Intravascular volume expansion in heat-stressed individuals restored the stroke volume to pulmonary capillary wedge pressure ratio during simulated hemorrhage to normothermic levels (4.8 vs 4.5 ml/mmHg; P=0.78).
Does volume expansion improve the stroke volume to pulmonary capillary wedge pressure ratio during reductions in central blood volume in heat-stressed males?
Volume infusion corrects the compromised Frank-Starling mechanism during simulated hemorrhage in heat-stressed individuals by shifting the operating point to a flatter portion of the curve.
Tasa de eventos absoluta: 4.8% vs 4.5%
valor p: p=0.78
During reductions in central blood volume while heat stressed, a greater decrease in stroke volume (SV) for a similar decrease in ventricular filling pressure, compared to normothermia, suggests that the heart is operating on a steeper portion of a Frank-Starling curve. If so, volume loading of heat-stressed individuals would shift the operating point to a flatter portion of the heat stress Frank-Starling curve thereby attenuating the reduction in SV during subsequent decreases in central blood volume. To investigate this hypothesis, right heart catheterization was performed in eight males from whom pulmonary capillary wedge pressure (PCWP), central venous pressure and SV (via thermodilution) were obtained while central blood volume was reduced via lower-body negative pressure (LBNP) during normothermia, whole-body heating (increase in blood temperature 1 degrees C), and during whole-body heating after intravascular volume expansion. Volume expansion was accomplished by administration of a combination of a synthetic colloid (HES 130/0.4, Voluven) and saline. Before LBNP, SV was not affected by heating (122 +/- 30 ml; mean +/- s.d.) compared to normothermia (110 +/- 20 ml; P = 0.06). However, subsequent volume loading increased SV to 143 +/- 29 ml (P = 0.003). LBNP provoked a larger decrease in SV relative to the decrease in PCWP during heating (8.6 +/- 1.9 ml mmHg(1)) compared to normothermia (4.5 +/- 3.0 ml mmHg(1), P = 0.02). After volume loading while heat stressed, the reduction in the SV to PCWP ratio during LBNP was comparable to that observed during normothermia (4.8 +/- 2.3 ml mmHg(1); P = 0.78). These data support the hypothesis that a Frank-Starling mechanism contributes to compromised blood pressure control during simulated haemorrhage in heat-stressed individuals, and extend those findings by showing that volume infusion corrects this deficit by shifting the operating point to a flatter portion of the heat stress Frank-Starling curve.
Bundgaard‐Nielsen et al. (Tue,) conducted a other in Heat stress and simulated hemorrhage (n=8). Intravascular volume expansion (synthetic colloid and saline) vs. Normothermia and whole-body heating without volume expansion was evaluated on Reduction in stroke volume to pulmonary capillary wedge pressure ratio during lower-body negative pressure (p=0.78). Intravascular volume expansion in heat-stressed individuals restored the stroke volume to pulmonary capillary wedge pressure ratio during simulated hemorrhage to normothermic levels (4.8 vs 4.5 ml/mmHg; P=0.78).