Treatment of transtentorial herniation unresponsive to hyperventilation using hypertonic saline. Effect on cerebral blood flow and metabolism

Objective: We tested the hypothesis that transtentorial herniation (TTH) represents a state of cerebral ischemia which can be reversed by hypertonic saline. Methods: We produced TTH (defined by acute dilatation of one or both pupils) in seven anesthetized mongrel dogs by creating supratentorial intracerebral hemorrhage with autologous blood injection. We measured serial regional CBF using radiolabeled microspheres; and cerebral oxygen extraction, and oxygen consumption (CMRO2) by serial sampling of cerebral venous blood from the saggital sinus. TTH (unresposive to hyperventilation) was successfully reversed following intravenous administration of 23.4% sodium chloride (1.4ml/kg) in all animals after a mean period of 25.7±4.9 minutes as documented by recovery of pupillary dilatation. Results: Compared to pre-hematoma ICP (14.1±1.7mm Hg, mean±SE), significant elevation in ICP was observed during TTH (36.2±7.2mm Hg). Compared to baseline values, there was significant reduction in rCBF(ml/100gm/min±SE) in brainstem (12.1±2.0 vs. 21.4±1.4); gray matter (18.2±2.1 vs. 31.4±1.8) and white matter (8.6±1.7 vs.18.7±0.9) in the hemisphere contralateral to the hematoma; and gray matter (12.9±2.9 vs. 27.9±2.2) and white matter (8.3±2.0 vs.19.9±1.0) in the ipsilateral hemisphere distant from the hematoma. Administration of 23.4% sodium chloride resulted in significant reduction in ICP at 15 minutes (12.7±1,4) and 30 minutes (15.6±3.1) post administration. rCBF values were restored in all regions studied after administration of 23.4% sodium chloride with an increase in CMRO2 (1.8±0.4 vs. 3.9±0.7 ml O2/100 gm/min). Compared with baseline values, significantly elevated rCBF in ipsilateral (31.7±2.5 vs. 63.4±11.7) and contralateral thalamus (28.7±1.9 vs. 45.5±5.7) were observed 15 minutes after administration of 23.4% sodium chloride. Conclusions; TTH represents a state of ischemia in brainstem and supratentorial gray and white matter. Hypertonic saline effectively reverses TTH, and restores both rCBF and CMRO2, although hyperemia may be observed immediately after reversal of TTH.