Kriemler S, Wilk B, Schurer W, Wilson W M, Bar-Or O
Children's Exercise and Nutrition Centre and Cystic Fibrosis Clinic, Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada.
Med Sci Sports Exerc. 1999 Jun;31(6):774-9. doi: 10.1097/00005768-199906000-00003.
In healthy children who exercise in the heat, the addition of flavor, carbohydrate, and 18 mmol x L(-1) NaCl to water induced a major increase in voluntary drink intake compared with the intake of unflavored water. This increase was sufficient to prevent voluntary dehydration. We hypothesized that, to achieve a similar effect in children with cystic fibrosis (CF), whose NaCl losses in sweat are markedly excessive, the drink should include an NaCl concentration higher than 18 mmol x L(-1).
Eleven subjects with CF (6 girls, 5 boys, ages 10.9-19.5 yr) attended three 3-h sessions of intermittent exercise of moderate intensity (four 20-min bouts), at 35 degrees C, 50% relative humidity. Either water (W), flavored water (FW), or a 30 mmol x L(-1) NaCl plus 6% carbohydrate solution (Na30) was offered ad libitum, in a counterbalanced sequence. Six subjects performed an additional session in which they drank a 50 mmol x L(-1) NaCl-6% CHO solution (Na50).
There was no significant drink effect on body fluid balance, core temperature, heart rate, or serum electrolytes with W, FW, or Na30. Serum osmolality decreased throughout the sessions from 290.6 +/- 1.1 (mean +/- SEM) to 281.3 +/- 1.2 mmol x kg(-1) (P < 0.0005), serum sodium from 143.1 +/- 0.5 to 141.1 +/- 0.7 mmol x L(-1) (P = 0.01) and serum chloride from 109.1 +/- 0.5 to 107.5 +/- 0.5 mmol X L(-1) (P < 0.001). In contrast, the 50 mmol x L(-1) NaCl drink induced a near significant (P = 0.08) higher fluid intake, and it significantly ameliorated the rate of progressive dehydration.
The marked loss of NaCl in the sweat of CF patients may induce an hypo-osmolar state in the serum, even when the drink contains 30 mmol x L(-1) NaCl. This may diminish the thirst drive triggered by hypothalamic osmoreceptors and may lead to voluntary dehydration. A flavored drink with an even higher salt content (50 mmol X L(-1)), however, enhances drinking and attenuates the voluntary dehydration.
在炎热环境中锻炼的健康儿童中，与饮用无味水相比，在水中添加调味剂、碳水化合物和18 mmol/L氯化钠可使自愿饮水量大幅增加。这种增加足以防止自愿性脱水。我们推测，对于囊性纤维化（CF）患儿，其汗液中氯化钠损失明显过多，要达到类似效果，饮料中的氯化钠浓度应高于18 mmol/L。
11名CF患儿（6名女孩，5名男孩，年龄10.9 - 19.5岁）参加了3次为时3小时的中等强度间歇运动（4次20分钟的运动回合），环境温度35℃，相对湿度50%。按平衡顺序随意提供水（W）、调味水（FW）或30 mmol/L氯化钠加6%碳水化合物溶液（Na30）。6名受试者额外进行了一次实验，饮用50 mmol/L氯化钠 - 6%碳水化合物溶液（Na50）。
饮用W、FW或Na30对体液平衡、核心体温、心率或血清电解质均无显著影响。整个实验过程中血清渗透压从290.6±1.1（均值±标准误）降至281.3±1.2 mmol/kg（P < 0.0005），血清钠从143.1±0.5降至141.1±0.7 mmol/L（P = 0.01），血清氯从109.1±0.5降至107.5±0.5 mmol/L（P < 0.001）。相比之下，50 mmol/L氯化钠饮料的液体摄入量几乎显著更高（P = 0.08），且显著改善了渐进性脱水的速率。
CF患者汗液中氯化钠的大量流失可能导致血清低渗状态，即使饮料中含有30 mmol/L氯化钠。这可能会减弱下丘脑渗透压感受器触发的口渴驱动力，并可能导致自愿性脱水。然而，含盐量更高（50 mmol/L）的调味饮料可增加饮水量并减轻自愿性脱水。
