ObjectiveTo determine whether direct retrograde ice saline infusion in the jugular vein without cardiopulmonary bypass protects rat brains after heatstroke.DesignRandomized, controlled, prospective study.SettingUniversity physiology research laboratory.SubjectsSprague-Dawley rats (270–320 g, males).InterventionsRats were randomized into three groups and given a) no resuscitation after onset of heat stroke (HS, n = 8); b) ice saline infusion in the femoral vein after onset of heat stroke (HS + F, n = 8); or c) retrograde ice saline infusion in the external jugular vein after onset of heat stroke (HS + J, n = 8). Rats were exposed to an ambient temperature of 43°C after vessel cannulation. Their mean arterial pressure, heart rate, colonic temperature, and brain temperature were continuously recorded. Survival time and brain pathology were checked.Measurements and Main ResultsAlthough colonic temperature decreased 0.8–1.0°C 15 mins after heatstroke in all groups, no treatment-related changes in colonic temperature were noted in any group. However, significant changes were observed in brain temperature. Fifteen minutes after heatstroke, brain temperature was 37.6 ± 0.4°C, 36.1 ± 0.4°C, and 33.6 ± 0.8°C in HS, HS + F, and HS + J, respectively. Survival time was 16.1 ± 2.1, 33.0 ± 3.8, and >120 mins in these groups, respectively. Neuron damage score was significantly lower in HS + J and without lateralization.ConclusionsWe successfully demonstrated that direct retrograde hypothermic perfusion via the jugular vein without cardiopulmonary bypass protected the brain after heat stroke. This technique cooled the brain but did not significantly interfere with body temperature.