DISSOCIATION BETWEEN HEMODYNAMICS AND SYMPATHETIC ACTIVATION DURING ANESTHETIC INDUCTION WITH DESFLURANES

Purpose: To compare the simultaneous haemodynamic effects, sympathetic activation and cardiac risks associated with desflurane used in a bal anced technique, with those of isoflurane anaesthesia, Methods: A pros pective, randomized, open label study was conducted at a University me dical centre. Forty patients undergoing major non-cardiac surgery were randomized to receive either desflurane or isoflurane as the primary anaesthetic agent. After premedication, fentanyl and thiopentone were administered iv, Anaesthesia was increased up to 1.0 MAC(ET) in O-2 vi a controlled mask ventilation and maintained at 1.0 MAC before trachea l intubation. Maintenance consisted of N2O, O-2 and desflurane or isof lurane for 10 min. During the study, HR and arterial BP were continuou sly measured, as were ECG ST-segments and ventricular dysrhythmias usi ng a 3-channel Holler ECG recorder: Left ventricular global and region al function were measured using precordial echocardiography, Serial pl asma catecholamine concentrations were measured. Results: For both gro ups, HR was maintained without increases over baseline values while sy stolic BP showed a progressive decrease during induction. Use of beta blockade during induction was higher in the desflurane (7/20 = 35%) th an in the isoflurane group (1/20 = 5%), P = 0.04, The plasma norepinep hrine concentrations progressively increased in the desflurane group b ut not in the isoflurane group. Four patients in-the desflurane and th ree in the isoflurane group developed transient worsening of regional function but no change in mean left ventricular ejection fraction area and no ECC; ischaemia occurred during anaesthetic induction. Conclusi ons: Desflurane differs from isoflurane in thats:sympathetic stimulati on persisted despite blunting of potential hyper dynamic haemodynamic responses by narcotic and beta blockade. However; this sympathetic act ivation did not appear to increase cardiac risks.