What is the role of vasopressin (VP) in managing a patient with catheter-related bloodstream infection (CRBSI), normal renal function, and septic shock?

Role of Vasopressin in Septic Shock

Vasopressin should be added as a second-line vasopressor at 0.03 units/minute when norepinephrine alone fails to maintain a mean arterial pressure (MAP) of 65 mmHg despite adequate fluid resuscitation, but never as initial monotherapy. 1, 2

First-Line Vasopressor Strategy

• Norepinephrine is the mandatory first-choice vasopressor for septic shock, including in patients with catheter-related bloodstream infections, with a target MAP of 65 mmHg 1
• Administer at least 30 mL/kg crystalloid fluid resuscitation in the first 3 hours before or concurrent with vasopressor initiation 1
• Norepinephrine requires central venous access, and arterial catheter placement should be established as soon as practical for continuous blood pressure monitoring 1, 2

When to Add Vasopressin

Add vasopressin at 0.03 units/minute when norepinephrine requirements remain elevated (typically ≥5-15 mcg/minute) or when target MAP cannot be achieved with norepinephrine alone 1, 2. The Society of Critical Care Medicine explicitly states that vasopressin must be added to norepinephrine, not used as the sole initial vasopressor 1.

Vasopressin Dosing Protocol

• Start at 0.01 units/minute and titrate up by 0.005 units/minute at 10-15 minute intervals until target MAP ≥65 mmHg is achieved 1
• Maximum dose should not exceed 0.03-0.04 units/minute for routine use 1, 2
• The pressor effect reaches its peak within 15 minutes and fades within 20 minutes after stopping the infusion 3
• Vasopressin causes vasoconstriction by binding to V1 receptors on vascular smooth muscle, and at therapeutic doses increases systemic vascular resistance while reducing norepinephrine requirements 3

Evidence Supporting Vasopressin Use

The landmark VASST trial demonstrated that low-dose vasopressin (0.01-0.03 units/minute) did not reduce overall mortality compared to norepinephrine alone (35.4% vs 39.3%, P=0.26), but showed a mortality benefit in the subgroup with less severe septic shock (26.5% vs 35.7%, P=0.05) 4. Recent observational data suggest that earlier vasopressin initiation at lower norepinephrine doses may be associated with improved outcomes 5.

Escalation for Refractory Hypotension

If target MAP cannot be achieved with norepinephrine plus vasopressin at 0.03 units/minute:

• Add epinephrine (0.05-2 mcg/kg/min) as a third vasopressor agent rather than increasing vasopressin beyond 0.03-0.04 units/minute 1
• Consider adding dobutamine (up to 20 mcg/kg/min) if persistent hypoperfusion exists despite adequate MAP, particularly when myocardial dysfunction is evident 1
• Doses of vasopressin above 0.03-0.04 units/minute should be reserved only for salvage therapy when all other vasopressors have failed, as higher doses are associated with cardiac, digital, and splanchnic ischemia 1, 2

Adjunctive Corticosteroid Therapy

• Consider hydrocortisone 200 mg/day for refractory shock when hemodynamic stability cannot be achieved despite adequate fluid resuscitation and escalating vasopressor therapy 1, 6
• The decision should be based on hemodynamic response, not a predetermined vasopressor dose cutoff 6
• Taper hydrocortisone when vasopressors are no longer required 6

Critical Monitoring Requirements

• Maintain continuous arterial blood pressure monitoring via arterial catheter 1, 2
• Assess tissue perfusion using lactate clearance, urine output, mental status, and skin perfusion in addition to MAP 1
• Consider measuring cardiac output when using pure vasopressors like vasopressin to ensure adequate flow is maintained 2

Common Pitfalls to Avoid

• Never use vasopressin as monotherapy—it must always be added to norepinephrine 1, 2
• Do not escalate vasopressin beyond 0.03-0.04 units/minute for routine management; add epinephrine instead 1
• Avoid dopamine as first-line therapy—it is associated with higher mortality and more arrhythmias compared to norepinephrine 1
• Do not use low-dose dopamine for renal protection—this practice is strongly discouraged and has no benefit 1
• Phenylephrine should not be used except when norepinephrine causes serious arrhythmias, cardiac output is high with persistent hypotension, or as salvage therapy 1

Special Considerations for Normal Renal Function

In patients with normal renal function and septic shock, vasopressin at therapeutic doses may increase urinary output and improve renal blood flow 7. The clearance of vasopressin is 9-25 mL/min/kg in patients with vasodilatory shock, with an apparent half-life of ≤10 minutes, and only about 6% is excreted unchanged in urine 3.