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Biomedical subjects

D I Sessler

Publications and source records attributed to D I Sessler.

At least 55 records · Page 3Linked to original sources
PubMed2001

Recovery of intraoperative microbicidal and inflammatory functions of alveolar immune cells after a tobacco smoke-free period.

BACKGROUND: Tobacco smoking inhibits alveolar macrophage function, but cessation of smoking markedly reduces the risk of postoperative pulmonary complications. The authors therefore evaluated the effect of nonsmoking duration on both antimicrobial and inflammatory functions of alveolar macrophages during anesthesia and surgery. METHODS: The authors studied 15 patients who had never smoked, 15 current smokers, and 41 former smokers, all of whom underwent general anesthesia. Former smokers were further allocated to one of three groups depending on their smoke-free periods: 2 months (n = 13), 3-5 months (n = 13), and 6-12 months (n = 15). Alveolar immune cells were collected by bronchoalveolar lavage immediately after induction of anesthesia, at 2 and 4 h after induction of anesthesia, and at the end of surgery. Opsonized and nonopsonized phagocytosis were measured. Microbicidal activity was determined as the ability of the macrophages to kill Listeria monocytogenes directly. Finally, we determined the expression of proinflammatory cytokines, including interleukin 1beta, interleukin 8, interferon gamma, and tumor necrosis factor alpha, and of antiinflammatory cytokines (interleukin 4 and 10) by semiquantitative polymerase chain reaction. RESULTS: Nonopsonized and opsonized phagocytosis and microbicidal activity of alveolar macrophages (antimicrobial functions) decreased 20-50%, and the expression of genes for all proinflammatory and antiinflammatory cytokines increased 3-30-fold over time in all groups. Starting 4 h after induction of anesthesia, the decreases in antimicrobial functions were 1.5-3 times greater in current and former smokers (2 months' abstinence) than in patients who had never smoked. Starting 4 h after anesthesia, the increase in expression of all cytokines, except interleukin 8, was twofold to fivefold less in current and former smokers (2-6 months' abstinence) than in patients who had never smoked. CONCLUSION: Our data suggest that former smokers may have a limited ability to mount effective pulmonary immune defenses for long as 6 months after stopping cigarette use.

Adult↗
PubMed2001

Body morphology and the speed of cutaneous rewarming.

BACKGROUND: Infants and children cool quickly because their surface area (and therefore heat loss) is large compared with their metabolic rate, which is mostly a function of body mass. Rewarming rate is a function of cutaneous heat transfer plus metabolic heat production divided by body mass. Therefore, the authors tested the hypothesis that the rate of forced-air rewarming is inversely related to body size. METHODS: Isoflurane, nitrous oxide, and fentanyl anesthesia were administered to infants, children, and adults scheduled to undergo hypothermic neurosurgery. All fluids were warmed to 37 degrees C and ambient temperature was maintained near 21 degrees C. Patients were covered with a full-body, forced-air cover of the appropriate size. The heater was set to low or ambient temperature to reduce core temperature to 34 degrees C in time for dural opening. Blower temperature was then adjusted to maintain core temperature at 34 degrees C for 1 h. Subsequently, the forced-air heater temperature was set to high (approximately 43 degrees C). Rewarming continued for the duration of surgery and postoperatively until core temperature exceeded 36.5 degrees C. The rewarming rate in individual patients was determined by linear regression. RESULTS: Rewarming rates were highly linear over time, with correlations coefficients (r2) averaging 0.98+/-0.02. There was a linear relation between rewarming rate (degrees C/h) and body surface area (BSA; m2): Rate (degrees C/h) = -0.59 x BSA (m2) + 1.9, r2 = 0.74. Halving BSA thus nearly doubled the rewarming rate. CONCLUSIONS: Infants and children rewarm two to three times faster than adults, thus rapidly recovering from accidental or therapeutic hypothermia.

Adult↗
PubMed2001

Preoperative intradermal acupuncture reduces postoperative pain, nausea and vomiting, analgesic requirement, and sympathoadrenal responses.

