We have examined the preventative effect of nafamostat mesilate, a kallikrein inhibitor, on pain on injection with propofol in a randomized, double-blind study. A control group (n = 110) and a nafamostat (n = 103) group received 5% glucose 0.02 ml kg-1 and nafamostat 0.02 mg kg-1 diluted with 5% glucose, respectively, followed 1 min later by 1% propofol injected at a rate of 200 mg min-1. Pain scores recorded during injection of propofol were significantly less in the nafamostat than in the control group. In another 10 patients, blood concentrations of nafamostat were measured after administration of nafamostat 0.02 mg kg-1 i.v. Mean nafamostat concentration 1 min after injection was 0.1 (SD 0.05) mumol litre-1, which is sufficient to inhibit plasma kallikrein activity. We conclude that pretreatment with nafamostat 0.02 mg kg-1 significantly reduced pain on propofol injection and this effect may be caused by a reduction in kallikrein activity.

The suitable type of local anesthetic may be lidocaine or mepivacaine, and the most effective water-diluted concentration is considered to be 0.2% to 0.25%.

The present study demonstrates lack of a linear relationship between injected volume of local anesthetic and spread of epidural anesthesia. Whether the cubic equation developed is clinically useful remains unclear because of the variability of the data.

Twelve elderly patients undergoing total knee arthroplasty received lumbar epidural anaesthesia and propofol infusion at 5 mg.kg(-1).h(-1) following a 1.5-2.0 mg.kg(-1) bolus dose with preservation of spontaneous respiration via a laryngeal mask airway. Circulatory, respiratory and metabolic variables were measured before and 1, 3, 5, 15 and 30 min after release of a pneumatic thigh tourniquet. The blood pressure was decreased at all time-points and the respiratory rate increased at 1 min. The P(a)CO(2) was increased only at 1 min. Arterial blood pH and base excess were decreased at 1 and 3 min and 1, 3 and 5 min, respectively. Arterial blood lactate levels were increased at all times. These characteristics were considered to be identical to those under regional anaesthesia with conscious spontaneous respiration, showing that spontaneous respiration under this anaesthetic regimen has a similar respiratory capacity to that of conscious spontaneous respiration.

Inspired O(2)(-) attenuates blood lactate concentrations. This may be attributed, in part, to the systemic stimulatory effect on superoxide dismutase activity, which accelerates oxidative phosphorylation in the mitochondria, thus attenuating lactate generation.