What is a good protocol for adding pressors, such as norepinephrine (vaso), epinephrine (epi), and levophed (levo), in the catheterization lab for patients with acute hypotension?

Pressor Protocol for Acute Hypotension in the Cath Lab

Norepinephrine is the mandatory first-line vasopressor for acute hypotension in the cath lab, started at 0.1-0.5 mcg/kg/min (approximately 8-12 mcg/min or 0.5 mg/h) via peripheral IV if central access is unavailable, targeting a mean arterial pressure of 65 mmHg. 1, 2

Immediate Pre-Vasopressor Requirements

Before initiating any vasopressor, address hypovolemia with fluid boluses to optimize cardiac output, as vasoconstriction in hypovolemic patients causes severe organ hypoperfusion despite "normal" blood pressure 1. However, in profound hypotension (systolic <70 mmHg or diastolic ≤40 mmHg), start norepinephrine as an emergency measure while fluid resuscitation continues rather than waiting for complete volume repletion 1, 3.

First-Line Agent: Norepinephrine (Levophed)

Preparation and Initial Dosing

• Standard concentration: Add 4 mg norepinephrine to 250 mL D5W (yields 16 mcg/mL) 1, 2
• Starting dose: 0.5 mg/h (approximately 8-12 mcg/min or 0.1-0.5 mcg/kg/min) 1, 2
• Target MAP: 65 mmHg for most patients; consider 70-75 mmHg in chronic hypertensives 1, 4

Administration Route

Central venous access is strongly preferred to minimize extravasation risk and tissue necrosis 1, 4. However, if central access is unavailable or delayed during the acute cath lab scenario, peripheral IV administration can be used temporarily with strict monitoring 5, 1. Place an arterial catheter as soon as practical for continuous blood pressure monitoring 5, 1.

Titration Protocol

• Monitor blood pressure every 5-15 minutes during initial titration 5, 1
• Increase dose by 0.5 mg/h every 4 hours as needed, to a maximum of 3 mg/h 1
• Assess tissue perfusion markers: lactate clearance, urine output >50 mL/h, mental status, capillary refill 1, 4

Extravasation Management

If extravasation occurs, infiltrate 5-10 mg phentolamine diluted in 10-15 mL saline at the site immediately to prevent tissue necrosis 1, 2.

Second-Line Agent: Vasopressin

Add vasopressin at 0.03 units/minute when norepinephrine reaches 0.25 mcg/kg/min and hypotension persists, rather than continuing to escalate norepinephrine alone. 5, 1, 4

Key Points

• Never use vasopressin as monotherapy—it must be added to norepinephrine 4
• Maximum dose: 0.03-0.04 units/minute for routine use; higher doses reserved for salvage therapy only 5, 4
• Vasopressin addition allows either raising MAP to target OR decreasing norepinephrine requirements 4

Third-Line Agent: Epinephrine

Add epinephrine at 0.1-0.5 mcg/kg/min when norepinephrine plus vasopressin fail to achieve target MAP. 1, 4

Critical Warnings

• Epinephrine increases risk of serious cardiac arrhythmias, particularly ventricular arrhythmias (RR 0.35; 95% CI 0.19-0.66 compared to norepinephrine alone) 4
• Causes transient lactic acidosis through β2-adrenergic stimulation, interfering with lactate clearance as a resuscitation endpoint 4, 6
• Increases myocardial oxygen consumption more than norepinephrine, making it less safe in patients with potential cardiac ischemia 4

Agents to AVOID in the Cath Lab

Dopamine

Do NOT use dopamine as first-line therapy—it is associated with higher mortality (11% absolute risk reduction with norepinephrine vs dopamine) and significantly more arrhythmias (53% risk reduction for supraventricular arrhythmias, 65% for ventricular arrhythmias with norepinephrine) 5, 4, 6. Reserve dopamine only for highly selected patients with absolute bradycardia and low risk of tachyarrhythmias 5, 4.

Phenylephrine

Avoid phenylephrine except in specific circumstances (norepinephrine-induced serious arrhythmias, high cardiac output with persistent hypotension, or salvage therapy) as it may raise blood pressure while actually worsening tissue perfusion 1, 4.

Inotropic Support: Dobutamine

Add dobutamine at 2.5-20 mcg/kg/min if persistent hypoperfusion exists despite adequate MAP and vasopressor therapy, particularly when myocardial dysfunction is evident. 5, 1, 4

Dosing

• Start at 2.5 mcg/kg/min, doubling every 15 minutes according to response 4
• Titration usually limited by excessive tachycardia, arrhythmias, or ischemia 4

Practical Algorithm for the Cath Lab

1. Immediate: Start norepinephrine 0.5 mg/h peripherally if no central access, target MAP 65 mmHg 1, 2
2. If MAP inadequate at norepinephrine 0.25 mcg/kg/min: Add vasopressin 0.03 units/min 1, 4
3. If still inadequate: Add epinephrine 0.1-0.5 mcg/kg/min 1, 4
4. If evidence of cardiac dysfunction with persistent hypoperfusion: Add dobutamine 2.5-20 mcg/kg/min 5, 4

Critical Monitoring Requirements

• Blood pressure every 5-15 minutes during titration 5, 1
• Continuous arterial monitoring via arterial catheter as soon as practical 5, 1
• Tissue perfusion markers: urine output, lactate, mental status, capillary refill 1, 4
• ECG monitoring for arrhythmias, especially with epinephrine 4

Common Pitfalls to Avoid

• Do NOT delay norepinephrine while pursuing aggressive fluid resuscitation in profound hypotension (diastolic ≤40 mmHg) 1, 3
• Do NOT use dopamine as first-line—mortality and arrhythmia risk are significantly higher 5, 4
• Do NOT escalate vasopressin above 0.03-0.04 units/min—higher doses cause cardiac, digital, and splanchnic ischemia 5, 4
• Do NOT use phenylephrine as first-line—it may compromise tissue perfusion despite raising blood pressure numbers 1, 4
• Do NOT mix norepinephrine with sodium bicarbonate or alkaline solutions—adrenergic agents are inactivated 1