Biphasic respiratory depression from neurolept anesthesia.

The recovery of patients following neurolept or fentanyl/nitrous oxide anesthesia is extremely variable due to variations in drug dosage, biotransformation and excretion idiosyncracies among individuals. The respiratory depressant effects of fentanyl or fentanyl/droperidol can far outlast the analgesic duration and can recur after having dissipated. The level of consciousness and the quality of breathing can be misleading indicators of complete recovery from neurolept anesthesia. Respiratory rate has been observed to return to control levels when simultaneous response to CO2 rebreathing was reduced and resting PeCO2 was increased. Naloxone can be used in dosages which will help ensure adequate ventilation without attenuating postoperative analgesia.