When to use epinephrine (adrenaline) vs norepinephrine (noradrenaline) as a vasopressor in hypotension?

Vasopressor Selection in Hypotension: Epinephrine vs Norepinephrine

Norepinephrine should be used as the first-line vasopressor for fluid-refractory hypotensive shock in adults, while epinephrine should be reserved as a second-line agent when norepinephrine alone is insufficient. 1

First-Line Vasopressor: Norepinephrine

Norepinephrine is recommended as the initial vasopressor of choice for several reasons:

• Provides reliable vasoconstrictor effects with minimal impact on heart rate
• Offers mild inotropic properties beneficial for cardiac output
• Associated with decreased all-cause mortality compared to dopamine (11% absolute risk reduction) 2
• Demonstrates better hemodynamic profile with improved central venous pressure, urinary output, and blood lactate levels 2
• Associated with lower risk of major adverse events and cardiac arrhythmias compared to other vasopressors 2

Dosing and Administration:

• Initial dose: 0.05-0.1 μg/kg/min
• Titrate according to patient response every 5-15 minutes 1
• Consider early administration in profound hypotension (diastolic BP ≤40 mmHg or diastolic shock index ≥3) 3

Second-Line Vasopressor Options

When norepinephrine alone is insufficient to maintain target blood pressure:

1. Add vasopressin (up to 0.03 U/min) as it:

   • Acts independently of catecholamine receptor stimulation
   • Is not affected by alpha-adrenergic receptor down-regulation 1
   • Recent evidence suggests earlier addition of vasopressin may be beneficial at lower norepinephrine doses (around 0.20 μg/kg/min) 4

2. Consider epinephrine when:

   • Patient has refractory shock despite adequate norepinephrine and vasopressin
   • There is evidence of myocardial dysfunction with persistent hypoperfusion
   • Additional inotropic support is needed alongside vasoconstriction 1

Special Clinical Scenarios

Cardiogenic Shock

• Norepinephrine is preferred over epinephrine due to epinephrine's higher risk of tachyarrhythmias and increased myocardial oxygen consumption
• Consider adding dobutamine (2.5-20 μg/kg/min) if evidence of myocardial dysfunction persists 1

Septic Shock

• Start with norepinephrine after initial fluid resuscitation (at least 30 mL/kg crystalloid) 1, 5
• Early administration of norepinephrine in septic shock may:
  • Rapidly increase and better stabilize arterial pressure
  • Improve end-organ perfusion
  • Reduce administered fluid volume
  • Potentially reduce mortality 3, 5

Refractory Shock

• Combination therapy with norepinephrine and vasopressin is recommended 1
• Add epinephrine if there is evidence of cardiac dysfunction or persistent hypoperfusion despite adequate blood pressure 1
• Consider hydrocortisone (up to 300 mg/day) in patients requiring escalating vasopressor doses 1

Monitoring and Goals

• Maintain mean arterial pressure (MAP) ≥65 mmHg (higher in patients with chronic hypertension) 1, 5
• Monitor continuously:
  • Blood pressure and heart rate
  • Urine output (target ≥0.5 ml/kg/h)
  • Skin perfusion and mental status
  • Lactate clearance
  • Renal and liver function tests 1

Common Pitfalls to Avoid

1. Delaying vasopressor initiation: Profound and prolonged hypotension worsens outcomes; don't rely solely on fluids when hypotension is severe 3, 5

2. Excessive fluid administration: Early norepinephrine may reduce fluid requirements and avoid complications of fluid overload 3

3. Failing to identify underlying causes: Always investigate for pericardial effusion, pneumothorax, hypoadrenalism, hypothyroidism, ongoing blood loss, increased intra-abdominal pressure, or inadequate source control of infection in refractory shock 1

4. Not adjusting targets for comorbidities: Patients with chronic hypertension may require higher MAP targets 5

5. Delaying addition of second vasopressor: Consider adding vasopressin earlier than traditionally practiced when norepinephrine requirements are increasing 4