Peripheral gangrene complicating beta-blockade

Does beta-blockade provoke intermittent claudication?

Intermittent claudication has been claimed to be a side-effect of beta-adrenoceptor blocking drugs. The confounding effect of coronary heart disease has not been controlled in earlier studies. In this case-control study, the cases were selected from a hospital material of patients with verified intermittent claudication and the controls from a nationwide health survey. The pool of potential cases and controls consisted of persons who had been treated with antihypertensives, but did not have coronary heart disease. The controls and cases were matched for age, sex, place of residence and time of examination. Comparison of current or previous use of beta-blocking drugs among our 55 case-control pairs revealed no association between intermittent claudication and beta-blockade. beta-Blockade is not a risk factor for intermittent claudication.

Tips and tricks on outpatient initiation and uptitration of beta-blockade in heart failure

beta-blockade has a therapeutic role across the continuum of patients with heart failure (HF), with a demonstrated mortality benefit in stage II and III HF. Concerns regarding initiation and uptitration linger as patients with resting bradycardia, pulmonary, or vascular disease are often unnecessarily excluded from receiving therapy. We will review the risk data on beta-blockade and offer therapeutic strategies to help overcome residual barriers to the initiation and uptitration of this important therapy in patients with HF.

The Influence of prolonged β-blockers treatment on male rabbit's sexual behavior and penile microcirculation

The aim of the study was to assess the effect of the prolonged intake of three beta-blocking drugs (propranolol, metoprolol and nebivolol) on the sexual behavior and penile microcirculation of rabbits. Drugs were administered p.o. for 9 weeks and every three weeks in each group (n=13) one subgroup (n=7) performed behavioral tests, whereas in the second subgroup (n=6) penile microcirculation was measured with a laser Doppler flowmeter. The copulation studies revealed significant impairment of sexual function only in the propranolol treated group. The measured behavioral parameters suggest that at a given dose propranolol affects more performance rather than arousal aspects of rabbits' sexual behavior. In the course of the whole study no significant difference was observed among groups in penile blood flow. The data indicate that among the beta-blockers given only propranolol interferes with sexual behavior, and that beta-blockers do not appear to have a negative effect on penile microcirculation.

Effect of beta-blockers on peripheral skin microcirculation in hypertension and peripheral vascular disease

OBJECTIVE

This study was undertaken to investigate the possible negative effect of beta-blockers on skin microcirculation in patients with intermittent claudication and hypertension. Methods and materials In this clinical crossover study, 20 patients with mild to moderate hypertension, treated with long-term beta-blockade, and intermittent claudication or ischemic rest pain, underwent assessment of peripheral circulation before and after 2-week withdrawal of beta-blocking therapy and again 2 weeks after restarting therapy. Replacement therapy (calcium antagonist) was given if considered necessary to control hypertension. Skin microcirculation was assessed with three noninvasive techniques: capillary microscopy of the hallux nailfold, transcutaneous oximetry of the forefoot, and laser Doppler fluxmetry of the great toe.

RESULTS

Mean initial blood pressure was 163/81 mm Hg. Mean heart rate significantly increased with withdrawal of beta-blocker, from 65 bpm to 85 bpm. No significant differences in skin microcirculation and blood pressure were found between measurements obtained before, during, and after withdrawal of beta-blocking therapy. Patients experienced no change in symptoms during the study.

CONCLUSION

beta-Blockers do not appear to have a negative effect on peripheral skin microcirculation and are therefore not contraindicated to treat hypertension when intermittent claudication or ischemic rest pain is also present.

Measurement and cardiovascular relevance of partial agonist activity (PAA) involving beta 1- and beta 2-adrenoceptors

