EFFECTS OF END-TIDAL GAS MONITORING AND FLOW-RATES ON HEMODYNAMIC STABILITY AND RECOVERY PROFILES

This study was designed to evaluate the impact of routine end-tidal an esthetic gas monitoring on the intraoperative hemodynamic stability an d early recovery profile in 253 consenting ASA physical status I-Ill p atients undergoing elective otolaryngologic procedures with isoflurane or enflurane anesthesia. Patients were randomly assigned to one of si x treatment groups: Group I, monitored high-flow isoflurane; Group II, unmonitored high-flow isoflurane; Group III, monitored low-flow isofl urane; Group TV,unmonitored low-flow isoflurane; Group V, monitored lo w-flow enflurane; or Group VI, unmonitored low-flow enflurane. After a standardized induction sequence, anesthesia was maintained by adminis tering variable concentrations of isoflurane or enflurane in an air/ox ygen mixture at two different total gas flow rates (0.7 L/min or 3.5 L /min, respectively). Mean arterial pressure (MAP), heart rate (HR), an d end-tidal (ET) anesthetic concentrations were recorded by a computer throughout the operation. The resident anesthesiologist was instructe d to maintain an adequate ''depth of anesthesia'' by varying the admin istration of isoflurane (Groups I-IV) or enflurane (Groups V and VI) w ith or without end-tidal gas monitoring. Intraoperative hemodynamic st ability was assessed in each patient and reported as the average error from the preincisional (baseline) MAP, average absolute error from th e baseline MAP, coefficients of variation for I-IR, systolic, diastoli c, and MAP values, and ET anesthetic concentrations. Recovery times fr om discontinuation of the volatile drug until awakening following comm ands, and postanesthesia care unit (PACU) discharge were recorded. The six study groups had similar intraoperative MAP and HR values, coeffi cients of variation, and numbers of episodes of hypertension, hypotens ion, tachycardia, and bradycardia. The groups were also similar with r espect to early recovery times and postoperative side effects. In conc lusion, end-tidal anesthetic monitoring did not improve intraoperative hemodynamic stability or decrease emergence times from general anesth esia with isoflurane or enflurane, even when low gas flows (0.7 L/min) were used in this patient population.