Naloxone and spinal fluid drainage as adjuncts in the surgical treatment of thoracoabdominal and thoracic aneurysms. Forty-seven patients who were treated for thoracoabdominal or thoracic aneurysms over a 5 1/2-year period were analyzed for neurologic deficit risk. Patients were divided into two groups for analysis. Twenty-four patients, who were treated from January 1984 to December 1986, did not undergo spinal fluid drainage or naloxone administration (group A). Twenty-three patients, who were treated from January 1987 to August 1989, had spinal fluid drainage (group B); 12 patients in this group also received naloxone as an intravenous drip at 1 microgram/kg/hr for 48 hours after surgery. Permanent neurologic deficits occurred in seven (29%) group A patients but in only one (4%) group B patient, who did not receive naloxone (p less than 0.03). The first two group B patients to receive naloxone showed complete reversal of neurologic deficits on waking from anesthesia. This significant reduction in neurologic deficit was associated with an increased 1-year survival rate (72% in group A, 91% in group B). We conclude that the use of naloxone and spinal fluid drainage reduces the incidence of neurologic deficit that is associated with repair of thoracoabdominal and thoracic aortic aneurysms. This reduction in neurologic deficit is associated with improved survival in the long term. The observed reversal of postoperative neurologic deficits with naloxone implicates opiates as a major factor in the pathophysiology of spinal cord ischemia. 