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Intraoperative hypothermia associated with lower extremity tourniquet deflation
B J Sanders1, J G D'Alessio, J R Jernigan
1Department of Anesthesiology, University of Tennessee Medical Center, Memphis 38103-2897, USA.
Study Objective:
To determine the rapidity and extent of core temperature decrease following release of a lower extremity pneumatic tourniquet.
Design:
Prospective study.
Setting:
Inpatient surgery in a university trauma center.
Patients:
11 ASA status I and II adults undergoing unilateral lower extremity fracture fixation in which a tourniquet was used, with general anesthesia.
Interventions:
Temperature was measured in the esophagus before and after lower extremity tourniquet release.
Measurements And Main Results:
Tourniquet times ranged from 41 to 129 minutes (mean 98.5 +/- 9.1 minutes). Following tourniquet deflation core temperature decreased in all patients, with a maximal decline at 10 minutes, the termination of measurements, although trending downward. Esophageal temperature decreased an average of 0.46 degree C +/- 0.2 degree C at 5 minutes, and 0.67 degree C +/- 0.2 degree C at 10 minutes following tourniquet release, respectively. Temperature changes were significant (p = 0.0001) at both time intervals.
Conclusion:
Core temperature drops significantly immediately following release of the tourniquet at the esophageal temperature monitoring site. This decrease is the result of cooling of systemic blood reperfusing the hypothermic limb, and mixing of cool, "washed out" blood with the systemic circulation. As the consequences of hypothermia are well-known, we recommend core temperature monitoring in all patients having lower extremity tourniquet placed during general anesthesia, as well as vigilant monitoring for prolonged effects of anesthetics in the postoperative period.