Ultrasonic measurement of sound velocity in whole blood. A comparison between an ultrasonic method and the conventional packed-cell-volume test for hematocrit determination.

A new ultrasonic instrument for the determination of sound velocity in tissue is described. The instrument has been used in this investigation to measure the sound velocity in heparinized whole blood samples. The corresponding hematocrit values of the blood samples were determined by the packed cell volume test. The measurements in the hematocrit range of approx. 30-55 indicate a high degree of correlation between the hematocrit value and the respective blood sound velocity (S.E.E.=1.3 and r=0.96). Repeated measurements of the same blood samples up to 1 hr after collection of the blood show very small changes in reading of sound velocity, provided the samples were kept at a constant temperature and well stirred. The ultrasonic measurement is quick and simple to perform, and the blood specimen is not changed by the measuring process.

The effect of spironolactone (Aldactone) and methyldopa in low and normal renin hypertension.

The effect on BP of 100 and 200 mg spironolactone/day has been compared with that of methyl-dopa, 750 mg/day, and with combined treatment with both drugs in 32 patients with essential hypertension. The 28 patients who completed the entire investigation were treated for 30 weeks, divided into 4 treatment periods and 4 placebo periods of equal duration. BP did not fall significantly during the initial placebo period, and at the end of each of the intervening placebo periods it rose to pretreatment levels. A signifcant decrease in mean BP was found during the 4 treatment periods. A fall exceeding 14% was registered in 32% of the patients after methyldopa, 750 mg/day, in 50% of the patients after spironolactone, 200 mg/day, in 89% after combined treatment with both drugs, and in 29% after spironolactone, 100 mg/day. Low renin hypertension was found in 9 of the 28 patients. The average decrease in mean BP after sironolactone, 200 mg/day, methyldopa, 750 mg/day, and after combined treatment did not differ significantly between the low and the normal renin group. The rationale for using diuretics such as spironolactone or thiazide as the basic therapy in essential hypertension is discussed. It is concluded that both are useful in the treatment of essential hypertension and might be used alone or in combination.