How to infuse vasopressin via a syringe pump?

Vasopressin Infusion via Syringe Pump

Vasopressin should be administered as a continuous intravenous infusion at a fixed dose of 0.03 units/minute (1.8 units/hour) without titration, preferably through a central venous catheter using a syringe pump with appropriate dilution and safety protocols. 1

Standard Preparation and Concentration

• Dilute vasopressin to an appropriate concentration for syringe pump administration - typical preparations include 20 units in 50 mL of normal saline or D5W (yielding 0.4 units/mL) or 40 units in 100 mL (yielding 0.4 units/mL). 2

• The infusion rate should be set to deliver 0.03 units/minute (1.8 units/hour), which translates to 4.5 mL/hour when using a 0.4 units/mL concentration. 1

Fixed Dosing - Critical Distinction from Other Vasopressors

• Vasopressin is NOT titrated like norepinephrine or other vasopressors - it is administered at a fixed low dose of 0.03 units/minute (up to maximum 0.04 units/minute). 1

• Doses higher than 0.03-0.04 units/minute should be reserved only for salvage therapy when other vasopressor agents have failed to achieve adequate mean arterial pressure. 1

• Vasopressin should never be used as a single initial vasopressor for treatment of sepsis-induced hypotension - it must be added to norepinephrine, not used alone. 1

Administration Route and Equipment Setup

• Central venous access is strongly preferred to minimize extravasation risk, though peripheral administration is possible in emergency situations with careful monitoring. 1, 3

• Use a dedicated syringe pump with low dead-space volume extension sets to minimize delays in drug delivery and prevent inadvertent boluses. 4, 5

• When using a double-syringe pump method (vasopressin plus carrier fluid), maintain a constant saline flow rate of 5 mL/hour through the carrier line to provide the most reliable delivery. 4

Critical Safety Protocols for Syringe Pump Operation

• Flush all tubing completely before connecting to the patient - inadequate flushing can cause 2-3 minute delays in drug delivery at low infusion rates. 5

• Never elevate the syringe pump significantly above the patient - elevation by 120 cm can cause up to 0.5 mL of unintended drug delivery even with the pump turned off. 5

• When changing syringes or stopping the infusion, be aware that an additional 0.05 mL may be delivered over 2-3 minutes after the pump is turned off due to residual pressure in the system. 5

• Ensure occlusion alarms are functioning - syringe pumps may take 18-22 minutes to alarm when infusing against a closed stopcock, potentially delivering 0.6-0.9 mL as a bolus when the stopcock is subsequently opened. 5

Clinical Context and Timing

• Vasopressin should be added when norepinephrine reaches approximately 0.25 mcg/kg/min and hypotension persists, with the intent of either raising MAP to target (65 mmHg) or decreasing norepinephrine dosage requirements. 1

• Ensure adequate fluid resuscitation (minimum 30 mL/kg crystalloid) before or concurrent with vasopressin initiation to prevent severe organ hypoperfusion from excessive vasoconstriction in hypovolemic patients. 3

• Place an arterial catheter as soon as practical for continuous blood pressure monitoring in all patients requiring vasopressors. 1

Pharmacokinetic Considerations

• Vasopressin reaches steady-state plasma concentrations after 30 minutes of continuous intravenous infusion, with peak pressor effect within 15 minutes. 2

• The pressor effect fades within 20 minutes after stopping the infusion, with an apparent half-life of ≤10 minutes at therapeutic doses. 2

• There is no evidence for tachyphylaxis or tolerance to the pressor effect of vasopressin in patients receiving continuous infusions. 2

Common Pitfalls to Avoid

• Never titrate vasopressin like other vasopressors - the dose remains fixed at 0.03 units/minute regardless of blood pressure response. 1

• Do not use vasopressin as monotherapy - it must always be combined with norepinephrine as the first-line agent. 1

• Avoid using vasopressin in patients who have not received adequate volume resuscitation, as this can cause severe splanchnic and peripheral ischemia. 6, 7

• Be vigilant for gastrointestinal hypoperfusion and ischemic skin lesions, which are known complications of vasopressin therapy. 8

• Do not mix vasopressin with alkaline solutions in the IV line, as this may affect drug stability. 3