Infusion of propofol to identify smallest effective doses for induction of anaesthesia in young and elderly patients.

We studied 110 patients older than 60 yr or aged 18-50 yr as separate groups in two stages to identify the smallest effective doses of propofol for induction of anaesthesia. In the elderly patients, in stage 1, at infusion rates of 25, 50 or 100 mg min-1 the mean (SD) doses administered were propofol 0.82 (0.14) mg kg-1, 1.22 (0.24) mg kg-1 and 1.65 (0.60) mg kg-1 and the induction times 140.1 (21.9) s, 103.2 (23.5) s and 69.4 (10.0) s, respectively. In stage 2, after induction with a fixed dose of 0.82 mg kg-1 as a bolus over 5 s or as an infusion at 25 mg min-1, the times for induction were 38.5 (14.0) s and 144.5 (36.6) s, respectively. In the young patients, at induction rates of 33.3, 50, 100 or 200 mg min-1, the doses administered were propofol 1.36 (0.28) mg kg-1, 1.46 (0.12) mg kg-1, 1.85 (0.43) mg kg-1 and 2.39 (0.50) mg kg-1 and the induction times 145.0 (25.4) s, 120.0 (18.4) s, 80.2 (19.2) s and 54.5 (10.4) s, respectively. In stage 2, a fixed induction dose of 1.46 mg kg-1 resulted in induction times of 35.0 (8.5) s and 134.0 (26.8) s, respectively. In stage 2 of each age group, induction was achieved with smaller doses than those recommended previously and there was no difference in the number of patients in whom induction of anaesthesia was successful or in the measured cardiorespiratory variables between the two induction regimens. This suggests the latter effects are caused by the dose administered and not the rate of administration.

Pethidine as a spinal anaesthetic agent--a comparison with plain bupivacaine in patients undergoing transurethral resection of the prostate.

This study compares the anaesthetic effects of intrathecal pethidine or bupivacaine in patients undergoing surgery for transurethral resection of the prostate. Patients were randomly allocated to receive 3.5 ml of 0.5% plain bupivacaine or 1 mg kg-1 of 5% pethidine. The onset, extent and duration of sensory and motor blockade were studied. The cardiovascular and respiratory variables and frequency of side-effects were noted, both in the intra-operative period and the first 24 h of the post-operative period. There were no significant differences in intra-operative conditions or post-operative complications. The duration of block was significantly shorter with pethidine but was not associated with a difference in post-operative pain or analgesic requirements; this may have advantages when early post-operative mobility is indicated. We conclude that spinal pethidine is a satisfactory agent for transurethral resection of the prostate.

Technical report: oxygen saturation monitoring during sedation for chemonucleolysis.

Pulse oximetry is widely used during anaesthetic practice to monitor heart rate and oxygenation and has been recommended as a monitor when sedative techniques are used. We monitored 25 patients receiving sedation for chemonucleolysis and showed that 17 became hypoxaemic at some stage of the procedure, none of whom had clinically detectable signs of respiratory depression. We recommend that monitoring with pulse oximetry is used in all patients receiving sedation for radiological procedures and that all radiologists administering sedation be trained in airway management.