Spinal cord protection with intravenous nimodipine. A functional and morphologic evaluation.

The purpose of this study is to determine the effects of ischemia in the spinal cord when a calcium channel blocker, nimodipine, is administered intravenously before, during, and after crossclamping of the thoracic aorta. In this series of experiments, 18 pigs underwent thoracotomies and had 17.5 to 18.0 cm of the thoracic aorta clamped for 30 minutes. By random selection, nine animals received intravenous nimodipine (2 micrograms/kg per minute) and nine control animals received only a carrier solution. Of the nine animals that received nimodipine, eight walked after the operation. In contrast, in the control group only two of nine animals walked. The ninth nimodipine-treated animals walked but had a severe delayed deterioration response. All animals, except one control animal, had a negative central spinal perfusion pressure. Morphologic examination of serial sections of spinal cords from control animals showed diffuse neuronal necrosis. In comparison, cords from the nimodipine group had swollen neurons accompanied by an inflammatory infiltrate and only occasional necrotic neurons. With this data, we conclude that certain calcium channel blockers, when administered in sufficient doses, can lend a protective effect to the spinal cord during ischemic events even when cord perfusion pressure has dropped to dangerously low levels.