Hypothermic Retrograde Jugular Vein Flush with Saline and Perfluorocarbons in Heatstroke of Rats

Abstract

Pathogenesis of heatstroke may be due to direct thermal injury of the thermoregulatory centers in the brain that thermoregulatory failure and shock. Cooling is the treatment of choice for heatstroke, whereas no pharmacologic agents are helpful. However, despite aggressive systemic cooling, residual brain damage occurs in about 20% of patients. Since brain cooling has been considered an effective method for reducing ischemic injury of the brain, we speculated on the effectiveness of hypothermic retrograde jugular vein flush (RJVF) to cool the brain. In many investigations, perfluorocarbons (PFCs), inert organic compounds had a high affinity for oxygen and carbon dioxide, have been proposed as a replacement for donor blood as well as a therapy for minimizing ischemic tissue damage. According to reports, the intravenous infusion of PFCs has been shown to be beneficial in the treatment of stroke and hemorrhagic shock in animals. In present study, the intravenous treatment with normal saline (NS), ice NS at 4℃,PFCs, and PFCs at 4℃ via femoral vein or right external retrograde jugular vein flush (RJVF) would be evaluated and compared the therapeutic efficacy in rats of heatstroke. In experiment of heatstroke induction, animals under anesthesia were exposed to high ambient temperature (Ta) of 43℃ until mean arterial pressure (MAP) and local cerebral blood flow (CBF) in the striatum began to decrease from peak level, which was arbitrarily defined as the onset of heatstroke. Normothermic control rats were exposed to a temperature of 24℃. The values of MAP and CBF after heatstroke onset were all significantly lower than those in control rats. However, the situation of cerebral ischemia and neuronal damage in the striatum were greater. In rats intravenously infused with ice NS at 4℃ via RJVF immediately after the onset of heatstroke, the values of survival time ( interval between the onset of heatstroke and animal death) were apparently prolonged in contrast with another groups. Meanwhile, the heatstroke-induced hyperthermia of brain, arterial hypotension, and high degree of neuronal damage in heatstroke rats were all attenuated significantly by ice NS at 4℃ via RJVF administered immediately at the onset of heatstroke. Nevertheless, in PFCs-treated rats groups, the values of survival time were shorter than heatstroke control rats. Our results suggested that the experimental heatstroke syndromes can be effectively improved by ice NS at 4℃ via RJVF and led to prolong the survival time. However, the intravenous treatments with PFC (FC-77) in heatstroke rats need to assess further and discuss more closely.