Beneficial effect of continuation of propranolol through coronary bypass surgery

Pharmacologic Prophylaxis

New-onset atrial fibrillation (AF) occurs frequently in patients after cardiac surgery. The purpose of this study was to review the published trials and to provide clinical practice guidelines for pharmacologic prophylaxis against postoperative AF. Trials of pharmacologic prophylaxis against AF after heart surgery were identified by searching MEDLINE, the Cochrane Controlled Trials Register, and the bibliographies of published reports. Evidence grades and clinical recommendation scores were assigned to each prophylactic drug based on published evidence. Ninety-one trials were identified. The primary study design was a randomized, controlled trial of one drug vs placebo/usual care. Pharmacologic therapies that are reviewed include Vaughan-Williams class II agents (ie, beta-receptor antagonists) [29 trials; 2,901 patients], Vaughan-Williams class III agents (ie, sotalol and amiodarone) [18 trials; 2,978 patients], Vaughan-Williams class IV agents (ie, verapamil and diltiazem) [5 trials; 601 patients], and Vaughan-Williams class I agents (ie, quinidine and procainamide) [3 trials; 246 patients], as well as digitalis (10 trials; 1,401 patients), magnesium (14 trials; 1,853 patients), dexamethasone (1 trial; 216 patients), glucose-insulin-potassium (3 trials; 102 patients), insulin (1 trial; 501 patients), triiodothyronine (2 trials; 301 patients), and aniline (1 trial; 32 patients). A consistent finding in this review is that antiarrhythmic drugs with beta-adrenergic receptor-blocking effects (ie, class II beta-blockers, sotalol, and amiodarone) demonstrated successful prophylaxis. Furthermore, those therapies that did not inhibit beta-receptors generally failed to demonstrate a decreased incidence in postoperative AF. While sotalol and amiodarone have been shown in some studies to be effective, their safety and the incremental prophylactic advantage in comparison with beta-blockers has not been conclusively demonstrated. On the basis of evidence that has been reviewed and graded for quality, it is recommended that strong consideration should be given to the prophylactic administration of Vaughan-Williams class II beta-blocking drugs as a means of lowering the incidence of new-onset post-cardiac surgery AF.

Cardiopulmonary bypass alters the pharmacokinetics of propranolol in patients undergoing cardiac surgery

The pharmacokinetics of propranolol may be altered by hypothermic cardiopulmonary bypass (CPB), resulting in unpredictable postoperative hemodynamic responses to usual doses. The objective of the present study was to investigate the pharmacokinetics of propranolol in patients undergoing coronary artery bypass grafting (CABG) by CPB under moderate hypothermia. We evaluated 11 patients, 4 women and 7 men (mean age 57 +/- 8 years, mean weight 75.4 +/- 11.9 kg and mean body surface area 1.83 +/- 0.19 m(2)), receiving propranolol before surgery (80-240 mg a day) and postoperatively (10 mg a day). Plasma propranolol levels were measured before and after CPB by high-performance liquid chromatography. Pharmacokinetic Solutions 2.0 software was used to estimate the pharmacokinetic parameters after administration of the drug pre- and postoperatively. There was an increase of biological half-life from 4.5 (95% CI = 3.9-6.9) to 10.6 h (95% CI = 8.2-14.7; P < 0.01) and an increase in volume of distribution from 4.9 (95% CI = 3.2-14.3) to 8.3 l/kg (95% CI = 6.5-32.1; P < 0.05), while total clearance remained unchanged 9.2 (95% CI = 7.7-24.6) vs 10.7 ml min(-1) kg(-1) (95% CI = 7.7-26.6; NS) after surgery. In conclusion, increases in drug distribution could be explained in part by hemodilution during CPB. On the other hand, the increase of biological half-life can be attributed to changes in hepatic metabolism induced by CPB under moderate hypothermia. These alterations in the pharmacokinetics of propranolol after CABG with hypothermic CPB might induce a greater myocardial depression in response to propranolol than would be expected with an equivalent dose during the postoperative period.

Prolonged bradycardia and hypotension after neostigmine administration in a patient receiving atenolol

A 78-year-old woman admitted for an elective hip operation was maintained on atenolol for control of her hypertension. She received neostigmine and atropine for reversal of muscle relaxation at the end of general anaesthesia. She then developed prolonged bradycardia and hypotension which necessitated the use of adrenaline and isoprenaline. Such an adverse reaction with atenolol has not been described previously.

