• J P Mathew, K J Weatherwax, C J East, W D White, and J G Reves.
• Division of Cardiothoracic Anesthesiology and Critical Care, Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA. mathe014@mc.duke.edu
• J Clin Anesth. 2001 Jun 1;13(4):301-5.

Study ObjectiveTo evaluate the hypothesis that the bispectral index (BIS) is not affected by the hypothermia that is associated with cardiopulmonary bypass (CPB).DesignProspective, observational study.SettingCardiac surgical operating suite of a university medical center.Patients100 patients undergoing cardiac surgery requiring CPB.InterventionsA constant effect site concentration of 2.2 ng/mL for fentanyl and 60 ng/mL for midazolam was maintained throughout surgery using a computer-assisted continuous infusion technique.MeasurementsThe BIS value, percent isoflurane administered, predicted brain concentrations of midazolam and fentanyl, and nasopharyngeal temperature were recorded before CPB, at 15 minutes after the onset of CPB, at placement of the aortic cross-clamp, at start of rewarming, on separation from CPB, and 15 minutes after the end of CPB. Data were analyzed using a repeated-measures mixed-effects method, taking into account temperature, age, and predicted level of each anesthetic.Main ResultsA significant overall association between temperature and BIS was observed independent of patient age, predicted brain midazolam or fentanyl concentration, percent isoflurane administered, and surgical time point (p < 0.001). The BIS is estimated to decrease by 1.12 units for each degree Celsius decrease in body temperature.ConclusionsHypothermia decreases the BIS by 1.12 units per degree Celsius decline in temperature.

33 keywords...

hide…