bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasma insulin concentrations and amino acid turnover in Merino sheep with high or low fleece weight
Authors: Adams N. R. , Liu S. M. , Briegel J. R. , Thompson M. J.
Published: August 2004

Although sheep with a relatively high fleece weight have reduced fat deposition and a lower reproductive rate, research has failed to identify any specific metabolic demand that growing a fleece places on the physiology of the sheep. This paper reports two experiments in which the effect of fleece weight was examined in ewes infused intravenously with amino acids. The first experiment was carried out when the ewes were 107 days pregnant, and the second 2 years later in non-pregnant ewes from the same flock. The ewes were derived initially from groups that differed in staple strength, but there was no effect of staple strength group on the characteristics measured in either experiment. In Expt 2, ewes were also infused with a bolus of l-[ring-d5] phenylalanine, and the enrichment in plasma determined by GC/mass spectrometry over the next 24 h. In both experiments, fasting plasma insulin concentrations were lower (P < 0.05) in ewes with a high fleece weight, and this difference continued during infusion in Expt 2 (P < 0.05). In Expt 1, infusion of ewes with amino acids resulted in higher (P < 0.05) plasma concentrations of α-amino nitrogen (indicating amino acids) in the ewes with a higher fleece weight, and in Expt 2, ewes with a high fleece weight had a 19% higher rate of appearance of endogenous phenylalanine (P < 0.05). We conclude that sheep with high wool growth rates have higher whole-body protein turnover rate, which may be achieved in part by lower insulin concentrations. Lower insulin in turn provides a mechanism through which wool growth rate may influence energy availability to other tissues.
Unique role of CD4+CD62L+regulatory T cells in the control of autoimmune diabetes in T cell receptor transgenic mice
Authors: You Sylvaine , Slehoffer Géraldine , Barriot Samia , Bach Jean-François , Chatenoud Lucienne
Published: August 2004

Converging experimental evidence indicates that CD4+regulatory T cells control progression of autoimmune insulitis in nonobese diabetic (NOD) mice. Here, we studied the nature of these regulatory T cells and their mode of action in diabetes-prone NODRag-/-or severe combined immunodeficient (SCID) mice harboring a transgenic T cell receptor derived from the diabetogenic T cell clone BDC2.5. We first show that diabetes onset is prevented in such mice by infusion of polyclonal CD4+T cells expressingl-selectin (CD62L) but not prevented or only marginally prevented by CD4+CD25+T cells. Similarly, we found with a cotransfer model that CD4+CD62L+T cells but not CD4+CD25+T cells inhibited diabetes transfer into NOD SCID recipients by transgenic NOD BDC2.5 SCID cells. Unexpectedly, cotransfer of transgenic NOD BDC2.5 SCID cells and spleen cells from WT diabetic NOD mice did not induce diabetes, whereas each individual population did so. Data are presented arguing for the role of CD4+CD62L+T cells present within the polyclonal diabetogenic population in mediating this apparently paradoxical effect. Collectively, these data confirm the central role of CD4+CD62L+regulatory T cells in controlling disease onset in a well defined transgenic model of autoimmune diabetes and suggest the intervention of homeostatic mechanisms as part of their mode of action.
Measurement of anisotropic energy transport in flowing polymers by using a holographic technique
Authors: Schieber Jay D. , Venerus David C. , Bush Kendall , Balasubramanian Venkat , Smoukov Stoyan
Published: August 2004

Almost no experimental data exist to test theories for the nonisothermal flow of complex fluids. To provide quantitative tests for newly proposed theories, we have developed a holographic grating technique to study energy transport in an amorphous polymer melt subject to flow. Polyisobutylene with weight-averaged molecular mass of 85 kDa is sheared at a rate of 10 s
–1
, and all nonzero components of the thermal conductivity tensor are measured as a function of time, after cessation. Our results are consistent with proposed generalizations to the energy balance for microstructural fluids, including a generalized Fourier's law for anisotropic media. The data are also consistent with a proposed stress-thermal rule for amorphous polymer melts. Confirmation of the universality of these results would allow numerical modelers to make quantitative predictions for the nonisothermal flow of polymer melts.
Effects of Sufentanil on Cerebral Hemodynamics and Intracranial Pressure in Patients with Brain Injury
Authors: Werner Christian , Kochs Eberhard , Bause Hanswerner , Hoffman William E. , Schulte am Esch Jochen
Published: August 2004

Background

The current study investigates the effects of sufentanil on cerebral blood flow velocity and intracranial pressure (ICP) in 30 patients with intracranial hypertension after severe brain trauma (Glasgow coma scale < 6).

Methods

Mechanical ventilation (FIO2 0.25-0.4) was adjusted to maintain arterial carbon dioxide tensions of 28-30 mmHg. Continuous infusion of midazolam (200 micrograms/kg/h intravenous) and fentanyl (2 micrograms/kg/h intravenous) was used for sedation. Mean arterial blood pressure (MAP, mmHg) was adjusted using norepinephrine infusion (1-5 micrograms/min). Mean blood flow velocity (Vmean, cm/s) was measured in the middle cerebral artery using a 2-MHz transcranial Doppler sonography system. ICP (mmHg) was measured using an epidural probe. After baseline measurements, a bolus of 3 micrograms/kg sufentanil was injected, and all parameters were continuously recorded for 30 min. The patients were assigned retrospectively to the following groups according to their blood pressure responses to sufentanil: group 1, MAP decrease of less than 10 mmHg, and group 2, MAP decrease of more than 10 mmHg.

