Greenleaf J E, Looft-Wilson R, Wisherd J L, Jackson C G, Fung P P, Ertl A C, Barnes P R, Jensen C D, Whittam J H
Gravitational Research Branch (239-11), NASA, Ames Research Center, Moffett Field, CA 94035-1000, USA.
Aviat Space Environ Med. 1998 Apr;69(4):374-86.
Plasma osmolality (Osm) is important for controlling and maintaining plasma volume (PV) and body water. The effect of oral rehydration fluids for ameliorating dehydration is well-established; but optimal composition and Osm of fluids for hyperhydrating normally hydrated subjects is less clear.
Six treatments were used without and with oral fluids of varying ionic and constituent concentrations for hyperhydrating six previously euhydrated men (30 +/- SD 8 yr, 76.84 +/- 16.19 kg, 73 +/- 12 ml.kg-1 PV, 40 +/- 10 ml.min-1.kg-1 peak VO2) sitting at rest for 90 min (VO2 = 0.39 +/- SE 0.02 L.min-1) and during subsequent 70 min of submaximal exercise (VO2 = 2.08 +/- SE 0.33 L.min-1, 70 +/- 7% peak VO2). The hypothesis was that the fluid composition is more important than plasma Osm for increasing PV in euhydrated subjects at rest and maintaining it during exercise. Drink formulation compositions, given at 10 ml.kg-1 body wt, (mean = 768 ml), for the sitting period were: Performance 1 (P1; 55 mEq Na+, 365 mOsm.kg H2O-1), P2 (97 mEq Na+, 791 mOsm.kg-1), P2G (113 mEq Na+, 4% glycerol, 1382 mOsm.kg-1), AstroAde (AA; 164 mEq Na+, 253 mOsm.kg-1), and 01 and 02 (no drinking). The exercise drink (10 ml.kg-1, 768 ml) was P1 for all treatments except 02 (no drinking); thus, drink designations were: P1/P1, P2/P1, P2G/P1, AA/P1, 0/P1, and 0/0.
PV at rest increased (p < 0.05) by 4.7% with P1 and by 7.9% with AA. Percent change in PV during exercise was +1% to +3% (NS) with AA/P1; -6% to 0% (NS) with P1/P1, P2/P1, P2G/P1, and 0/P1; and -8% to -5% (p < 0.05) with 0/0. AA, with the lowest Osm of 253 mOsm.kg-1, increased PV at rest (as did P1) and maintained it during exercise, whereas the other drinks with lower Na+ and higher Osm of 365-1382 mOsm.kg-1 did not.
Drink composition appears to be more important than its Osm for increasing PV at rest and for maintaining it during exercise in previously euhydrated subjects.
血浆渗透压（Osm）对于控制和维持血浆容量（PV）及身体水分至关重要。口服补液对改善脱水的效果已得到充分证实；但对于使正常水合状态的受试者达到水合过度状态的液体的最佳成分和渗透压尚不清楚。
对6名先前处于正常水合状态的男性（年龄30±标准差8岁，体重76.84±16.19千克，血浆容量73±12毫升·千克⁻¹，峰值摄氧量40±10毫升·分钟⁻¹·千克⁻¹）进行了6种处理，分别是不给予口服补液以及给予不同离子和成分浓度的口服补液。受试者静息90分钟（摄氧量=0.39±标准误0.02升·分钟⁻¹），随后进行70分钟次最大强度运动（摄氧量=2.08±标准误0.33升·分钟⁻¹，为峰值摄氧量的70±7%）。假设是在静息状态下，对于增加正常水合状态受试者的血浆容量以及在运动期间维持该容量，液体成分比血浆渗透压更重要。在静息期，按体重10毫升·千克⁻¹（平均768毫升）给予的饮料配方成分如下：Performance 1（P1；55毫当量钠，365毫渗量·千克H₂O⁻¹）、P2（97毫当量钠，791毫渗量·千克⁻¹）、P2G（113毫当量钠，4%甘油，1382毫渗量·千克⁻¹）、AstroAde（AA；164毫当量钠，253毫渗量·千克⁻¹），以及01和02（不饮水）。除02（不饮水）外，所有处理的运动饮料（10毫升·千克⁻¹，768毫升）均为P1；因此，饮料标识为：P1/P1、P2/P1、P2G/P1、AA/P1、0/P1和0/0。
静息时，P1使血浆容量增加（p<0.05）4.7%，AA使其增加7.9%。运动期间，AA/P1组血浆容量的百分比变化为+1%至+3%（无统计学意义）；P1/P1、P2/P1、P2G/P1和0/P1组为-6%至0%（无统计学意义）；0/0组为-8%至-5%（p<0.05）。AA的渗透压最低，为253毫渗量·千克⁻¹，在静息时增加了血浆容量（P1也是如此），并在运动期间维持该容量，而其他钠含量较低、渗透压为365 - 1382毫渗量·千克⁻¹的饮料则没有。
对于先前正常水合状态的受试者，在静息时增加血浆容量以及在运动期间维持该容量，饮料成分似乎比其渗透压更重要。