BACKGROUND: In a controlled and double-blind study, the authors tested the hypothesis that preoperative insertion of intradermal needles at acupoints 2.5 cm from the spinal vertebrae (bladder meridian) provide satisfactory postoperative analgesia. METHODS: The authors enrolled patients scheduled for elective upper and lower abdominal surgery. Before anesthesia, patients undergoing each type of surgery were randomly assigned to one of two groups: acupuncture (n = 50 and n = 39 for upper and lower abdominal surgery, respectively) or control (n = 48 and n = 38 for upper and lower abdominal surgery, respectively). In the acupuncture group, intradermal needles were inserted to the left and right of bladder meridian 18-24 and 20-26 in upper and lower abdominal surgery before induction of anesthesia, respectively. Postoperative analgesia was maintained with epidural morphine and bolus doses of intravenous morphine. Consumption of intravenous morphine was recorded. Incisional pain at rest and during coughing and deep visceral pain were recorded during recovery and for 4 days thereafter on a four-point verbal rating scale. We also evaluated time-dependent changes in plasma concentrations of cortisol and catecholamines. RESULTS: Starting from the recovery room, intradermal acupuncture increased the fraction of patients with good pain relief as compared with the control (P < 0.05). Consumption of supplemental intravenous morphine was reduced 50%, and the incidence of postoperative nausea was reduced 20-30% in the acupuncture patients who had undergone either upper or lower abdominal surgery (P < 0.01). Plasma cortisol and epinephrine concentrations were reduced 30-50% in the acupuncture group during recovery and on the first postoperative day (P < 0.01). CONCLUSION: Preoperative insertion of intradermal needles reduces postoperative pain, the analgesic requirement, and opioid-related side effects after both upper and lower abdominal surgery. Acupuncture analgesia also reduces the activation of the sympathoadrenal system that normally accompanies surgery.

Abdomen↗
PubMed2001

Effectiveness of resistive heating compared with passive warming in treating hypothermia associated with minor trauma: a randomized trial.

OBJECTIVES: To determine the occurrence of hypothermia in patients with minor trauma, to test the hypotheses that resistive heating during transport is effective treatment for hypothermia and that this treatment reduces patients' thermal discomfort, pain, and fear, and to evaluate the accuracy of oral temperatures obtained at the scene of injury. PATIENTS AND METHODS: In December 1999 and January 2000, 100 patients with minor trauma were randomly assigned to passive warming or resistive heating. All patients were covered with a carbon-fiber resistive warming blanket and a wool blanket, but the warming blanket was activated only in those assigned to resistive heating. Core (tympanic membrane) and oral temperatures, heart rate, pain, fear, and overall satisfaction of patients were compared between the 2 groups on arrival at a hospital. RESULTS: Hypothermia was noted in 80 patients at the time of rescue. Mean initial core temperatures were 35.4 degrees C (95% confidence interval [CI], 35.2 degrees C - 35.6 degrees C) in the patients who received passive warming and 35.3 degrees C (95% CI, 35.1 degrees C - 35.5 degrees C) in those who received resistive heating. From the time of rescue until arrival at the hospital, mean core temperature decreased 0.4 degrees C/h (95% CI, 0.3 degrees C/h - 0.5 degrees C/h) with passive warming, whereas it increased 0.8 degrees C/h (95% CI, 0.7 degrees C/h - 0.9 degrees C/h) with resistive heating. Oral and tympanic membrane temperatures were similar. Mean heart rate decreased 23 beats/min in those assigned to resistive heating but remained unchanged in those assigned to passive warming. Patients in the resistive heating group felt warmer, had less pain and anxiety, and overall were more satisfied with their care. CONCLUSIONS: Oral temperatures are sufficiently accurate for field use. Hypothermia is common even in persons with minor trauma. Resistive heating during transport augments thermal comfort, increases core temperature, reduces pain and anxiety, and improves overall patient satisfaction.

Aged↗
PubMed2000

Supplemental perioperative oxygen to reduce the incidence of surgical-wound infection.