Results

Heart rate, arterial blood gases, and esophageal temperature did not change over time in all patients. In 18 patients, MAP did not decrease after sufentanil (group 1). In 12 patients, sufentanil decreased MAP > 10 mmHg from baseline despite norepinephrine infusion (group 2). ICP was constant in patients with maintained MAP (group 1) but was significantly increased in patients with decreased MAP. Vmean did not change with sufentanil injection regardless of changes in MAP.

Conclusions

The current data show that sufentanil (3 micrograms/kg intravenous) has no significant effect on middle cerebral artery blood flow velocity and ICP in patients with brain injury, intracranial hypertension, and controlled MAP. However, transient increases in ICP without changes in middle cerebral artery blood flow velocity may occur concomitant with decreases in MAP. This suggests that increases in ICP seen with sufentanil may be due to autoregulatory decreases in cerebral vascular resistance secondary to systemic hypotension.
Postoperative Analgesia Using Epidural Infusions of Fentanyl with Bupivacaine
Authors: Scott David A. , Beilby David S. N. , McClymont Calum
Published: August 2004

Background

Epidural fentanyl/bupivacaine infusions often are limited to high dependency units or intensive care units. One thousand fourteen patients receiving epidural fentanyl/bupivacaine infusions for analgesia after major surgery who were managed in the general surgical ward were prospectively surveyed.

Methods

Patients leaving the recovery room with an epidural catheter in situ were assessed three times a day by acute pain service personnel for quality of pain relief, using a rating scale that accounted for pain on movement. The presence of side effects and complications was assessed.

Results

Data were collected from February 1990 to May 1993. The average duration of infusion was 3 days. A patient's pain relief was rated as good to excellent on 82.6% of visits. Side effects possibly attributable to fentanyl included sedation (7.4%), pruritus (10.2%), nausea and vomiting (3.1%), and respiratory depression (1.2%). Respiratory depression commonly was associated with sedation and was detected easily on the postsurgical ward, with only four patients requiring naloxone (0.4%). Side effects possibly related to bupivacaine included unpleasant sensory block (2.6%), significant lower limb motor block (3.0%), and hypotension (6.6%). There were two cases of epidural hematoma. Inflammation at the epidural catheter insertion site occurred in 3.8% (38), of which 42% (16) had some cutaneous purulence detected. There were no epidural space infections. Mechanical problems, including dislodgment of the catheter, accounted for 18.7% of infusion discontinuations within the first 72 h.

Conclusions

Postoperative epidural fentanyl/bupivacaine infusions are effective and can be managed readily in general postsurgical wards with minimal complications provided that appropriate patient observations are performed.
Near-infrared Measurement of Cerebral Oxygenation
Authors: Levy Warren J. , Levin Serle , Chance Britton
Published: August 2004

Background

The application of phase-modulated near-infrared techniques for measurement of the oxygen saturation of cerebral tissue requires both validation by conventional measures of cerebral oxygenation and determination of normal and abnormal values. This study was undertaken to validate phase-modulated near-infrared measurements of cerebral oxygen saturation by comparing them with electroencephalographic evidence of cerebral ischemia during implantation of cardioverting defibrillators. This comparison also yields an estimate of the ischemic threshold as measured with near-infrared techniques.

Methods

Electroencephalograms and near-infrared measurements were performed during 85 episodes of ventricular fibrillation in ten patients. Light at 754, 785, and 816 nm was modulated at 200 MHz, transmitted through the skull, and the path lengths of the reflected light were determined by measuring the phase shifts. The electroencephalogram was inspected for changes during the hypotension associated with the arrhythmia and the oxygen saturation was calculated from the near-infrared path lengths. Changes in oxygen saturation were then compared with electroencephalographic evidence of cerebral ischemia.

Results

The mean saturation before fibrillation was 56.5% +/- 1.2 (SEM). In 40 (47%) of the events, electroencephalographic evidence of ischemia was observed. Such changes were related to the minimum saturation observed during ventricular fibrillation (44% +/- 2.5 vs. 56% +/- 1.9 in the absence of electroencephalographic changes; P < 0.001). The ischemic threshold was estimated to be 47% saturation. The sensitivity of this technique was estimated to be 0.6, the specificity 0.84, and the predictive accuracy 0.73.

Conclusions

Near-infrared measurements reflect changes in cerebral oxygenation as indicated by electroencephalographic evidence of cerebral ischemia.
Effects of Perioperative Analgesic Technique on Rate of Recovery after Colon Surgery
Authors: Liu Spencer S. , Carpenter Randall L. , Mackey David C. , Thirlby Richard C. , Rupp Stephen M. , Shine Timothy S. J. , Feinglass Neil G. , Metzger Philip P. , Fulmer Jack T. , Smith Stephen L.
Published: August 2004

Background

Choice of perioperative analgesia may affect the rate of recovery of gastrointestinal function and thus duration and cost of hospitalization after colonic surgery.

Methods

Fifty-four patients undergoing partial colectomy surgery were randomized into four groups. All groups received a standardized general anesthetic. Group MB received a preoperative bolus of epidural bupivacaine and morphine followed by an infusion of morphine and bupivacaine. Group M received a preoperative bolus of epidural morphine followed by an infusion of morphine. Group B received a preoperative bolus of bupivacaine followed by an infusion of bupivacaine. Group P received a preoperative bolus of intravenous morphine followed by intravenous patient-controlled morphine postoperatively. All patients participated in a standardized recovery program to minimize the influence of nonanalgesic factors on recovery of gastrointestinal function. All epidural groups were double-blinded. All patients were deemed ready for discharge according to prospectively defined criteria.

