Plasma volume changes with long-term beta-adrenergic blockade

Decreased renal plasma flow during propranolol treatment in essential hypertension

The pharmacodynamic effect of propranolol (80 mg b.i.d.) on the renal and systemic circulation was studied after 1 and 8 months of treatment in 13 patients with essential hypertension, using non-invasive radioisotope techniques. Effective renal plasma flow (ERPF) fell from (mean +/- S.E.M.) 244 +/- 18 to 208 +/- 14 after 1 month and to 187 +/- 13 ml/min.m2 after 8 months of treatment. Concomitantly cardiac index (CI) fell from 3.24 +/- 0.15 to 2.62 +/- 0.11 and 2.75 +/- 0.10 l/min.m2, respectively. The coefficient of correlation between the decreases in ERPF and CI was 0.49. Mean arterial blood pressure decreased from 138 +/- 5 to 118 +/- 5 and 116 +/- 4 mmHg, respectively. Left ventricular work was reduced by 30.2 and 27%, while peripheral resistance was unchanged. Total plasma volume was increased from 19.3 +/- 0.5 to 20.3 +/- 0.6 ml/cm after 1 month, but was within the same range as the control values after 8 months of treatment. Pulmonary plasma volume was unchanged, indicating that there was no pooling of plasma in the pulmonary circulation. The interventricular circulation time was increased from 6.9 +/- 0.4 s to 8.4 +/- 0.3 s and varied with the change in heart rate. It is concluded that the fall in ERPF might be explained by reduced cardiac output in addition to interference with the hemodynamic autoregulation in the kidney.

Changes in plasma volume and extracellular fluid volume and after addition of hydralazine to propranolol treatment in patients with hypertension

In 16 patients with hypertension, BP could not be controlled satisfactorily by treatment with propranolol alone (mean dosage 325 mg/day). Plasma volume (PV) (T-1824) and extracellular fluid volume (ECV) (82Br-distribution space) were determined in these patients before and after the addition of hydralazine for three months (mean dosage 135 mg/day). After the addition of hydralazine, PV and ECV increased significantly, by 9% and 3%, respectively. Systolic and diastolic BPs decreased, by 15% and 13%. The mechanisms inducing fluid retention during treatment with hydralazine and the clinical significance of the problem are discussed. It is concluded that the addition of a diuretic to propranolol-hydralazine treatment is often well indicated.

Hemodynamic effects of combined beta-adrenoceptor blockade and precapillary vasodilatation in hypertension

Carvedilol (BM14190) is a new compound with combined properties of nonselective beta-adrenoceptor blockade, devoid of ISA, and precapillary vasodilatation. Its acute hemodynamic effects were studied with invasive technique (dye-dilution using Cardio-Green) in 10 patients taking 25 mg orally and noninvasive (fore-arm plethysmography) in 10 patients taking 25 mg and in 10 patients taking 50 mg orally, all with essential hypertension. Significant reductions of systolic and diastolic blood pressures (p less than 0.05 - 0.001) were observed in all groups. TPR did not change acutely whereas resistance in the fore-arm was reduced by 16% (p less than 0.05). When a comparison with propranolol (80 mgx2) was made in a randomized, double-blind placebo controlled trial comprising 30 patients with essential hypertension, carvedilol acutely reduced blood pressure significantly 13/6 mm Hg (25 mg) and 17/10 mm Hg (50 mg) in contrast to propranolol. Resistance in the fore-arm (plethysmography) fell significantly with carvedilol 50 mg whereas propranolol caused a significant rise. After 4 weeks both compounds had reduced blood pressure significantly and to the same extent. Blood flow was still reduced with propranolol in contrast to the findings with carvedilol. We conclude that carvedilol given orally has a useful antihypertensive effect both acutely and during prolonged treatment. It has an attractive hemodynamic profile.