BACKGROUND: Destruction by oxidation, or oxidative killing, is the most important defense against surgical pathogens and depends on the partial pressure of oxygen in contaminated tissue. An easy method of improving oxygen tension in adequately perfused tissue is to increase the concentration of inspired oxygen. We therefore tested the hypothesis that the supplemental administration of oxygen during the perioperative period decreases the incidence of wound infection. METHODS: We randomly assigned 500 patients undergoing colorectal resection to receive 30 percent or 80 percent inspired oxygen during the operation and for two hours afterward. Anesthetic treatment was standardized, and all patients received prophylactic antibiotic therapy. With use of a double-blind protocol, wounds were evaluated daily until the patient was discharged and then at a clinic visit two weeks after surgery. We considered wounds with culture-positive pus to be infected. The timing of suture removal and the date of discharge were determined by the surgeon, who did not know the patient's treatment-group assignment. RESULTS: Arterial oxygen saturation was normal in both groups; however, the arterial and subcutaneous partial pressure of oxygen was significantly higher in the patients given 80 percent oxygen than in those given 30 percent oxygen. Among the 250 patients who received 80 percent oxygen, 13 (5.2 percent; 95 percent confidence interval, 2.4 to 8.0 percent) had surgical-wound infections, as compared with 28 of the 250 patients given 30 percent oxygen (11.2 percent; 95 percent confidence interval, 7.3 to 15.1 percent; P=0.01). The absolute difference between groups was 6.0 percent (95 percent confidence interval, 1.2 to 10.8 percent). The duration of hospitalization was similar in the two groups. CONCLUSIONS: The perioperative administration of supplemental oxygen is a practical method of reducing the incidence of surgical-wound infections.

Colon↗
PubMed2000

Perioperative collagen deposition in elderly and young men and women.

HYPOTHESIS: Women deposit more collagen after major abdominal surgery than men. DESIGN: A post hoc analysis of data obtained from 2 prospective, randomized, double-blind clinical trials. SETTING: University hospital general surgical service. PATIENTS: One hundred sixteen patients undergoing colon resection. MAIN OUTCOME MEASURES: Protein and hydroxyproline (collagen) deposition during the first 7 postoperative days in expanded polytetrafluoroethylene implants positioned subcutaneously. RESULTS: On univariate analysis, men and women deposited comparable amounts of collagen (257 +/- 120 vs 281 +/- 117 ng/mm, respectively). When potential confounding factors were entered into a generalized mixed-effects model, only the interaction between age and sex was a significant factor (P = .047). Collagen deposition decreased with age in men, being 317 +/- 133 ng/mm in men younger than 45 years, but only 238 +/- 113 ng/mm in those older than 45 years (P = .03). In contrast, collagen deposition was virtually identical in women younger than 45 years (280 +/- 133 ng/mm) and in those older than 45 years (281 +/- 110 ng/mm). Only 3 of these women were receiving hormone replacement therapy. CONCLUSIONS: Collagen deposition after surgery decreased significantly with age in men, while remaining unchanged in women. Younger men and women deposited similar amounts of collagen. Therefore, older men made less collagen after surgery than older women, perhaps explaining the consistent observation that wound dehiscence is twice as common in men than in women. Our results differ from previous studies conducted in healthy, nonsurgical volunteers, which showed that (1) young women made significantly more collagen than young men and (2) collagen deposition was reduced in postmenopausal women, but deposition returned to premenopausal values with hormone replacement therapy. Differences between our results and those reported previously likely stem from the populations studied. In particular, multiple perioperative factors decrease collagen deposition, which apparently obscures the differences observed previously in healthy, unstressed volunteers.

Abdominal Muscles↗
PubMed2000

The influence of 2 surgical bandage systems on wound tissue oxygen tension.

HYPOTHESIS: Local wound heating improves tissue oxygen tension in postoperative patients. SETTING: University hospital. PATIENTS: Forty normothermic and well-hydrated patients recovering from elective open abdominal surgery. INTERVENTIONS: A comparison between an experimental bandage system (Warm-Up; Augustine Medical Inc, Eden Prairie, Minn) and conventional gauze covered with elastic adhesive (Medipore Dress-it; 3M, St Paul, Minn). The experimental system is heated to 38 degrees C and does not touch the wound. MAIN OUTCOME MEASURES: Subcutaneous tissue oxygen tension was measured postoperatively and on the first postoperative day. In a subgroup, we also evaluated the effects of bandage pressure per se on tissue oxygen. RESULTS: Initial postoperative tissue oxygen tensions were approximately 30 mm Hg greater with the experimental bandage, even before warming. Subcutaneous oxygen tension during heating remained significantly greater in patients with the warmed bandage than the conventional elastic bandage (116 +/- 40 vs 85 +/- 34 mm Hg, respectively) while the patients were breathing approximately 50% oxygen. The difference was smaller on the first postoperative day, but still statistically significant (82 +/- 30 vs 65 +/- 22 mm Hg, respectively). In the subgroup analysis, tissue oxygen tension increased significantly by 12 +/- 4 mm Hg when the heating bandage was substituted for a conventional bandage (P<.001). CONCLUSION: In normothermic and well-hydrated surgical patients, much benefit from the heating bandage system appears to result from pressure relief. These data suggest that relieving wound pressure markedly improves tissue perfusion and oxygenation.

