DESFLURANE REDUCES THE FEBRILE RESPONSE TO ADMINISTRATION OF INTERLEUKIN-2

Background: Intraoperative fever is relatively rare considering how of ten pyrogenic causes are likely to be present and how common fever is postoperatively. This low incidence suggests that general anesthesia p er se inhibits the normal response to pyrogenic stimulation. The autho rs therefore tested the hypothesis that desflurane-induced anesthesia produces a dose-dependent inhibition of the febrile response. Methods: Eight volunteers were studied, each on 3 study days. Each was given a n 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 desflur ane 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. Thermoreg ulatory vasoconstriction was evaluated using forearm-minus-fingertip s kin temperature gradients; shivering was evaluated with electromyograp hy. Integrated and peak temperatures during anesthesia were compared w ith repeated-measures analysis of variance and Scheffe's F tests. Resu lts: Values are presented as mean +/- SD. Desflurane reduced the integ rated (area under the curve) febrile response to pyrogen, from 7.7 +/- 2.0 degrees C h on the control day to 2.1 +/- 2.3 degrees C.h during 0.6 MAC and to -1.4 +/- 3.1 degrees C.h during 1.0 MAC desflurane-indu ced 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 dur ing 1.0 MAC desflurane anesthesia. Rising core temperature was always associated with fingertip vasoconstriction and often with shivering. C onclusions: Desflurane-induced anesthesia produced a dose-dependent de crease in integrated and peak core temperatures after administration o f pyrogen, with 1.0 MAC essentially obliterating fever. Anesthetic-ind uced inhibition of the pyrogenic response is therefore one reason that fever is an inconsistent clinical response to inflammation during sur gery.