Investigations on the antihypertensive activity of timolol and bendroflumethiazide and the combination in dogs and rats

The effects of timolol and bendroflumethiazide, either alone or combined in a fixed ratio of 4:1, on blood pressure, plasma renin activity, and plasma potassium concentration, have been investigated in normotensive and renal hypertensive dogs, and in normotensive and spontaneously hypertensive rats. In addition, the urinary kallikrein excretion has been measured in normotensive and hypertensive rats. When administered to hypertensive dogs and rats, the drug combination significantly reduced the blood pressure. Marginal reductions were observed in normotensive animals or after the administration of the single drugs. The thiazide-induced hypokalaemia and hyperreninaemia were almost completely antagonised by the concomitant administration of timolol in both animal species. A highly significant elevation of urinary kallikrein excretion was also observed in rats treated with the drug combination. A less marked increase of kallikrein excretion was noted in the bendroflumethiazide treated rats. The possibility that renal haemodynamic changes, in addition to the inhibition of the increase in plasma renin, play a role in the observed antihypertensive effects is discussed.

Hemodynamic effects of celiprolol in essential hypertension

The immediate and short-term (2 week) hemodynamic and humoral effects of the beta-1 antagonist, beta-2 agonist, celiprolol, were compared with those of more prolonged atenolol therapy in 12 patients with essential hypertension. Celiprolol produced an immediate dose-dependent decrease in mean arterial pressure (113 +/- 3 to 102 +/- 2 mm Hg; p less than 0.001) and total peripheral resistance (49 +/- 3 to 38 +/- 1 U/m2; p less than 0.005) that was associated with an increased heart rate (67 +/- 1 to 73 +/- 2 beats/min; p less than 0.01) and cardiac index (2,347 +/- 129 to 2,708 +/- 111 ml/min/m2; p less than 0.01). Both celiprolol and atenolol reduced mean arterial pressure with short-term treatment (p less than 0.01); this was associated with a reduced total peripheral resistance with celiprolol (from 24 +/- 1 to 21 +/- 1 U/m2; p less than 0.02) and was not observed with atenolol. Moreover, in contrast with atenolol, celiprolol did not change heart rate or stroke and cardiac indexes. Splanchnic and forearm vascular resistances decreased with celiprolol (p less than 0.05) but not with atenolol; neither beta-blocking drug altered renal blood flow. These results demonstrate that the hemodynamic effects of celiprolol were strikingly different from atenolol; celiprolol reduced arterial pressure and total peripheral and certain vascular resistances without altering heart rate, cardiac index or regional blood flows. These effects may be explained by celiprolol's cardiac beta-1 receptor inhibitory and peripheral beta-2 receptor agonistic effects.

Vasodilatory beta-blockers: systemic and regional hemodynamic effects

The systemic and regional hemodynamic alterations in hypertension and of the beta-adrenergic receptor inhibiting agents are reviewed. Hemodynamically, hypertension may be regarded as persistent elevation of arterial pressure associated with increased total peripheral resistance. In early or mild essential hypertension, however, increased total peripheral resistance may not readily be recognized because of the overriding effect of increased cardiac output. Clearly, the hemodynamics of blood pressure control are complex, and the mechanisms of antihypertensive agents must be used appropriately. The early beta-blockers reduced heart rate and cardiac output immediately after intravenous administration without immediately reducing arterial pressure, and calculated total peripheral resistance was increased. With prolonged oral treatment, arterial pressure decreased while maintaining a reduced heart rate and cardiac output. Total peripheral resistance, however, remained elevated. Recent beta-blockers, such as celiprolol, provide an improved physiologic response by instantly reducing arterial pressure and total peripheral resistance without reducing heart rate or cardiac output or expanding intravascular volume.

Blood volume after coronary artery bypass grafting

Patients with stable angina pectoris are reported to have a markedly reduced blood volume (BV). In the present study, average BV was still 19% less than that predicted in 77 men examined 5 years after coronary artery bypass grafting. Beneficial effects of the operation such as relieved angina, absence of medication, complete revascularization status at repeat angiography, and restored physical fitness were not found to be associated with a normalization of the BV. No significant correlation was found between BV and body weight, heart volume, exercise capacity, ejection fraction or left ventricular end-diastolic pressure. The reduced BV in patients with angina pectoris after successful revascularization and the absence of correlation with physiological variables indicate a persisting disturbed regulation mechanism.

