Should metoprolol be continued on the day of surgery, and what is the recommended peri‑operative dosing strategy (oral versus intravenous) and contraindications for withholding it?

Metoprolol and Anesthesia: Perioperative Management

Patients already taking metoprolol should continue it through the perioperative period, while initiating metoprolol on the day of surgery is harmful and should not be done. 1

For Patients Already on Metoprolol

Continue metoprolol through the perioperative period based on stable dosing and clinical circumstances 1. The evidence strongly supports that abrupt withdrawal of chronic beta-blockers is harmful, particularly in patients with established cardiovascular disease 2. This represents a Class I recommendation from the 2024 ACC/AHA guidelines.

Dosing Strategy for Chronic Users:

• Oral route preferred: Continue the patient's home dose of oral metoprolol on the day of surgery with a sip of water
• If NPO or unable to take oral: Convert to IV metoprolol at approximately 1:2.5 ratio (e.g., metoprolol 50 mg PO = metoprolol 5 mg IV) 3
• Titrate perioperatively: Adjust doses based on hemodynamics during the perioperative period, but maintain therapy unless clear contraindications arise 1
• Ensure continuation at discharge: Critical to restart and continue beta-blockers postoperatively 1

For Beta-Blocker Naïve Patients

Do NOT initiate metoprolol on the day of surgery - this is a Class III (Harm) recommendation 1. The landmark POISE trial demonstrated that starting high-dose metoprolol (100 mg) within 2-4 hours of surgery increased all-cause mortality and stroke risk, despite reducing myocardial infarction 4, 5.

If New Indication for Beta-Blockade Exists:

Initiate at least 7 days before surgery (optimally >7 days) to permit assessment of tolerability and dose titration 1, 2. Starting beta-blockers <7 days before surgery showed higher mortality risk in observational studies, while initiation 8-30 days prior showed no excess mortality but also no perioperative benefit 1.

Specific dosing for new initiation:

• Start with low doses (e.g., metoprolol tartrate 25 mg twice daily)
• Titrate gradually based on heart rate and blood pressure tolerance
• Target heart rate 60-70 bpm, but "tight" heart rate control is not strongly supported 2
• Assess for tolerability (hypotension, bradycardia, bronchospasm)

Contraindications to Perioperative Metoprolol

Absolute contraindications:

• Heart rate <50 beats/min
• Second or third-degree heart block without pacemaker
• Decompensated heart failure
• Active bronchospasm or severe asthma
• Cardiogenic shock
• Severe hypotension (systolic BP <90 mmHg)

Relative contraindications requiring careful consideration:

• High stroke risk (beta-blockers increase stroke risk perioperatively) 1
• Severe peripheral arterial disease
• Chronic obstructive pulmonary disease
• First-degree AV block or significant bradycardia (50-60 bpm)

Intraoperative IV Metoprolol Protocol

When IV administration is necessary 3:

For acute myocardial infarction during surgery:

• Give 5 mg IV bolus over 2 minutes
• Repeat every 2 minutes for total of 3 doses (15 mg maximum)
• Monitor BP, HR, and ECG continuously
• Transition to oral metoprolol 50 mg every 6 hours starting 15 minutes after last IV dose

For rate control intraoperatively:

• Give 2.5-5 mg IV boluses
• Titrate to heart rate and blood pressure response
• Maximum 15 mg in early treatment phase

Critical Pitfalls to Avoid

1. Starting high-dose metoprolol acutely: The POISE trial used 100 mg metoprolol succinate started immediately preoperatively, which proved harmful 4, 1. If initiating perioperatively is absolutely necessary (which it rarely is), use low doses with careful titration.

2. Discontinuing chronic beta-blockers: Even brief withdrawal increases risk of rebound tachycardia, hypertension, and myocardial ischemia 2.

3. Ignoring hemodynamic instability: While continuation is recommended, clinical judgment must prevail - titrate or temporarily hold if severe hypotension or bradycardia develops, but restart as soon as clinically appropriate 1.

4. Assuming all patients benefit: The evidence shows beta-blockers reduce MI but increase stroke and may increase mortality when started acutely 1. The risk-benefit calculation depends heavily on individual patient factors.

Evidence Quality Considerations

The 2024 ACC/AHA guidelines explicitly exclude several DECREASE trials due to concerns about data reliability 1. The remaining evidence, particularly POISE (8,351 patients), shows that while perioperative beta-blockers reduce nonfatal MI (RR 0.71), they increase stroke and all-cause mortality when initiated acutely 5. Multiple smaller trials (POBBLE, MaVS, DIPOM) showed no significant benefit from perioperative beta-blockade 6, 7, reinforcing that routine prophylactic use is not indicated.

The current evidence supports a conservative approach: continue chronic therapy, avoid acute initiation, and only consider starting beta-blockers weeks in advance when there is a clear long-term indication beyond surgery alone.