Abdomen↗
PubMed2000

Resistive heating is more effective than metallic-foil insulation in an experimental model of accidental hypothermia: A randomized controlled trial.

STUDY OBJECTIVE: We study a resistive-heating blanket in a volunteer model of severe accidental hypothermia to evaluate differences in rates of rewarming, core temperature afterdrop, and body heat content and distribution during active and passive rewarming. METHODS: Eight volunteers participated in a crossover design on 2 days. The volunteers were anesthetized and cooled to 33 degrees C (91.4 degrees F); anesthesia was subsequently discontinued, and shivering was prevented with meperidine. On one randomly assigned day, the volunteers were rewarmed passively with reflective foil (passive insulation), whereas on the other they were covered with a carbon fiber-resistive heating blanket set to 42 degrees C (107.6 degrees F; active rewarming). Trunk and head temperature and heat content were calculated from core (tympanic membrane) temperature. Peripheral (arm and leg) tissue temperature and heat content were estimated by using fourth-order regressions and integration over volume from 30 tissue and skin temperatures. RESULTS: Core heat content increased 73+/-14 kcal (mean+/-SD) during 3 hours of active warming, but only 31+/-24 kcal with passive insulation, a difference of 41+/-20 kcal (95% confidence interval [CI] 27 to 55 kcal; P <. 001). Peripheral tissue heat content increased linearly by 111+/-16 kcal during active warming but only by 38+/-31 kcal during passive warming, a difference of 74+/-34 kcal (95% CI 50 to 97; P <.001). Consequently, total body heat increased 183+/-22 kcal during active warming but only 68+/-54 kcal with passive insulation, a difference of 115+/-42 kcal (95% CI 86 to 144 kcal; P <.001). Core temperature increased from 32.9 degrees C+/-0.2 degrees C to 35.2 degrees C+/-0. 4 degrees C during 3 hours of active warming, a difference of 2.3 degrees C+/-0.4 degrees C. In contrast, core temperature with foil insulation only increased from 32.9 degrees C+/-0.2 degrees C to 33. 8 degrees C+/-0.5 degrees C, a difference of only 0.8 degrees C+/-0. 4 degrees C. The difference in the core temperature increase between the two treatments was thus 1.5 degrees C+/-0.4 degrees C (95% CI 1. 2 degrees C to 1.7 degrees C; P <.001 between treatments). Active warming was not associated with an afterdrop, whereas the afterdrop was 0.2 degrees C+/-0.2 degrees C and lasted a median of 45 minutes (interquartile range, 41 to 64 minutes) with passive insulation. CONCLUSION: Resistive heating more than doubles the rewarming rate compared with that produced by reflective metal foil and does so without producing an afterdrop. It is therefore likely to be useful in the prehospital setting.

Adult↗
PubMed2000

Less adrenergic activation during cataract surgery with total intravenous than with local anesthesia.

BACKGROUND: Previous studies reported that, contrary to local anesthesia, cataract surgery under inhalational anesthesia is associated with substantial adrenergic activation. We tested the hypothesis that total intravenous anesthesia (TIVA) with propofol and alfentanil produces less or comparable adrenergic activation during cataract surgery than local anesthesia. METHODS: Patients were randomly assigned to peribulbar local block (n=10) or TIVA (n=10). The heart rate, blood pressure, plasma concentrations of catecholamines, cortisol, and glucose were assessed at seven pre-, intra-, and post-operative time points. RESULTS: In the patients given local anesthesia, plasma concentrations of epinephrine, norepinephrine and cortisol did not change significantly. In contrast, plasma epinephrine decreased by roughly 66% during TIVA: from 45+/-16 to 15+/-8 pg/ml. Plasma norepinephrine concentration decreased by roughly 50%, from 462+/-265 to a minimum value of 219+/-6 pg/ml and plasma cortisol concentrations decreased by roughly 61%, from 16.4 ng/ml to 6.4 ng/ml. Blood pressure and heart rates remained near baseline values during local anesthesia. In contrast, systolic blood pressure decreased by 30% and heart rate by 12 beats/min during TIVA. CONCLUSION: The presented study and available data clearly suggest that local anesthesia produces the best adrenergic and hemodynamic stability during cataract surgery. Contrary to previously reported results on inhalational anesthesia (thiopentone/enflurane), the TIVA regimen used effectively prevents the adrenergic and metabolic response during cataract surgery.