Plasma volume in resistant hypertension: guide to pathophysiology and therapy

It might be expected that the tremendous increase in available antihypertensives would eliminate resistant hypertension by allowing many alternatives to its treatment. In spite of this, resistant hypertension remains a common problem due, the authors feel, to a poor understanding of the pathophysiology of this condition, particularly an understanding of whether plasma volume expansion mediates resistance to antihypertensive therapy. The authors evaluated the status of plasma volume as a major determinant of response to therapy in nine patients with resistant hypertension. Measuring plasma volume using I125 radiolabeled albumin, they found eight patients with elevated plasma volumes and one patient with a contracted plasma volume at the time of presentation with resistant hypertension. In all eight patients with plasma volume expansion, aggressive diuretic therapy allowed goal blood pressure to be achieved. The patient with plasma volume contraction achieved goal blood pressure with vasodilator therapy. Plasma volume expansion is common in resistant hypertension and it mediates resistance to therapy. Measurement of plasma volume gives the clinician important insight into the pathophysiology of resistant hypertension and increases the likelihood of successful management of the resistant hypertensive patient.

The heart in hypertension: unresolved conceptual challenges. Special lecture

Much has been learned over the past 25 years concerning the role of the heart in hypertension. In a multiplicity of areas a great deal has been clarified but a number of issues remain unresolved. This personal overview outlines some of these challenging areas for investigation, including questions relating to the cardiogenic reflexes, mechanisms underlying total body autoregulation that may involve not only the adaptation of arterioles but also venoconstriction in hypertension, postcapillary constriction also involving the efferent glomerular arterioles, the mechanisms underlying the development and regression of hypertrophy as well as the function of the hypertrophied and "regressed hypertrophy" heart, and the precise hemodynamic actions of atrial natriuretic factor.

Renal hemodynamics and pharmacokinetics of bevantolol in patients with impaired renal function

The effects of bevantolol on renal blood flow and glomerular filtration rate and the drug's pharmacokinetics were studied for 7 days in 18 patients (mean age 50 years) with varying degrees of renal dysfunction. Patients were divided into 3 groups: group 1 had a creatinine clearance of 50 to 80 ml/min, group 2, 20 to 49 ml/min and group 3, less than 20 ml/min. After baseline inulin and paraaminohippuric acid clearance values were obtained, patients were given a single, 150-mg "priming" administration of bevantolol. The kinetics of the drug (including plasma drug levels, plasma half-life and plasma clearance) and its effects on renal function were observed for 24 hours. On days 4 to 6 of the study, patients received 150 mg of bevantolol twice daily, with only a single dose given on day 7. Bevantolol did not significantly affect either inulin or paraaminohippuric acid clearance in patients with differing degrees of renal function. In 50% of patients with a creatinine clearance of less than or equal to 50 ml/min, both the half-life and maximum trough serum levels were higher than the ranges seen in healthy subjects. However, neither value appears to be clinically relevant because bevantolol has a wide therapeutic range. Renal impairment did not change the percentages of the bevantolol dosage excreted unchanged or as conjugated drug in the urine, and no toxic or active drug metabolites accumulated in the blood. From these results, it appears that bevantolol may be used safely in short-term therapy of patients with renal impairment.

An office-based primary care trial of pindolol ('Visken') in essential hypertension

A large, open, multi-centre study was performed by physicians in general practice to evaluate the efficacy and tolerance of pindolol (10 to 20 mg per day) in the treatment of patients with essential hypertension. The records of 7324 patients who completed the 6-week protocol with pindolol alone or in combination with a diuretic were analyzed by computer. Substantial reductions in both systolic and diastolic blood pressure were obtained in the majority of patients regardless of age, sex or race. No difference in blood pressure response was found between patients taking diuretics concurrently and those on pindolol alone. Side-effects were generally not troublesome and a trend toward a reducing incidence of side-effects was noted in all patients as the duration of therapy increased. Black patients tended to complain of fewer side-effects than did white patients.

