Prevention of spinal cord ischemia by selective intercostal arterial infusion of prostaglandin E1

Purpose: A new protective method against the spinal cord ischemia that occurs during aortic clamping was investigated in dogs. Oxygenated blood containing prostaglandin E-1 (PGE(1)) was administered at the clamped aortic segment, and the effect was evaluated by measurement of the sensory evoked spinal potential (SESP). Methods: In 30 dogs, a thoracotomy was made with dissection of the thoracic aorta. After intravenous heparin (100 units/kg) was administered, the proximal and distal descending thoracic aortas were cross-clamped for 60 minutes. Group A (n = 10) received oxygenated blood at the rate of 1.0 ml/kg/min. Groups B (n = 10) and C (n = 10) received oxygenated blood at the same rate, with PGE(1) at the dosage of 25 and 50 ng/kg/min, respectively. The infusion was continuously administered throughout the entire period of ischemia. SESP was measured with epidural electrodes before clamping, 10 and 60 minutes after clamping, and 10 and 60 minutes after declamping. Neurologic outcome was assessed at 24 hours after the operation and graded according to the method of Tarlov. Results: There was no significant hemodynamic change in any group. At 60 minutes after clamping and at 10 and 60 minutes after declamping, the amplitude of SESP was lower than that at preclamping in groups A and B (p < 0.05). At 60 minutes after clamping and at 10 and 60 minutes after declamping, the SESP was more markedly decreased in group A compared with groups B and C. Regarding postoperative neurologic outcome, the dogs with SESP amplitude of more than 50% of the preclamping control value at 60 minutes after clamping showed neither paralysis nor paraplegia. Seven of nine dogs with less than 50% SESP amplitude showed neurogenic deficit. In a comparison of groups A, B, and C, the Tarlov score for group A dogs was significantly lower than that for group C dogs (p < 0.05). Conclusion: In this model, PGE(1) administration at the rate of 50 ng/kg/min showed sufficient spinal cord protection against ischemia without a decrease in the blood pressure. Further studies are needed to determine the dose that will provide the maximal protective effect and to determine the maximum duration of ischemia against which PGE(1) shows protective effects.