In the normal heart the ratio of beta 1/beta 2-receptors in both atria and ventricles is about 75:25; in the failing heart the ratio is about 60:40. Stimulation of either beta 1- or beta 2-receptors results in a positive chronotropic and inotropic response. In the periphery, with the exception of lipolysis, renin release, control of intraocular pressure and intestinal relaxation, beta 2-related activity predominates. The nature of the beta 2-receptor is being unravelled and it has now been cloned. The beta-receptor antagonist is 'anchored' via disulfide bonding. Subsequent events involve the regulatory protein guanine nucleotide which couples the receptor to adenylate cyclase. beta-receptor density may by up- or down-regulated. beta-stimulation down-regulates (uncouples and internalizes or sequestrates) and beta-antagonism up-regulates beta-receptor numbers, but the functional implications of such changes are not always clear. A partial agonist occupies a receptor site and competitively inhibits the full agonist (e.g. noradrenaline). A partial agonist differs from a full agonist in that maximal response of a tissue is less. When background sympathetic activity is absent or very low a partial agonist will act as an agonist, e.g. increase heart rate, but when background tone is high the partial agonist will behave functionally as an antagonist, e.g. decrease heart rate. In animals partial agonist activity (PAA) can be assessed in many ways. In the catecholamine-depleted (reserpine or syrosingopine), vagotomized or pithed, intact animal beta-activity can be assessed via changes in heart rate, cardiac contractility and atrioventricular conduction. Isolated organs can also be used such as atria, papillary muscle, tracheal, mesenteric artery and uterine preparations. The choice of animal is important as marked species differences in response can occur. In man assessing PAA is difficult due to the presence of an intact sympathetic system: the problem can be overcome by autonomic blockade of constrictor and vagal reflexes with prazosin, clonidine and atropine but leaving the beta-receptor mediated responses unimpaired. beta 1- and beta 2-selective PAA can also be gauged via an increased sleeping heart rate (basal sympathetic tone) in the presence and absence of a beta 1- and beta 2-selective antagonist. beta 1-selective PAA can also cause an increase in resting systolic blood pressure, beta 2-selective PAA may be further assessed by a fall in DBP, increased blood flow, fall in peripheral resistance or increased finger tremor.(ABSTRACT TRUNCATED AT 400 WORDS)

Peripheral vascular effects of beta-adrenoceptor blockade: comparison of two agents

1. The effects of atenolol (100 mg), a beta 1-adrenoceptor blocker, and bevantolol (200 mg) were compared on heart rate, blood pressure, lung function and on the peripheral circulation in normal volunteers before and after isoprenaline infusion. Recordings were obtained 2 and 24 h following a single dose and 24 h after continuous dosage for 7 days. 2. The effect of atenolol on the blockade of beta-adrenergic stimuli, as measured by the ability to reduce isoprenaline-induced tachycardia, was greater than that of bevantolol. Though both drugs achieved a similar reduction in systolic pressure there was a significantly greater reduction in diastolic pressure with bevantolol. The lung function tests gave similar results to those with other beta-adrenoceptor blockers. 3. Atenolol produced a fall in peripheral blood flow consistent with unopposed peripheral alpha-adrenoceptor stimulation. The effect of bevantolol differs from that of atenolol, an initial fall in peripheral blood flow being followed by a rapid recovery to baseline or greater. This effect may be due to partial alpha-adrenoceptor agonist activity.

Different effects of beta-1-adrenergic blocking agents with ISA or without ISA on peripheral blood flow

Until recently beta-adrenergic blocking agents were considered contraindicated in peripheral arterial occlusive disease (PAOD). However, in recent years several studies have failed to show negative effects on peripheral blood flow. It was the aim of this study to compare the effects of celiprolol, a beta-1-adrenergic blocking agent with intrinsic sympathomimetic activity (ISA), and of metoprolol, a beta-1-adrenergic blocking agent without ISA, on peripheral blood flow of patients with and without PAOD. In an acute trial 24 patients (group I: 12 patients with PAOD stage I and II; group II: 12 patients without PAOD received a single dose of 200 mg celiprolol or 200 mg metoprolol in a double-blind crossover design. Celiprolol induced no significant changes in calf and skin blood flow at rest or during reactive hyperemia. Basal vascular resistance (BVR) and minimal vascular resistance (MVR) were not affected. Metoprolol, however, significantly reduced muscle blood flow and increased BVR in both groups. Subsequently the patients were treated in a randomized double-blind design with a daily dose of 200 mg celiprolol or metoprolol for three weeks. In long-term treatment skin and muscle blood flow at rest and during reactive hyperemia, BVR, and MVR were not affected by celiprolol. Metoprolol significantly lowered calf blood flow at rest in patients with PAOD; other parameters remained unchanged. In patients without PAOD, metoprolol caused a significant decrease of calf blood flow at rest and an increase of BVR. Calf blood flow during reactive hyperemia, as well as skin blood flow at rest and during reactive hyperemia, showed no significant changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the effects of atenolol, sotalol and labetalol on muscle blood flow in man

