Beta blockers and anesthesia Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diab. DCA, Dip. Software statistics PhD ( physiology) – IDRA, FICA

Mainly non cardiac surgeries

What are they ? Preferentially blocks beta receptors of the adrenergic system

Classify ? Nonselective blockers. – With ISA (Intrinsic sympathetic activity): Pindolol. – With MSE (Membrane stabilising effect): Propranolol, sotolol, timolol. – Both ISA and MSE: Alprenolol, oxyprenolol. – Neither ISA or MSE: Nadolol. • Cardioselective blockers. – With ISA: Practolol, acebutolol – With MSE: Acebutolol – Neither ISA or MSE: Atenolol, metoprolol, esmolol Pro – BBB cross Aten – no

Actions !! Reduce heart rate Reduce contractility - reduce cardiac output Decrease AV nodal conduction Decrease arrythmogenicity - phase IV decrease Reduced rennin angiotensin activity Peripheral vasoconstriction Bronchospasm Decreased glucagon response to hypoglycemia Decrease IOP ISA activity ?

Carvidolol-- some vasodilation Nebivolol nitric oxide potentiation

Indications Hypertension Angina Sinus tachycardia and paroxysmal atrial tachycardia Coronary artery disease Dissection aorta Hypertrophic obstructive cardiomyopathy QT–prolongation syndrome Cyanotic spells in tetralogy of Fallot.

Other indications Prophylaxis of migraine Essential tremor Anxiety Alcohol withdrawal syndrome. Thyrotoxicosis Glaucoma

Contraindications to beta blockers Peripheral arterial disease AV blocks Bronchospasm Frank CCF ! -- Slow start and slow rise Bradycardia and hypotension and hypoglycemia in fetus – beware

Anesthetic beta blocker Esmolol is effective in quick control of supraventricular tachyarrhythmias in patients with acute myocardial infarction where it reduces heart rate and myocardial oxygen demand. It is also used to control perioperative hypertension with tachycardia. Dose of esmolol 50 to 200 mcg/kg/min. rapid onset (within 20 seconds) short duration of action (9 to 10 min). 10 mg / ml – 10 ml vial

Acts better when sympathetic activity is high !!

When its working ? Heart rate around 55 Less than 20 % increase with stress Should not be any AV block Then its working

They don’t do !! Beta-blockers do not affect the serum electrolytes, particularly serum potassium/serum uric acid levels, but glucose tolerance deteriorates in some non-insulin dependent diabetics also .

Anesthetic considerations

Premedication Already on drugs continue Think of using in hypotensive anesthesia

Anesthetic considerations volatile agents produce more CVS depression

Bradycardia may be more severe In general anesthesia Fentanyl Vecuronium Neostigmine Succinyl choline Bradycardia may be more severe

General anesthesia – concerns . Normal sympathetic response to blood loss, acute hypovolaemia may be obtunded: Simultaneous use of calcium channel blockers cause additive myocardial depression Bradycardia following acute blood loss should be anticipated. Avoid Hypercarbia should be avoided - hypotension because the vasodilatation produced by carbon dioxide is no longer offset by tachycardia due to activation of the adrenergic system

Can we reverse ?? Atropine–dose - 2 to 3 mg intravenously. Isoprenaline–specific antagonist for beta adrenergic blocking drugs. It is given as an infusion with a dose of 2 to 5 mcg/min Calcium chloride–increases myocardial contractility. Dose: 500 to 100 mg over 10 to 20 min. Aminophylline–5 mg/kg/IV, inhibits phosphodiesterase, Glucagon 5-10 mg I/V Cardiac pacing.

Other uses To abolish hypertensive response to laryngoscopy. Adjunct to nitroprusside induced hypotension. Postoperative hypertension in coronary artery bypass graft patients. For by pass surgery on beating heart. Supraventricular arrhythmias.

In neuraxial anesthesia Heart rate fall and hypotension more Test dose may not be foolproof Other causes of tachycardia ruled out – think of beta blockers Ephedrine – unopposed alpha activity

POISE (Peri Operative ISchemic Evaluation) showed the benefit of a perioperative β blockade in terms of reduction in cardiovascular death and MI, but with an increased risk of stroke and total mortality. 1 week prior to surgery – important Postop continue

Summary What drugs Classification Effects Uses Contraindications General anesthesia Regional POISE trial