-air warming" (n = 37) groups. Throughout the intraoperative and early postoperative periods, the routine care group received standard thermal care, and the forced-air warming group received forced-air skin-surface warming. Core temperature, forearm minus fingertip skin-surface temperature gradient, and plasma concentrations of epinephrine, norepinephrine, and cortisol were measured throughout the perioperative period, and the two groups were compared. In addition, heart rate and arterial blood pressure were compared between groups.

Results
The routine care and forced-air warming groups did not differ with regard to age, sex, type of surgical procedures, anesthetic techniques, or postoperative analgesia. Mean core temperature was lower in the routine care group on admission to the postanesthetic care unit (routine care, 35.3 +/- 0.1 degree C; forced-air warming, 36.7 +/- 0.1 degree C; P = 0.0001) and remained lower during the early postoperative period. Forearm minus fingertip skin-surface temperature gradient (an index of peripheral vasoconstriction) was greater in the routine care group in the early postoperative period. The mean norepinephrine concentration (pcg/ml) was greater in the routine care group immediately after surgery (480 +/- 70 vs. 330 +/- 30, P = 0.02) and at 60 min (530 +/- 50 vs. 340 +/- 30, P = 0.002) and 180 min (500 +/- 80 vs. 320 +/- 30, P = 0.004) postoperatively. Mean epinephrine concentrations were not significantly different between groups. Mean cortisol concentrations were increased in both groups during the early postoperative period (P < 0.01), but the differences between groups were not significant. Systolic, mean, and diastolic arterial blood pressures were significantly higher in the routine care group.

Conclusions
Compared with patients in the forced-air warming group, patients receiving routine thermal care had lower core temperatures, a greater degree of peripheral vasoconstriction, higher norepinephrine concentrations, and higher arterial blood pressures in the early postoperative period. These findings suggest a possible mechanism for hypothermia-related cardiovascular morbidity in the perioperative period.
Analysis of Strategies to Decrease Postanesthesia Care Unit Costs
Authors: Dexter Franklin , Tinker John H. 
Published: November 2003

Background
The goal of this study was to identify interventions that anesthesiologists can make to decrease total costs of a postanesthesia care unit (PACU).

Methods
Data were collected retrospectively from patients who underwent ambulatory surgery at our tertiary care center.

Results
Supplies and medications accounted for only 2% of PACU charges. Personnel costs, which depend on the peak number of patients in the PACU, accounted for almost all PACU costs. If nausea and vomiting could have been eliminated in each patient who suffered this complication, without causing sedation, the total time to discharge for all patients would have been decreased by less than 4.8% (95% confidence interval < 7.3%). Arrival rates to and times to discharge from the PACU followed triangular and log-normal distributions, respectively. Computer simulations, using published times to discharge for drugs with "faster recovery," such as propofol, showed that the use of these drugs would only decrease PACU costs if operating rooms were consistently scheduled to run later each day. Such earlier discharge also might be beneficial if used at night, but only if the PACU could close after a single patient leaves. However, reasonably achievable decreases in the times to discharge for all patients undergoing general anesthesia are unlikely to substantively decrease PACU costs. In contrast, arranging an operating room schedule to optimize admission rates would greatly affect the number of PACU nurses needed.

Conclusions
Anesthesiologists have little control over PACU economics via choice of anesthetic drugs. The major determinant of PACU costs is the distribution of admissions.
Sensitization of Spinal Neurons by Non-noxious Stimuli in the Awake but Not Anesthetized State
Authors: Herrero Juan F. , Headley Max P. 
Published: November 2003

Background
The observation that peripheral trauma causes enhanced spinal neuronal excitability has provided the scientific rationale for the concept of "pre-emptive analgesia." The premise has been that only noxious stimuli cause sensitization in sensory pathways, but this premise has not been tested in the conscious state.

Methods
Responses of single spinal neurons were recorded in instrumented sheep that were untrained and free from drugs or recent surgery, in either fully conscious or halothane-anesthetized states. Receptive field (RF) size was measured before and after non-noxious mechanical conditioning stimulation.

Results
Noxious conditioning stimuli in anesthetized sheep caused enlargement of RF areas, as expected. Conditioning with nonpainful scratching or other stimuli was without effect in anesthetized animals; in marked contrast, it caused enlargement of RF size in conscious animals, in which 29 of 33 wide dynamic range units but only 1 of 12 low-threshold mechanoreceptive neurons were affected.