A double-blind study of the effect of three beta-adrenoceptor blocking drugs (beta-blockers) on exercise muscle blood flow (MBF) in 14 normotensive volunteers was carried out. MBF was measured by the xenon-133 clearance technique. MBF was not altered by placebo, sotalol or labetalol. Atenolol significantly reduced MBF compared with placebo, sotalol and labetalol. We conclude that sotalol and labetalol may be more useful than conventional beta-blockers for treatment of hypertension or angina in association with peripheral vascular disease.

Cold sensitivity in essential hypertension: the effect of beta- and combined alpha- and beta-blockade

The presence of cold sensitivity was investigated in three groups of patients; untreated hypertensives and hypertensives treated by a beta-adrenoceptor blocker (propranolol) or by a combined alpha- and beta-adrenoceptor blocker (labetalol) at two ambient temperatures. At a comfortable ambient (24 degrees C) one-third of the untreated and those treated with beta-blockade only showed cold sensitivity as compared with 16% of patients on the combined therapy. Under conditions of mild cold stress (20 degrees C) cold sensitivity increased in frequency in all three groups, more than half of the untreated and beta-blocked patients were affected and greater than one-third of those with alpha- and beta-blockade. These findings indicate that in the general population of hypertensives treatment with beta-adrenoceptor blockade alone may have little effect on the peripheral vasculature and that a useful degree of protection may be provided by therapy which blocks both receptors.

Effect of propranolol on the tone of collateral arteries in patients with occlusion of the superficial femoral artery

The effect of administration of 0.5 mg propranolol into the femoral artery in eight patients with lower limb ischaemia and superficial femoral artery occlusion on collateral arterial resistance was studied in supine and tilted head-up position. Mean blood pressures were recorded directly from the femoral and popliteal artery and femoral blood flow was measured by an indicator dilution technique. After beta-receptor blockade in the supine position the collateral arterial resistance increased by 7 +/- 2%, femoral blood flow decreased 10 +/- 4%, and popliteal artery pressure increased by 4 mmHg (8 +/- 3%). During head-up tilt there was no change in femoral blood flow and collateral arterial resistance after propranolol. The peripheral vasoconstrictor effect of propranolol, therefore, seems not to be harmful to patients with vascular disease.

Lower extremity ischemia due to combined drug therapy for migraine

Three days after initiation of migraine headache therapy with ergotamine tartrate and propranolol, severe acute arterial insufficiency of the lower extremities developed in a 48-year-old woman who had been in general good health. Angiography revealed hypoplastic aortoiliac arteries, with tubular narrowing of the leg arteries. Lower extremity blood pressures rapidly returned to normal with a single intraarterial injection of 25 mg of tolazoline. Cases of peripheral ischemia due to either ergotamine or propranolol have been reported. Combined use of these two drugs may enhance the risk of acute arterial compromise.

Non-surgical management of peripheral vascular disease: a review

Although the outlook for a pronounced improvement in the ischaemic limb that cannot be surgically treated remains bleak, cessation of smoking, encouragement of exercise, and the withdrawal of vasoconstricting agents may give some symptomatic relief. There is little evidence that vasodilators or antiplatelet agents have much to offer.

Effects of propranolol and metoprolol on the peripheral circulation

The effects of single doses of propranolol and metoprolol on skin temperature and skin and muscle blood flow were compared in 10 normal subjects and four patients with essential hypertension. In normal subjects the mean skin temperature fell by 1.30 +/- 0.62 degrees C 90 minutes after 80 mg propranolol and 0.15 +/- 0.05 degrees C after 100 mg metoprolol. Skin blood flow and resting muscle blood flow were not affected by metoprolol but fell significantly after propranolol. Both drugs reduced post-exercise muscle hyperaemia, propranolol by more than metoprolol. Similar changes were seen in the hypertensive patients. Propranolol should be used with care in patients with known vascular disease.