Blood concentration of propofol in a patient with delayed emergence from propofol-nitrous oxide anesthesia

We measured the blood concentration of propofol in a patient with delayed emergence from propofol-nitrous oxide anesthesia. A 78-year-old man underwent subtotal gastrectomy under both epidural and propofol-nitrous oxide anesthesia and did not regain consciousness soon after termination of propofol infusion. Preoperative laboratory examination revealed anemia and a low blood total protein concentration, but there was no evidence of impaired liver function. While the anesthesiologists were waiting for the patient to regain consciousness, a surgeon mentioned that the common hepatic artery might have been occluded during surgical manipulation. Arterial blood samples were obtained 50 and 80 minutes after termination of propofol infusion, and the blood concentration of propofol was measured. We considered that clearance of propofol through the hepatic route may have been impaired; however, the actual blood concentrations of propofol were not significantly increased compared with the respective blood concentrations obtained in the simulation. Therefore, the acute liver damage did not significantly impair elimination of propofol. Because most propofol molecules in the blood bind to proteins and erythrocytes, it is suspected that the anemia and low blood total protein concentration led to an increase in the free fraction of propofol in the blood, thereby delaying emergence from anesthesia.