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Beta Blockers In Anesthesia. Introduction. Sir James Black.
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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 (cont.) • On the vessels: • Dominant alpha-adrenoceptormediated vasoconstrictor influence.
Pharmacology of beta blockers (cont.) Therapeutic Indications
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.
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
Beta blockers in non-cardiac surgery(cont.) Care should be taken in applying recommendations on beta-blocker therapy to patients with decompensatedheart failure, nonischemiccardiomyopathy, or severe valvular heart disease in the absence of coronary heart disease.
The Best Protocol To Initiate Perioperative Β-blockade? • Beta blockers in non-cardiac surgery(cont.) • Started a week before surgery • Titrated to heart rate-decreasing effect • Use shorter acting BB to facilitate adjustment
POISE • Beta blockers in non-cardiac surgery(cont.) Perioperative Ischemic Evaluation (POISE) trial, a randomized controlled trial of metoprolol versus placebo in 10,000 patients undergoing noncardiac surgery.
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(cont.) • ESC/ACC/AHAGuidelines : • 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
Sotalol • Beta blockers in cardiac surgery(cont.) • Class II and III antiarrhythmic effects. • Lower frequency of postoperative AF. • Combination therapy • Titrated carefully with regular QT interval monitoring. • Caution in renal insufficiency.
Esmolol • Beta blockers in cardiac surgery(cont.) • Cardioselective beta1 blocker. • Ultra-short–acting(10 minutes). • Uses: • Perioperative control of blood pressure. • Control of arrhythmias.
Esmolol • Beta blockers in cardiac surgery(cont.) • 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
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