• C Negishi, R Lenhardt, D I Sessler, J De Witte, T Ikeda, A Kurz, and E Lobo.
• Department of Anesthesia and Perioperative Care, University of California, San Francisco, 94143-0648, USA.
• Anesthesiology. 1998 May 1;88(5):1162-9.

BackgroundIntraoperative fever is relatively rare considering how often pyrogenic causes are likely to be present and how common fever is postoperatively. This low incidence suggests that general anesthesia per se inhibits the normal response to pyrogenic stimulation. The authors therefore tested the hypothesis that desflurane-induced anesthesia produces a dose-dependent inhibition of the febrile response.MethodsEight volunteers were studied, each on 3 study days. Each was given an intravenous injection of 50,000 IU/ kg of interleukin-2 (elapsed time, 0 h), followed 2 h later by 100,000 IU/kg. One hour after the second dose, the volunteers were assigned randomly to three doses of desflurane to induce anesthesia: (1) 0.0 minimum alveolar concentration (MAC; control), (2) 0.6 MAC, and (3) 1.0 MAC. Anesthesia continued for 5 h. Core temperatures were recorded from the tympanic membrane. Thermoregulatory vasoconstriction was evaluated using forearm-minus-fingertip skin temperature gradients; shivering was evaluated with electromyography. Integrated and peak temperatures during anesthesia were compared with repeated-measures analysis of variance and Scheffé's F tests.ResultsValues are presented as mean +/- SD. Desflurane reduced the integrated (area under the curve) febrile response to pyrogen, from 7.7 +/- 2.0 degrees C x h on the control day to 2.1 +/- 2.3 degrees C x h during 0.6 MAC and to -1.4 +/- 3.1 degrees C x h during 1.0 MAC desflurane-induced anesthesia. Peak core temperature (elapsed time, 5-8 h) decreased in a dose-dependent fashion: 38.6 +/- 0.5 degrees C on the control day, 37.7 +/- 0.7 degrees C during 0.6 MAC and 37.2 +/- 1.0 degrees C during 1.0 MAC desflurane anesthesia. Rising core temperature was always associated with fingertip vasoconstriction and often with shivering.ConclusionsDesflurane-induced anesthesia produced a dose-dependent decrease in integrated and peak core temperatures after administration of pyrogen, with 1.0 MAC essentially obliterating fever. Anesthetic-induced inhibition of the pyrogenic response is therefore one reason that fever is an inconsistent clinical response to inflammation during surgery.

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