DESFLURANE AND ISOFLURANE - A COMPARISON OF EMERGENCE TIMES AND HEMODYNAMICS DURING SURGICAL-PROCEDURES

Objectives. The new volatile anaesthetic desflurane is characterized b y very low blood-gas and tissue-blood partition coefficients, so that rapid induction of anaesthesia and shorter recovery times can be expec ted. The aim of this investigation was to compare the effects of desfl urane and isoflurane on haemodynamics and recovery time when used as p art of a balanced anaesthesia technique for elective surgery. Methods. Fifty patients (18 years and older, ASA status I-III) scheduled for e lective surgery (no laparoscopies) of at least 60 min duration were in cluded in this open, randomised, phase-III clinical trial. After oral premedication with midazolam 7.5 mg 45 min before transfer to theatre, anaesthesia was induced with fentanyl 0.1 mg and thiopental 5 mg/kg; succinylcholine or vecuronium facilitated intubation. Desflurane and i soflurane, respectively, were used for maintenance of anaesthesia, bot h in 50% N2O, with the inspired concentration adapted to the degree of stimulation. All patients were ventilated in a semi-closed system; mu scle relaxation was achieved with vecuronium. The electrocardiogram, h eart rate (HR), and direct arterial blood pressure (sp) were recorded continuously and anaesthetic gas detection was performed by an infrare d absorption technique. With termination of surgery the volatile anaes thetic was discontinued and the following emergence times recorded: sp ontaneous ventilation (V-T>300 ml), extubation, eye opening, correctly answering the date of birth, arrival in and possible discharge from t he post-anaesthesia care unit (PACU). Results. In all, 49 patients wer e studied at random (desflurane n=24, isoflurane n=25). Data of demogr aphics and anaesthetic technique were comparable in both groups (Table s 2 and 3). Anaesthetic elimination (expressed as F-A/F-AO) was signif icantly more rapid in the desflurane group 3 min after termination of anaesthesia (Fig. 1). Comparing the emergence times, there was no sign ificant difference between desflurane and isoflurane: in both groups p atients opened their eyes 12 min (median time) after termination of th e operation (Table 4). Haemodynamics (HR, systolic and diastolic BP) w ere comparable at intubation, skin incision, end of surgery, extubatio n, and in the PACU (Fig. 2a, b). In 2 patients a rapid increase in the inspired concentration of desflurane during induction of anaesthesia produced a profound sympathoadrenergic reaction with an excessive incr ease in BP and HR. Similar reactions in other patients did not occur w hen the inspired concentration of desflurance was slowly increased. Co nclusions. Despite the physicochemical properties of the new agent, em ergence times were similar for desflurane and isoflurane in our study. These results, which are in contrast to those of some other authors, are most probably due to the study design, which included the use of p remedicants (midazolam) and a low dose of fentanyl. The reported sympa tho-adrenergic reactions after rapid changes in the inspired concentra tion of desflurane during induction of anaesthesia have been observed by others as well. It seems that this initial cardiovascular stimulati on can be avoided by slow increases in desflurane concentration. In su mmary, desflurane compares to isoflurane in balanced anaesthesia for g eneral surgical procedures with regard to haemodynamics, while the tim e to awakening is not necessarely reduced.