Anesthetic Induction with Fentanyl

Abstract

The efficacy of fentanyl, 30 μg/kg, was evaluated as an anesthetic induction agent in 72 ASA I–III patients scheduled for 2–4-hr operations. The effect of preinduction pretreatment with pancuronium and/or diazepam and the incidence of loss of consciousness (anesthesia), recall, rigidity, abnormal muscle movements, and hemodynamic changes were documented. Seventy-four percent of all patients became anesthetized. Diazepam pretreatment enhanced but did not ensure success of anesthetic induction. There was a significant correlation between age and the incidence of unconsciousness (P = 0.0287) and all patients over 60 yr old were anesthetized with 30 μg/kg of fentanyl. The incidence and severity of rigidity was reduced by pancuronium (P = 0.0002) but not by diazepam pretreatment. However, pancuronium plus diazepam produced a significant reduction in the incidence of rigidity when compared to pancuronium alone (P = 0.031). A significant positive correlation between age and the incidence of rigidity (P = 0.003) was found. Six patients had focal and one patient global tonic-clonic abnormal muscle movements. Diazepam but not pancuronium significantly decreased both heart rate (P = 0.05) and blood pressure (P = 0.04). Seventeen patents required reversal of narcotic effect to restore adequate spontaneous respiration after surgery. No patient required postoperative mechanical ventilatory assistance. The results of this study demonstrate that 30 μ/kg of fentanyl is not a reliable anesthetic induction dose in patients less than 60 yr old. Both age arid premedication enhance the anesthetic capabilities of induction with fentanyl. However, increasing age is associated with an increased incidence of rigidity and diazepam pretreatment may compromise hemodynamic stability. Significant postoperative respiratory depression can occur with 30 μg/kg of fentanyl used for induction of anesthesia in operations lasting 2–4 hr.