Alfentanil infusion in neurosurgical patients

Alfentanil administered by constant rate infusion was evaluated as a main anesthetic in craniotomy patients. Eleven patients (ASA II) received either an induction dose of 200 microg/kg alfentanil followed by a 1 microg/kg/min infusion, or a 150 microg/kg bolus followed by a 1.5 microg/kg/min infusion. The infusion was stopped at least 1 h before the end of surgery. In addition to routine clinical neuroanesthesia monitoring, cardiovascular parameters, extubation conditions, and recovery scores were systematically recorded. Plasma alfentanil levels were determined in all patients during and for 6 h after the infusion. Finally, pharmacokinetic studies were carried out in five patients from both groups. This technique provided a remarkable cardiovascular stability, excellent extubation conditions, a comfortable recovery period, and no signs of prolonged or recurrent narcotization. No difference in clinical signs or alfentanil blood concentrations between the two drug regimens could be found. Pharmacokinetic parameters found were comparable to those obtained after single bolus drug elimination. Despite large individual variations and sometimes very prolonged infusion, there was no evidence of delayed drug administration. All of the above findings warrant the use of alfentanil infusion in neuroanesthesia and confirm the unique pharmacological properties of this drug among existing narcotics.