DESFLURANE CONTROLS THE HEMODYNAMIC-RESPONSE TO SURGICAL STIMULATION MORE RAPIDLY THAN ISOFLURANE

Study Objective: To compare the control of hemodynamic response to sur gical stimulus of desflurane to that of isoflurane. Design: Prospectiv e randomized study. Setting: Operating room of a major U.S. teaching h ospital. Patients: 59 ASA status I, II, and III patients 18 to 80 year s of age and were undergoing orthopedic or intra-abdominal surgical pr ocedures of I or more hours in duration. Interventions: Group 1 (n = 2 9) received desflurane in oxygen (O-2) for their surgical procedure. G roup 2 (n = 30) received isoflurane in O-2 for their surgical procedur e. Thiopental sodium 4 mg/kg and fentanyl 3 mu g/kg provided induction ; vecuronium 0.1 mg/kg facilitated intubation. Prior to incision the v olatile anesthetic drug was titrated to maintain systolic blood pressu re (Ssp) within 20% of preinduction (baseline) values. Any time after incision, an SEP increase greater than 20% of baseline was treated wit h a 30% increase in inspired anesthetic concentration for 3 minutes, o r until SEP was within 10% of baseline. Another three 30% increases we re allowed at 3 minute intervals to return SEP to 10% of baseline. If four 30% increases did not return SEP to 10% of baseline, additional f entanyl up to 5 mu g/kg or labetalol in 5 mg increments was given. Mea surements and Main Results: Measurement of hemodynamics and anesthetic concentration occurred every 2 minutes prior to shin incision and eve ry 5 minutes thereafter. Measurement of hemodynamics and anesthetic co ncentration occurred every minute during treatment of blood pressure ( BP) response to surgical stimulus. Desflurane allowed for more rapid c ontrol of BP response to surgical stimulus median 2 minutes (range 1 t o 12 minutes) for desflurane versus 6 minutes (range 1 to 12 minutes, p = 0.011). The desflurane group required fewer 30% incremental anesth etic increases than the isoflurane group (1.8 versus 2.5, p = 0.016) t o control increased SEP. End tidal/inspired drug concentration ratios were closer to unity in the desflurane patients both before (0.94 vers us 0.80) and after (0.86 versus 0.70) changes in drug concentration to treat increased SEP. Conclusion: Anesthetic depth can be more rapidly titrated with desflurane compared to isoflurane. Alveolar/inspired co ncentration ratio approaches unity more rapidly with desflurane anesth esia.