GLOBAL CEREBRAL-ISCHEMIA - EFFECTS OF PENTASTARCH AFTER REPERFUSION

There has been considerable interest in the use of synthetic hydroxyet hyl starch macromolecules (e.g., pentastarch, a colloid used for intra vascular fluid replacement) to reduce microvascular permeability and r eperfusion injury after cerebral ischemia. A recent report found that hemodilution with pentastarch reduced brain injury and cerebral edema after temporary focal ischemia. We compared the effects of pentastarch versus 0.9% saline on brain edema after reperfusion in a model of tem porary global ischemia in halothane-anesthetized rabbits. To ensure th e validity of our model, we studied an additional group of animals in which we deliberately raised plasma osmolality with hypertonic saline (1.5%) in the expectation of finding a decreased brain water content a t the conclusion of the experiment. Animals were hemodiluted to a hema tocrit of 20% with normal saline (control group) (n = 9), pentastarch (n = 7), or hypertonic saline (n = 5). After hemodilution, the animals underwent a 25-min period of global cerebral ischemia, followed by 18 0 min of reperfusion. The animals were then killed and brain water con tent was assessed by microgravimetry and by the wet-dry weight method. As anticipated, colloid osmotic pressure was maintained in the pentas tarch group, and plasma osmolality became significantly increased in t he hypertonic saline group. There were no intergroup differences at an y time for central venous pressure, mean arterial pressure, intracrani al pressure, or Pace,. Brain water content was significantly decreased in the hypertonic saline group. No difference in brain water content was detected between the control group and the pentastarch group. In t his model of global cerebral ischemia, no decrease in brain water cont ent could be associated with the administration of pentastarch.