Why administer a beta‑blocker preoperatively to adult patients undergoing coronary artery bypass grafting or valve surgery, particularly those with coronary artery disease, hypertension, or prior angina?

Why Give Beta Blockers Before Open Heart Surgery

Beta blockers should be administered for at least 24 hours before CABG to all patients without contraindications, primarily to reduce the incidence and clinical sequelae of postoperative atrial fibrillation, and should be continued in all patients already taking them for established indications. 1

Primary Indications for Preoperative Beta Blockade in CABG

Class I Recommendations (Must Do)

Continuation of existing therapy is the strongest indication—beta blockers must be continued in patients already receiving them for treatment of conditions with ACCF/AHA Class I guideline indications (angina, symptomatic arrhythmias, hypertension, prior MI, heart failure). 1 Stopping these medications perioperatively can cause rebound hypertension and increase cardiovascular complications. 2

Prevention of postoperative atrial fibrillation is the primary benefit—beta blockers administered preoperatively significantly reduce AF incidence in CABG patients, which is why they should be given for at least 24 hours before surgery. 1

Class IIa Recommendations (Probably Should Do)

Reduction of in-hospital mortality in patients with LVEF >30%—preoperative beta blockers can be effective in reducing perioperative death risk, with observational data showing mortality rates of 2.8% in beta-blocker users versus 3.4% in non-users. 1

Prevention of perioperative myocardial ischemia—beta blockers reduce ischemic episodes by decreasing heart rate, myocardial oxygen demand, and blunting sympathetic nervous system activation during the stress of surgery. 1, 3

Mechanisms of Cardiac Protection

Beta blockers provide multiple protective effects during cardiac surgery: 3

• Heart rate reduction: Slower heart rates increase diastolic filling time and coronary perfusion while decreasing myocardial oxygen consumption
• Blunted catecholamine response: Prevents stress-induced sympathetic activation and catecholamine release during surgical manipulation
• Decreased myocardial contractility: Reduces oxygen demand without compromising adequate cardiac output
• Preserved coronary perfusion pressure: Maintains adequate myocardial blood flow in the presence of coronary stenoses

Critical Dosing and Titration Principles

Dose titration is essential—the key lesson from the POISE trial is that routine administration of high-dose beta blockers without titration is harmful and increases mortality. 1 The trial showed that fixed higher-dose extended-release metoprolol started on the day of surgery increased stroke risk and total mortality despite reducing MI. 1

Target heart rate control—beta blockers should be titrated to achieve heart rate and blood pressure goals while avoiding bradycardia (<60 bpm) and hypotension (SBP <100 mmHg). 1 Higher doses and tighter heart rate control are associated with reduced ischemia and troponin release when properly monitored. 4

Timing matters—initiation should occur well before surgery (at least 24 hours, ideally longer) to allow for proper dose adjustment, not on the day of surgery. 1

Contraindications and Cautions

Absolute Contraindications 1

• Active bronchospasm requiring treatment
• Decompensated heart failure
• High-grade AV block without pacemaker
• Severe bradycardia

Uncertain Benefit (Class IIb) 1

LVEF <30%—the effectiveness of preoperative beta blockers in reducing mortality is uncertain in patients with severely reduced ejection fraction, though they should not be routinely withheld if already prescribed for heart failure indications.

Common Pitfalls to Avoid

Do not routinely discontinue beta blockers before CABG—this is the most frequent error and contradicts all guideline recommendations. 2 Withdrawal can precipitate rebound hypertension, tachycardia, and ischemia.

Do not start high-dose beta blockers on the day of surgery—this approach from POISE increased mortality and stroke risk. 1 Beta-blocker naive patients require gradual titration starting days to weeks before elective surgery.

Do not ignore hemodynamic monitoring—hypotension (HR 1.55 for significant hypotension, HR 2.74 for significant bradycardia in POISE) and bradycardia are associated with increased mortality and stroke. 1 Persistent tachycardia may indicate alternative causes (sepsis, hypovolemia, pulmonary embolism, anemia) that warrant investigation rather than dose escalation. 1

Do not use intravenous beta blockers routinely—IV administration may precipitate uncontrolled hypotension; oral agents are preferred when feasible. 2

Postoperative Management

Reinstitute beta blockers as soon as possible after CABG in all patients without contraindications to continue AF prevention and reduce long-term mortality. 1, 5 They should be prescribed at hospital discharge and continued indefinitely, as long-term use reduces mortality across all patient subgroups, even those without perioperative ischemia or heart failure. 1

Integration with Other Perioperative Medications

Beta blockers are part of comprehensive guideline-directed therapy: 6

• Aspirin: Continue until surgery, restart within 6 hours postoperatively
• Statins: Never discontinue perioperatively (Class III harm to stop)
• ACE inhibitors/ARBs: Reinstitute once hemodynamically stable postoperatively