EFFECT OF NITROUS-OXIDE ON POSTOPERATIVE NAUSEA AND VOMITING DURING PROPOFOL ANESTHESIA FOR SHORT SURGICAL OPERATIONS

One hundred patients of ASA status I or II, undergoing gynaecological or urological surgery were studied. Opioids were omitted from premedic ation and anaesthesia. Patients were allocated randomly to one of two equal groups and were anaesthetized using a computer controlled infusi on system, programmed to achieve theoretically any target blood propof ol concentration. One group received 60% nitrous oxide in oxygen while the other group received 100% oxygen. Six patients in the nitrous oxi de group had nausea and three of these patients vomited. Two patients in the oxygen group had nausea but no patient vomited. The frequency o f nausea and vomiting in the two groups was not statistically differen t (P>0.05). Theoretical blood propofol concentration shown to produce surgical anaesthesia was maintained in all patients. However 12% of th e patients that received nitrous oxide and 40% of the patients that di d not, responded to the surgical stimulus by limb movement. Patients i n the oxygen group required higher rates of propofol infusion to maint ain surgical anaesthesia.