What are the clinical uses and dosages of vasopressin?

Clinical Uses and Dosages of Vasopressin

Vasopressin is primarily indicated to increase blood pressure in adults with vasodilatory shock who remain hypotensive despite fluids and catecholamines, with specific dosing recommendations for septic shock (0.01 to 0.07 units/minute) and post-cardiotomy shock (0.03 to 0.1 units/minute). 1

Mechanism of Action and Physiological Effects

• Vasopressin acts via V1-receptors on vascular smooth muscle to cause vasoconstriction and via V2-receptors in the renal collecting duct system to mediate antidiuretic effects 2
• Its action is independent of catecholamine receptor stimulation, making it effective even when alpha-adrenergic receptor down-regulation occurs in septic shock 3
• At low plasma concentrations, vasopressin can mediate vasodilation in coronary, cerebral, and pulmonary arterial circulations 2

Clinical Uses

Septic Shock

• Vasopressin is recommended as an adjunct to norepinephrine (not as a first-line agent) in septic shock 3
• It can be added to norepinephrine with the intent of either:
  • Raising mean arterial pressure (MAP) to target levels, or
  • Decreasing norepinephrine dosage requirements 3
• Recommended dosage: 0.01 to 0.07 units/minute 1
• The Surviving Sepsis Campaign guidelines specifically recommend up to 0.03 units/minute 3

Post-Cardiotomy Shock

• Vasopressin can be used for vasodilatory shock following cardiac surgery 1
• Recommended dosage: 0.03 to 0.1 units/minute 1

Refractory Shock

• Vasopressin doses higher than 0.03-0.04 units/minute should be reserved for salvage therapy when other vasopressor agents have failed to achieve target MAP 3

Dosage and Administration

• Preparation: Dilute 20 units/mL multiple dose vial contents with normal saline (0.9% sodium chloride) or 5% dextrose in water (D5W) to either 0.1 units/mL or 1 unit/mL for intravenous administration 1
• Discard unused diluted solution after 18 hours at room temperature or 24 hours under refrigeration 1
• Titration: Vasopressors should be titrated to end points of perfusion pressure (MAP-central venous pressure) or systemic vascular resistance (SVR) that promote optimum urine output and creatinine clearance 3

Cautions and Contraindications

• Contraindicated in patients with known allergy or hypersensitivity to 8-L-arginine vasopressin or chlorobutanol 1
• Not recommended as the single initial vasopressor for treatment of sepsis-induced hypotension 3
• Not currently recommended for treatment of cardiogenic shock without ScvO2/cardiac output monitoring 3
• Infusions exceeding 0.04 units/minute may lead to adverse vasoconstriction-mediated events 2
• Can worsen cardiac function and may cause reversible diabetes insipidus 1

Adverse Effects

• Most common adverse reactions include decreased cardiac output, bradycardia, tachyarrhythmias, hyponatremia, and ischemia (coronary, mesenteric, skin, digital) 1
• Excessive vasoconstriction may compromise microcirculatory flow 3
• Decreases in platelet count and increases in liver enzymes have been reported 4

Special Populations

• Pregnancy: May induce uterine contractions 1
• Pediatric Use: Safety and effectiveness have not been established 1
• The safety and efficacy of low-dose arginine vasopressin have yet to be demonstrated in children with septic shock 3

Clinical Evidence and Outcomes

• The Vasopressin and Septic Shock Trial (VASST) showed no significant difference in 28-day mortality between vasopressin and norepinephrine (35.4% vs. 39.3%, P=0.26) 5
• However, in the subgroup with less severe septic shock, mortality was lower in the vasopressin group than in the norepinephrine group at 28 days (26.5% vs. 35.7%, P=0.05) 5
• Vasopressin infusion of 0.01 to 0.04 units/minute increases plasma vasopressin levels to those observed in patients with hypotension from other causes 2

Monitoring Recommendations

• All patients requiring vasopressors should have an arterial catheter placed as soon as practical if resources are available 3
• Monitor platelet count, liver function tests, electrolytes, and osmolality in patients treated with vasopressin 4
• Aggressive fluid therapy may prevent adverse hemodynamic effects linked to vasopressin infusion 4