Regional cerebral blood flow following resuscitation from hemorrhagic shock with hypertonic saline. Influence of a subdural mass

After severe hemorrhage, hypertonic saline restores systemic hemodynamics and decreases intracranial pressure (ICP), but its effects on regional cerebral blood flow (rCBF) when used for resuscitation of experimental animals with combined shock and intracranial hypertension have not been reported. We compared rCBF changes (by radiolabeled microsphere technique) after resuscitation from hemorrhage with either 0.8 or 7.2% saline in animals with and without a right hemispheric subdural mass. We studied 24 mongrel dogs anesthetized with 0.5% halothane and 60% nitrous oxide. In group 1 (n = 12), hemorrhage reduced mean arterial pressure (MAP) to 45 mmHg for 30 min. In group 2 (n = 12), ICP was increased and maintained constant at 15 mmHg, whereas hemorrhage reduced MAP to 55 mmHg for 30 min (cerebral perfusion pressure [CPP] ~ 40 mmHg in each group). After the 30-min shock period, 6 animals in each group received one of two randomly assigned resuscitation fluids over a 5-min interval: 1) 7.2% hypertonic saline (HS; sodium 1,232 mEq·l^-1, volume 6.0 ml·kg^-1); or 2) 0.8% isotonic saline (SAL; sodium 137 mEq·l^-1, volume 54 ml·kg^-1). Once fluid resuscitation began, ICP was permitted to vary independently in both groups. Data were collected at baseline (before subdural balloon inflation in group 2), midway through the shock interval (T15), immediately after fluid infusion (T35), and 60 and 90 min later (T95, T155). In groups 1 and 2, ICP was significantly less in animals resuscitated with HS compared to those receiving SAL (P < 0.05). In group 2, rCBF in the right hemisphere was significantly greater in HS-treated than in SAL-treated dogs (P < 0.05). We conclude that when used for resuscitation from hemorrhagic shock with associated intracranial hypertension, 7.2% HS reduces ICP and increases rCBF.