Labetalol Infusion Protocol for Severe Hypertension
Initial Dosing
Start labetalol infusion at 2 mg/min (0.4-1.0 mg/kg/hour, approximately 30-80 mg/hour for a 70-80 kg adult), prepared by adding 200 mg labetalol to 200 mL of compatible IV fluid (1 mg/mL concentration) and infusing at 2 mL/min. 1, 2, 3
Preparation Options:
- Standard concentration: Add 40 mL labetalol (200 mg) to 160 mL IV fluid = 200 mL total at 1 mg/mL, infuse at 2 mL/min 3
- Alternative concentration: Add 40 mL labetalol (200 mg) to 250 mL IV fluid = approximately 2 mg/3 mL, infuse at 3 mL/min 3
Compatible IV Fluids:
- Normal saline, lactated Ringer's, D5W, D5NS (various concentrations) 3
- Avoid: 5% sodium bicarbonate (incompatible) 3
Titration Strategy
Increase infusion rate based on blood pressure response, up to maximum of 3 mg/kg/hour (approximately 200-240 mg/hour for 70-80 kg adult). 1, 2
Practical Titration Steps:
- Low-dose: 30-50 mg/hour (0.4-0.7 mg/kg/hour) 2
- Moderate-dose: 70-120 mg/hour (1.0-1.7 mg/kg/hour) 2
- High-dose: 150-210 mg/hour (2.1-3.0 mg/kg/hour) 2
- Maximum cumulative dose: 300 mg total (standard practice), though up to 800 mg/24 hours used in specific populations 2, 3
Blood Pressure Targets
Aim for 10-15% reduction in mean arterial pressure, NOT normalization, to avoid compromising organ perfusion. 1, 4, 2
Context-Specific Targets:
- Hypertensive emergency (general): Reduce MAP by 20-25% over several hours 2
- Acute ischemic stroke (non-thrombolytic eligible): 10-15% reduction if SBP >220 mmHg or DBP 121-140 mmHg 1, 2
- Acute ischemic stroke (thrombolytic eligible): Maintain BP <185/110 mmHg 1, 2
- Acute hemorrhagic stroke: Target SBP <180 mmHg 2
- Severe preeclampsia/eclampsia: Target SBP <160 mmHg and DBP <105 mmHg 2
Example Calculation:
For BP 200/120 mmHg, target approximately 170-180/102-108 mmHg initially 4
Monitoring Requirements
Check blood pressure every 15 minutes for first 2 hours, then every 30 minutes for 6 hours, then hourly for 16 hours. 1, 4, 2
Critical Monitoring Points:
- Keep patient supine during entire infusion to prevent orthostatic hypotension 3
- Establish ability to tolerate upright position before allowing ambulation 3
- Monitor for bradycardia, especially with prolonged infusions 5
- Watch for sedation, nausea, diaphoresis (most common side effects) 6
Transition to Oral Therapy
Begin oral labetalol when supine diastolic blood pressure starts to rise after stopping infusion. 3
Oral Transition Protocol:
- Initial oral dose: 200 mg 3
- Second dose: 200-400 mg given 6-12 hours after first dose, based on BP response 3
- Subsequent titration:
- Inpatient titration: May increase daily while monitoring response 3
Overlap Strategy:
- Stop infusion when satisfactory BP response achieved 3
- Wait for BP to begin rising before starting oral therapy 3
- No specific overlap period recommended; transition is sequential, not concurrent 3
When to Stop Infusion
Discontinue infusion when target blood pressure is achieved and sustained, typically after 50-200 mg total dose (effective range), then transition to oral therapy. 3
Stopping Criteria:
- Satisfactory BP response obtained 3
- Maximum 300 mg cumulative dose reached 1, 3
- Steady-state not reached during typical infusion (half-life 5-8 hours) 3
- Adverse effects requiring discontinuation (rare) 6
Absolute Contraindications
Do NOT use labetalol in patients with:
- 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 1, 2
Alternative Bolus Method (If Preferred)
If continuous infusion not feasible, use repeated IV boluses: 1
- Initial: 10-20 mg IV over 1-2 minutes 1
- Repeat: 40 mg or 80 mg every 10 minutes 1
- Maximum: 300 mg cumulative dose 1
- Measure BP at 5 and 10 minutes after each injection 3
- Maximum effect occurs within 5 minutes of injection 3