Conclusions
Sensitization of spinal sensory neurons evidently is a process that is not restricted to pathologic pain states but rather that occurs under normal physiologic conditions independent of painful stimuli. The significance of such sensitization processes therefore needs reevaluation. The sensitization triggered by non-nociceptive afferents is likely to be opioid-resistant and therefore may contribute to the rather disappointing results seen in several clinical trials of "pre-emptive analgesia."
General Anesthetics Modify the Kinetics of Nicotinic Acetylcholine Receptor Desensitization at Clinically Relevant Concentrations
Authors: Raines Douglas E. , Rankin Saffron E. , Miller Keith W. 
Published: November 2003

Background
General anesthetics are thought to induce anesthesia through their actions on ligand-gated ion channels. One such channel, the nicotinic acetylcholine receptor (nAcChoR), can be found in different subtypes in the central nervous system and at the periphery in the neuromuscular junction. The latter subtype of the nAcChoR is a useful model for examining interactions between general anesthetics and ligand-gated ion channels, because it can be isolated and purified in sufficient quantities to allow for biophysical and biochemical studies. This study examines the actions of general anesthetics on agonist-induced conversion of the nAcChoR to inactive desensitized conformational states.

Methods
Nicotinic acetylcholine receptor membranes were purified from the electric organ of Torpedo nobiliana. Agonist-induced desensitization was characterized from the time-dependent increase in fluorescence intensity that results from the binding of the fluorescent acetylcholine analog, Dns-C6-Cho, to the nAcChoR.

Results
Mixing Dns-C6-Cho with nAcChoR-rich membranes results in an increase in fluorescence that is characterized by four rate processes. Concentrations of isoflurane and butanol, which range from subclinical to toxic increase the rates of the third and fourth components of fluorescence, corresponding to fast and slow desensitization, respectively. At concentrations that are twice their EC50s for anesthesia, isoflurane, butanol, chloroform, methanol, and cyclopentanemethanol increase the apparent rates of fast and slow desensitization by an average of 92 +/- 22% and 108 +/- 22%, respectively.

Conclusions
The concentration range over which general anesthetics modify the kinetics of nAcChoR desensitization is similar to those reported for anesthetic actions on the GABAA receptor. Thus, the nAcChoR, like other members of this superfamily, is a sensitive target of general anesthetics.
Phase I Safety Assessment of Intrathecal Neostigmine Methylsulfate in Humans
Authors: Hood David D. , Eisenach James C. , Tuttle Robin 
Published: November 2003

Background
In dogs, sheep, and rats, spinal neostigmine produces analgesia alone and enhances analgesia from alpha 2-adrenergic agonists. This study assesses side effects and analgesia from intrathecal neostigmine in healthy volunteers.

Methods
After institutional review board approval and informed consent, 28 healthy volunteers were studied. The first 14 volunteers received neostigmine (50-750 micrograms) through a #19.5 spinal needle followed by insertion of a spinal catheter. The remaining 14 volunteers received neostigmine through a #25 or #27 spinal needle without a catheter. Safety measurements included blood pressure, heart rate, oxyhemoglobin saturation, end-tidal carbon dioxide, neurologic evaluation, and computer tests of vigilance and memory. Analgesia in response to ice water immersion was measured.

Results
Neostigmine (50 micrograms) through the #19.5 needle did not affect any measured variable. Neostigmine (150 micrograms) caused mild nausea, and 500-750 micrograms caused severe nausea and vomiting. Neostigmine (150-750 micrograms) produced subjective leg weakness, decreased deep tendon reflexes, and sedation. The 750-micrograms dose was associated with anxiety, increased blood pressure and heart rate, and decreased end-tidal carbon dioxide. Neostigmine (100-200 micrograms) in saline, injected through a #25 or #27 needle, caused protracted, severe nausea, and vomiting. This did not occur when dextrose was added to neostigmine. Neostigmine by either method of administration reduced visual analog pain scores to immersion of the foot in ice water.

