Intravascular volume, extracellular fluid volume, and total body water in obese and nonobese hypertensive patients.

Intraarterial blood pressure, plasma volume, extracellular and interstitial (IFV) fluid volumes, and total and intracellular (IBV) body water were evaluated in 50 men: 16 obese hypertensive patients, 16 nonobese hypertensive patients, and 18 normal subjects of similar age. In obese hypertensive subjects, the IBW/IFV ratio was significantly increased (p less than 0.01) in comparison with both control subjects and nonobese hypertensive patients. After body weight reduction, blood pressure (p less than 0.01), heart rate (p less than 0.05), and the IBW/IFV ratio (p less than 0.01) significantly decreased. The decrease in the ratio was due to an absolute increase in the interstitial fluid volume, related to a shift of fluid volume from the intracellular to the interstitial space. Thus, obese hypertensive patients have an increased water cell content, causing an altered partition between the intracellular and the interstitial spaces.