What are the indications for inotropes (inotropic agents) and vasopressors in patients with shock?

Indications of Inotropes and Vasopressors in Shock Patients

Vasopressors are indicated when mean arterial pressure (MAP) remains below 65 mmHg despite adequate fluid resuscitation, while inotropes are indicated when there is evidence of myocardial dysfunction with low cardiac output and persistent signs of hypoperfusion despite adequate fluid resuscitation and vasopressor therapy. 1

Vasopressor Indications

First-Line Vasopressor Therapy

• Norepinephrine is recommended as the first-choice vasopressor for all types of shock when fluid resuscitation fails to maintain adequate MAP (≥65 mmHg) 1
• Early use of vasopressors is recommended as it reduces the incidence of organ failure 1
• All patients requiring vasopressors should have an arterial catheter placed as soon as practical if resources are available 1, 2

Second-Line Vasopressor Therapy

• Epinephrine can be added to or substituted for norepinephrine when an additional agent is needed to maintain adequate blood pressure 1, 2
• Vasopressin (up to 0.03 U/min) can be added to norepinephrine with the intent of either raising MAP or decreasing norepinephrine dosage 1, 2, 3
• Higher doses of vasopressin (>0.03-0.04 U/min) should be reserved for salvage therapy when other vasopressors fail to achieve target MAP 1

Alternative Vasopressors

• Dopamine may be considered as an alternative to norepinephrine only in highly selected patients with low risk of tachyarrhythmias and absolute or relative bradycardia 1
• Phenylephrine is not recommended except in specific circumstances: (a) when norepinephrine causes serious arrhythmias, (b) when cardiac output is known to be high but blood pressure remains low, or (c) as salvage therapy 1, 2
• Low-dose dopamine should not be used for renal protection 1

Inotrope Indications

Primary Indications

• Dobutamine (up to 20 μg/kg/min) is indicated when there is evidence of myocardial dysfunction with elevated cardiac filling pressures and low cardiac output 1, 4
• Inotropes are indicated when signs of hypoperfusion persist despite adequate fluid resuscitation and vasopressor therapy to maintain MAP 1, 4
• In cardiogenic shock, dobutamine (2.5-10 μg/kg/min) is recommended when there is evidence of low cardiac output 4, 5

Monitoring Parameters

• Inotrope therapy should be titrated to targeted responses such as improvements in mixed venous oxygen saturation (SvO₂), myocardial function indices, and reduction in lactate levels 1
• The combination of dobutamine and norepinephrine is recommended as first-line treatment in patients with low cardiac output and hypotension 1, 6
• Routine use of inotropes is not recommended without evidence of cardiac dysfunction 1

Shock-Specific Considerations

Septic Shock

• Norepinephrine is the first-line vasopressor for septic shock 1
• If hypotension persists despite norepinephrine, vasopressin (up to 0.03 U/min) can be added to reduce norepinephrine requirements 1
• In septic shock with myocardial depression, adding dobutamine or using epinephrine as a single agent may be beneficial 1, 6

Cardiogenic Shock

• Norepinephrine is recommended as the first-line vasopressor in cardiogenic shock 4, 5
• Dobutamine is indicated for low cardiac output states in cardiogenic shock 4, 5, 7
• Phosphodiesterase III inhibitors (e.g., milrinone) may be considered in cases of low cardiac output and normal arterial pressure, particularly in patients previously treated with beta-blockers 1, 5

Hypovolemic/Hemorrhagic Shock

• The primary treatment is fluid resuscitation and control of bleeding 1
• Vasopressors may be used transiently for life-threatening hypotension while addressing the underlying cause 1

Obstructive Shock

• Treatment should focus on relieving the obstruction (e.g., thrombolytic therapy or mechanical intervention for pulmonary embolism) 4
• Vasopressors may be used as a bridge to definitive treatment 4

Common Pitfalls and Caveats

• Vasopressors should not be used as a substitute for adequate fluid resuscitation in hypovolemic states 1, 2
• Inotropes can increase myocardial oxygen consumption and may worsen ischemia in patients with coronary artery disease 6, 5
• High doses of epinephrine or dopamine carry excessive risk of adverse events and should be avoided 6, 8
• Targeting supranormal cardiac index levels is not recommended and may be harmful 1
• The optimal MAP should be individualized, as it may need to be higher in patients with pre-existing hypertension 1, 2