Effects of Hypothermia on Halothane MAC and Isoflurane MAC in the Rat

Vitez, Terry S.; White, Paul F.; Eger, Edmond I.

doi:10.1097/00000542-197407000-00020

Cited by 144 publications

(56 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Minimum alveolar concentrations were corrected for the actual body tem-perature. 7 In accordance, halothane concentrations ranged between 0.45% and 1%. The right femoral artery was cannulated by a polyethylene catheter (PE-50; NeoLab, Heidelberg, Germany) for continuous monitoring of blood pressure, heart frequency, and blood gases during the experiment.…”

Section: Methodsmentioning

confidence: 86%

Different Degrees of Hypothermia After Experimental Stroke

Kollmar

Blank

Han

et al. 2007

Stroke

View full text Add to dashboard Cite

Background and Purpose-The neuroprotective role of mild therapeutic hypothermia was established in animal models of cerebral ischemia. Still, several issues, including optimal target temperature, remain unclear. The optimal depth of hypothermia in a rat model of focal cerebral ischemia was investigated. Methods-Eighty-four male Wistar rats (nϭ84) were subjected to filament occlusion of the middle cerebral artery for 90 minutes. Sixty animals were equally split into 6 groups kept at core temperatures of 37°C, 36°C, 35°C, 34°C, 33°C, and 32°C over a period of 4 hours starting 90 minutes after middle cerebral artery occlusion. Twenty-four hours later, after performing a neuroscore, animals were killed and brains examined for infarct size, edema, and invasion of leukocytes.In the second part, 24 animals (8 per group) were kept at 33°C, 34°C, and 37°C for 4 hours, allowed to survive for 5 days, and underwent additional investigation of transferase dUTP nick-end labeling. Results-In the first part, one animal in each treatment group and 2 animals in group 37°C died. The infarct size and edema were smaller for 34°C and 33°C compared with all other groups (PϽ0.05) over 24 hours. These animals also had better functional outcome (PϽ0.05) with an advantage for 34°C versus 33°C (PϽ0.05). Leukocyte count was lower for 34°C and 33°C as compared with the 37°C group. Similar results were obtained in the second part of the study with an advantage for 34°C versus 33°C. Conclusion-Our results suggest that the optimal depth of therapeutic hypothermia in temporary middle cerebral artery occlusion is 34°C.

show abstract

Section: Methodsmentioning

confidence: 86%

Different Degrees of Hypothermia After Experimental Stroke

Kollmar

Blank

Han

et al. 2007

Stroke

View full text Add to dashboard Cite

show abstract

“…2,3 Our intraoperative and extubation hormonal data suggest that mild hypothermia may further lower the stress hormonal response at the constant dose of isoflurane or iv lidocaine.…”

Section: Extubationmentioning

confidence: 90%

“…1 However, it is not clear whether mild intraoperative hypothermia enhances stress responses during surgery since, on the other hand, it has been reported that hypothermia reduces the minimum alveolar concentration (MAC) of anesthetics by about 5% per 1°C. 2,3 We hypothesized that, under a constant anesthetic concentration or dose, under hypothermic conditions, the stress hormonal and hemodynamic responses to the same stimuli could be decreased in hypothermic patients. In this study, during cerebral aneurysm surgery under anesthesia with 1.2% isoflurane and 50% nitrous oxide, the body temperature was decreased to 34°C.…”

mentioning

confidence: 99%

Intraoperative mild hypothermia does not increase the plasma concentration of stress hormones during neurosurgery

Z.¹,

Choi

Lee

et al. 2001

Can J Anesth/J Can Anesth

View full text Add to dashboard Cite

P Pu ur rp po os se e: : To determine how mild hypothermia (34°C) affects the hemodynamic and the stress hormonal responses intraoperatively and during extubation in patients undergoing cerebral aneurysm surgery.M Me et th ho od ds s: : After induction, anesthesia was maintained with 1.2% isoflurane and 50% nitrous oxide. For the normothermia and the hypothermia groups, the body temperature was maintained at 36.9 ± 0.3°C and 34.2 ± 0.2°C respectively up to the recovery room. Hemodynamic changes were recorded continuously. Stress hormones comprising epinephrine, norepinephrine, ADH, ACTH, and cortisol were measured at the awake control, intraoperative, and extubation periods.R Re es su ul lt ts s: : Vital signs of the intraoperative and postextubation time periods were not significantly different between the normothermia and hypothermia groups except for a statistically lower pulse rate intraoperatively in the hypothermia group (P <0.05). In the control awake state, all five hormonal concentrations were similar between the two groups. Intraoperatively, all of the hormonal levels tended to be lower in the hypothermia group compared to the normothermia group, but only the epinephrine level decreased sufficiently to reach statistical significance (P <0.05). During extubation, all stress hormone concentrations, except norepinephrine, were lower in the hypothermia group (epinephrine: P <0.05; ADH: P <0.05; ACTH: P <0.05; cortisol: P <0.05).C Co on nc cl lu us si io on ns s: : Our data suggest that intraoperative mild hypothermia neither significantly affects the blood pressure response nor increases the concentrations of stress hormones intraoperatively. Furthermore, mild hypothermia significantly decreased the plasma concentrations of stress hormones during the extubation period.

show abstract

“…The vessel was then preconstricted with the thromboxane analogue U46619 1 µM for five minutes, since the response of the cerebral vessels to U46619 was previously demonstrated not to be influenced by SAH. 5 The vessel was then subjected to isoflurane 0, 1, or 2 minimum alveolar concentration (MAC; 1 MAC = approximately 1.2% in rats) 12 by adding the anesthetic to the 95% O 2 -5% CO 2 mixture bubbling the Krebs buffer solution, using an in-line bubble-through vaporizer. In a preliminary experiment, using gas chromatography (GC), it took less than ten minutes for isoflurane to reach a steady state concentration after it was introduced in the vessel chamber.…”

mentioning

confidence: 99%