LONGITUDINAL-STUDY OF CEREBRAL SPINAL-FLUID DRAINAGE IN POLYETHYLENE-GLYCOL CONJUGATED SUPEROXIDE-DISMUTASE IN PARAPLEGIA ASSOCIATED WITH THORACIC AORTIC CROSS-CLAMPING

It has been hoped that pharmacologic prophylaxis in thoracic aortic cross-clamping may avert the unpredictable complication of spinal cord paraplegia, may avoid the mechanical difficulties associated with shunts, partial bypass, or monitoring devices, and may serve as a substitute for or as an adjunct to cerebral spinal fluid drainage. Toward this end 21 mongrel dogs were studied in four groups and underwent 60 minutes of thoracic aortic cross-clamping: group I, five with thoracic aortic cross-clamping; group II, five with thoracic aortic cross-clamping and cerebral spinal fluid drainage; group III, five with thoracic aortic cross-clamping, cerebrospinal fluid drainage and intravenous administration of a single dose (5000 units/kg) of polyethylene glycol-conjugated superoxide dismutase (PEG-SOD) given 15 to 20 minutes before thoracic aortic cross-clamping; and group IV, six with thoracic aortic cross-clamping and PEG-SOD. Paraplegia was graded by the Tarlov method at 24 hours and up to 5 days after thoracic aortic cross-clamping. The carotid and femoral artery pressures, the central venous pressure, and core temperature, taken during the experiment and at the time the dogs were killed, were found to be similar between groups. At 24 hours all dogs in group I were paraplegic; groups II and III had no paraplegic dogs (p < 0.01), and group IV had fewer paraplegic dogs (two of six) than group I (p < 0.05). Paraplegia was averted in all dogs treated with cerebral spinal fluid drainage, even 5 days after thoracic aortic cross-clamping. However, in group IV (PEG-SOD) delayed paraplegia developed in two dogs, but two other dogs continued to be fully intact neurologically over the 5-day study. These observations suggest that free oxygen radicals may play a role in the clinical morbidity associated with thoracic aortic cross-clamping, but longitudinal studies with larger numbers of experimental subjects are necessary to evaluate fully the effectiveness of scavenger therapy in this setting.