Alternative pharmacologic approaches to the initial management of hypertension

Recent clinical trials in hypertension report more deaths due to coronary heart disease in mild hypertensives who received aggressive antihypertensive drug therapy and achieved better blood pressure control. Subset analyses of these trials suggest that diuretic therapy may have contributed to this outcome, possibly through a reduction in serum potassium or an elevation in serum lipids. Because of this, patients with an abnormal pretreatment electrocardiogram, history of myocardial infarction, unstable coronary heart disease, or diuretic-induced hyperlipidemia or hypokalemia unresponsive to management are candidates for alternative antihypertensive agents. A review of the literature suggests that most of the currently available beta-blockers, the alpha 1-antagonist prazosin, the angiotensin-converting enzyme inhibitor captopril, and the vasodilator hydralazine are effective alternatives to thiazide therapy in the initial management of hypertension and are recommended for particular subgroups of patients. Monotherapy with the centrally and peripherally acting sympatholytic agents is not recommended because of the frequent side effects encountered and the inferior hypotensive efficacy reported. Calcium channel blocking agents also appear to be suitable alternatives to thiazides in hypertension, but more experience with these is needed. Alternative pharmacologic agents may be selected on the basis of age, and, to a lesser extent, race.

Effect of selective and nonselective beta-adrenoceptor blockade on thermoregulation during prolonged exercise in heat

The effect of selective and nonselective beta-adrenoceptor blockade on the thermoregulatory responses of 11 physically active, healthy, young adult men was studied during 2-hour block-stepping in heat. The trial consisted of 3 periods of 6 days each during which propranolol (160 mg/day), atenolol (100 mg) or matching placebo was administered in a randomized, double-blind crossover fashion. Propranolol and atenolol induced similar, significant (p less than 0.001) increases in subjective ratings of perceived exertion. The mechanism of this increased fatigue was not evident from the documented alterations in serum electrolyte, blood glucose and blood lactate levels or ventilatory parameters. Propranolol did, however, induce a postexercise delayed serum-potassium reversion. Although rectal and mean skin temperature responses were essentially unaltered by beta-adrenoceptor blockade during block-stepping, an increased total sweat loss was observed with propranolol (p less than 0.01 versus placebo) and to a lesser degree with atenolol (p = not significant versus placebo). This indicates that persons receiving beta-adrenoceptor blockers have an increased need to adhere to a strict fluid-replacement regimen during exercise. This potentially adverse response was minimal with atenolol in contrast to propranolol, and this in turn suggests the use of beta1-selective adrenoceptor blockers during prolonged exercise when adequate fluid replacement is not possible.

Beta-blocking drugs for arrhythmias, hypertension, and ischemic heart disease

Beta-blocking drugs have provided significant improvement in the medical therapy of many types of heart disease. They are more effective in treating young hypertensive patients than elderly hypertensive patients. These drugs reduce the ventricular rate seen in atrial flutter and fibrillation, and they also reduce the frequency of ventricular ectopy. Beta blockers are important adjuncts for control of angina pectoris. When these drugs are given for a period of 1 to 3 years after myocardial infarction they reduce the incidence of reinfarction and the frequency of sudden death as well as reduce the overall mortality rate. Factors that may contribute to the overall decreased mortality include the reduction in the reinfarction rate and an increased threshold for ventricular fibrillation as well as those mechanisms that reduce myocardial oxygen utilization.

Pharmacologic and physiologic considerations of adrenoceptor blockade

The beta-adrenergic receptor blocking drugs have been in use for the treatment of hypertension for almost two decades. Although the mechanism of their antihypertensive action still is not precisely known, they have become an established major class of therapy for the disease. Most agents produce an immediate reduction in heart rate and cardiac output, later followed by a reduction in pressure. The exceptions include: those agents that possess intrinsic sympathomimetic activity and produce little reduction in heart rate and output; and labetalol, an agent that reduces pressure immediately (associated with the cardiac effects) because it possesses alpha- as well as beta-adrenoceptor blocking effects. Just because a beta-blocking drug reduces cardiac output significantly, it does not follow that renal blood flow will decrease; this depends upon the number and affinity of receptors in the renal circulation. Most beta blockers (including labetalol) reduce renal vascular resistance in patients with uncomplicated hypertension. Other actions of this class of adrenoceptor blocking agents are discussed. As we learn more of the physiologic effects of adrenoceptor blocking agents, there is no doubt that we shall gain more insight into the underlying mechanisms of hypertensive diseases as well as their pharmacologic properties.

