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Respiratory Depression following Administration of Intrathecal Bupivacaine to an Opioid-Dependent Patient

OBJECTIVE: To document two cases of respiratory depression in patients receiving morphine once the stimulating effect of pain on respiration was removed by bupivacaine. CASE SUMMARIES: Case 1: A 72-year-old 84-kg white man with cancer of the bladder and bone metastases had intense back and leg pain that was treated with intrathecal morphine for 6 months at an increasing dosage up to 10 mg twice daily. The intrathecal route was avoided for 4 days because of a suspected local infection at the site of the intrathecal catheter. During this 4-day period the patient received extended-release morphine and subcutaneous morphine daily. When the intrathecal route was used again, he received an identical dose of morphine plus bupivacaine and epinephrine. Ten minutes after the injection, fatal respiratory distress occurred. Case 2: A 92-year-old white woman was admitted for revascularization of arteritis on her left leg. To treat a painful sacrum and heel bedsores, she received extended-release oral morphine for 8 days. Induction of the intrathecal anesthesia was performed with bupivacaine. After 10 minutes, the patient became subcomatose, with miosis and apnea. Intravenous naloxone restored spontaneous respiration and normal consciousness. CONCLUSIONS: Pain is a physiologic antagonist of the respiratory depressant effects of opioid analgesics. By reducing pain stimulation, bupivacaine may make patients more susceptible to opioid respiratory depression. Such situations require titration of bupivacaine and other analgesics as well as increased monitoring of the patient.