Results

Groups B and MB reported superior analgesia with activity (P < 0.01). Group M had a greater incidence of pruritus (P < 0.05). Group B had a greater incidence of orthostatic hypotension (P = 0.04). Groups B and MB recovered gastrointestinal function and fulfilled discharge criteria approximately 1.5 days earlier than groups M and P (P < 0.005).

Conclusions

Epidural analgesia with bupivacaine and morphine provided the best balance of analgesia and side effects while accelerating postoperative recovery of gastrointestinal function and time to fulfillment of discharge criteria after colon surgery in relatively healthy patients within the context of a multimodal recovery program.
Propofol Modulates the Effects of Chemoconvulsants Acting at GABAergic, Glycinergic, and Glutamate Receptor Subtypes
Authors: Bansinath Mylarrao , Shukla Vijay Kumar , Turndorf Herman
Published: August 2004

Background

Propofol has been used to treat status epilepticus, but its use in patients with seizure disorders remains controversial, because of concerns that it produces paroxysmal motor phenomenon. Chemoconvulsants act by known discrete mechanisms and neurotransmitters, and therefore, they are useful tools for screening anticonvulsant activity. The main objective of this study was to characterize the effect of propofol pretreatment on convulsions induced by picrotoxin, bicuculline, and strychnine, all which decrease inhibitory neurotransmission, and by N-methyl-D-aspartic acid, kainic acid, and quisqualic acid, which enhance excitatory neurotransmission.

Methods

Groups of male Swiss Webster mice (n > or = 10/group) were given either vehicle (intralipid, 10 ml.kg-1, control groups) or propofol (50 mg.kg-1, test groups) injected intraperitoneally. Five min after injection, convulsions were induced with either bicuculline (1.36-5.44 nmoles), picrotoxin (0.21-1 nmol), N-methyl-D-aspartic acid (0.51-2 nmol), quisqualic acid (1-10 nmol), kainic acid (0.252-2 mole), or strychnine (1.35-10.78 nmol) injected intracerebroventricularly. The number of animals with convulsions after each dose was recorded. Analysis of statistical significance was based on the log-probit lines of the quantal dose-response for the respective control and test groups, calculated 50% effective doses (ED50), the potency ratios (ED50higher/ED50lower) and their 95% confidence limits.

Results

Propofol pretreatment decreased the potency ratio of both bicuculline (0.47, 95% confidence interval = 0.23-0.94) and picrotoxin (0.61, 0.47-0.79), signifying an anticonvulsant effect. Conversely, propofol pretreatment significantly enhanced the convulsive potency of kainic acid (potency ratio and 95% confidence interval = 1.66, 1.21-2.29), quisqualic acid (3.17, 1.98-5.09), and strychnine (1.76, 0.79-3.89).

Conclusions

Current results suggest that propofol augments the paroxysmal motor phenomenon induced by kainic acid, quisqualic acid, and strychnine. This action may be, at least partly, responsible for the motor manifestations reported after propofol administration. These in vivo results on modulation of gamma-aminobutyric acid, glycine, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, and kainate receptor-mediated transmission may be of significance in understanding the mechanism of propofol action at the excitatory and inhibitory amino acid receptors.
The Effect of Anesthetic Technique on Postoperative Outcomes in Hip Fracture Repair
Authors: O’Hara Dorene A. , Duff Amy , Berlin Jesse A. , Poses Roy M. , Lawrence Valerie A. , Huber Elizabeth C. , Noveck Helaine , Strom Brian L. , Carson Jeffrey L.
Published: August 2004

Background

The impact of anesthetic choice on postoperative mortality and morbidity has not been determined with certainty.

Methods

The authors evaluated the effect of type of anesthesia on postoperative mortality and morbidity in a retrospective cohort study of consecutive hip fracture patients, aged 60 yr or older, who underwent surgical repair at 20 US hospitals between 1983 and 1993. The primary outcome was defined as death within 30 days of the operative procedure. The secondary outcomes were postoperative 7-day mortality, postoperative myocardial infarction, postoperative pneumonia, postoperative congestive heart failure, and postoperative change in mental status. Numerous comorbid conditions were controlled for individually and by several comorbidity indices using logistic regression.

Results

General anesthesia was used in 6,206 patients (65.8%) and regional anesthesia in 3,219 patients (3,078 spinal anesthesia and 141 epidural anesthesia). The 30-day mortality rate in the general anesthesia group was 4.4%, compared with 5.4% in the regional anesthesia group (unadjusted odds ratio = 0.80; 95% confidence interval = 0.66-0.97). However, the adjusted odds ratio for general anesthesia increased to 1.08 (0.84-1.38). The adjusted odds ratios for general anesthesia versus regional anesthesia for the 7-day mortality was 0.90 (0.59-1.39) and for postoperative morbidity outcomes were as follows: myocardial infarction: adjusted odds ratio = 1.17 (0.80-1.70); congestive heart failure: adjusted odds ratio = 1.04 (0.80-1.36); pneumonia: adjusted odds ratio = 1.21 (0.87-1.68); postoperative change in mental status: adjusted odds ratio = 1.08 (0.95-1.22).

Conclusions

The authors were unable to demonstrate that regional anesthesia was associated with better outcome than was general anesthesia in this large observational study of elderly patients with hip fracture. These results suggest that the type of anesthesia used should depend on factors other than any associated risks of mortality or morbidity.
The Incidence and Mechanisms of Pharyngeal and Upper Esophageal Dysfunction in Partially Paralyzed Humans
Authors: Sundman Eva , Witt Hanne , Olsson Rolf , Ekberg Olle , Kuylenstierna Richard , Eriksson Lars I.
Published: August 2004

Background

Residual neuromuscular block caused by vecuronium alters pharyngeal function and impairs airway protection. The primary objectives of this investigation were to radiographically evaluate the swallowing act and to record the incidence of and the mechanism behind pharyngeal dysfunction during partial neuromuscular block. The secondary objective was to evaluate the effect of atracurium on pharyngeal function.