Causes of inadequate response to antihypertensive drugs. Volume factors

Diuretic therapy, by producing a negative salt and water balance, eliminates the false tolerance to sympatholytic drugs that often occurs during long-term monotherapy. This tolerance results from salt and water retention produced by the drugs. Review of published results suggests a primacy for arterial pressure reduction in this fluid because suppressed renal sympathetic activity should facilitate salt and water excretion through lessened alpha-adrenergic influence on tubular reabsorption, and beta-adrenergic inhibition would diminish renin release thus promoting natriuresis. The return of hypertension that characterizes the false tolerances seems paradoxical because these drugs cause venodilation, which should provide ample storage of expanded blood volume without affecting cardiac output. However, animal studies have suggested that dilated veins have decreased compliance; if that is so, in humans it would mean that fluid retention would be accompanied by a redistribution of blood into the central circulation, with a rise in cardiac output.

Effects of pindolol and methyldopa on blood pressure and plasma norepinephrine

Thirty patients with essential hypertension (supine diastolic blood pressure 100 to 115 mm Hg) were treated in a randomized, double-blind study with either pindolol (mean dose 28 +/- 5 mg twice a day) or methyldopa (673 +/- 158 mg three times a day) for 12 weeks after a 3-week, single-blind placebo period. In 17 pindolol-treated patients mean supine blood pressure was 163 +/- 3/106 +/- 1 during the placebo period and 155 +/- 3/99 +/- 2 mm Hg (p less than 0.01) during the high-dose period. In 13 patients treated with methyldopa mean supine blood pressure fell from 160 +/- 4/104 +/- 1 to 156 +/- 5/97 +/- 2 mm Hg. Mean standing heart rate was reduced during pindolol therapy from 84 +/- 2 to 79 +/- 2 bpm (p less than 0.05) but was unchanged during methyldopa treatment. Mean supine pretreatment plasma norepinephrine fell from 379 +/- 40 to 337 +/- 33 pg/ml in patients on pindolol therapy and from 448 +/- 76 to 223 +/- 39 pg/ml (p less than 0.02) in the methyldopa-treated group. Although norepinephrine generally decreased in pindolol responders and not in nonresponders, changes in supine diastolic blood pressure and supine plasma norepinephrine did not correlate. In contrast, norepinephrine declined consistently in methyldopa-treated patients regardless of the blood pressure response; changes in diastolic blood pressure and norepinephrine correlated (r = 0.59; p less than 0.05). The results suggest that suppression of sympathetic nervous system activity may play a role in the hypotensive effect of both pindolol and methyldopa.

Diuretic potency of combined hydrochlorothiazide and furosemide therapy in patients with azotemia

The effect of combined hydrochlorothiazide and furosemide therapy was studied in eight hypertensive patients with renal insufficiency who had poor response to either furosemide or hydrochlorothiazide alone. The study was divided into two parts. In part A, five patients had an inadequate response to furosemide in doses of 160 to 240 mg/day followed a strict protocol in order to compare the effect of increased doses of furosemide with combined hydrochlorothiazide-furosemide administration. All had azotemia, presumable from nephrosclerosis, and had serum creatinine concentrations ranging from 2.3 to 4.9 mg/dl. Four of the five patients had inadequate arterial pressure control, and the remaining patients had fluid retention from the administration of minoxidil. In all five patients, plasma volume was either increased or normal, despite long-term treatment with furosemide. Increasing the dose of furosemide to between 320 and 480 mg/day had only a modest additional diuretic effect, and plasma volume and arterial pressure were not significantly changed. Adding hydrochlorothiazide, 25 to 50 mg twice a day, produced a marked diuresis, and a significant reduction in weight, plasma volume and mean arterial pressure (p less than 0.025 for all three patients). In part B, combined hydrochlorothiazide-furosemide therapy was used to treat three additional patients who had an inadequate response to either diuretic alone. The results indicate that combined hydrochlorothiazide-furosemide is a potent diuretic regimen and is effective in many patients wit chronic renal failure who have a poor response to furosemide alone.

Pharmacokinetics of propranolol

The pharmacokinetics of propranolol after the administration of 40, 80, and 120 mg p.o. and 10 mg i.v. was studied in nine healthy male volunteers. Propranolol was analyzed after extraction and derivatization by gas-liquid chromatography. A multiexponential curve-stripping program was used for the pharmacokinetic analysis. The volume of distribution was about 6 liters . kg-1, bioavailability around 25%, with a mean terminal half-life of 6 hr. There was no evidence of either dose dependent disposition kinetics or an oral threshold dose. A slight increase in urine volume was observed after propranolol administration.