Beta-adrenergic blocker withdrawal

Abrupt withdrawal of long-term beta-blocker therapy in patients with angina may be associated with unstable angina and myocardial infarction. It appears that an "overshoot" in heart rate from pretreatment values occurs, which increases myocardial oxygen demand. This increase in heart rate may be secondary to increased beta receptor numbers or increased receptor sensitivity. Another possible mechanism for the increased risk of myocardial infarction after beta-blocker withdrawal is increased platelet aggregability. Withdrawal reactions may be less severe with beta blockers that have partial agonist activity. In patients undergoing coronary artery bypass surgery, beta-blocker withdrawal reactions have also been observed. Maintenance of beta-blocker therapy on the morning of surgery appears to reduce this risk. Gradual withdrawal regimens in outpatients with angina may be associated with lower risk for a beta-blocker withdrawal reaction. The gradual withdrawal of beta blockers in hypertensive patients requires further study.

Incidence and prevention of supraventricular tachyarrhythmias after coronary bypass surgery

Supraventricular tachyarrhythmias are a frequent complication encountered after coronary artery bypass grafting. A retrospective survey of 102 consecutive patients undergoing exclusive bypass grafting at St. Mary's Hospital supplemented by a review of 16 published reports over a period of 10 years revealed a mean incidence of post-operative tachyarrhythmia of 33.4% in 1344 patients (range 11.4-100%). One hundred and thirty two patients undergoing exclusive bypass surgery, were randomised prospectively in double blind fashion to receive either oral timolol or matched placebo approximately 24 hours after surgery. In the 66 patients receiving timolol, there was a significant reduction of post-operative arrhythmias compared to the 66 patients receiving placebo: from 19.7 to 7.5% (P less than 0.05). Of all arrhythmias, two thirds appeared under 48 hours after surgery. In the timolol group, 4 patients developed systemic hypotension. This was readily reversed by withdrawing the drug. No other side effects were noted. The use of oral timolol after coronary artery surgery significantly lowers the incidence of post-operative supraventricular arrhythmias.

Prevention of atrial fibrillation or flutter by acebutolol after coronary bypass grafting

Supraventricular tachyarrhythmias are common after coronary artery bypass graft surgery (CABG) and may have deleterious hemodynamic consequences. To determine if acebutolol, a cardioselective beta-blocking drug, prevents such tachyarrhythmias after CABG, 100 consecutive patients, aged 30 to 77 years (mean +/- standard deviation 53 +/- 9), were entered into a randomized, controlled study. Exclusion criteria were: contraindications to beta-blocking drugs, left ventricular aneurysm, major renal failure, history of cardiac arrhythmia and cardiac arrhythmia during the immediate postoperative period. From 36 hours after surgery until discharge (usually on the seventh day), 50 patients were given 200 mg of acebutolol (or 400 mg if weight was more than 80 kg) orally twice a day (dosage than modified to maintain a heart rate at rest between 60 and 90 beats/min). The 50 patients in the control group did not receive beta-blocking drugs after CABG. The 2 groups were comparable in angina functional class, ejection fraction, number of diseased vessels, antianginal therapy before CABG, number of bypassed vessels and duration of cardiopulmonary bypass All patients were clinically evaluated twice daily and had continuous electrocardiographic monitoring and daily electrocardiograms. A 24-hour continuous electrocardiogram was recorded in the last 20 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevention by acebutolol of rhythm disorders following coronary bypass surgery

Seventy-one patients submitted routinely to coronary artery bypass surgery were randomized into 2 groups. Group A (32 patients) received 24 hr after initiation of surgery an intravenous perfusion of 100 mg of acebutolol given over 24 hr (22 cases) or 600 mg administered orally (10 cases). On subsequent days, they received 1200 mg of acebutolol/day orally. Group B (39 patients) was used as control. The groups were comparable in terms of age, sex, severity of coronary disease, preoperative therapy, duration of extracorporeal circulation, aortic clamping time, and immediate postoperative haemodynamic findings. No patient received digitalis. During hospital stay (10 days), 1 group A patient (3%) and 13 group B patients (33%; P less than 0.001) developed a sustained episode of atrial arrhythmia (fibrillation, flutter or atrial ectopic tachycardia). The majority of these rhythm disorders developed between days 2 and 4. On Holter monitoring on days 7-10, malignant ventricular extrasystoles (grades IV and V of Lown's classification) were more frequent in group B (65.2%) than in group A (19.3%; P less than 0.001). Haemodynamic measurements taken at rest performed in 27 patients on days 7-10 (16 patients of group A; 11 of group B). No difference was observed between the two groups. Acebutolol is a safe and efficacious drug for the prevention of arrhythmias following coronary surgery.

