[Abnormal Low Blood Pressure after Induction of General Anesthesia in a Patient on Medication for Depression]

A patient under medication for depression underwent orthopedic surgery for osteoarthritis of the knee four times. For the second surgery, general anesthesia was induced with propofol, remifentanil, and rocuronium. Immediately after induction, she developed severe hypotension that was resistant to vasopressors. The hypotension likely resulted from the effect of psychotropic drugs, including levomepromazine, olanzapine, and clomipramine, which she had been receiving for a long time. Although her blood pressure recovered, the surgery was cancelled. We performed spinal anesthesia for the subsequent surgery to minimize interactions between anesthetic and psychotropic agents. A continuous infusion of the local anesthetic bupivacaine through a epidural catheter was started during the surgery. Although her general condition was stable during surgery, she developed hypotension after returning to the ward. We suspected an interaction with the psychotropic agents, and thus stopped infusion of the local anesthetic, after which, her blood pressure gradually increased. The first and fourth surgeries were performed uneventfully under spinal anesthesia. This case suggests that anesthesiologists should pay special attention to the interaction between anesthetic and psychotropic agents during anesthesia. Further, psychotropic drug withdrawal before surgery should be considered, if possible. Moreover, vasopressin may be utilized to treat catecholamine-resistant hypotension.