Acute volume expansion attenuates hyperthermia-induced reductions in cerebral perfusion during simulated hemorrhage

作者：Schlader Zachary J; Seifert Thomas; Wilson Thad E; Bundgaard Nielsen Morten; Secher Niels H; Crandall Craig G^*

来源：Journal of Applied Physiology, 2013, 114(12): 1730-1735.

DOI：10.1152/japplphysiol.00079.2013

• lower-body negative pressure
• heat stress
• brain blood flow
• volume infusion

Hyperthermia reduces the capacity to withstand a simulated hemorrhagic challenge, but volume loading preserves this capacity. This study tested the hypotheses that acute volume expansion during hyperthermia increases cerebral perfusion and attenuates reductions in cerebral perfusion during a simulated hemorrhagic challenge induced by lower-body negative pressure (LBNP). Eight healthy young male subjects underwent a supine baseline period (pre-LBNP), followed by 15- and 30-mmHg LBNP while normothermic, hyperthermic (increased pulmonary artery blood temperature similar to 1.1 degrees C), and following acute volume infusion while hyperthermic. Primary dependent variables were mean middle cerebral artery blood velocity (MCAv(mean)), serving as an index of cerebral perfusion; mean arterial pressure (MAP); and cardiac output (thermodilution). During baseline, hyperthermia reduced MCAv(mean) (P = 0.001) by 12 +/- 9% relative to normothermia. Volume infusion while hyperthermic increased cardiac output by 2.8 +/- 1.4 l/min (P %26lt; 0.001), but did not alter MCAv(mean) (P = 0.99) or MAP (P = 0.39) compared with hyperthermia alone. Relative to hyperthermia, at 30-mmHg LBNP acute volume infusion attenuated reductions (P %26lt; 0.001) in cardiac output (by 2.5 +/- 0.9 l/min; P %26lt; 0.001), MAP (by 5 +/- 6 mmHg; P = 0.004), and MCAv(mean) (by 12 +/- 13%; P = 0.002). These data indicate that acute volume expansion does not reverse hyperthermia-induced reductions in cerebral perfusion pre-LBNP, but that it does attenuate reductions in cerebral perfusion during simulated hemorrhage in hyperthermic humans.

• 出版日期2013-6