Clinical experience with a fixed rate of alfentanil infusion

Twenty-seven patients received an alfentanil loading dose of 100 micrograms kg-1 in two 50-micrograms aliquots followed by a fixed rate infusion of 1 microgram kg-1 min-1. At clinical signs of response to surgical stimulus, an alfentanil dose of 1 mg was added. Patients were ventilated with a N2O/O2 mixture. Muscle relaxation was achieved with a vecuronium infusion. No other drugs were given during the procedure. Major orthopaedic or maxillo-facial surgery patients were studied. The duration of infusion was from 2-7 h (mean of 3.9 +/- 1.6 h SD). In 25 of 27 cases the anaesthesia was considered adequate and stable. A mean of two additional doses per patient were needed in 25 patients, with a range of zero to four doses in the group. This study supports the view that after an appropriate loading dose a fixed-rate infusion of alfentanil at 1 microgram kg-1 min-1 can be given for up to 7 h to provide satisfactory stable analgesia without undue post-operative ventilatory depression or prolonged recovery in the majority of cases.