Methods

Twenty healthy volunteers were studied while awake during liquid-contrast bolus swallowing. The incidence of pharyngeal dysfunction was studied by fluoroscopy. The initiation of the swallowing process, the pharyngeal coordination, and the bolus transit time were evaluated. Simultaneous manometry was used to document pressure changes at the tongue base, the pharyngeal constrictor muscles, and the upper esophageal sphincter. After control recordings, an intravenous infusion of atracurium was administered to obtain train-of-four ratios (T4/T1) of 0.60, 0.70, and 0.80, followed by recovery to a train-of-four ratio of more than 0.90.

Results

The incidence of pharyngeal dysfunction was 6% during the control recordings and increased (P < 0.05) to 28%, 17%, and 20% at train-of-four ratios 0.60, 0.70, and 0.80, respectively. After recovery to a train-of-four ratio of more than 0.90, the incidence was 13%. Pharyngeal dysfunction occurred in 74 of 444 swallows, the majority (80%) resulting in laryngeal penetration. The initiation of the swallowing reflex was impaired during partial paralysis (P = 0.0081). The pharyngeal coordination was impaired at train-of-four ratios of 0.60 and 0.70 (P < 0.01). A marked reduction in the upper esophageal sphincter resting tone was found, as well as a reduced contraction force in the pharyngeal constrictor muscles. The bolus transit time did not change significantly.

Conclusion

Partial neuromuscular paralysis caused by atracurium is associated with a four- to fivefold increase in the incidence of misdirected swallowing. The mechanism behind the pharyngeal dysfunction is a delayed initiation of the swallowing reflex, impaired pharyngeal muscle function, and impaired coordination. The majority of misdirected swallows resulted in penetration of bolus to the larynx.
Investigation of Effective Anesthesia Induction Doses Using a Wide Range of Infusion Rates with Undiluted and Diluted Propofol
Authors: Kazama Tomiei , Ikeda Kazuyuki , Morita Koji , Kikura Mutsuhito , Ikeda Takehiko , Kurita Tadayoshi , Sato Shigehito
Published: August 2004

Background

The influence of infusion rate on the induction dose-response relation has not been investigated over a wide range of infusion rates. In this study, the authors defined the effect of different propofol infusion rates on the times and doses necessary to reach clinical induction of anesthesia.

Methods

The subjects of the study were 250 patients classified as American Society of Anesthesiologists physical status I or II aged 25-55 yr. For induction with undiluted propofol, 180 patients were allocated randomly to one of two groups of 90 patients each (A and B). Each group was further divided into nine subgroups (10 patients each) that were administered propofol infusion at rates of 10, 15, 20, 30, 40, 60, 100, 200, and 300 mg/kg-1/h-1. The remaining 70 patients (group C) were allocated randomly into seven subgroups (10 patients each), and these groups were induced with diluted propofol (0.5 mg/ ml) at the rates of 10, 15, 30, 60, 100, 200, and 300 mg/kg-1/ h-1. Group B was given crystalloid at the same infusion rates as group C via a catheter in the opposite arm. Induction time, induction dose, plasma arterial propofol concentration at loss of consciousness, and percentage decrease of systolic blood pressure were measured. A previously reported three-compartment model with an effect-site rate constant for propofol of 0.456/min was used to predict the induction time and dose at each infusion rate.

Results

The differences between predicted induction time and dose and the observed time and dose could be explained by factoring in the lag time from infusion site to central compartment (lag time circulation) and the amount of propofol in transit during this time (residual dose circulation). Residual dose circulation and lag time circulation correlated with infusion time from 20 to 60 s for undiluted and from 0 to 40 s for diluted propofol. At the infusion rates greater than 80 mg/kg-1/h-1, rapid circulation because of incomplete mixing in the central compartment decreased the excess induction time and dose. The use of diluted propofol significantly attenuated the decrease in systolic blood pressure provoked by the residual dose circulation.

Conclusions

Induction dose and time are dependent on infusion rate in a complex manner, and residual dose circulation was a factor in overdose and hemodynamic depression. Hypotension during induction was attenuated by diluted propofol.
Transesophageal Echocardiographic Hemodynamic Monitoring during Preoperative Acute Normovolemic Hemodilution
Authors: Bak Zoltan , Abildgård Lars , Lisander Björn , Janerot-Sjöberg Birgitta
Published: August 2004

Background

Preoperative acute normovolemic hemodilution may compromise oxygen transport. The aims of our study were to describe the hemodynamic effects of normovolemic hemodilution and to determine its effect on systolic and diastolic cardiac function by multiplane transesophageal echocardiography.

Methods

In eight anesthetized patients (aged 13-51 yr) without heart disease, hemoglobin was reduced in steps from 123 +/- 8 (mean +/- SD) to 98 +/- 3 and to 79 +/- 5 g/l. Hemodynamic measurements (intravascular pressures, thermodilution cardiac output, and echocardiographic recordings) were obtained during a stabilization period and at each level of hemodilution. Left ventricular wall motion was monitored continuously, and Doppler variables, annular motion, and changes in ejection fractional area were analyzed off-line.

Results

During hemodilution, cardiac output by thermodilution increased by 16 +/- 7% and 26 +/- 10%, corresponding well to the increase in cardiac output as measured by Doppler (difference, 0.32 +/- 1.2 l/min). Systemic vascular resistance fell 16 +/- 14% and 23 +/- 9% and pulmonary capillary wedge pressure increased slightly (2 +/- 2 mmHg), whereas other pressures, heart rate, wall motion, and diastolic Doppler variables remained unchanged. Ejection fractional area change increased from 44 +/- 7% to 54 +/- 10% and 60 +/- 9% as a result of reduced end-systolic and increased end-diastolic left ventricular areas.