Short-term systemic hemodynamic adaptation to beta-adrenergic inhibition with atenolol in hypertensive patients

Early systemic hemodynamic adjustments to antihypertensive therapy with the cardioselective beta inhibitor, atenolol, were investigated in 12 hospitalized men, mean age 52 years, with uncomplicated mild-to-moderate essential hypertension. Twice daily measurements of cardiac output (CO) by CO2 rebreathing, blood pressure by cuff, and heart rate were performed in all subjects for 3 days before and 5 days after initiation of oral atenolol therapy (50 or 100 mg daily). Cardiac output by CO2 rebreathing was checked with dye dilution just before, and 4 hours and 4 days after the start of therapy. Plasma volume (radioiodinated albumin) was measured before therapy and on Day 5 of therapy. The CO results obtained with the two methods were not significantly different (r = 0.88, p less than 0.01, n = 12). A reduction in heart rate, 18 +/- 2 beats/min (mean +/- SE), occurred in all patients while taking atenolol. By 4 hours after the first dose of atenolol, CO fell from 5.49 +/- 0./30 to 4.24 +/- 0.21 liters/min (p less than 0.01), while the control mean arterial pressure (MAP) of 108 +/- 4 mm Hg was not significantly changed, 110 +/- 4 mm Hg. At 24 hours, CO returned near baseline (5.10 +/- 0.21 liters/min) but MAP was reduced (95 +/- 3 mm Hg, p less than 0.001) and remained so thereafter. CO remained at baseline at 48 hours (5.50 +/- 0.29 liters/min) but fell again (p less than 0.01) to 4.81 +/- 0.11 on Day 4 and to 4.68 +/- 0.25 liters/min on Day 5 of atenolol therapy. Plasma volume, 3110 +/- 100 ml before therapy, was reduced to 2850 +/- 100 by Day 5 of atenolol therapy (p less than 0.01). The findings indicate a delayed onset of the antihypertensive action of atenolol. The transient return to baseline of CO on Day 2 and 3 of atenolol therapy suggests a reverse autoregulatory adjustment to the initial fall in CO.

Effect of atenolol on left ventricular function in hypertensive patients

No information is available about the effects of oral atenolol, a cardioselective beta-adrenergic blocking agent with no intrinsic sympathomimetic activity, on left ventricular function. Atenolol, 100 mg/day, was given to 12 hypertensive patients for 8 weeks, and its effects on mean arterial pressure (MAP), cardiac index (CI) and ejection indexes of myocardial performance were examined by echocardiography. Echocardiographic studies were performed before treatment, after 4 weeks of placebo, and repeated after 4 and 8 weeks of atenolol therapy. MAP fell by 14% and 21% after 4 and 8 weeks, respectively. CI fell by 22% and 20% and stroke index (SI) fell by 11% and 7%. Calculated peripheral resistance did not change significantly. Fractional shortening, ejection fraction and normalized mean rate of circumferential fiber shortening did not change. The normalized mean posterior wall velocity decreased after 4 weeks but returned to pretreatment levels after 8 weeks. The septal velocity increased after 8 weeks. End-diastolic volume index (EDVI) did not change, and there was no relationship between changes in heart rate and EDVI. The study shows that atenolol in the resting state has no effect on certain echocardiographic indexes of left ventricular (LV) function when given orally to hypertensive patients with normal LV size and function. The reduction in CI and SI were presumably secondary to a decrease in cardiac venous filling.

A study of the effects of atenolol and propranolol on renal function in patients with essential hypertension

1 The effects of propranolol and atenolol given in random order in a cross-over study to fifteen patients with essential hypertension have been studied. 2 Both drugs were effective in lowering blood pressure and side effects were not markedly different. 3 There was no change in exchangeable sodium or potassium or in total body potassium during treatment with either drug. 4 Ambulant plasma renin activity was reduced by both drugs but the fall in blood pressure was not related to initial plasma renin. 5 Despite equal mean reduction in blood pressure with the two drugs, creatinine clearance fell significantly only during treatment with propranolol. 6 These observations suggest that intra-renal beta 2-adrenoceptors may be of importance in the regulation of renal function.

