Hydroxyethyl-starch in transient experimental focal cerebral ischemia

In a model of focal cerebral ischaemia in the cat (transorbital occlusion of the middle cerebral artery for 60 minutes, thereafter 6 hours reperfusion by clip removal), hydroxyethyl-starch (HAES) (ELOHES; Leopold Pharma GmbH, Graz, Austria) was administered intravenously before and during the ischaemic episode as a 6% or as a 10% solution in a randomised manner (6 animals each group). The size of the developing cerebral infarct was not significantly different when comparing the 6% and the 10% group with the controls (SALINE). Collateral circulation to the infarct border (pial arteries on the suprasylvian gyrus) was also not significantly different between the two groups, except for the first hour of reperfusion, where vessels of the 6% group were wider than vessels of the 10% group. At the infarct border (ectosylvian gyrus) small resistance vessels were significantly more dilated in the 6% than in the 10% group both during the occlusion period and during the reperfusion episode after removal of the clip. Pial arteries dilated less in both HAES-groups than in the controls. It can be assumed, that HAES-incuded decrease of plasma viscosity led to an elevation of blood flow velocity and blood flow quantity (CBF). But the latter might be counteracted by autoregulation of CBF, i.e. vasoconstriction. Thus, a possible positive effect of HAES might in part be counteracted by autoregulation, which explains that no significant therapeutic effect could be achieved.