Mechanisms of orthostatic intolerance during heat stress

Zachary J. Schlader, Thad E. Wilson, Craig G. Crandall

Research output: Contribution to journalReview articlepeer-review

51 Scopus citations


Heat stress profoundly and unanimously reduces orthostatic tolerance. This review aims to provide an overview of the numerous and multifactorial mechanisms by which this occurs in humans. Potential causal factors include changes in arterial and venous vascular resistance and blood distribution, and the modulation of cardiac output, all of which contribute to the inability to maintain cerebral perfusion during heat and orthostatic stress. A number of countermeasures have been established to improve orthostatic tolerance during heat stress, which alleviate heat stress induced central hypovolemia (e.g., volume expansion) and/or increase peripheral vascular resistance (e.g., skin cooling). Unfortunately, these countermeasures can often be cumbersome to use with populations prone to syncopal episodes. Identifying the mechanisms of inter-individual differences in orthostatic intolerance during heat stress has proven elusive, but could provide greater insights into the development of novel and personalized countermeasures for maintaining or improving orthostatic tolerance during heat stress. This development will be especially impactful in occuational settings and clinical situations that present with orthostatic intolerance and/or central hypovolemia. Such investigations should be considered of vital importance given the impending increased incidence of heat events, and associated cardiovascular challenges that are predicted to occur with the ensuing changes in climate.

Original languageEnglish
Pages (from-to)37-46
Number of pages10
JournalAutonomic Neuroscience: Basic and Clinical
StatePublished - Apr 1 2016

Bibliographical note

Funding Information:
We would like to express gratitude to the NIH — National Heart, Lung, and Blood Institute , the Department of Defense , NIOSH Education and Research Center , and the American Heart Association for supporting much of our work presented in this review.

Publisher Copyright:
© 2015 Elsevier B.V.


  • Cardiovascular control
  • Cutaneous blood flow
  • Hyperthermia
  • Orthostasis
  • Sympathetic nerve activity

ASJC Scopus subject areas

  • Endocrine and Autonomic Systems
  • Clinical Neurology
  • Cellular and Molecular Neuroscience


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