What is a good vasopressor algorithm for managing hypotension?

Vasopressor Algorithm for Managing Hypotension

Initial Resuscitation and First-Line Vasopressor

Start with adequate fluid resuscitation (minimum 30 mL/kg crystalloid) followed immediately by norepinephrine as the first-line vasopressor, targeting a mean arterial pressure (MAP) of 65 mmHg. 1, 2

Pre-Vasopressor Requirements

• Administer at least 30 mL/kg of crystalloid fluids for initial volume resuscitation in hypotensive patients 2
• In life-threatening hypotension with imminent cerebral or coronary ischemia, start norepinephrine concurrently with fluid resuscitation rather than delaying 2
• Place an arterial catheter as soon as practical for continuous blood pressure monitoring in all patients requiring vasopressors 1, 2
• Establish central venous access when possible, though norepinephrine can be started peripherally while awaiting central access 2

Norepinephrine Dosing Protocol

• Initial dose: 0.02 mg/kg/min, titrated up to 0.1-0.2 mg/kg/min to maintain MAP ≥65 mmHg 2
• Target MAP of 65 mmHg is appropriate for most patients 1, 2
• Monitor continuously with arterial catheter and assess tissue perfusion using lactate levels, skin perfusion, mental status, and urine output 2

Escalation for Refractory Hypotension

Second-Line Agent: Add Vasopressin

When norepinephrine alone fails to achieve target MAP, add vasopressin at 0.03 units/minute rather than escalating norepinephrine dose further. 1, 3

• Vasopressin dose: 0.03 units/minute (range 0.01-0.07 units/minute for septic shock) 1, 3
• Never use vasopressin as monotherapy—it must be added to norepinephrine, not used alone 1
• Doses higher than 0.03-0.04 units/minute should be reserved for salvage therapy only 1
• FDA-approved dosing for post-cardiotomy shock: 0.03-0.1 units/minute 3

Third-Line Options

If target MAP remains unachieved despite norepinephrine plus vasopressin:

• Add epinephrine (0.05-2 mcg/kg/min) as the preferred third agent, particularly when myocardial dysfunction is present 1, 2
• Add dobutamine (up to 20 mcg/kg/min) if persistent hypoperfusion exists despite adequate vasopressor support, especially with evidence of low cardiac output 1, 2

Agents to Avoid

Dopamine

• Strongly avoid dopamine except in highly selected patients with low risk of tachyarrhythmias or absolute/relative bradycardia 1, 2
• Dopamine is associated with higher mortality and more arrhythmias compared to norepinephrine 1, 2
• Never use low-dose dopamine for renal protection—this provides no benefit and is strongly discouraged 1, 2

Phenylephrine

• Avoid phenylephrine as first-line therapy—it may raise blood pressure numbers while actually worsening tissue perfusion 1, 2
• Use phenylephrine only in specific circumstances: when norepinephrine causes serious arrhythmias, when cardiac output is documented to be high with persistent hypotension, or as salvage therapy when all other agents have failed 1, 2

Special Considerations for Trauma Patients

Hemorrhagic Shock Algorithm

In trauma patients with hemorrhagic shock, prioritize restricted volume replacement with permissive hypotension (systolic BP 80-90 mmHg) until bleeding is controlled, adding norepinephrine only if systolic BP falls below 80 mmHg. 4

• Target systolic arterial pressure of 80-90 mmHg during active hemorrhage (except in traumatic brain injury) 4
• Use 0.9% sodium chloride or balanced crystalloid solution for initial fluid resuscitation 4
• Avoid hypotonic solutions like Ringer's lactate in patients with severe head trauma 4
• Add norepinephrine only when restricted volume replacement fails to achieve target BP and systolic pressure drops below 80 mmHg 4
• Consider low-dose arginine vasopressin (bolus of 4 IU followed by 0.04 IU/min) to decrease blood product requirements in severe hemorrhagic shock 4

Inotropic Support in Trauma

• Infuse dobutamine when myocardial dysfunction is present 4

Critical Monitoring and Pitfalls

Essential Monitoring

• Continuous arterial blood pressure monitoring via arterial catheter 1, 2
• Assess tissue perfusion markers: lactate levels, skin perfusion, mental status, urine output 2
• Monitor for signs of excessive vasoconstriction: digital ischemia, decreased urine output, rising lactate, worsening organ dysfunction despite adequate MAP 1

Common Pitfalls to Avoid

• Do not use vasopressors as a substitute for adequate fluid resuscitation—this causes excessive vasoconstriction and organ ischemia 2
• Do not titrate to supranormal blood pressure targets—excessive vasoconstriction compromises microcirculatory flow 1
• Do not increase vasopressin beyond 0.03-0.04 units/minute—add epinephrine instead if additional support is needed 1
• Avoid restricting colloids due to adverse effects on hemostasis in trauma patients 4