The role of diazepam and fentanyl in the production of balanced anaesthesia.

The effects of diazepam-fentanyl combinations on consciousness, superficial nociception, respiration and circulation during N2O+O2 inhalation were studied in 40 premedicated patients during induction of anaesthesia. The balance between antinociception and anaesthesia was closest to the optimum in patients receiving 0.2 mg/kg of diazepam plus 1 micrograms/kg of fentanyl; the eyelid reflex was negative in all patients and only two out of ten patients reacted to abdominal pinching. When only 0.2 mg/kg of diazepam was given with N2O+O2, the eyelid reflex was negative in all patients, but half of them reacted to pinching. When the dose of diazepam was reduced to 0.1 mg/kg and patients received 1 or 2 micrograms/kg of fentanyl, the balance between anaesthesia and antinociception was good, but 30-50% of patients had a positive eyelid reflex and reacted to pinching. No distinct respiratory depression was observed in patients given 0.2 mg/kg of diazepam, whereas seven patients given 0.1mg/kg of diazepam plus 2 micrrograms/kg of fentanyl had apnoea lasting more than 60 s associated with a significant (P less than 0.05-0.001) increase in end-tidal CO2 and PCO2 in arterialised venous blood. No significant changes were observed in blood pressure or heart rate after any of the drug combinations studied. It appears that an optimal balance between anaesthesia and antinociception with minimal side-effects during balanced general anaesthesia requires reinforcement of N2O+O2 anaesthesia not only with fentanyl but also with hypnotics for sedatives.