In an adult with cardiogenic shock (e.g., post‑myocardial infarction, severe heart failure, or postoperative myocardial dysfunction), what are the recommended first‑line vaso‑inotropic agents, their dosing, and when should additional inotropes or mechanical circulatory support be considered?

Inotropes in Cardiogenic Shock

First-Line Pharmacologic Management

In cardiogenic shock, dobutamine is the recommended first-line inotropic agent (2-20 mcg/kg/min), with norepinephrine (starting at 0.03 mcg/min) added immediately if systolic blood pressure remains <90 mmHg despite inotropic support. 1, 2

Initial Stabilization Algorithm

Step 1: Immediate Assessment and Monitoring

• Establish invasive arterial line monitoring for continuous blood pressure tracking 2
• Perform urgent echocardiography to assess left and right ventricular function and exclude mechanical complications 1, 2
• Target mean arterial pressure ≥65 mmHg and systolic blood pressure >90 mmHg 1, 2

Step 2: Fluid Assessment

• Administer a fluid challenge (250 mL over 10 minutes) only if there are no signs of overt fluid overload (no pulmonary congestion, elevated JVP, or pulmonary edema) 1, 2
• If signs of volume overload are present, proceed directly to inotropic/vasopressor therapy 1

Step 3: Inotropic Therapy Selection

For normotensive or mildly hypotensive patients (SBP 70-100 mmHg):

• Dobutamine 2-20 mcg/kg/min as first-line inotrope 1, 2
• Titrate to improve cardiac output and organ perfusion markers (urine output, lactate clearance, mental status) 1, 2

For persistently hypotensive patients (SBP <90 mmHg) with tachycardia:

• Add norepinephrine (starting 0.03 mcg/min, titrate up to 30 mcg/min) as the primary vasopressor 1, 2
• Continue dobutamine for inotropic support 2

For hypotensive patients with bradycardia:

• Dopamine 5-15 mcg/kg/min may be considered instead of dobutamine 1
• However, dopamine increases risk of tachyarrhythmias and should be used cautiously 1

Alternative and Adjunctive Agents

Levosimendan may be considered as an alternative to dobutamine, particularly in patients on chronic beta-blocker therapy where dobutamine may be ineffective 1, 2, 3

Phosphodiesterase III inhibitors (milrinone, enoximone) are second-line options but should be used with caution in patients with coronary artery disease due to potential increased medium-term mortality 1

Critical Timing for Mechanical Support

Intra-aortic balloon pump (IABP) should be considered when cardiogenic shock is not quickly reversed with pharmacological therapy, serving as a bridge to urgent revascularization 1

Indications for Escalation to Mechanical Circulatory Support:

• Failure to achieve SBP >90 mmHg despite combination inotrope/vasopressor therapy 1, 2
• Persistent signs of organ hypoperfusion (oliguria, elevated lactate, altered mental status) despite optimized medical therapy 1, 2
• Need for escalating doses of multiple inotropes 2

Rather than combining multiple high-dose inotropes, mechanical circulatory support should be considered 2

Revascularization as Definitive Therapy

Early revascularization (PCI or CABG) within 18 hours of shock onset is the definitive treatment and should be performed as soon as possible, with a mortality benefit of 13 lives saved per 100 patients treated 1, 2

• This applies to patients <75 years with cardiogenic shock developing within 36 hours of MI 1
• Selected patients ≥75 years with good prior functional status may also benefit 1
• Patients should be transferred immediately to a tertiary center with 24/7 cardiac catheterization capabilities and mechanical circulatory support availability 2

Monitoring Targets and Perfusion Markers

Target the following endpoints rather than arbitrary hemodynamic numbers:

• Urine output restoration (>0.5 mL/kg/hr) 1, 2
• Lactate clearance (decreasing serial measurements) 1, 2
• Improved mental status 1, 2
• Cardiac index ≥2.5 L/min/m² 1, 2
• Mixed venous oxygen saturation ≥70% 4

Pulmonary artery catheter monitoring can be useful for guiding therapy in cardiogenic shock 1

Special Considerations by Etiology

Afterload-dependent states (severe aortic stenosis, mitral stenosis):

• Use phenylephrine or vasopressin rather than agents that increase contractility 1
• Avoid dobutamine which may worsen hemodynamics 1

Right ventricular infarction:

• Assess with right precordial lead V4R and echocardiography 1
• Maintain adequate preload; avoid excessive diuresis 1

Critical Pitfalls to Avoid

• Do not use beta-blockers or calcium channel blockers in acute cardiogenic shock with pulmonary congestion or low-output state 1
• Avoid aggressive simultaneous use of hypotensive agents (nitrates, diuretics, ACE inhibitors) which can precipitate iatrogenic shock 1
• Do not use epinephrine as an inotrope or vasopressor in cardiogenic shock; reserve only for cardiac arrest 1
• Phenylephrine should be reserved for salvage therapy only 1
• Do not delay revascularization for prolonged medical optimization; pharmacologic support is a bridge to definitive therapy 1, 2
• Dobutamine may be ineffective in patients on chronic carvedilol due to beta-receptor blockade 2

Dosing Summary Table

Agent	Starting Dose	Maximum Dose	Primary Indication
Dobutamine	2 mcg/kg/min	20 mcg/kg/min	First-line inotrope [1]
Norepinephrine	0.03 mcg/min	30 mcg/min	Persistent hypotension [1,2]
Dopamine	5 mcg/kg/min	15 mcg/kg/min	Bradycardia with hypotension [1]
Vasopressin	0.01 U/min	0.03 U/min	Afterload-dependent states [1]