Intracarotid saline infusion improves outcome from incomplete ischemia in rats

Previous studies suggest that rheological changes associated with ischemia may produce postischemic hypoperfusion. We tested whether intracarotid or intravenous infusions of saline improve neurological outcome from incomplete cerebral ischemia in rats. Rats were anesthetized with 1.4% isoflurane in air, and ischemia was produced by unilateral carotid artery ligation combined with hemorrhagic hypotension to 30 mm Hg for 30 minutes. Intracarotid (n = 10) or intravenous (n = 10) saline infusion (0.3 ml/min) decreased hematocrit 20% compared with control rats (n = 10). Neurological outcome was significantly improved in rats infused with intracarotid (p less than 0.05) but not intravenous saline during ischemia without a change in brain temperature. Cerebral blood flow, measured in a separate study using laser Doppler flowmetry (n = 5), decreased 70% (p less than 0.01) during carotid ligation and hypotension but was not changed by intracarotid saline infusion (p greater than 0.30). These results show that perfusion of ischemic brain with saline improves outcome by factors not related to changes in hematocrit, brain temperature, or intraischemic tissue blood flow.