Conclusions

A reduction in hemoglobin to 80 g/l during acute normovolemic hemodilution does not normally compromise systolic or diastolic myocardial function as determined by transesophageal echocardiography. Preload, left ventricular ejection fraction, and cardiac output increase with a concomitant fall in systemic vascular resistance.
Ophthalmic Regional Anesthesia: Medial Canthus Episcleral (Sub-Tenon) Anesthesia Is More Efficient than Peribulbar Anesthesia
Authors: Ripart Jacques , Lefrant Jean-Yves , Vivien Bruno , Charavel Pierre , Fabbro-Peray Pascale , Jaussaud Alain , Dupeyron Gerard , Eledjam Jean-Jacques
Published: August 2004

Background

Regional anesthesia and especially peribulbar anesthesia commonly is used for cataract surgery. Failure rates and need for reinjection remains high, however, with peribulbar anesthesia. Single-injection high-volume medial canthus episcleral (sub-Tenon's) anesthesia has proven to be an efficient and safe alternative to peribulbar anesthesia.

Methods

The authors, in a blind study, compared the effectiveness of both techniques in 66 patients randomly assigned to episcleral anesthesia or single-injection peribulbar anesthesia. Motor blockade (akinesia) was used as the main index of anesthesia effectiveness. It was assessed using an 18-point scale (0-3 for each of the four directions of the gaze, lid opening, and lid closing, the total being from 0 = normal mobility to 18 = no movement at all). This score was compared between the groups 1, 5, 10, and 15 min after injection and at the end of the surgical procedures. Time to onset of the blockade also was compared between the two groups, as was the incidence of incomplete blockade with a need for supplemental injection and the satisfaction of the surgeon, patient, and anesthesiologist.

Results

Episcleral anesthesia provided a quicker onset of anesthesia, a better akinesia score, and a lower rate of incomplete blockade necessitating reinjection (0 vs. 39%; P < 0.0001) than peribulbar anesthesia. Even after supplemental injection, peribulbar anesthesia had a lower akinesia score than did episcleral anesthesia. Peribulbar anesthesia began to wear off during surgery, whereas episcleral anesthesia did not.

Conclusion

Medial canthus single-injection episcleral anesthesia is a suitable alternative to peribulbar anesthesia. It provides better akinesia, with a quicker onset and more constancy in effectiveness.
Patients with Diabetic Neuropathy Are at Risk of a Greater Intraoperative Reduction in Core Temperature
Authors: Kitamura Akira , Hoshino Takeshi , Kon Tadashi , Ogawa Ryo
Published: August 2004

Background

Core hypothermia develops after the induction of general anesthesia, but intraoperative vasoconstriction usually prevents its progression. However, diabetes mellitus is often associated with autonomic neuropathy, which leads to abnormal peripheral neurovascular function. Accordingly, we tested the hypothesis that diabetic patients experience a greater reduction in core temperature during general anesthesia than nondiabetic patients.

Methods

We studied 36 nondiabetic patients (control group) and 27 diabetic patients (diabetic group) undergoing elective abdominal surgery. Both groups were divided into young (< 60 yr) and older age (>/= 60 yr) groups. Standard noninvasive autonomic tests (heart rate variation at deep periodical breathing, Valsalva maneuver, and head-up tilt) were carried out for each patient. The relation between the results of these tests of autonomic function and the tympanic membrane temperature during general anesthesia was assessed in relation to peripheral vasoconstriction.

Results

Thirteen patients in the diabetic group showed abnormal responses to two or more of the basal autonomic function tests (patients with autonomic dysfunction). Changes in core temperature among the groups were similar at 90 min after the induction of anesthesia. However, the core temperature of the diabetic patients with autonomic dysfunction was lower from 120 min (35.1 degrees C) onward compared with the young or older nondiabetic patients and the diabetic patients with normal autonomic function. Peripheral vasoconstriction, evaluated using the forearm-fingertip skin surface temperature gradient, was delayed in patients with autonomic dysfunction compared with the others.

Conclusions

The current results indicate that diabetic autonomic neuropathy is associated with more severe intraoperative hypothermia. We postulate that diabetic patients become more hypothermic because their peripheral neuropathy delays the onset of thermoregulatory vasoconstriction and reduces its efficacy once triggered. These patients may therefore fail to develop a normal core temperature plateau.
Predictors of Hypothermia during Spinal Anesthesia
Authors: Frank Steven M. , El-Rahmany Hossam K. , Cattaneo Christine G. , Barnes Rachel A.
Published: August 2004

Background

Body temperature often is ignored during regional anesthesia, despite evidence that hypothermia occurs commonly. Because hypothermia is associated with adverse clinical outcomes, it is important to recognize predictors of hypothermia and to monitor and control body temperature in patients at risk. The current study was designed to determine the predictors of core hypothermia in patients receiving spinal anesthesia for radical retropubic prostatectomy.

Methods

Forty-four patients undergoing radical retropubic prostatectomy were studied. A lumbar intrathecal injection of 18-22 mg bupivacaine, 0.75%, with 20 microg fentanyl was given. No active warming measures were used other than intravenous fluid warming. The following clinical variables were assessed as potential predictors of core (tympanic) temperature at admission to the postanesthesia care unit: duration of surgery, average ambient operating room temperature, body habitus, age, and spinal blockade level.

