Blood Pressure Lowering In Patients Research Articles

How diuretics lower blood pressure

Thiazides produce an average loss of 2 L of extracellular fluid volume, of which about 300 ml is plasma volume, during the first 48 hours of administration, and this reduction is maintained without further loss for as long as the drug is given. Do thiazides lower blood pressure by volume depletion or by direct vasodilator action? As evidence against the vasodilator theory, these facts may be adduced: (1) thiazides do not lower blood pressure in patients (with renal disease) who cannot obtain a diuresis, and (2) other diuretics and diets very low in sodium also reduce blood pressure and volume to a similar degree. A related hypothesis is that thiazides reduce total peripheral vascular resistance (TPR) by “dehydrating” vascular walls. However, direct measurements in small arteries failed to confirm such changes. There is, however, a fall in TPR after long-term treatment, although initially cardiac output falls and TPR remains unchanged. How these long-term readjustments occur remains unknown, although several hypotheses have been advanced.

Intravenous diazoxide in treatment of hypertension associated with recent myocardial infarction.

Twenty patients with blood pressure over 180/110 mm Hg one hour after admission to a coronary care unit with recent acute myocardial infarction were given intravenous diazoxide in a bolus of 300 mg. The average blood pressure before diazoxide was 194/122 mm Hg. Blood pressure fell considerably in all patients, though six patients required two injections. The average fall was 58 mm Hg systolic and 40 mm Hg diastolic. No patient became severely hypotensive. The heart rate increased by an average of 10 beats/min. In nine patients the electrocardiographic changes immediately after the administration of diazoxide suggested an increase in myocardial injury. Though none of the patients seemed to deteriorate clinically from the diazoxide the electrocardiographic changes suggested that the use of intravenous diazoxide to lower blood pressure in patients with acute myocardial infarction might possibly be deleterious.