Pediatric Vasopressin Dosing
For pediatric patients with vasodilatory shock, start vasopressin at 0.0002-0.0005 units/kg/min (0.2-0.5 milliunits/kg/min) and titrate up to a maximum of 0.002 units/kg/min (2 milliunits/kg/min) based on hemodynamic response. 1, 2, 3
Standard Dosing Range
The typical starting dose is 0.0005 units/kg/min (0.5 milliunits/kg/min), which can be titrated to a maximum of 0.002 units/kg/min (2 milliunits/kg/min). 4, 3
In the context of septic shock, vasopressin should be used at doses ≤0.04 units/kg/min (40 milliunits/kg/min) as an adjunctive agent, though pediatric-specific dosing typically remains much lower at 0.0002-0.002 units/kg/min. 1
The dose range of 0.0002-0.002 units/kg/min has been associated with significant hemodynamic improvement including increased blood pressure, decreased catecholamine requirements, and improved urine output in pediatric patients after cardiac surgery. 3
Preparation Using "Rule of 6"
For simplified preparation in pediatric patients, use the "Rule of 6": multiply 0.6 × body weight (kg) to determine the number of milligrams, then dilute to a total of 100 mL of saline; infusing at 1 mL/h delivers 0.1 mcg/kg/min. 5
This preparation method allows for easy titration at the bedside without complex calculations. 5
Clinical Context and Indications
Vasopressin should be reserved as a rescue therapy for catecholamine-resistant vasodilatory shock, not as a first-line agent. 1, 2
The American College of Critical Care Medicine recommends adding vasopressin (0.03-0.04 units/min in adults) when norepinephrine reaches 0.25 mcg/kg/min and hypotension persists, though pediatric dosing follows the weight-based ranges above. 1
Vasopressin is particularly useful in post-cardiopulmonary bypass vasodilatory shock, where it has demonstrated efficacy in both left and right heart anomalies. 3
Hemodynamic Effects and Monitoring
Vasopressin administration is associated with rapid increases in mean arterial pressure, systemic vascular resistance, and decreased concurrent catecholamine requirements within 2 hours of initiation. 3
Monitor for increased urine output, which typically improves after vasopressin initiation despite concerns about renal effects. 3, 6
Continuous hemodynamic monitoring is essential, including blood pressure, heart rate, central venous pressure, and markers of tissue perfusion such as lactate and central venous oxygen saturation. 6
Important Adverse Effects and Precautions
Renal function may be adversely affected with higher doses or prolonged duration of infusion, manifesting as increased creatinine and decreased urine output; these effects are typically reversible. 6
Platelet counts may decrease significantly during vasopressin infusion and should be monitored. 6
In noncardiac patients, there may be increases in conjugated bilirubin and AST levels, particularly with higher cumulative doses or longer duration of infusion. 6
Avoid using vasopressin without adequate volume resuscitation, as excessive vasoconstriction in hypovolemic patients can cause severe organ hypoperfusion. 1
Critical Evidence Limitations
A multicenter randomized controlled trial found that low-dose vasopressin (0.0005-0.002 units/kg/min) did not demonstrate beneficial effects compared to placebo in pediatric vasodilatory shock, with a concerning trend toward increased mortality (30% vs 15.6%, though not statistically significant). 4
Despite this negative RCT, observational studies continue to show hemodynamic benefits, and vasopressin remains recommended as rescue therapy when other vasopressors fail. 2, 3
The safety and efficacy of vasopressin in pediatric septic shock remain uncertain pending results of ongoing randomized controlled trials. 1
Alternative Considerations
Terlipressin, a long-acting form of vasopressin, has been reported to reverse vasodilatory shock in pediatric patients, though specific dosing recommendations are less well-established. 1, 2
In pediatric septic shock where vasopressin is unavailable or ineffective, norepinephrine and epinephrine are recommended equally as first-line agents, with dopamine reserved only when these are unavailable. 7