COMPLETE PREVENTION OF POSTISCHEMIC SPINAL-CORD INJURY BY MEANS OF REGIONAL INFUSION WITH HYPOTHERMIC SALINE AND ADENOSINE

Spinal cord injury after operations on the descending thoracic and tho racoabdominal aorta remains a persistent clinical problem. Previous at tempts to decrease the risk of this devastating complication by loweri ng the rate of metabolism of the spinal cord have met with varying suc cess. We hypothesized that the tolerance of the spinal cord to an isch emic insult could be improved by means of adenosine. Twenty New Zealan d white rabbits underwent 40 minutes of isolated infrarenal aortic occ lusion after heparin anticoagulation. Clamps were placed both below th e left renal vein and above the aortic bifurcation. In 10 rabbits (gro up A), a bolus of adenosine (100 mg) was infused into the isolated aor tic segment immediately after crossclamping and this bolus was followe d by a flush of hypothermic saline (8 degrees C, 30 ml/kg) over the fi rst 10 minutes of ischemia. In one control group of five animals (grou p B), the descending infrarenal aorta was crossclamped without infusio n of adenosine or saline. In another control group of five animals (gr oup C), the aortic segment was flushed with normothermic saline (37 de grees C) in a fashion identical to that of the study group. The aortic clamps were removed after 40 minutes, the abdomen was closed, and the animals were allowed to recover from anesthesia. Spinal cord function was assessed 12, 24, 48, 72, and 96 hours after operation by the Tarl ov scale. All animals were put to death at 96 hours after operation an d spinal cords were harvested for histologic analysis. The spinal cord function of all group A animals was fully intact with Tarlov scores o f 5; group B and group C animals were all paraplegic with Tarlov score s of 0 (p < 0.001, general linear models analysis of variance). Histol ogic examination of spinal cords from group A rabbits revealed no evid ence of cord injury, whereas spinal cords from groups B and C had evid ence of extensive cord injury with central gray necrosis, axonal swell ing, dissolution of Nissl substance, and astrocyte and macrophage infi ltration. Regional infusion of the crossclamped infrarenal rabbit aort a with hypothermic saline and adenosine completely prevented paraplegi a in our model despite a 40-minute ischemic insult.