What is the recommended dosage of IV labetalol in mg/hour?

Labetalol Infusion Dosing in mg/hour

For hypertensive emergencies requiring IV labetalol infusion, start at 0.4-1.0 mg/kg/hour (approximately 30-80 mg/hour for a 70-80 kg adult), titrating up to a maximum of 3 mg/kg/hour (approximately 200-240 mg/hour) based on blood pressure response. 1

Standard Infusion Protocol

Initial infusion rate:

• Start at 0.4-1.0 mg/kg/hour 1, 2
• For a 70 kg patient, this equals approximately 28-70 mg/hour
• The American College of Cardiology recommends starting at 2 mg/min (120 mg/hour) and titrating to blood pressure response 2

Maximum infusion rate:

• Up to 3 mg/kg/hour 1, 2
• For a 70 kg patient, this equals approximately 210 mg/hour
• Adjust rate based on urgency and blood pressure response 1

Total cumulative dose considerations:

• Standard maximum is 300 mg per 24 hours 1, 3
• However, doses exceeding 300 mg/24 hours (up to 800 mg) have been used safely in specific populations, particularly neurosurgical patients and severe preeclampsia 2, 3

Clinical Context-Specific Dosing

Acute ischemic stroke (thrombolytic-eligible patients with BP >185/110 mmHg):

• Give 10-20 mg IV bolus over 1-2 minutes first 1, 2
• If bolus dosing fails, switch to infusion at 2-8 mg/min (120-480 mg/hour) 1
• Target: maintain BP <185/110 mmHg 1, 2

Acute ischemic stroke (non-thrombolytic patients with systolic >220 or diastolic 121-140 mmHg):

• Aim for 10-15% reduction in blood pressure 1
• Use infusion rates of 0.4-1.0 mg/kg/hour up to 3 mg/kg/hour 1

Severe preeclampsia/eclampsia:

• Target systolic BP <160 mmHg and diastolic BP <105 mmHg 2
• Maximum cumulative dose should not exceed 800 mg/24 hours to prevent fetal bradycardia 2
• Infusion rate: 0.4-1.0 mg/kg/hour up to 3 mg/kg/hour 1

Aortic dissection:

• Target systolic BP ≤120 mmHg and heart rate ≤60 bpm 2
• Use in combination with ultra-short acting vasodilators 2

Monitoring Requirements

Blood pressure monitoring frequency:

• Every 15 minutes for first 2 hours 1, 2
• Every 30 minutes for next 6 hours 1, 2
• Every hour for subsequent 16 hours 1, 2

Target blood pressure reduction:

• Aim for 20-25% reduction in mean arterial pressure over several hours 2
• Avoid rapid or excessive falls in blood pressure 2

Critical Safety Considerations

Absolute contraindications:

• Second- or third-degree heart block 1, 2
• Bradycardia 1, 2
• Decompensated heart failure 1, 2
• Reactive airways disease (asthma) 1, 2
• Chronic obstructive pulmonary disease (COPD) 1, 2

Common pitfalls:

• Prolonged infusions in ICU settings require vigilance for severe cardiovascular depression 4
• Have glucagon, beta-agonists, phosphodiesterase inhibitors, insulin, and vasopressin readily available when using labetalol infusions 4
• Monitor for bradycardia and hypotension, which may require immediate intervention 4

Adverse effects to monitor:

• Hypotension (may require elevating foot of bed) 5
• Bradycardia 1
• Nausea, scalp tingling, burning sensations 5
• May worsen heart failure 1

Practical Conversion

For ease of calculation at bedside:

• Low-dose infusion: 30-50 mg/hour (0.4-0.7 mg/kg/hour for 70 kg patient)
• Moderate-dose infusion: 70-120 mg/hour (1.0-1.7 mg/kg/hour for 70 kg patient)
• High-dose infusion: 150-210 mg/hour (2.1-3.0 mg/kg/hour for 70 kg patient)

The American College of Cardiology's recommendation of starting at 2 mg/min (120 mg/hour) represents a moderate-to-high initial dose that can be titrated based on response 2.