Nitrous oxide and anesthetic requirement for loss of response to command during propofol anesthesia

Abstract

The blood concentration associated with loss of response (LOR) to command in 50% of subjects (CP50LOR) is an important measure of anesthetic potency. We therefore determined the CP50LOR in 40 healthy surgical patients, aged 18-60 yr old, receiving propofol alone or propofol with 67% nitrous oxide (N2O). Patients were randomized to receive 100% oxygen or 67% N2O in oxygen via facemask. Three minutes later, a target-controlled propofol infusion was commenced at a concentration determined by the response of the previous patient in the same group. Fifteen minutes later, response to command was assessed by a blinded observer. Arterial blood samples were taken for propofol assay, and the bispectra..