What are the recommended dosages in mcg/min for norepinephrine, vasopressin, and epinephrine to treat acute hypotension in an adult patient in the cath lab?

Vasopressor Dosing in mcg/min for Acute Hypotension in the Cath Lab

For acute hypotension in an adult cath lab patient, start norepinephrine at 7-35 mcg/min (0.1-0.5 mcg/kg/min for a 70 kg adult), vasopressin at 1.2-2.8 mcg/min (0.02-0.04 units/min), and epinephrine at 3.5-35 mcg/min (0.05-0.5 mcg/kg/min). 1, 2, 3, 4

Norepinephrine (First-Line Agent)

Initial Dosing

• Start at 7-35 mcg/min (equivalent to 0.1-0.5 mcg/kg/min in a 70 kg adult) via continuous IV infusion 1, 2
• Alternative starting point: 8.3 mcg/min (0.5 mg/h) for severe hypotension 1
• Titrate every 10-15 minutes in increments of 3.5-14 mcg/min (0.05-0.2 mcg/kg/min) to achieve target MAP ≥65 mmHg 1, 2

Concentration Preparation

• Standard concentration: Add 4 mg norepinephrine to 250 mL D5W = 16 mcg/mL 1
• Alternative concentration: Add 1 mg to 100 mL saline = 10 mcg/mL 1

Maximum Dosing

• Typical maximum: 140 mcg/min (2 mcg/kg/min for 70 kg adult) 5
• Absolute maximum: 50 mg/h = 833 mcg/min, though doses >167 mcg/min (>10 mcg/min in older units) are associated with increased mortality 2

Administration Route

• Central venous access strongly preferred to prevent tissue necrosis 1, 2
• Peripheral IV acceptable temporarily if central access delayed, but transition to central line as soon as practical 1

Vasopressin (Second-Line Agent)

Initial Dosing

• Start at 1.2-2.8 mcg/min (0.02-0.04 units/min = 0.03 units/min typical) 4, 1
• Add when norepinephrine reaches 17.5 mcg/min (0.25 mcg/kg/min) and hypotension persists 1
• Do NOT increase above 2.8 mcg/min (0.04 units/min) - higher doses reserved only for salvage therapy 1

Concentration Preparation

• Dilute 20 units/mL vial with normal saline or D5W to either 0.1 units/mL or 1 unit/mL 4
• Discard unused diluted solution after 18 hours at room temperature or 24 hours refrigerated 4

Specific Indications

• Post-cardiotomy shock: 1.8-6 mcg/min (0.03-0.1 units/min) 4
• Septic shock: 0.6-4.2 mcg/min (0.01-0.07 units/min) 4

Epinephrine (Third-Line Agent)

Initial Dosing

• Start at 3.5-35 mcg/min (0.05-0.5 mcg/kg/min for 70 kg adult) 3, 6
• Add when norepinephrine reaches 17.5 mcg/min (0.25 mcg/kg/min) and hypotension persists 1
• Titrate every 10-15 minutes in increments of 3.5-14 mcg/min (0.05-0.2 mcg/kg/min) 3

Concentration Preparation

• Dilute 1 mg epinephrine in 1,000 mL of D5W or D5W with saline = 1 mcg/mL 3
• Store diluted solutions up to 4 hours at room temperature or 24 hours refrigerated 3
• Avoid saline-only dilution - not recommended 3

Maximum Dosing

• Typical maximum: 140 mcg/min (2 mcg/kg/min for 70 kg adult) 3

Special Considerations

• Reserved for persistent hypoperfusion despite adequate norepinephrine and vasopressin 6
• Higher rate of metabolic and cardiac adverse effects compared to norepinephrine 7

Critical Administration Principles

Pre-Administration Requirements

• Administer minimum 30 mL/kg crystalloid bolus (2,100 mL for 70 kg patient) before or concurrent with vasopressor initiation 1
• In severe hypotension (systolic <70 mmHg), start norepinephrine immediately while continuing fluid resuscitation rather than waiting 1

Target Blood Pressure

• Target MAP ≥65 mmHg for most patients 1, 2, 4
• Consider MAP 70-80 mmHg in patients with chronic hypertension 1
• Titrate to tissue perfusion markers: lactate clearance, urine output >50 mL/h, mental status, capillary refill 1

Monitoring Requirements

• Check blood pressure every 5-15 minutes during initial titration 1, 2
• Place arterial catheter as soon as practical for continuous monitoring 1
• Monitor for extravasation signs continuously 2

Extravasation Management

• If extravasation occurs, immediately infiltrate phentolamine 5-10 mg diluted in 10-15 mL saline into the site 1, 2

Critical Pitfalls to Avoid

• Never use dopamine as first-line - associated with higher mortality and arrhythmias compared to norepinephrine 1, 7
• Never mix vasopressors with sodium bicarbonate or alkaline solutions in IV line - causes inactivation 1
• Never use phenylephrine as first-line - may raise blood pressure while worsening tissue perfusion 1
• Never rely solely on fluids in profound hypotension (diastolic ≤40 mmHg) - start norepinephrine early 8