Respiratory depression associated with meperidine spinal anaesthesia

Intrathecal meperidine administration can provide surgical anaesthesia and postoperative analgesia for about two to six hours. We have observed two cases of respiratory depression associated with meperidine spinal anaesthesia. An 81-yr-old woman received 50 mg intrathecal meperidine for inguinal hernia repair. Supplemental oxygen was administered at 3 L.min-1 by nasal prongs. About 40 min later, the patient's oxygen saturation decreased from 97% to 87% and she was asked to take big breaths. She responded immediately and oxygen saturation returned to 97%. Two more similar episodes followed in the next five minutes. Naloxone 0.1 mg iv was administered and the oxygen saturation remained at 96-97% until completion of surgery about 15 min later. She had an uneventful recovery. A 24-yr-old healthy woman presented for tubal ligation eight hours after vaginal delivery of an infant. The surgical procedure was performed under spinal anaesthesia produced by 50 mg meperidine. During surgery, midazolam 2 mg iv was given for anxiolysis. About five minutes after admission to the postanaesthesia care unit, the patient's respiratory rate decreased to ten breaths per minute and oxygen saturation decreased to 89%. Supplemental oxygen at 3 L.min-1 was administered by nasal prongs. The patient was encouraged to take big breaths and the arterial oxygen saturation rapidly increased to 98-99%. Forty minutes later, nasal oxygen was discontinued. The patient maintained her oxygen saturation while breathing room air. She was then discharged to the ward and had an uneventful recovery course. We recommend that a patient's respiratory variables and oxygenation be closely monitored for at least one hour after intrathecal meperidine administration.