Blood Flow Distribution during Heat Stress: Cerebral and Systemic Blood Flow

• Published in: Journal of cerebral blood flow and metabolism Vol. 33; no. 12; pp. 1915 - 1920
• Main Authors: Ogoh, Shigehiko, Sato, Kohei, Okazaki, Kazunobu, Miyamoto, Tadayoshi, Hirasawa, Ai, Morimoto, Keiko, Shibasaki, Manabu
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.12.2013; Sage Publications Ltd; Nature Publishing Group
• Subjects: Age; Blood Flow Velocity; Brain - blood supply; Cardiac Output; Carotid Artery, Common - diagnostic imaging; Carotid Artery, Common - physiology; Cerebrovascular Circulation; Hemodynamics; Humans; Hyperthermia, Induced; Original; Regional Blood Flow; Stress, Physiological; Ultrasonography; Vertebral Artery - diagnostic imaging; Vertebral Artery - physiology; Young Adult; cardiac output; arterial pressure; hyperthermia; Doppler ultrasound; humans
• ISSN: 0271-678X; 1559-7016; 1559-7016
• DOI: 10.1038/jcbfm.2013.149

The purpose of the present study was to assess the effect of heat stress-induced changes in systemic circulation on intra- and extracranial blood flows and its distribution. Twelve healthy subjects with a mean age of 22±2 (s.d.) years dressed in a tube-lined suit and rested in a supine position. Cardiac output (Q), internal carotid artery (ICA), external carotid artery (ECA), and vertebral artery (VA) blood flows were measured by ultrasonography before and during whole body heating. Esophageal temperature increased from 37.0±0.2°C to 38.4±0.2°C during whole body heating. Despite an increase in Q (59±31%, P<0.001), ICA and VA decreased to 83±15% (P=0.001) and 87±8% (P=0.002), respectively, whereas ECA blood flow gradually increased from 188±72 to 422±189 mL/minute (+135%, P<0.001). These findings indicate that heat stress modified the effect of Q on blood flows at each artery; the increased Q due to heat stress was redistributed to extracranial vascular beds.