Colloid volume loading does not mitigate decreases in central blood volume during simulated hemorrhage while heat stressed

TY - JOUR

T1 - Colloid volume loading does not mitigate decreases in central blood volume during simulated hemorrhage while heat stressed

AU - Crandall, Craig G

AU - Wilson, Thad E

AU - Marving, Jens

AU - Bundgaard-Nielsen, Morten

AU - Seifert, Thomas

AU - Klausen, Thomas

AU - Andersen, Flemming

AU - Secher, Niels

AU - Hesse, Birger

PY - 2012/2

Y1 - 2012/2

N2 - Heat stress results in profound reductions in the capacity to withstand a simulated haemorrhagic challenge; however, this capacity is normalized if the individual is volume loaded prior to the challenge. The present study tested the hypothesis that volume loading during passive heat stress attenuates the reduction in regional blood volumes during a simulated haemorrhagic challenge imposed via lower-body negative pressure (LBNP). Seven subjects underwent 30 mmHg LBNP while normothermic, during passive heat stress (increased internal temperature ∼1°C), and while continuing to be heated after intravenous colloid volume loading (11 ml kg -1). Relative changes in torso and regional blood volumes were determined by gamma camera imaging with technetium-99m labelled erythrocytes. Heat stress reduced blood volume in all regions (ranging from 7 to 16%), while subsequent volume loading returned those values to normothermic levels. While normothermic, LBNP reduced blood volume in all regions (torso: 22 ± 8%; heart: 18 ± 6%; spleen: 15 ± 8%). During LBNP while heat stressed, the reductions in blood volume in each region were markedly greater when compared to LBNP while normothermic (torso: 73 ± 2%; heart: 72 ± 3%; spleen: 72 ± 5%, all P < 0.001 relative to normothermia). Volume loading during heat stress did not alter the extent of the reduction in these blood volumes to LBNP relative to heat stress alone (torso: 73 ± 1%; heart: 72 ± 2%; spleen: 74 ± 3%, all P > 0.05 relative to heat stress alone). These data suggest that blood volume loading during passive heat stress (via 11 ml kg -1 of a colloid solution) normalizes regional blood volumes in the torso, but does not mitigate the reduction in central blood volume during a simulated haemorrhagic challenge combined with heat stress.

AB - Heat stress results in profound reductions in the capacity to withstand a simulated haemorrhagic challenge; however, this capacity is normalized if the individual is volume loaded prior to the challenge. The present study tested the hypothesis that volume loading during passive heat stress attenuates the reduction in regional blood volumes during a simulated haemorrhagic challenge imposed via lower-body negative pressure (LBNP). Seven subjects underwent 30 mmHg LBNP while normothermic, during passive heat stress (increased internal temperature ∼1°C), and while continuing to be heated after intravenous colloid volume loading (11 ml kg -1). Relative changes in torso and regional blood volumes were determined by gamma camera imaging with technetium-99m labelled erythrocytes. Heat stress reduced blood volume in all regions (ranging from 7 to 16%), while subsequent volume loading returned those values to normothermic levels. While normothermic, LBNP reduced blood volume in all regions (torso: 22 ± 8%; heart: 18 ± 6%; spleen: 15 ± 8%). During LBNP while heat stressed, the reductions in blood volume in each region were markedly greater when compared to LBNP while normothermic (torso: 73 ± 2%; heart: 72 ± 3%; spleen: 72 ± 5%, all P < 0.001 relative to normothermia). Volume loading during heat stress did not alter the extent of the reduction in these blood volumes to LBNP relative to heat stress alone (torso: 73 ± 1%; heart: 72 ± 2%; spleen: 74 ± 3%, all P > 0.05 relative to heat stress alone). These data suggest that blood volume loading during passive heat stress (via 11 ml kg -1 of a colloid solution) normalizes regional blood volumes in the torso, but does not mitigate the reduction in central blood volume during a simulated haemorrhagic challenge combined with heat stress.

U2 - 10.1113/jphysiol.2011.223602

DO - 10.1113/jphysiol.2011.223602

M3 - Journal article

C2 - 22219334

SN - 0022-3751

SP - 1287

EP - 1297

JO - Journal of Physiology

JF - Journal of Physiology

ER -