Attenuation of circulatory shock and cerebral ischemia injury in heat stroke by combination treatment with dexamethasone and hydroxyethyl starch.

Background: Increased systemic cytokines and elevated brain levels of monoamines, and hydroxyl radical productions are thought to aggravate the conditions of cerebral ischemia and neuronal damage during heat stroke. Dexamethasone (DXM) is a known immunosuppressive drug used in controlling inflammation, and hydroxyethyl starch (HES) is used as a volume-expanding drug in cerebral ischemia and/or cerebral injury. Acute treatment with a combined therapeutic approach has been repeatedly advocated in cerebral ischemia experiments. The aim of this study is to investigate whether the combined agent (HES and DXM) has beneficial efficacy to improve the survival time (ST) and heat stroke-induced cerebral ischemia and neuronal damage in experimental heat stroke.

Methods: Urethane-anesthetized rats underwent instrumentation for the measurement of colonic temperature, mean arterial pressure (MAP), local striatal cerebral blood flow (CBF), heart rate, and neuronal damage score. The rats were exposed to an ambient temperature (43 degrees centigrade) to induce heat stroke. Concentrations of the ischemic and damage markers, dopamine, serotonin, and hydroxyl radical productions in corpus striatum, and the serum levels of interleukin-1 beta, tumor necrosis factor-alpha and malondialdehyde (MDA) were observed during heat stroke.

Results: After heat stroke, the rats displayed circulatory shock (arterial hypotension), decreased CBF, increased the serum levels of cytokines and MDA, increased cerebral striatal monoamines and hydroxyl radical productions release, and severe cerebral ischemia and neuronal damage compared with those of normothermic control rats. However, immediate treatment with the combined agent at the onset of heat stroke confers significant protection against heat stroke-induced circulatory shock, systemic inflammation; cerebral ischemia, cerebral monoamines and hydroxyl radical production overload, and improves neuronal damage and the ST in rats.

Conclusions: Our results suggest that the combination of a colloid substance with a volume-expanding effect and an anti-inflammatory agent may provide a better resuscitation solution for victims with heat stroke.