Skin heating during simulated hemorrhage lowers arterial blood pressure but not tolerance following exercise in a cold environment

Skin heating helps avoid hypothermia in trauma victims but may influence the systolic (SBP) and mean arterial blood pressures (MAP) helping to guide resuscitation. We examined the effect of skin heating on tolerance and arterial blood pressure during lower body negative pressure (LBNP) across four trials. Nine participants completed 15 exercise intervals [60 s 88% peak power output (PPO) and 60 s 10% PPO] in a cold environment (0 degrees C, 70% RH) lowering mean skin temperature (Tsk) before undergoing LBNP to pre syncope where Tsk remained low (Cold Trial: 27.6 +/- 1.1 degrees C) or was increased via a water-perfused suit 60 s into LBNP to 32.3 +/- 0.7 degrees C (Normothermic Trial), 34.8 +/- 0.4 degrees C (Warm Trial), or 36.1 +/- 0.8 degrees C (Hot Trial). Tsk was different between trials (P = 0.001). Core temperature was not different between trials, increasing with exercise (36.9 +/- 0.3 degrees C to 37.9 +/- 0.4 degrees C) and remaining elevated during LBNP (37.7 +/- 0.4 degrees C). During LBNP, MAP was greatest in the Cold Trial (88 +/- 7 mmHg) and relatively lowered in the Normothermic (83 +/- 5 mmHg), Warm (82 +/- 5 mmHg), and Hot Trials (79 +/- 7 mmHg; all P <= 0.017 vs. Cold). SBP was greatest in the Cold (111 +/- 9 mmHg) and Normothermic Trials (110 +/- 10 mmHg) and relatively lowered in the Warm (105 +/- 7 mmHg) and Hot Trials (103 +/- 11 mmHg; both P <= 0.037). LBNP tolerance was not different between trials (P = 0.746). Following exercise in a cold environment, skin heating during simulated hemorrhage lowers arterial blood pressures and has implications for prehospital care of trauma victims. NEW & NOTEWORTHY Skin heating helps avoid hypothermia in trauma victims but may influence arterial blood pressures, thus helping to guide resuscitation depending on the type of injury. Following exercise in a cold environment, arterial blood pressure was elevated during LBNP with cold skin but lowered with skin heating without changing LBNP tolerance. These findings are important for understanding the effect of skin heating on arterial blood pressure control in the prehospital and combat casualty care of trauma victims.