• T Shine and M Nugent.
• Department of Anesthesiology, Mayo Clinic, Rochester, MN.
• J Cardiothorac Anesth. 1990 Apr 1; 4 (2): 185-93.

AbstractParaplegia is a devastating complication of surgery on the descending thoracic aorta. During surgical repair, the aorta is cross-clamped, and nitroprusside is often used to treat arterial hypertension that can occur above the cross-clamp. Twenty-one dogs were studied to determine the effects of nitroprusside on intraspinal pressures, mean aortic pressures below the cross-clamp, and spinal cord perfusion pressure. Perfusion pressure in spinal radicular arteries originating below the aortic cross-clamp was estimated as the distal aortic pressure minus intraspinal pressure. Nitroprusside was used to return the mean arterial pressure above the cross-clamp to values similar to the pre-cross-clamp levels in 7 dogs. Fourteen animals did not receive sodium nitroprusside. Aortic cross-clamping resulted in small but significant increases in intraspinal pressure (4.3 +/- 0.8 to 7.5 +/- 0.9 mm Hg in non-nitroprusside-treated dogs, and 3.4 +/- 1.0 to 5.6 +/- 1.5 mm Hg in the nitroprusside group before nitroprusside). Nitroprusside caused a further increase in intraspinal pressure (5.6 +/- 1.5 to 8.3 +/- 2.2 mm Hg) and a decrease in aortic pressure below the cross-clamp (26 +/- 5 to 18 +/- 4 mm Hg). The increase in intraspinal pressure and the decrease in aortic pressure below the cross-clamp after nitroprusside resulted in a decrease in spinal cord perfusion pressure from 19 +/- 5 mm Hg to 11 +/- 4 mm Hg. Because nitroprusside decreases spinal cord perfusion pressure and may increase the risk of spinal cord ischemia, the avoidance of large doses of nitroprusside to arbitrarily return mean arterial pressure above the cross-clamp to pre-cross-clamp levels is recommended.

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