What is the proper dosing protocol for vasopressin (Vasopressin) in patients with hypotension?

Vasopressin Dosing Orders for Hypotension

For vasodilatory shock, order vasopressin as a continuous IV infusion at 0.01-0.04 units/minute (NOT units/kg/min), diluted to 0.1 units/mL or 1 unit/mL concentration, administered via central line when possible, and used only as an adjunct to norepinephrine—never as initial monotherapy. 1, 2

Preparation and Dilution

Standard Concentration Options:

• Option 1: Add 20 units (1 mL of 20 units/mL vial) to 200 mL of normal saline or D5W = 0.1 units/mL 2
• Option 2: Add 20 units (1 mL of 20 units/mL vial) to 20 mL of normal saline or D5W = 1 unit/mL 2
• Alternative concentration from guidelines: 25 units in 250 mL of D5W or normal saline = 0.1 units/mL 3

Critical storage requirement: Discard unused diluted solution after 18 hours at room temperature or 24 hours under refrigeration 2

Dosing Protocol by Clinical Scenario

Septic Shock (Most Common Indication)

• Starting dose: 0.01 units/minute 2
• Titration range: 0.01-0.07 units/minute 2
• Maximum dose: 0.04 units/minute (do NOT exceed this in routine practice) 1, 2
• When to initiate: Add vasopressin when norepinephrine reaches 0.25 mcg/kg/min and hypotension persists (MAP <65 mmHg) 1

Post-Cardiotomy Shock

• Dose range: 0.03-0.1 units/minute 2
• This is the ONLY scenario where doses >0.04 units/min are FDA-approved 2

Anaphylaxis (Refractory to Epinephrine)

• Dose range: 0.01-0.04 units/minute 3
• Use only when epinephrine and fluid resuscitation have failed 3

Administration Route and Monitoring

Route of Administration:

• Central venous access is strongly preferred 1
• Peripheral IV can be used temporarily if central access is unavailable 1

Mandatory Monitoring:

• Place arterial catheter for continuous blood pressure monitoring 1
• Monitor ECG continuously 1
• Check blood pressure and heart rate every 5-15 minutes during initiation 1
• Assess tissue perfusion markers: lactate clearance, urine output, mental status, capillary refill 1

Critical Pre-Administration Requirements

Before starting vasopressin, you MUST:

1. Ensure adequate fluid resuscitation: Minimum 30 mL/kg crystalloid bolus 1
2. Start norepinephrine first: Vasopressin is NEVER first-line monotherapy 1, 2
3. Verify norepinephrine dose: Should be at least 0.25 mcg/kg/min before adding vasopressin 1
4. Exclude hypovolemia and cardiac dysfunction: Vasopressin in hypovolemic patients causes severe organ hypoperfusion 1

Sample Order Set

Written Order Example:

Vasopressin 20 units in 200 mL normal saline (0.1 units/mL)
Start at 0.01 units/minute IV via central line
Titrate by 0.01 units/min every 10-15 minutes
Target MAP ≥65 mmHg
Maximum dose: 0.04 units/minute
Monitor: Continuous arterial line BP, ECG, hourly urine output

Titration Strategy

Upward titration:

• Increase by 0.01 units/min every 10-15 minutes based on MAP response 1
• Goal: Achieve MAP ≥65 mmHg OR allow reduction of norepinephrine dose 1
• STOP at 0.04 units/min for septic shock—do NOT exceed this dose 1, 2

Downward titration (weaning):

• Wean norepinephrine first before reducing vasopressin 1
• Once norepinephrine is <0.1 mcg/kg/min, begin tapering vasopressin by 0.01 units/min every 30-60 minutes 1

Common Pitfalls to Avoid

Never use vasopressin as first-line therapy: It must be added to norepinephrine, not used alone 1, 2

Never exceed 0.04 units/min in septic shock: Higher doses increase risk of cardiac ischemia, mesenteric ischemia, and digital ischemia without additional benefit 1, 2

Never use vasopressin without adequate volume resuscitation: This causes severe vasoconstriction and organ hypoperfusion 1

Do not confuse units/minute with mcg/kg/min: Vasopressin is dosed in absolute units/minute (NOT weight-based like norepinephrine) 2, 4

Watch for hyponatremia: Vasopressin causes water retention via V2 receptors, leading to dilutional hyponatremia 2

Adverse Effects to Monitor

Cardiovascular:

• Decreased cardiac output 2
• Bradycardia 2
• Tachyarrhythmias 2

Ischemic complications:

• Coronary ischemia 2
• Mesenteric ischemia 2
• Skin/digital ischemia 2

Metabolic:

• Hyponatremia (most common) 2
• Reversible diabetes insipidus 2

Drug Interactions

Additive pressor effects: Catecholamines (norepinephrine, epinephrine) have additive effects with vasopressin—this is intentional for combination therapy 2

Indomethacin: May prolong vasopressin effects 2

Ganglionic blockers or drugs causing SIADH: May increase pressor response 2

Drugs causing diabetes insipidus: May decrease pressor response 2

Special Populations

Pregnancy: Vasopressin may induce uterine contractions—use with extreme caution 2

Pediatric patients: Safety and effectiveness have NOT been established in children 2

Geriatric patients: No specific dose adjustments required, but monitor closely for ischemic complications 2

Contraindications

Absolute contraindications:

• Known allergy to 8-L-arginine vasopressin 2
• Known allergy to chlorobutanol (preservative) 2