What is the recommended dosing regimen for a labetolol (labetalol) infusion in acute hypertension?

Labetalol Infusion Dosing for Acute Hypertension

For acute hypertensive emergencies, labetalol should be administered as an IV infusion at 0.4-1.0 mg/kg/h up to 3 mg/kg/h, with an initial bolus of 0.3-1.0 mg/kg (maximum 20 mg) followed by continuous infusion adjustment based on blood pressure response. 1

Initial Bolus Administration

• Start with a loading dose of 0.3-1.0 mg/kg (maximum 20 mg) administered by slow IV injection over 1-2 minutes 1
• Monitor blood pressure immediately before injection and at 5 and 10 minutes after injection
• Additional bolus doses of 40-80 mg can be given at 10-minute intervals if needed
• Maximum cumulative bolus dose: 300 mg 2

Continuous Infusion Preparation and Administration

Two standard methods for preparing the infusion:

1. Method 1:

   • Add 40 mL of labetalol (200 mg) to 160 mL of compatible IV fluid
   • Final concentration: 1 mg/mL
   • Administer at 2 mL/min to deliver 2 mg/min 2

2. Method 2:

   • Add 40 mL of labetalol (200 mg) to 250 mL of compatible IV fluid
   • Final concentration: approximately 2 mg/3 mL
   • Administer at 3 mL/min to deliver approximately 2 mg/min 2

Titration and Monitoring

• Adjust infusion rate according to blood pressure response
• Typical effective IV dose range: 50-200 mg (total dose up to 300 mg may be required) 2
• Target a 10-15% reduction in blood pressure during the first hour 1, 3
• Monitor blood pressure every 15 minutes for the first 2 hours, then every 30 minutes for 6 hours, and hourly thereafter 1
• Watch for signs of excessive blood pressure reduction or organ hypoperfusion

Compatible IV Fluids

Labetalol is compatible with:

• Ringer's Injection
• Lactated Ringer's Injection
• 5% Dextrose Injection
• 0.9% Sodium Chloride Injection
• Various combinations of dextrose and saline solutions 2

NOT compatible with 5% Sodium Bicarbonate Injection 2

Contraindications and Precautions

Labetalol is contraindicated in patients with:

• Second or third-degree heart block
• Severe bradycardia
• Decompensated heart failure
• Asthma or COPD 1, 3

Adverse Effects to Monitor

• Bradycardia
• Hypotension (particularly orthostatic)
• Bronchospasm
• Heart failure exacerbation 2, 4

Special Considerations

• In pre-eclampsia/eclampsia, the cumulative dose should not exceed 800 mg/24h to prevent fetal bradycardia 3
• For patients with acute aortic dissection, target systolic BP ≤120 mmHg and heart rate ≤60 bpm 1, 3
• Patients should remain supine during administration to prevent orthostatic hypotension 2
• Have rescue medications available (glucagon, beta-agonists, vasopressors) in case of severe cardiovascular depression 4

Transitioning to Oral Therapy

• Begin oral labetalol when blood pressure is stabilized
• Recommended initial oral dose: 200 mg
• Follow with 200-400 mg in 6-12 hours based on blood pressure response 2

Continuous infusion of labetalol is generally preferred over repeated bolus injections for better blood pressure control and fewer side effects 5. However, vigilance is required during prolonged administration in critically ill patients due to potential for profound cardiovascular compromise 4.