Results

The mean core temperature at admission to the postanesthesia care unit was 35.1 +/- 0.6 degrees C (range, 33.6-36.3 degrees C). Duration of surgery, ambient operating room temperature, and body habitus were not predictors of hypothermia. A high level of spinal blockade and increasing age were predictors of hypothermia. For each incremental increase in block level, core temperature decreased by 0.15 degrees C, and for each increase in age, core temperature decreased by 0.3 degrees C.

Conclusions

Although high-level spinal blockade has been associated with decreased thermoregulatory thresholds, no previous study has shown that a higher level of blockade is associated with a greater magnitude of core hypothermia in the clinical setting. As with general anesthesia, advanced age is associated with hypothermia during spinal anesthesia.
The Action of Sevoflurane on Vascular Smooth Muscle of Isolated Mesenteric Resistance Arteries (Part 2)
Authors: Akata Takashi , Izumi Kaoru , Nakashima Mikio
Published: August 2004

Background

The precise mechanisms behind the direct inhibitory action of sevoflurane on vascular smooth muscle have not been fully elucidated.

Methods

Endothelium-denuded smooth muscle strips were prepared from rat small mesenteric arteries. Isometric force and intracellular Ca2+ concentration ([Ca2+]i) were measured simultaneously in the fura-2-loaded strips. In another series of experiments, only isometric force was measured in the beta-escin-membrane-permeabilized strips.

Results

Sevoflurane (3-5%) inhibited the increases in both the [Ca2+]i and the force induced by either norepinephrine (0.5-10 microm) or 40 mm K+. Sevoflurane still inhibited the increase in [Ca2+]i induced by norepinephrine after depletion of intracellular Ca2+ stores with ionomycin, although it little influenced the increase in [Ca2+]i induced by norepinephrine after treatment with verapamil. In the fura-2-loaded membrane-intact muscle, sevoflurane caused a rightward shift of Ca2+-force relation during force development to stepwise increment of extracellular Ca2+ concentration during 40-mm K+ depolarization in either the presence or the absence of norepinephrine. In contrast, sevoflurane did not influence Ca2+-activated contraction in the beta-escin-permeabilized muscle, in which alpha-adrenergic receptor coupling was not retained.

Conclusions

The inhibitory effects of sevoflurane on both norepinephrine- and potassium chloride (KCl)-induced contractions are caused by reduction of [Ca2+]i in vascular smooth muscle and inhibition of the myofilament Ca2+ sensitivity. The [Ca2+]i-reducing effect of sevoflurane observed in both the norepinephrine- and the K+-stimulated muscle is mainly caused by inhibition of voltage-gated Ca2+ influx. The inhibitory effect of sevoflurane on Ca2+ activation of contractile proteins seems to be mediated by the cell membrane or by some diffusible substances that are lost in the beta-escin-permeabilized cells.
Magnesium Increases Morphine Analgesic Effect in Different Experimental Models of Pain
Authors: Begon Sophie , Pickering Gisèle , Eschalier Alain , Dubray Claude
Published: August 2004

Background

An excess of excitatory pathway activation via N-methyl-D-aspartate (NMDA) receptors has been described in neuropathic pain that responds poorly to morphine. However, in this situation, several published data sets show that coadministration of NMDA receptor antagonists restores the efficacy of opioids. Considering that magnesium behaves like an NMDA receptor antagonist, we investigated the effect of the combination of magnesium and morphine in experimental models of chronic and tonic pain.

Methods

Mechanical hyperalgesia was assessed with the paw-pressure test in mononeuropathic (chronic constrictive injury model) and diabetic rats. Behavioral reactions were scored in a model of inflammation induced by formalin. The animals were assigned to one of three groups according to the intraperitoneal pretreatment: magnesium (30 mg/kg x 3), magnesium (30 mg/kg), and saline. Before testing, morphine was injected intravenously in mononeuropathic (0.3 mg/kg) and diabetic rats (1 mg/kg) and by the subcutaneous route in rats with the formalin test (1.5 mg/kg).

Results

Magnesium alone induced a significant antihyperalgesic effect in mononeuropathic and diabetic rats after a cumulative dose of 90 mg/kg. Furthermore, it significantly increased morphine analgesia, regardless of the loading dose used (30 or 90 mg/kg) in the two models of neuropathic pain. In the formalin test, magnesium alone did not have a significant effect. However, in combination with morphine, it revealed the analgesic effect of this opiate.

Conclusions

These data show that magnesium amplifies the analgesic effect of low-dose morphine in conditions of sustained pain. Considering the good tolerability of magnesium, these findings may have clinical applications in neuropathic and persistent pain.
Comparison of the Effects of Racemic Bupivacaine, Levobupivacaine, and Ropivacaine on Ventricular Conduction, Refractoriness, and Wavelength
Authors: Aya Antoine G. M. , de La Coussaye Jean E. , Robert Emmanuelle , Ripart Jacques , Cuvillon Philippe , Mazoit Jean Xavier , Jeannes Pascal , Fabbro-Péray Pascale , Eledjam Jean-Jacques
Published: August 2004

Background

The study was designed to compare the effects of equimolar concentrations of racemic bupivacaine, levobupivacaine, and ropivacaine on ventricular conduction, anisotropy, duration and homogeneity of refractoriness, and wavelengths, and to provide a potency ratio for effects on conduction velocity.

Methods

Isolated frozen rabbit hearts (which leave a thin layer of surviving epicardial muscle) were treated with 0.1, 1, and 10 mum racemic bupivacaine, levobupivacaine, or ropivacaine. Left ventricular longitudinal and transverse conduction velocities, anisotropic ratio, minimum pacing cycle length, use dependency, duration and dispersion of ventricular effective refractory period, and wavelengths were studied. A high-resolution mapping system was used for data acquisition. In addition to two-way analysis of variance for repeated measures, data for conduction velocities were fitted simultaneously using a nonlinear mixed-effect modeling program to allow intergroup comparison.