Adult↗
PubMed2000

Inhaled nitric oxide reduces pulmonary vascular resistance more than prostaglandin E(1) during heart transplantation.

UNLABELLED: Heart transplantation in patients with increased pulmonary vascular resistance is often associated with postbypass right heart failure. We therefore compared the abilities of prostaglandin E(1) (PGE(1)) and inhaled nitric oxide to reduce pulmonary vascular resistance during heart transplantation. Patients undergoing orthotopic heart transplantation for congestive heart failure were randomly assigned to either a PGE(1) infusion at a rate of 8 ng. kg. (-1)min(-1) starting 10 min before weaning from cardiopulmonary bypass (CPB) (n = 34) or inhalation of 4 ppm nitric oxide starting just before weaning from CPB (n = 34). Both treatments were increased stepwise, if necessary, and were stopped 6 h postoperatively. Hemodynamic values were recorded after the induction of anesthesia, 10 and 30 min after weaning from CPB, and 1 h and 6 h postoperatively. Immediately after weaning from CPB, pulmonary vascular resistance was nearly halved in the nitric oxide group but reduced by only 10% in the PGE(1) group. Pulmonary artery pressure was decreased approximately 30% during nitric oxide inhalation, but only approximately 16% during the PGE(1) infusion. Six hours after surgery, pulmonary vascular resistance and pulmonary artery pressure were similar in the two groups. The ratio between pulmonary vascular resistance and systemic vascular resistance was significantly less in the nitric oxide patients at all postbypass times. In contrast, the pulmonary-to-systemic vascular resistance ratio increased approximately 30% in the patients given PGE(1). Cardiac output, heart rate, mean arterial pressure, right atrial pressure, and pulmonary wedge pressure did not differ between the groups. Weaning from CPB was successful in all patients assigned to nitric oxide inhalation; in contrast, weaning failed in six patients assigned to PGE(1) (P = 0.03). IMPLICATIONS: Nitric oxide inhalation selectively reduces pulmonary vascular resistance and pulmonary artery pressure immediately after heart transplantation which facilitates weaning from cardiopulmonary bypass.

Administration, Inhalation↗
PubMed2000

Cardiopulmonary bypass produces greater pulmonary than systemic proinflammatory cytokines.

Cardiopulmonary bypass (CPB) impairs pulmonary endothelial injury in part by increasing expression of adhesion molecules that results in neutrophil influx. Although numerous proinflammatory cytokines up-regulate these responses, the extent to which systemic and pulmonary proinflammatory cytokines increase remains unknown. We therefore examined systemic and pulmonary gene expression and production of proinflammatory cytokines during CPB. Bronchoalveolar lavage and peripheral blood sampling were performed just after the induction of anesthesia and at the end of surgery in 80 patients undergoing CPB. RNA was extracted from harvested cells and cDNA was synthesized by reverse transcription. The expression of interleukin (IL)-6, IL-8, and tumor necrosis factor-alpha (TNF-alpha) was measured by semiquantitative polymerase chain reaction using beta-actin as an internal standard. We also measured these cytokines in cultured alveolar macrophages and plasma monocytes in standard medium alone, or in the presence of lipopolysaccharide. We found 2- to 20-fold increases in gene expression for these cytokines in both plasma and alveolar leukocytes at the end of surgery. However, the increases were 4-8 times greater in alveolar than plasma leukocytes. Alveolar macrophages obtained at the end of surgery produced 1.5-3 times more IL-6, IL-8, and TNF-alpha than those obtained at the beginning (P < 0.0001). Although plasma monocytes produced more IL-8 at the end of surgery (P < 0.001), TNF-alpha and IL-6 did not increase. The production of all cytokines was 1.5-3 times greater in alveolar macrophages obtained at the end of surgery than in plasma monocytes obtained simultaneously (P < 0.005). Our data thus suggest that CPB provokes a greater pulmonary than systemic inflammatory response.

