Myhre L G, Robinson S
J Appl Physiol Respir Environ Exerc Physiol. 1977 Feb;42(2):252-6. doi: 10.1152/jappl.1977.42.2.252.
Six unacclimatized men rested for 4 h in a hot, dry environment (Ta 50 degrees C, Tw 26 degrees C; wind speed 0.5 m/s) without fluid replacement (DH). Another group of six men were exposed to the same thermal stress, replacing evaporative fluid loss with warm 0.1% NaCl solution (FRP). Total grams of circulating hemoglobin, determined by CO immediately prior to and again during the last minutes of heat exposure, increased an insignificant 1.6 and 1.3% during DH and FRP, respectively. With DH, body weight loss of 2.6% was accompanied by a 7.8% reduction in calculated plasma volume (PV). Even when body weight was maintained (FRP), PV decreased 2.9% during the heat exposure. Total circulating serum protein did not change as a result of the heat stress with either DH or FRP. In a test-retest series of experiments on four men, DH was not detrimental to sweat rate which averaged 251 g/m2-h compared with 239 g/m2-h with FRP. It was concluded that hemodilution is not a general response to acute heat exposure, and the disproportionately large reduction in PV during thermal dehydration was confirmed.
六名未经适应性训练的男性在炎热干燥的环境（气温50摄氏度，湿球温度26摄氏度；风速0.5米/秒）中休息4小时，期间不补充液体（脱水组）。另一组六名男性暴露于相同的热应激环境中，用温热的0.1%氯化钠溶液补充蒸发掉的液体损失（补液组）。在热暴露前即刻以及热暴露最后几分钟时通过一氧化碳法测定的循环血红蛋白总量，在脱水组和补液组中分别仅增加了微不足道的1.6%和1.3%。在脱水组中，体重减轻2.6%的同时，计算所得的血浆容量（PV）减少了7.8%。即使在体重得以维持的情况下（补液组），热暴露期间血浆容量仍减少了2.9%。无论是脱水组还是补液组，热应激均未导致循环血清总蛋白发生变化。在对四名男性进行的重复试验系列实验中，脱水组对出汗率并无不利影响，其平均出汗率为251克/平方米·小时，而补液组为239克/平方米·小时。研究得出结论，血液稀释并非急性热暴露的普遍反应，并且证实了热脱水期间血浆容量不成比例的大幅减少。