Results

Each agent induced a concentration- and use-dependent slowing of conduction velocities, with no change of the anisotropic ratio. The use-dependent effect of levobupivacaine is similar to that of racemic bupivacaine concerning longitudinal conduction velocity. Fitting of conduction velocities provided a racemic bupivacaine to levobupivacaine and to ropivacaine ratio of 1:1.38 for concentration effect at 1,000-ms pacing cycle length, and 1:0.74 for use-dependent effect at 600-ms pacing cycle length. Racemic bupivacaine and levobupivacaine prolonged the ventricular effective refractory period, whereas ropivacaine did not. No dispersion in ventricular effective refractory period values occurred. All three agents induced significant decreases in wavelengths. This effect was not different among groups.

Conclusions

Differences among racemic bupivacaine, levobupivacaine, and ropivacaine at equimolar concentrations are mainly caused by the use-dependent effects on conduction velocities and the concentration-dependent effects on ventricular effective refractory period. Therefore, one must take into account the corresponding pacing rates when comparing the potency ratios of local anesthetics.
Effects of Dantrolene on Extracellular Glutamate Concentration and Neuronal Death in the Rat Hippocampal CA1 Region Subjected to Transient Ischemia
Authors: Nakayama Ryosuke , Yano Toshiyuki , Ushijima Kazuo , Abe Eiji , Terasaki Hidenori
Published: August 2004

Background

Excessive extracellular glutamate produced by cerebral ischemia has been proposed to initiate the cascade toward neuronal cell death. Changes in extracellular glutamate concentration are closely linked to changes in intracellular calcium ion concentration. Dantrolene inhibits calcium release from intracellular calcium stores. In this study, the authors investigated the effects of dantrolene on extracellular glutamate accumulation and neuronal degeneration in a rat model of transient global forebrain ischemia.

Methods

Male Wistar rats weighing 230-290 g were anesthetized with halothane in nitrous oxide-oxygen and were subjected to 10 min of transient forebrain ischemia using a four-vessel occlusion technique. Fifteen minutes before ischemic injury, dantrolene sodium (5 mm), dimethyl sulfoxide as a vehicle for dantrolene, or artificial cerebrospinal fluid as a control was intracerebroventricularly administered (n = 8 in each group). In the hippocampal CA1 subfield, the extracellular glutamate concentration in vivo was measured during the periischemic period with a microdialysis biosensor, and the number of intact neurons was evaluated on day 7 after reperfusion.

Results

Both dantrolene and dimethyl sulfoxide significantly reduced the ischemia-induced increase in glutamate concentration to a similar extent, i.e., by 53 and 51%, respectively, compared with artificial cerebrospinal fluid (P < 0.01). The number of intact hippocampal CA1 neurons (mean +/- SD; cells/mm) in dantrolene-treated rats (78 +/- 21) was significantly higher than that in artificial cerebrospinal fluid- (35 +/- 14; P < 0.001) and dimethyl sulfoxide-treated (56 +/- 11; P < 0.05) animals. Dimethyl sulfoxide also significantly increased the number of preserved neurons in comparison with artificial cerebrospinal fluid (P < 0.05).

Conclusions

Intracerebroventricular dantrolene prevents delayed neuronal loss in the rat hippocampal CA1 region subjected to transient ischemia; however, this neuroprotection cannot be accounted for only by the reduced concentrations of extracellular glutamate during ischemia.
Effects of Recruiting Maneuvers in Patients with Acute Respiratory Distress Syndrome Ventilated with Protective Ventilatory Strategy
Authors: Grasso Salvatore , Mascia Luciana , Del Turco Monica , Malacarne Paolo , Giunta Francesco , Brochard Laurent , Slutsky Arthur S. , Marco Ranieri V.
Published: August 2004

Background

A lung-protective ventilatory strategy with low tidal volume (VT) has been proposed for use in acute respiratory distress syndrome (ARDS). Alveolar derecruitment may occur during the use of a lung-protective ventilatory strategy and may be prevented by recruiting maneuvers. This study examined the hypothesis that the effectiveness of a recruiting maneuver to improve oxygenation in patients with ARDS would be influenced by the elastic properties of the lung and chest wall.

Methods

Twenty-two patients with ARDS were studied during use of the ARDSNet lung-protective ventilatory strategy: VT was set at 6 ml/kg predicted body weight and positive end-expiratory pressure (PEEP) and inspiratory oxygen fraction (Fio2) were set to obtain an arterial oxygen saturation of 90-95% and/or an arterial oxygen partial pressure (Pao2) of 60- 80 mmHg (baseline). Measurements of Pao2/Fio2, static volume-pressure curve, recruited volume (vertical shift of the volume-pressure curve), and chest wall and lung elastance (EstW and EstL: esophageal pressure) were obtained on zero end-expiratory pressure, at baseline, and at 2 and 20 min after application of a recruiting maneuver (40 cm H2O of continuous positive airway pressure for 40 s). Cardiac output (transesophageal Doppler) and mean arterial pressure were measured immediately before, during, and immediately after the recruiting maneuver. Patients were classified a priori as responders and nonresponders on the basis of the occurrence or nonoccurrence of a 50% increase in Pao2/Fio2 after the recruiting maneuver.

