Urapidil enhances subcutaneous tissue oxygen tension during convective rewarming of mildly hypothermic rats

Abstract To investigate whether urapidil ( α 1 -adrenergic antagonist/5-HT 1A agonist) enhances subcutaneous tissue oxygen tension (P sq O 2 ) during convective rewarming, we performed a prospective, randomized, placebo-controlled animal study. Mild hypothermia was achieved by surface cooling. Protocol A: before rewarming : i.v. bolus of 1.0 ml NaCl 0.9%/kg body weight; Protocol B: before rewarming: i.v. bolus of 5 mg urapidil/kg body weight. Urapidil significantly reduced the rewarming time (placebo: 30.2±2.9 min, urapidil: 24.2±2.3 min, P = 0.0 1 2 ) and the P sq O 2 during rewarming was significantly enhanced ( P = 0.0 2 3 , AUC P sq O 2 ‐ placebo versus AUC P sq O 2 ‐ urapidil ). The α 1 -adrenergic antagonist/5-HT 1A agonist urapidil accelerates convective rewarming and enhances P sq O 2 during rewarming in mildly hypothermic rats. Obviously, urapidil therapy increased the shift of heat from the periphery to the core. It is known that 5-HT 1A receptor agonists reduce thermoregulatory thresholds to cold. Therefore, a reduction in oxygen consumption with an increased oxygen delivery to subcutaneous tissues by urapidil is a further possible mechanism.