Angiotensin II blockade during combined thiazide-beta-blocker treatment

Sixteen patients (11 M, 5 F), median age 41 years, with essential hypertension insufficiently controlled on hydrochlorothiazide 75 mg/day (DBP greater than or equal to 100 mmHg) were investigated. Plasma renin concentration (PRC), angiotensin II concentration (PA II), aldosterone concentration (PAC), plasma noradrenaline concentration (PNAC), plasma volume (PV) and exchangeable sodium (NaE) were determined and a saralasin-infusion (5.4 nmol/kg/min) was carried out while the patients were on thiazide alone, and in fourteen cases, repeated 3 months later after addition of a beta-blocker (propranolol 6, metoprolol 6 and atenolol 2 patients). On thiazide alone PRC, PA II and PAC was higher than normal in the group as a whole and the angiotensin II-inhibitor, saralasin, caused a significant decrease in MAP in twelve out of sixteen patients. After addition of a beta-blocker SBP and DBP decreased from 164/109 mmHg to 136/94 mmHg. PRC and PA II decreased by 40% and 58%, respectively. At this point saralasin caused no significant change in MAP. No close correlation was found between changes in BP on beta-blocker treatment and either PRC, PA II or saralasin response on thiazide treatment. PV, NaE, PAC and PNAC did not change sigificantly. It is concluded that in pts with thiazide-induced stimulation of the renin-angiotensin system (RAS) addition of a beta-blocker leads to suppression of RAS and the angiotensin II dependence of the blood pressure is nearly abolished. This mechanism might well contribute to the antihypertensive effect of beta-blockade in this particular situation. However, the pharmacological changes induced by beta-blockade are very complex, and most likely other factors are involved in the antihypertensive effect of beta-blocking drugs.

Individual factors influencing the response to a beta-adrenergic blocking agent given alone and in combination with a diuretic on arterial hypertension

103 patients with arterial hypertension were treated with timolol + placebo for 7 weeks in a multicentre trial, and with timolol + hydrochlorothiazide and amiloride for a further 7-week period. The decrease in blood pressure (BP) produced by timolol alone was influenced neither by the dose of timolol, initial heart rate, magnitude of pretreatment BP nor by age. 64% of the patients less than 40 years of ages, and 48% of the older patients, were well regulated on beta-blocker monotherapy. When the diuretic was given in addition, the BP response in the older age group improved, whereas younger patients showed no change. A significant correlation was found between age or magnitude of untreated BP and the decrease in BP caused by the diuretic. The cardiothoracic ratio increased significantly on timolol alone, whereas no change was found on the combined therapy. Weight changes in the two different treatment periods showed a significant correlation, but they were not related to the observed reduction in BP. The results suggest that in younger patients, beta-blocker therapy is just as effective as a combined treatment with a diuretic, whereas in older patients considerably better regulation is achieved by combined therapy.

Beta-adrenoceptor blockade and anaesthesia. Beta-adrenoceptor antagonism during anaesthesia for coronary artery surgery

Twenty-six patients with severe coronary artery disease, receiving long term beta-adrenoceptor blocking drugs were anaesthetised for aorto-coronary bypass operations. Beta-adrenoceptor blocking drugs were withdrawn 2 to 8 days before surgery in ten patients only. In the remaining sixteen patients there were no serious complications due to the presence of a degree of beta-blockade during anaesthesia and surgery. The undesirable cardiovascular responses to laryngoscopy and tracheal intubation were diminished in these patients, and the rise in heart rate/systolic pressure product, and indicator of myocardial oxygen consumption, was less in this group. The need for peripheral vasodilators to treat systemic arterial pressure rises in response to surgery was also reduced. There appeared to be no contraindication to the continuation of beta-adrenoceptor blockade before operation in patients undergoing aorto-coronary bypass procedures when suitable anaesthetic agents were selected and when an appropriate blood volume was maintained.

