What are the recommended maintenance infusion rates for common continuous‑infusion drugs in a 100‑kg adult patient?

Maintenance Infusion Protocols for a 100 kg Patient

The question lacks specificity regarding which drug, but I'll provide the most commonly used continuous infusion protocols for a 100 kg adult patient based on the strongest guideline evidence.

Hypertensive Emergency Medications

For blood pressure control in hypertensive emergencies, the following weight-based maintenance infusions apply to a 100 kg patient 1, 2:

First-Line Agents

• Nicardipine: Start 5 mg/h, titrate by 2.5 mg/h every 5 minutes to maximum 15 mg/h (not weight-based)

• Clevidipine: Start 1-2 mg/h, double every 90 seconds until BP approaches target, then increase by less than double every 5-10 minutes; maximum 32 mg/h (not weight-based)

• Esmolol:

  • Loading: 50-100 mg over 1 minute (500-1000 mcg/kg/min)
  • Maintenance: Start at 5 mg/min (50 mcg/kg/min), increase in 5 mg/min increments to maximum 20 mg/min (200 mcg/kg/min)

• Labetalol:

  • Bolus option: 30-100 mg slow IV every 10 minutes (0.3-1.0 mg/kg, max 20 mg)
  • Infusion: Start 40-100 mg/h (0.4-1.0 mg/kg/h), titrate up to 300 mg/h (3 mg/kg/h)

Alternative Agents

• Sodium Nitroprusside: Start 30-50 mcg/min (0.3-0.5 mcg/kg/min), increase by 50 mcg/min increments to maximum 1000 mcg/min (10 mcg/kg/min). Critical caveat: Requires arterial line monitoring; cyanide toxicity risk with rates ≥400 mcg/min or duration >30 minutes 2

• Nitroglycerin: Start 5 mcg/min, increase by 5 mcg/min every 3-5 minutes to maximum 20 mcg/min (not weight-based)

• Fenoldopam: Start 10-30 mcg/min (0.1-0.3 mcg/kg/min), increase by 5-10 mcg/min every 15 minutes to maximum 160 mcg/min (1.6 mcg/kg/min)

Sedation in ICU

For continuous sedation in mechanically ventilated patients 3, 4:

• Propofol:

  • Loading: 25 mg over 5 minutes (0.25 mg/kg) if hemodynamically stable
  • Maintenance: Start 6 mg/kg/h (600 mg/h for 100 kg), titrate to 5-50 mcg/kg/min (30-300 mg/h)

• Midazolam:

  • Loading: 5 mg over several minutes (0.05 mg/kg)
  • Maintenance: 2-10 mg/h (0.02-0.1 mg/kg/h)

• Lorazepam:

  • Loading: 2-4 mg (0.02-0.04 mg/kg, max 2 mg)
  • Maintenance: 1-10 mg/h (0.01-0.1 mg/kg/h, max 10 mg/h)

• Dexmedetomidine:

  • Loading: 100 mcg over 10 minutes (1 mcg/kg) - avoid in hemodynamically unstable patients
  • Maintenance: 20-70 mcg/h (0.2-0.7 mcg/kg/h), may increase to 150 mcg/h (1.5 mcg/kg/h)

Vasopressor/Inotrope Support

For shock states 5:

• Norepinephrine: 2-20 mcg/kg/min (200-2000 mcg/min for 100 kg)

• Epinephrine: 0.1-1.0 mcg/kg/min (10-100 mcg/min for 100 kg), up to 5 mcg/kg/min in exceptional circumstances

• Dopamine: 2-20 mcg/kg/min (200-2000 mcg/min for 100 kg)

• Dobutamine: 2-20 mcg/kg/min (200-2000 mcg/min for 100 kg)

Critical Considerations

Common pitfalls to avoid:

1. Esmolol and labetalol are contraindicated in bradycardia, heart block, decompensated heart failure, and reactive airway disease 1, 2, 6

2. Nitroprusside requires cyanide toxicity monitoring with prolonged use or high doses; consider co-administration of thiosulfate 2

3. Propofol carries risk of propofol-related infusion syndrome at high doses/prolonged duration; monitor triglycerides 3

4. Lorazepam can cause propylene glycol toxicity with prolonged infusions, leading to metabolic acidosis and nephrotoxicity 3

5. All vasopressors require central line access when possible; extravasation causes severe tissue injury. Have phentolamine 10 mg in 10 mL saline ready for intradermal injection at extravasation sites 5, 7

Titration principles:

• Hypertensive emergency agents should reduce BP by no more than 25% in first hour, then to 160/100 mmHg over 2-6 hours 2
• Sedation requires frequent reassessment (every 5-10 minutes initially) using validated scales (Ramsay, RASS) 3, 4
• Vasopressors should be titrated to MAP ≥65 mmHg or clinical endpoints of perfusion