Actins↗
PubMed2000

Neutrophil number and interleukin-8 and elastase concentrations in bronchoalveolar lavage fluid correlate with decreased arterial oxygenation after cardiopulmonary bypass.

Atelectasis is a major cause of decreased arterial oxygenation after cardiopulmonary bypass (CPB). There is a close relationship between atelectasis and inflammatory responses. We therefore tested the hypothesis that neutrophil number and the concentrations of proinflammatory cytokines and elastase in plasma and bronchoalveolar lavage fluid correlate with changes in arterial oxygenation. Bronchoalveolar lavage was performed just after the induction of anesthesia and at the end of surgery in 80 patients undergoing CPB. Peripheral blood was sampled simultaneously. Arterial oxygenation was quantified by PaO(2)/fraction of inspired oxygen (FIO(2)) and intrapulmonary shunt (Q(s)/Q(t)). PaO(2)/FIO(2) and Q(s)/Q(t) decreased significantly at the end of surgery, whereas neutrophil number, interleukin (IL)-6, IL-8, tumor necrosis factor-alpha, and elastase concentrations in the lavage fluid increased significantly. The increase in neutrophil count from the lavage fluid correlated significantly with the increases in IL-8 and elastase concentrations. The increase in neutrophil number and IL-8 and elastase concentrations in the lavage fluid correlated significantly with PaO(2)/FIO(2) and Q(s)/Q(t) at the end of surgery. In contrast, none of the plasma values correlated with these variables. Significant correlation between immune mediators and decreased arterial oxygenation suggests that inflammatory responses in the distal airway are strongly related to a decrease in arterial oxygenation after CPB.

Bronchoalveolar Lavage Fluid↗
PubMed2000

Temperature monitoring and management during neuraxial anesthesia: an observational study.

UNLABELLED: Temperature monitoring and thermal management are rare during spinal or epidural anesthesia because clinicians apparently restrict monitoring to patients with an expected risk of hypothermia. This implies that anesthesiologists can predict patient thermal status without monitoring core temperature. We therefore, tested the hypotheses that during neuraxial anesthesia: 1) amount of core hypothermia depends on the magnitude and duration of surgery; 2) temperature monitoring and thermal management are used selectively in patients at high risk of hypothermia; and 3) anesthesiologists can estimate patient thermal status. We evaluated thermal status on arrival in the recovery room along with intraoperative thermal management and monitoring in 120 patients. Anesthesiologists were asked if their patients were hypothermic (<36 degrees C). There was no correlation between the magnitude or duration of surgery and initial postoperative core temperature in unwarmed patients. Temperature monitoring and thermal management were not used selectively in high-risk patients. Initial postoperative tympanic membrane temperatures were <36 degrees C in 77% of patients and <35 degrees C in 22%. Body temperature was monitored intraoperatively in 27% of the patients and forced-air warming was used in 31%. Anesthesiologists failed to accurately estimate whether their patients were hypothermic. Our results suggest that temperature monitoring and management during neuraxial anesthesia is currently inadequate. IMPLICATIONS: In this observational study, we evaluated core temperatures and intraoperative thermal management in patients undergoing spinal or epidural anesthesia. Hypothermia was common, however, rarely detected either by temperature monitoring or estimates by anesthesiologists. In addition, it was not treated with active warming. Consequently, temperature monitoring and management have to be done during neuraxial anesthesia.

Aged↗
PubMed2000

Aggressive warming reduces blood loss during hip arthroplasty.

