Cerebrovascular Effects of Small Volume Resuscitation from Hemorrhagic Shock

Abstract

To determine if hypertonic and hyperoncotic resuscitation solutions exerted comparable effects on cerebral hemodynamics following hemorrhagic shock, we compared randomly assigned, equal volumes (6.0 ml/kg) of hypertonic (7.2%) saline (HS) and hyperoncotic (20%) hydroxyethyl starch (HES) for resuscitation from acute experimental hemorrhage in 12 anesthetized dogs. Regional cerebral blood flow (radiolabeled microspheres), intracranial pressure (cisternal catheter), and systemic hemodynamics were recorded. Rapid hemorrhage reduced the mean arterial pressure to 45 mm Hg for 30 min. Resuscitation fluids were infused over 5 min. Both fluids restored mean arterial pressure and cardiac output equally. However, at 60 min following resuscitation, cardiac output decreased in the HS group in comparison to the HES group (1.7 +/- 0.1 vs. 3.1 +/- 0.2 L/min, p <0.05). Cardiac output rapidly declined, however, in the HS group in comparison to the HES group (p <0.05 60 min following resuscitation). Intracranial pressure and cerebral perfusion pressure were similar at all intervals. Regional cerebral blood flow was similar following both fluids. Neither fluid restored cerebral oxygen transport to baseline values. Based on these data, the authors conclude that, following severe hemorrhagic shock of brief duration, systemic and cerebral hemodynamic values are restored equally well by highly concentrated colloid or by hypertonic saline, although hypertonic saline only transiently improves cardiac output.