Whole Body Hematocrit: Large Vessel Hematocrit Ratio in Hypertension

Whole body hematocrit/large vessel hematocrit (WBH/LVH ratio) has been examined in 21 normotensive and 35 hypertensive subjects and found to be the same, presumably as an expression of a uniform distribution of the blood volume in the two groups. Moderate renal impairment, the degree of the retinopathy, or the height of the diastolic blood pressure do not seem to influence the ratio figures. The WBH/LVH ratio was examined during treatment with various hypotensive drugs. A significant increase in the ratio was demonstrated during the influence of a single effective intravenous dose of pentolinium. Similar results were obtained during short‐term treatment with guanethidine alone and during long‐term treatment with guanethidine and hydrochlorothiazide. Treatment with hydrochlorothiazide alone caused an increase in ratio after one week and after three months, but these increases were not significant. The possible causes of these alterations in the WBH/LVH ratio are discussed. The advantage of employing a double isotope technique in preference to a quicker single isotope technique has been analyzed in relation to the determination of the total blood volume in patients during treatment with hypotensive drugs.