Vasopressors

Background

The goal of vasopressor use is to reach critical organ perfusion pressure. Estimated required mean arterial pressures (MAP) are listed below. It is generally safe to aim for a goal map of 65 mmHg. Vasopressors also promote increased venous return.

• Brain: MAP of 50 mmHg
• Heart: MAP of 65 mmHg
• Kidneys: MAP 65-75 mmHg

Norepinephrine

Indication

• Septic shock (1st line)
• Cardiogenic shock:
  • If marked hypotension (SBP <70)
  • If used with dobutamine

Primary Receptor

• α1 >> β1

Relative Effects

• ↑↑↑SVR
• ↑HR
• ↑SV

Dosing

• Start 2mcg/min
  • Incr by 1-2mcg/min
  • Max dose is 40mcg/min
• Replace volume before starting

Rate of Titration

• Q2-5 min

Adverse Effects

• If extravasates use phentolamine 5-10mg into affected area

Notes

More potent vasoconstrictor than dopamine and phenylephrine.

Dopamine

Indication

• Hypotension caused by:
  • Septic shock
  • MI
  • Trauma/spinal shock
  • Heart failure

Primary Receptor

• Low dose: DA, β1
• High dose: DA, α1 >> β1

Relative Effects

• Low dose: Natriuresis, ↑↑HR, ↑↑SV
• High dose: ↑SVR and ↑SV

Contraindication

• Tachyarrhythmias

Dosing

• Low dose:
  • 1-5 mcg/kg/min - Vasodilation (renal, mesenteric, coronary)
  • 5-10 mcg/kg/min - predominant β1
• High dose: 10-20 mcg/kg/min - predominant α1
• Titrate to clinical effect
  • Use lowest dose possible (prevent tachyphylaxis)
• May use in peripheral IV temporarily
  • Avoid using in same line as alkaline infusions

Rate of Titration

• Q2-5 min

Adverse Effects

• Low doses:
  • Hypotension
• High doses:
  • Hypertension, ectopic beats
• Tissue necrosis (if extravasates)
  • If occurs use phentolamine 5-10mg in affected area

Dobutamine

Indication

• Cardiogenic shock
• Low-output heart failure
• Tricyclic overdose

Primary Receptor

• β1
• β2

Relative Effects

• ↑↑↑SV
• ↑↑HR
• ↓SVR (transient, from β2 agonism)

Dosing

• 2-20mcg/kg/min
  • 10mcg works for most
• May use in peripheral IV

Rate of Titration

• Q2-5 min

Adverse Effects

• Tachyarrhythmias
• Myocardial ischemia
• Hypotension as β2 effect may result in vasodilation
  • Caution if SBP <90

Phenylephrine

Indication

• Neurogenic Shock

Primary Receptor

• α1

Relative Effects

• ↑SVR
• ↓HR (reflex bradycardia)

Dosing

• Start 100-200mcg/min then taper down
  • 40-60mcg/min works for most

Adverse Effects

• Baroreceptor-mediated reflex bradycardia
• If extravasates use phentolamine

Notes

• Use with caution in pts with spinal cord injury-related bradycardia
• Useful for treatment of vasodilatory shock when norepinephrine or dopamine have precipitated tachyarrhythmias
• In pts with ↓LV function, unopposed α1 may lead to decreased CO or myocardial ischemia
  • However clinical trials do not support these effects when used in clinically appropriate dose range

Vasopressin

Indication

• Adjunct for septic shock

Primary Receptor

• V1

Relative Effects

• ↑SVR
• ↓HR

Dosing

• 0.04 units/min

Rate of Titration

• Fixed dose (do not titrate)

Adverse Effects

• Bradycardia
• Limb ischemia
• Myocardial ischemia
• Splanchnic ischemia

Notes

• Adverse effects are dose-dependent
• Acts on V1 receptors leading to ↑vasoconstriction and

↑sensitivity to catecholamines in pts with shock

Epinephrine

Indication

• Anaphylaxis

Primary Receptor

• β1
• α1
• β2

Relative Effects

• ↑↑↑HR
• ↑↑↑SV
• ↑↑↑SVR
• Bronchodilation (β2)

Dosing

• Dose-dependent effects:
• 1-10 mcg/min - increase HR and SV
• 10-20 mcg/min - increase SVR

Rate of Titration

• Q2-5 min

Adverse Effects

• Tachyarrhythmias
• Myocardial ischemia
• ↑Serum lactate
• Splanchnic ischemia

Notes

• ↑lactate occurs primarily from ↑glycolysis/glycogenolysis within skeletal muscles not tissue hypoperfusion
• Use with caution in pts with CAD
  • However clinical trials have not demonstrated worsened outcomes

Milrinone

Primary Receptor

• PDE-3 inhibitor

Relative Effects

• ↑HR
• ↑↑↑SV
• ↓SVR

Dosing

• Normal renal function:

0.25 - 0.75 mcg/kg/min

• Creatinine clearance < 50mL/min, reduce infusion rate

Rate of Titration

• Q2H; slower titration rate if renal insufficiency

Adverse Effects

• Tachyarrhythmias
• Hypotension
• Myocardial ischemia

Notes

• Can use as alternative to dobutamine in pts with cardiogenic shock and on b-blockers
• Causes pulmonary vasodilation, may be good choice in pts with RV failure
• ↑cAMP in cardiac myocytes and vascular smooth muscle, thereby ↑HR and ↑SV while decreasing ↓SVR
• Use with caution in pt with renal failure and hypovolemia

Push Dose Pressors

• Use when need temporary BP or CO boost
  • Post-intubation hypotension
  • Propofol-induced hypotension
  • A-fib w/ hypotension
    • Easier to convert well-perfused heart

Epinephrine

• Mix 9mL of NS with 1mL of 1:10,000 epi
  • Now have 10mL of 10mcg/mL
    • Use 0.5-2mL q2-5min (similar to epi drip)
    • Same as 2% lido with epi
      • Ok to give peripherally
• Onset - 1min
• Duration - 5-10min

Phenylephrine

• Pure alpha (no effect on heart)
• Place 1mL of 10mg/mL vial in 100mL NS
  • Now have 100mcg/mL
  • Draw up 10mL
  • Use 0.5-2mL q2-5min (50-200mcg)
• Onset - 1min
• Duration - 20min

Source

• EmCrit Podcast 6