Hemostatic responses to exercise, dehydration, and simulated bleeding in heat-stressed humans
Abstract
Heat stress followed by an accompanying hemorrhagic challenge may influence hemostasis. We tested the hypothesis that hemostatic responses would be increased by passive heat stress, as well as exercise-induced heat stress, each with accompanying central hypovolemia to simulate a hemorrhagic insult. In aim 1, subjects were exposed to passive heating or normothermic time control, each followed by progressive lower-body negative pressure (LBNP) to presyncope. In aim 2 subjects exercised in hyperthermic environmental conditions, with and without accompanying dehydration, each also followed by progressive LBNP to presyncope. At baseline, pre-LBNP, and post-LBNP (30)] to 5.1% post-LBNP compared with 1.5% (time control) and 2.7% in N-LBNP ( P = 0.05 for main effect). Hyperthermia also potentiated increased platelet counts post-LBNP as follows: 274 K/µl for H-LBNP, 246 K/µl for N-LBNP, and 196 K/µl for time control ( P 30) was increased to 6–10% when subjects were dehydrated compared with an increase to 2–4% when hydrated ( P = 0.05 for treatment). Central hypovolemia via LBNP is a primary driver of hemostasis compared with hyperthermia and dehydration effects. However, hyperthermia does induce significant thrombocytosis and by itself causes an increase in clot lysis. Dehydration associated with exercise-induced heat stress increases clot lysis but does not affect exercise-activated or subsequent hypovolemia-activated hemostasis in hyperthermic humans. Clinical implications of these findings are that quickly restoring a hemorrhaging hypovolemic trauma patient with cold noncoagulant fluids (crystalloids) can have serious deleterious effects on the body’s innate ability to form essential clots, and several factors can increase clot lysis, which should therefore be closely monitored.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Feb 01, 2019
- Source ID
- 10.1152/ajpregu.00223.2018
Entities
People
- Andrew P Cap
- Craig G Crandall
- Daniel Gagnon
- Eric Rivas
- James K. Aden
- Jena Kern
- Matthew A. Borgman
- Morten Zaar
- Natalie J. Koons
- Victor A Convertino
- Zachary J Schlader
Organizations
- Institute for Exercise and Environmental Medicine
- National Institutes of Health
- San Antonio Military Medical Center
- Texas Tech University
- United States Army Institute of Surgical Research
- United States Department of Defense
- University at Buffalo
- University of Texas at Austin
- Université de Montréal