Results

Recruiting maneuvers increased Pao2/Fio2 by 20 +/- 3% in nonresponders (n = 11) and by 175 +/- 23% (n = 11; mean +/- standard deviation) in responders. On zero end-expiratory pressure, EstL (28.4 +/- 2.2 vs. 24.2 +/- 2.9 cm H2O/l) and EstW (10.4 +/- 1.8 vs. 5.6 +/- 0.8 cm H2O/l) were higher in nonresponders than in responders (P < 0.01). Nonresponders had been ventilated for a longer period of time than responders (7 +/- 1 vs. 1 +/- 0.3 days; P < 0.001). Cardiac output and mean arterial pressure decreased by 31 +/- 2 and 19 +/- 3% in nonresponders and by 2 +/- 1 and 2 +/- 1% in responders (P < 0.01).

Conclusions

Application of recruiting maneuvers improves oxygenation only in patients with early ARDS who do not have impairment of chest wall mechanics and with a large potential for recruitment, as indicated by low values of EstL.
Perioperative Visual Changes
Authors: Warner Mary E. , Fronapfel Paul J. , Hebl James R. , Herman David C. , Warner David O. , Decker Paul , Warner Mark A.
Published: August 2004

Background

The goal of this project was to describe the frequency and natural history of perioperative changes in vision.

Methods

The authors performed a prospective evaluation of changes in visual accommodation and acuity in adult patients undergoing various surgical procedures. Patients were evaluated preoperatively and at 1 and 3 days postoperatively. For patients who had persistent blurring of vision on the third postoperative day, surveillance was extended to 1.5 yr to determine how long the visual changes persisted and if the patients required eye-care provider attention for the condition.

Results

Twenty-eight of 671 patients (4.2%) reported new onset of blurred vision lasting at least 3 days after surgery. Seven of these 28 patients (1% of total) required either new corrective lens or changes in eyeglass or contact prescriptions because of persistent blurry vision. Most of the remaining patients reported resolution of blurry vision within 1 to 2 months. No significant risk factors for this problem were identified.

Conclusions

In this surgical population, changes in visual acuity manifest primarily by blurred vision were reported at a surprisingly high frequency. For many of these patients, the blurring resolved within 2 months without complication, but 25% of patients who had blurred vision for 3 days or longer required visits to eye-care providers and either new corrective lens or changes in existing prescriptions.
Peripheral Antinociceptive Action of Morphine and the Synergistic Interaction with Lamotrigine
Authors: Argüelles Carlos F. , Torres-López Jorge E. , Granados-Soto Vinicio
Published: August 2004

Background

Lamotrigine inhibits glutamate release through the preferential blockade of voltage-dependent Na+ channels. In contrast, morphine reduces release of excitatory amino acids through the activation of opioid receptors and also inhibits tetrodotoxin-resistant Na+ channels on peripheral afferent neurons. The current study was designed to investigate the antinociceptive effects of locally administered morphine and lamotrigine. The interaction between morphine and lamotrigine at the periphery was also examined.

Methods

Morphine, lamotrigine, or a combination of morphine and lamotrigine was administered locally to female Wistar rats, and the antinociceptive effect was determined in the formalin test. Isobolographic analyses were used to define the nature of the functional interactions between morphine and lamotrigine.

Results

Peripheral administration of either morphine or lamotrigine produced a dose-related antinociceptive effect. Isobolographic analyses revealed that peripheral morphine and lamotrigine interacted synergistically in the formalin test.

Conclusions

The study shows a functional interaction between lamotrigine and morphine at the peripheral level.
Radical Scavengers Protect Murine Lungs from Endotoxin-induced Hyporesponsiveness to Inhaled Nitric Oxide
Authors: Raveh Yehuda , Ichinose Fumito , Orbach Pini , Bloch Kenneth D. , Zapol Warren M.
Published: August 2004

Background

Sepsis is associated with an impaired pulmonary vasodilator response to inhaled nitric oxide (NO). A combination of NO and other inflammatory mediators appears to be responsible for endotoxin-induced pulmonary vascular hyporesponsiveness to inhaled NO. The authors investigated whether scavengers of reactive oxygen species could preserve inhaled NO responsiveness in endotoxin-challenged mice.

Methods

The vasorelaxation to inhaled NO was studied in isolated, perfused, and ventilated lungs obtained from mice 16 h after an intraperitoneal challenge with saline or 50 mg/kg Escherichia coli lipopolysaccharide. In some mice, challenge with saline or lipopolysaccharide was followed by intraperitoneal administration of N-acetylcysteine, dimethylthiourea, EUK-8, or polyethylene glycol-conjugated catalase.

Results

The pulmonary vasodilator response of U46619-preconstricted isolated lungs to ventilation with 0.4, 4, and 40 ppm inhaled NO in lipopolysaccharide-challenged mice was reduced to 32, 43, and 60%, respectively, of that observed in saline-challenged mice (P < 0.0001). Responsiveness to inhaled NO was partially preserved in lipopolysaccharide-challenged mice treated with a single dose of N-acetylcysteine (150 or 500 mg/kg) or 20 U/g polyethylene glycol-conjugated catalase (all P < 0.05 vs. lipopolysaccharide alone). Responsiveness to inhaled NO was fully preserved by treatment with either dimethylthiourea, EUK-8, two doses of N-acetylcysteine (150 mg/kg administered 3.5 h apart), or 100 U/g polyethylene glycol-conjugated catalase (all P < 0.01 vs. lipopolysaccharide alone).

Conclusions

When administered to mice concurrently with lipopolysaccharide challenge, reactive oxygen species scavengers prevent impairment of pulmonary vasodilation to inhaled NO. Therapy with scavengers of reactive oxygen species may provide a means to preserve pulmonary vasodilation to inhaled NO in sepsis-associated acute lung injury.