UNLABELLED: We evaluated the effects of aggressive warming and maintenance of normothermia on surgical blood loss and allogeneic transfusion requirement. We randomly assigned 150 patients undergoing total hip arthroplasty with spinal anesthesia to aggressive warming (to maintain a tympanic membrane temperature of 36.5 degrees C) or conventional warming (36 degrees C). Autologous and allogeneic blood were given to maintain a priori designated hematocrits. Blood loss was determined by a blinded investigator based on sponge weight and scavenged cells; postoperative loss was determined from drain output. Results were analyzed on an intention-to-treat basis. Average intraoperative core temperatures were warmer in the patients assigned to aggressive warming (36.5 degrees +/- 0.3 degrees vs 36.1 degrees +/- 0.3 degrees C, P< 0.001). Mean arterial pressure was similar in each group preoperatively, but was greater intraoperatively in the conventionally warmed patients: 86+/-12 vs 80+/-9 mm Hg, P<0.001. Intraoperative blood loss was significantly greater in the conventional warming (618 mL; interquartile range, 480-864 mL) than the aggressive warming group (488 mL; interquartile range, 368-721 mL; P: = 0.002), whereas postoperative blood loss did not differ in the two groups. Total blood loss during surgery and over the first two postoperative days was also significantly greater in the conventional warming group (1678 mL; interquartile range, 1366-1965 mL) than in the aggressively warmed group (1,531 mL; interquartile range, 1055-1746 mL, P = 0.031). A total of 40 conventionally warmed patients required 86 units of allogeneic red blood cells, whereas 29 aggressively warmed patients required 62 units (P = 0.051 and 0.061, respectively). We conclude that aggressive intraoperative warming reduces blood loss during hip arthroplasty. IMPLICATIONS: Aggressive warming better maintained core temperature (36.5 degrees vs 36.1 degrees C) and slightly decreased intraoperative blood pressure. Aggressive warming also decreased blood loss by approximately 200 mL. Aggressive warming may thus, be beneficial in patients undergoing hip arthroplasty.

Adult↗
PubMed2000

The nonimmobilizer 1,2-dichlorohexafluorocyclobutane does not affect thermoregulation in the rat.

Inhaled and other anesthetics profoundly affect the central nervous system, causing amnesia, immobility in the face of noxious stimulation, and depression of thermoregulation. Nonimmobilizers, inhaled compounds whose lipophilicity suggests that they should be anesthetics, do not produce immobility, but they do cause amnesia. Their effects on thermoregulation were the subject of the present study. We gave eight rats isoflurane on one occasion and the nonimmobilizer 2N (1,2-dichlorolhexafluorocyclobutane) on another. We measured the effect of various concentrations of each compound on thermoregulation provoked by body cooling. The specific outcome was increased metabolism, as reflected in increased output of carbon dioxide. Isoflurane decreased the temperature threshold for such increases and the maximum response intensity, doing so in a concentration-dependent manner, whereas 2N had a minimal or no effect at any concentration up to 0.9 minimum alveolar concentration (estimated from its lipophilicity). Thus, 2N may be a useful tool for studies of the mechanisms mediating the thermoregulatory depression produced by anesthetics: 2N should not affect such a mechanism.

Anesthetics↗
PubMed2000

Temperature-dependent pharmacokinetics and pharmacodynamics of vecuronium.

BACKGROUND: The authors evaluated the influence of temperature on the pharmacokinetics and pharmacodynamics of vecuronium because mild core hypothermia doubles its duration of action. METHODS: Anesthesia was induced with alfentanil and propofol and maintained with nitrous oxide and isoflurane in 12 healthy volunteers. Train-of-four stimuli were applied to the ulnar nerve, and the mechanical response of the adductor pollicis was measured. Volunteers were actively cooled or warmed until their distal esophageal temperatures were in one of four ranges: < 35.0 degrees C, 35.0-35.9 degrees C, 36.0-36.9 degrees C, and > or = 37.0 degrees C. With temperature stabilized, vecuronium was infused at 5 microg x kg(-1) x min(-1) until the first response of each train-of-four had decreased by 70%. Arterial blood (for vecuronium analysis) was sampled at intervals until the first response recovered to at least 90% of its prevecuronium level. Vecuronium, 20 microg x kg(-1) x min(-1), was then infused for 10 min, and arterial blood was sampled at intervals for up to 7 h. Population-based nonlinear mixed-effects modeling was used to examine the effect of physical characteristics and core temperature on vecuronium pharmacokinetics and pharmacodynamics. RESULTS: Decreasing core temperature over 38.0-34.0 degrees C decreases the plasma clearance of vecuronium (11.3% per degrees C), decreases the rate constant for drug equilibration between plasma and effect site (0.023 min(-1) per degrees C), and increases the slope of the concentration-response relationship (0.43 per degrees C). CONCLUSIONS: Our results show that reduced clearance and rate of effect site equilibration explain the increased duration of action of vecuronium with reducing core temperature. Tissue sensitivity to vecuronium is not influenced by core temperature.

Adult↗