Efficacy and safety of timolol for prevention of supraventricular tachyarrhythmias after coronary artery bypass surgery

Forty-one patients undergoing coronary artery bypass grafting were randomly assigned to receive prophylactic timolol or placebo, given in a double-blind fashion. beta-Adrenoceptor-blocking therapy was stopped at least one half-life before surgery. Three to 7 hr after surgery (304 +/- 56 min), 0.5 mg of timolol or placebo was given intravenously twice daily in a double-blind manner. When oral medications were resumed postoperatively, 10 mg of timolol twice daily or placebo was continued orally. Continuous electrocardiograms were recorded for 24 hr before and for 7 days after surgery with a standard cassette recorder. No patient received digoxin. Both groups were comparable for frequency of preoperative supraventricular arrhythmias, left ventricular ejection fraction, duration of cardiopulmonary bypass, aortic cross-clamp time, number of bypass grafts, and total duration of monitoring. Analysis of arrhythmias was done by hand counts, and supraventricular arrhythmias were divided into supraventricular tachycardia and atrial fibrillation and/or flutter. Timolol decreased the frequency of supraventricular tachycardia (581 episodes placebo vs 84 timolol; p less than .05) and of atrial fibrillation and/or flutter (291 episodes placebo vs five timolol; p less than .05). Timolol decreased the number of patients with severe (heart rate greater than 200 beats/min, duration greater than 50 beats) episodes of supraventricular tachycardia (four placebo vs 0 timolol; p less than .05) and also decreased the number of episodes of severe (heart rate greater than 200 beats/min, duration greater than 5 min) atrial fibrillation and/or flutter (16 placebo vs one timolol; p less than .005). There were differences in the durations of supraventricular arrhythmias.(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardial protective effect of maintained beta-blockade in aorto-coronary bypass surgery

Twenty-nine patients were randomly allocated to two groups before undergoing aorto-coronary bypass surgery. In one group the beta-blocking medication was withdrawn three days preoperatively, and in the other group it was maintained. The patients in the latter group were additionally given 100 mg metoprolol per os two hours before surgery. The degree of myocardial injury, as judged from cumulated activity of S-CK B, was less when the beta-blockade was maintained.

Acebutolol and coronary artery surgery. Plasma levels following oral pre-operative treatment

Plasma levels of acebutolol and its major human metabolite, diacetolol, were determined before, during and after aortocoronary bypass grafting in 10 patients who had received a chronic oral regimen of acebutolol 200 mg t.d.s. for at least 6 days before surgery, a 200 mg dose with the premedication and 5-10 mg intravenously immediately before intubation. It was found that this regimen produced beta-adrenoceptor antagonist levels which were within the range in which attenuation of hypertension and tachydysrhythmia occurs. These effective plasma levels were sustained throughout surgery and persisted into the early recovery period.

The interactions between beta-blockers and anaesthetics. Experimental observations

The possibility of interactions between beta-adrenoceptor antagonists and anaesthetic drugs is particularly relevant to the anaesthetic management of patients suffering from arterial hypertension and ischaemic heart disease. Maintenance of adrenergic beta-receptor blockade in patients with ischaemic heart disease and arterial hypertension is now widely accepted in order to avoid the cardiac risks of its sudden withdrawal and also to minimize the effects of sympathetic overactivity on the cardiovascular system. However, maintenance of adrenergic beta-receptor blockade may impose some constraints on the choice of the anaesthetic agent. While no adverse interaction has been found between beta blockade and anaesthesia with halothane, halothane supplementing nitrous oxide, or isoflurane, substantial reductions of cardiac performance have been observed in the case of the association of beta blockade and anaesthesia using methoxyflurane or trichloroethylene. An adverse interaction has also been observed between propranolol and enflurane anaesthesia but not between oxprenolol and enflurane anaesthesia. Recent studies of the effects of anaesthesia in the presence of critically narrowed coronary arteries have shown that both halothane and enflurane may cause regional myocardial dysfunction. This dysfunction is minimized by oxprenolol and it appears that adrenergic beta-receptor blockade, besides improving cardiovascular stability, protects the myocardium supplied by narrowed coronary arteries.

Digoxin and propranolol in the prophylaxis of supraventricular tachydysrhythmias after coronary artery bypass surgery

Supraventricular tachydysrhythmia is a bothersome and potentially harmful occurrence after coronary artery bypass graft operation (CABG). Use of digoxin prophylaxis preoperatively has yielded conflicting results in lowering the incidence of supraventricular tachydysrhythmia. In this study, three groups of patients were formed. Group 1 served as the control; no prophylactic medication was given. Group 2 was given digoxin prophylaxis beginning immediately after operation. Group 3 received digoxin postoperatively as did Group 2, plus orally administered propranolol beginning on postoperative day 2. No difference in the incidence of supraventricular tachydysrhythmia was found between Groups 1 and 2 (28.2% versus 28.9%). However, the incidence in Group 3 was 2.2%, and this represented a statistically significant difference (p less than 0.005) compared with either Group or 2. The combined use of digoxin and propranolol postoperatively significantly reduced the incidence of supraventricular tachydysrhythmia after CABG.