Plasma volume and blood viscosity during 4 h sitting in a dry environment: effect of prehydration.
BACKGROUND
Deep vein thrombosis and pulmonary thromboembolism are potential problems for travelers, including those who fly. We hypothesized that prehydration with an electrolyte-glucose beverage (EGB) would be better than water for maintaining body fluid balance and preventing increased blood viscosity in immobilized men.


METHODS
There were 12 healthy men (24-38 yr) who participated in crossover trials of prehydration using EGB and H2O as well as a control condition (Con) with no prehydration. Fluid intake was set at 6 ml x kg(-1) body weight (mean 418 ml). For each trial, subjects sat for 4 h at a dry-bulb temperature of 23.0-23.5 degrees C and a relative humidity of 18-36%. Plasma volume (PV) and whole blood viscosity (Bvis) were determined every hour; routine laboratory hematological tests, urine volume, and body weight were recorded at 2 h and 4 h.


RESULTS
For Con, subjects lost approximately 110 ml h(-1); at 2 h, PV had decreased significantly by 3.4%, and Bvis had increased significantly by 9.3%, with no further change at 4 h. For prehydration, retention of the consumed fluid at 2 h was significantly higher for EGB (57%) than for H2O (38%), while both drinks prevented significant change in PV and Bvis. There were no significant differences between trials in coagulation variables, but Bvis measured at higher shear rates for EGB were significantly attenuated compared with Con.


CONCLUSIONS
EGB and water prevented the increase of blood viscosity that occurred without prehydration. EGB was better than water for maintaining body fluid balance and preventing hypovolemia.
Doi
Tatsuya
T
Saga Nutraceuticals Research Institute, Otsuka Pharmaceutical Co., Ltd., Higashisefuri, Kanzaki, Saga 842-0195, Japan. t_doi@research.otsuka.co.jp
Sakurai
Masao
M
Hamada
Koichiro
K
Matsumoto
Keitaro
K
Yanagisawa
Kae
K
Kikuchi
Noriaki
N
Morimoto
Taketoshi
T
Greenleaf
John E
JE
D000328:Adult; D001809:Blood Viscosity; D003681:Dehydration / Q000517:prevention & control; D005440:Fluid Therapy; D006801:Humans; D007103:Immobilization; D008297:Male; D010953:Plasma Volume; D014882:Water-Electrolyte Balance