Conclusions
The incidence and severity of these adverse events from intrathecal neostigmine appears to be affected by dose, method of administration, and baricity of solution. These effects in humans are consistent with studies in animals. Because no unexpected or dangerous side effects occurred, cautious examination of intrathecal neostigmine alone and in combination with other agents for analgesia is warranted.
An Evaluation of the Effect of Anesthetic Technique on Reproductive Success after Laparoscopic Pronuclear Stage Transfer
Authors: Vincent Robert D. , Syrop Craig H. , Van Voorhis Bradley J. , Chestnut David H. , Sparks Amy E. T. , McGrath Joan M. , Choi Won W. , Bates James N. , Penning Donald H. 
Published: November 2003

Background
Laparoscopic pronuclear stage transfer (PROST) is the preferred method of embryo transfer after in vitro fertilization in many infertility programs. There are scant data to recommend the use or avoidance of any particular anesthetic agent for use in women undergoing this procedure. The authors hypothesized that propofol would be an ideal anesthetic for laparoscopic PROST because of its characteristic favorable recovery profile that includes minimal sedation and a low incidence of postoperative nausea and vomiting. The purpose of the study was to compare propofol and isoflurance with respect to postanesthetic recovery and pregnancy outcomes after laparoscopic PROST.

Methods
One hundred twelve women scheduled for laparoscopic PROST were randomized to receive either propofol/nitrous oxide or isoflurane/nitrous oxide for maintenance of anesthesia.

Results
Visual analog scale scores for sedation were lower in the propofol group than in the isoflurance group at all measurements between 30 min and 3 h after surgery. More women experienced emesis and were given an antiemetic during recovery in the isoflurance group than in the propofol group. However, the percentage of pregnancies with evidence of fetal cardiac activity was 54% in the isoflurane group compared with only 30% in the propofol group (P = 0.023). Also, the ongoing pregnancy rate was greater in the isoflurane group than in the propofol group (54% vs. 29%, P = 0.014).

Conclusions
Propofol/nitrous oxide anesthesia was associated with lower clinical and ongoing pregnancy rates compared with isoflurane/nitrous oxide anesthesia.
Distribution of Cerebral Blood Flow during Anesthesia with Isoflurane or Halothane in Humans
Authors: Reinstrup Peter , Ryding Erik , Algotsson Lars , Messeter Kenneth , Asgeirsson Bogi , Uski Tore 
Published: November 2003

Background
Halothane and isoflurane have been shown to induce disparate effects on different brain structures in animals. In humans, various methods for measuring cerebral blood flow (CBF) have produced results compatible with a redistribution of CBF toward deep brain structures during isoflurane anesthesia in humans. This study was undertaken to examine the effects of halothane and isoflurance on the distribution of CBF.

Methods
Twenty ASA physical status patients (four groups, five in each) anesthetized with either isoflurane or halothane (1 MAC) during normo- or hypocapnia (PaCO2 5.6 or 4.2 kPa (42 or 32 mmHg)) were investigated with a two-dimensional CBF measurement (CBFxenon, intravenous 133xenon washout technique) and a three-dimensional method for measurement of the regional CBF (rCBF) distribution with single photon emission computer-aided tomography (SPECT; 99mTc-HMPAO). In the presentation of SPECT data, the mean CBF of the brain was defined as 100%, and all relative flow values are related to this value.

Results
The mean CBFxenon level was significantly influenced by the PaCO2 as well as by the anesthetic used. At normocapnia, patients anesthetized with halothane had a mean CBFxenon of 40 +/- 3 (SE) ISI units. With isoflurane, the flow was significantly (P < 0.01, 33 +/- 3 ISI units) less than with halothane. Hypocapnia decreased mean CBFxenon (P < 0.0001) during both anesthetics (halothane 24 +/- 3, isoflurane 13 +/- 2 ISI units). The effects on CBFxenon, between the anesthetics, differed significantly (P < 0.01) also during hypocapnia. There were significant differences in rCBF distribution measured between the two anesthetics (P < 0.05). During isoflurane anesthesia, there was a relative increase in flow values in subcortical regions (thalamus and basal ganglia) to 10-15%, and in pons to 7-10% above average. Halothane, in contrast, induced the highest relative flow levels in the occipital lobes, which increased by approximately 10% above average. The rCBF level was increased approximately 10% in cerebellum with both anesthetics. Changes in PaCO2 did not alter the rCBF distribution significantly.

Conclusions
There is a difference in the human rCBF distribution between halothane and isoflurane with higher relative flows in subcortical regions during isoflurane anesthesia. However, despite this redistribution, isoflurane anesthesia resulted in a lower mean CBFxenon than did anesthesia with halothane.