We describe the use of a novel endothermic surface cooling device, CAERvest®, on 3 marthon runners who had rectal temperatures (proxy for core body temperature, CBT) above 40°C. Two recovered rapidly and completely and were discharged home from hospital the same day. The third runner, with a rectal temperature of42.1°C, cooled to 37.5°C within 32 minttes. He required hospital admission for severe heat illness-‐associated complications but survived. There were no adverse effects from CAERvest
use. Mean rates of CBT fall were 0.126°C/min. User acceptability was high, with positive qualitative feedback on ease of use and efficacy. In these patients, CAERvest has reduced CBT rapidly and safely in heatstroke.