[Plasma renin activity in venous renal blood and its stimulation by hydralazine and theophylline (author's transl)]

Hazards of therapy for excessive hypertension in acute stroke

Six cases with acute onset of neurological symptoms and extremely high blood pressure (BP) are reviewed. Hypertensive crisis or stroke were the main differential diagnoses. According to what is advocated for both situations, prompt antihypertensive therapy was instituted. Although recommended doses of hydralazine, reserpine or furosemide were given, the systolic BPs fell to less than 100 mmHg. Intracerebral hemorrhage or infarction was subsequently established in all patients and only one survived. Convincing evidence for a beneficial effect of BP reduction in acute stroke is lacking. Our data indicate excessive response to therapy in some patients. Also, moderate lowering of BP might reduce cerebral blood flow in these patients, often chronically hypertensive and with raised intracranial pressure. Extreme caution with antihypertensive therapy seems therefore warranted if the diagnosis of hypertensive crisis is not certain and a stroke is suspected.

[The influence of propranolol, practolol and theophylline on the plasma renin activity (author's transl)]

The stimulating effect of theophylline on the plasma renin activity (PRA) under beta-receptor blockade by propranolol or practolol was investigated in 27 patients with essential hypertension of degree I-II. After propranolol and also practolol PRA decreased about thirty per cent of the basal value, increased however by the factor of 2 to 3 after application of theophylline, in spite of the blockade of the beta-receptors indicated by a slight decrease of systolic blood pressure and heart rate. The effect of propranolol and practolol on the basal PRA was not different. Our results show the possibility, to stimulate renin secretion despite blockade of beta receptors by propranolol or practolol, respectively.

[Plasma aldosterone and plasma renin activity in patients with essential and renal hypertension under acute stimulation with saline depletion and acute suppression with saline infusion]

Plasma aldosterone, plasma renin activity, sodium and potassium in the plasma and the urine were determinated under acute stimulation with saline-depletion (furosemide) and under acute suppression with saline infusion in 40 patients with primary hypertension stage I, 19 patients with primary hypertension stages II and III, and 11 patients with renal hypertension (chronic glomerulonephritis and chronic pyelonephritis). The majority of the patients with primary hypertension stage I showed a good stimulation of the plasma aldosterone and the plasma renin activity under acute salt depletion. Three out of the 40 patients with primary hypertension stage I, and 13 of the 19 patients with primary hypertension stages II and III did not show any stimulation of the renin secretion ("low renin hypertension"). In all these patients the plasma aldosterone stimulation remained intact. With infusion of saline all the groups showed suppression of the plasma aldosterone and the plasma renin activity. A good stimulation of the plasma renin activity, demonstrates that in our experiments the renin-angiotensin system cannot be responsible for the increase in aldosterone secretion under salt depletion. Most likely the increase of the plasma aldosterone, in spite of the fixed renin activity, is stimulated by the sodium depletion due to diuretics. In all patients with primary hypertension we did not find an inadequate reaction of the aldosterone secretion under saline infusion. The patients with renal hypertension showed a minimal stimulation and suppression of the plasma renin activity. The plasma aldosterone secretion increased only slightly under sodium depletion and the decrease under saline infusion was statistically not significant. Thus we conclude that these patients show an inadequate reaction of the plasma aldosterone and renin secretion under salt infusion and depletion.