[The importance of changes in whole-body balance of sodium and noradrenaline in essential hypertension (author's transl)]

In 22 patients with essential hypertension plasma levels and urine excretions of sodium and noradrenaline were studied before, during and after long-term beta-blockade with pindolol. The relation between mean blood pressure and the quotient of sodium-/noradrenaline-excretion changed during treatment (placebo r=-0.34; pindolol r=+0.31). During placebo there existed a significant (p is less than 0.03) correlation between blood pressure and sodium-excretion which disappeared during beta-blockade. No correlation between blood pressure and noradrenaline was seen during placebo, whereas during beta-blockade a significant (p is less than 0.003) correlation was observed. In contrast to the placebo period there was a significant positive correlation between sodium- and noradrenaline-excretion during long-term treatment with pindolol. It is concluded that whole-body balance of sodium and noradrenaline is an important factor in essential hypertension.

The second Lilly Prize Lecture, University of Newcastle, July 1977. beta-Adrenergic receptor blockade in hypertension, past, present and future

All beta-adrenoceptor blocking drugs that have been described share the common property of being competitive inhibitors. They differ in their associated properties, the presence or absence of cardioselectivity, membrane stabilizing activity, and partial agonist activity. Recently some beta-adrenoceptor blocking drugs have been reported which also possess alpha-adrenoceptor blocking activity. The associated properties have been used as a basis for classifying beta-adrenoceptor blocking drugs (Fitzgerald, 1969, 1972). The presence or absence of cardioselectivity is most useful for dividing beta-adrenoceptor blocking drugs. The non-selective drugs (Division I) can be further divided according to the presence or absence of intrinsic sympathomimetic activity (ISA) and membrane stabilizing activity (Fitzgerald's groups I-IV). Group I possess both membrane activity and ISA, e.g. alprenolol, oxprenolol, group II just membrane action, e.g. propanolol, group III ISA but no membrane action, e.g. pindolol. Fitzgerald placed pindolol in group I but should be placed in group III as it possesses a high degree of beta-adrenoceptor blocking potency in relation to its membrane activity (Prichard, 1974). Finally drugs in group IV have neither ISA nor membrane action, e.g. sotalol, timolol. The cardioselective drugs (Division II) can be similarly sub-divided into groups I-IV according to the presence or absence of ISA or membrane action (Fitzgerald grouped all these together as group V). Lastly there are new beta-adrenergic receptor blocking drugs which in addition have alpha- adrenergic receptor blocking properties (Division III).

Hemodynamic, reflexive, and metabolic alterations induced by acute and chronic timolol therapy in hypertensive man

The hemodynamic, cardiovascular, and metabolic effects of acute (intravenous) and prolonged (four weeks oral) timolol treatment were assessed in 16 patients with mild or moderate essential hypertension. Fifteen patients completed the outpatient study and ten showed a fall in mean arterial pressure of at least 10 mm Hg. They also demonstrated a significant fall in supine systolic (7%), diastolic (9%), and mean arterial pressure. Hemodynamic evaluation was performed in 13 patients and cardiac index was found to be reduced with both intravenous (20%) and oral timolol (13%). There was no correlation between the decrease in cardiac index and arterial pressure. Calculated total peripheral resistance rose with intravenous timolol and returned toward, but not below, pretreatment values with the oral therapy. Left ventricular ejection rate also fell significantly with intravenous timolol but returned toward pretreatment levels with oral therapy. Plasma renin activity was reduced similarly with both modes of administration and its reduction also did not correlate with the fall in arterial pressure. Plasma volume fell in eight of 13 patients. Reflexive responses to the Valsalva maneuver were considerably modified by both intravenous and oral timolol but responses to 50 degrees upright tilt and handgrip were not. Timolol is an effective oral antihypertensive agent with similar hemodynamic and metabolic effects to propranolol.

The effect of pindolol on plasma renin activity in patients with essential hypertension

Twenty-two patients with essential hypertension were treated for 3 months with pindolol, and blood pressure and plasma renin activity were measured at rest and after stimulation (upright posture stimulation and insulin induced hypoglycaemia stimulation). Beta-receptor blockade produced a significant decrease in systolic and diastolic blood pressure. After treatment with pindolol the plasma renin activity was significantly lower. Under conditions of renin stimulation such as orthostasis and insulin produced hypoglycaemia, plasma renin activity was significantly lower in treated patients. There was no correlation between the fall of plasma renin activity and the decrease of blood pressure. Renin suppression is probably only one of the factors involved in the reduction in the blood pressure in these patients.