Baroreceptor unloading does not limit forearm sweat rate during severe passive heat stress

• This study tested the hypothesis that sweat rate during passive heat stress is limited by baroreceptor unloading associated with heat stress. Two protocols were performed in which healthy subjects underwent passive heat stress that elicited an increase in intestinal temperature of similar to 1.8 degrees C. Upon attaining this level of hyperthermia, in protocol 1 (n = 10, 3 females) a bolus (19 ml/kg) of warm (similar to 38 degrees C) isotonic saline was rapidly (5-10 min) infused intravenously to elevate central venous pressure (CVP), while in protocol 2 (n = 11, 5 females) phenylephrine was infused intravenously (60-120 mu g/min) to return mean arterial pressure (MAP) to normothermic levels. In protocol 1, heat stress reduced CVP from 3.9 +/- 1.9 mmHg (normothermia) to -0.6 +/- 1.4 mmHg (P < 0.001), while saline infusion returned CVP to normothermic levels (5.1 +/- 1.7 mmHg; P > 0.999). Sweat rate was elevated by heat stress (1.21 +/- 0.44 mg.cm(-2).min(-1)) but remained unchanged during rapid saline infusion (1.26 +/- 0.47 mg.cm(-2).min(-1), P = 0.5), whereas cutaneous vascular conductance increased from 77 +/- 10 to 101 +/- 20% of local heating max (P = 0.029). In protocol 2, MAP was reduced with heat stress from 85 +/- 7 mmHg to 76 +/- 8 mmHg (P = 0.048). Although phenylephrine infusion returned MAP to normothermic levels (88 +/- 7 mmHg; P > 0.999), sweat rate remained unchanged during phenylephrine infusion (1.39 +/- 0.22 vs. 1.41 +/- 0.24 mg.cm(-2).min(-1); P > 0.999). These data indicate that both cardiopulmonary and arterial baroreceptor unloading do not limit increases in sweat rate during passive heat stress.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Hälsovetenskap -- Folkhälsovetenskap, global hälsa, socialmedicin och epidemiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Health Sciences -- Public Health, Global Health, Social Medicine and Epidemiology (hsv//eng)

Nyckelord

arterial baroreceptors

cardiopulmonary baroreceptors

hyperthermia

central venous pressure

skin ood flow

sweat rate

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)