Beta Blockers In Anesthesia

Introduction Introduction

Sir James Black Sir James Whyte Black, OM, FRS, FRSE, FRCP (born 14 July 1924) is a Scottish doctor and pharmacologist who invented Propranolol, synthesized Cimetidine and was awarded the Nobel Prize for Medicine in 1988 for these discoveries.

Pharmacology Of Beta Blockers

 Sympatholytic drugs  On the heart: heart rate, contractility, conduction velocity, relaxation rate. Pharmacology of beta blockers

 On the vessels: Dominant alpha- adrenoceptor mediated vasoconstrictor influence. Pharmacology of beta blockers (cont.)

Pharmacology of commonly used or novel beta blockers

Therapeutic Indications Pharmacology of beta blockers (cont.)

Contraindications for BB Absolute – Asthma – Sick Sinus Syndrome – Severe peripheral vascular disease – Second or third degree heart block Relative – COPD – Raynaud phenomenon – Bradycardia – Hypoglycemia-prone diabetics in whom the early and warning symptoms of hypoglycemia may be masked.

Beta blockers in non-cardiac surgery

 Non-cardiac surgery is associated with an increase in catecholamines, which results in : an increase in blood pressure, heart rate free fatty acid concentrations.  Beta blockers suppress the effects of increased catecholamines and as a result may prevent perioperative cardiovascular events. Beta blockers in non-cardiac surgery

Noncardiac Surgery-Evidence Mangano Study (NEJM 1996;335:1713) – 200 high-risk patients in a RCT DB of atenolol IV peri-op and orally post-op ( 2 days prior and 7 days after) – Long-term follow-up for 2 years – Excluded those who did not survive hospital stay – Reduction in overall and cardiac-related deaths at 6 mo, 1 year and 2 years in the atenolol group.

Noncardiac Surgery-Evidence Poldermans Study (NEJM 1999) – High risk patients with positive dobutamine echocardiograms (n=111) – Randomized to placebo or bisoprolol – Cardiac deaths were reduced from 17% to 3.4% – Nonfatal MI occurred in 17% of placebo group compared to 0% in bisoprolol group

ACC 2006 Guidelines Class I : pre-op BB used for angina or hypertension should be continued. Class I : High cardiac risk patients undergoing vascular surgery should have BB. Class IIa : if preop assessment reveals untreated hypertension, known CAD, or major risk factors for CAD. Class IIb : if preop assessment reveals patients undergoing vascular surgery with low or intermediate cardiac risk. Class III – Contraindication to BB

Care should be taken in applying recommendations on beta-blocker therapy to patients with decompensated heart failure, nonischemic cardiomyopathy, or severe valvular heart disease in the absence of coronary heart disease. Beta blockers in non-cardiac surgery(cont.)

The Best Protocol To Initiate Perioperative Β-blockade? Started a week before surgery Titrated to heart rate-decreasing effect Use shorter acting BB to facilitate adjustment Beta blockers in non-cardiac surgery(cont.)

POISE Perioperative Ischemic Evaluation (POISE) trial, a randomized controlled trial of metoprolol versus placebo in 10,000 patients undergoing noncardiac surgery. Beta blockers in non-cardiac surgery(cont.)

Beta blockers in cardiac surgery

10% of cost of cardiac surgery is for treatment of complications = 1 billion $ in US annually BB reduce post-op atrial fibrillation (AFIB) which is associated with > LOS > cost ($10,000), and > risk of stroke. Withdrawal of BB in the peri-operative period doubles the risk of AF Mainly studied as a post-operative therapy to prevent AF Beta blockers in cardiac surgery

 ESC/ACC/AHA Guidelines : Beta blockers as a first-line medication for prevention of AF after CABG in patients without contraindications. In patients undergoing cardiac surgery on pre-existing beta-blocker therapy, this treatment should be continued unless contraindications develop Beta blockers in cardiac surgery(cont.)

 NICE Guidelines on AF management post- operativly should be reduced by: Amiodarone Beta-blocker Sotalol or Ratelimiting calcium antagonists Beta blockers in cardiac surgery(cont.)

Sotalol  Class II and III antiarrhythmic effects.  Lower frequency of postoperative AF.  Combination therapy  Titrated carefully with regular QT interval monitoring.  Caution in renal insufficiency. Beta blockers in cardiac surgery(cont.)

Esmolol  Cardioselective beta1 blocker.  Ultra-short–acting(10 minutes).  Uses: Perioperative control of blood pressure. Control of arrhythmias. Beta blockers in cardiac surgery(cont.)

Esmolol  Recently used to induce “minimal myocardial contraction”  It gives myocardial protection equivalent to cardioplegia.  Scorsin et al(Thor & Cardiovas Sur2003) Esmolol and potassium Continuous normothermic retrograde blood cardioplegia markedly decreased myocardial oxygen consumption with esmolol Beta blockers in cardiac surgery(cont.)

Recommendations

 Administrative data may be able to provide some evidence as to baseline rates.  Exact criteria for use need to be clarified.  Clarification is needed as to the exact timing of therapy and the appropriate patient population

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