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Hemodynamic responses to severe heat stress in rats: implications for blood pressure regulation (1104.20)
Author(s) -
Charkoudian Nisha,
Quinn Carrie,
Duran Rocio,
Leon Lisa
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.1104.20
Subject(s) - heart rate , dehydration , hemodynamics , blood pressure , thermoregulation , heat stress , cardiac output , medicine , hysteresis , core temperature , endocrinology , cardiology , chemistry , zoology , biology , biochemistry , physics , quantum mechanics
Increases in heart rate (HR) and cardiac output, and redistribution of blood flow to the periphery are key cardiovascular responses to heat exposure. We previously observed hysteresis in the HR response to heating in rats, whereby HR was higher for a given core temperature (Tc) during cooling/recovery compared to during heating. In the present study, we evaluated whether this hysteresis was associated with dehydration, and whether specific cardiovascular response patterns were associated with more negative outcomes. Tc, HR and arterial pressure were measured via radiotelemetry in conscious male Fischer 344 rats (n=22; 272.4 ± 4.7 g) during exposure to 37°C (heating phase) and during recovery at 20°C (cooling phase). HR increased substantially during heating. At Tc = 39.5°C, HR was 386 ± 5 bpm during the heating phase and 490 ± 14 bpm during the cooling phase (P< 0.001). HR hysteresis in recovery was coincident with substantial dehydration (7‐8%BW), but returned to baseline after ~20 min despite continued dehydration, suggesting these events were not linked. Independent of hysteresis, rats with the worst outcomes demonstrated a drop‐off in HR at end of heating. These findings provide further insight into multiple simultaneous stressors placed on integrative cardiovascular regulation during and immediately following heat stress. Research supported by USAMRMC. Author views not official US Army or DoD policy.