EFFECT OF NITROUS-OXIDE ON MIDDLE-EAR PRESSURE - A COMPARISON BETWEENINHALATIONAL ANESTHESIA WITH NITROUS-OXIDE AND TIVA

We have investigated the effect of nitrous oxide on the middle ear pre ssure, comparing inhalational anaesthesia with nitrous oxide and halot hane and total intravenous anaesthesia with propofol-alfentanil. Fifty patients with normal healthy ears were divided into two groups. In on e group (n=25), anaesthesia was induced with thiopentone 6 mg kg(-1), and maintained with halothane 1% and nitrous oxide 66% in oxygen. In t he other group (n=25), anaesthesia was induced with alfentanil 25 mu g kg(-1) and propofol 2 mg kg(-1), and maintained with an infusion of a lfentanil 10 mu g kg(-1) min(-1) for the first 10 min and then with 0. 5 mu g kg(-1) min(-1) and with propofol 10 mg kg(-1) h(-1) for the fir st 10 min, 8 mg kg(-1) h(-1) for the following 10 min and 6 mg kg(-1) h(-1) thereafter. Patients were ventilated with an oxygen-air mixture (F1O2=0.33). Middle ear pressures were measured during the pre-, intra - and post-anaesthetic period in both ears. A progressive rise was obs erved (P<0.05) in the first group, whereas values were within the norm al limits clinically and there was no statistically significant change in those receiving total intravenous anaesthesia during the intra-ana esthetic period. The time to reach peak pressure with inhalational ana esthesia was 60 min (181.5 mmH(2)O) and to return to normal was 30 min (49.5mmH(2)O) after cessation of nitrous oxide administration. The in cidence of nausea and vomiting was less in the patients not receiving nitrous oxide.