Cardiogenic shock

Background

• Leading cause of death in patients with ACS who reach the hospital alive

Etiologies

• Myocardial infarction
  • Pump failure
  • Mechanical complications
  • Acute mitral regurgitation (papillary muscle rupture)
  • VSD
  • Free-wall rupture
• RV infarction
• Decreased forward flow
  • Sepsis
  • Rate-related
    • Bradycardia
    • Tachycardia
  • Myocarditis
  • Myocardial contusion
  • Cardiomyopathy
• Mechanical obstruction to forward flow
  • Aortic stenosis
  • HOCM
  • Mitral stenosis
  • Pericardial
• LV regurgitation
  • Chordal rupture
  • Aortic Insufficiency
• Toxic/metabolic
  • Severe acidosis, severe hypoxemia

Clinical Features

Physical Exam

• Assess for signs of CHF
  • elevated JVD, pulmonary edema, S3
• Assess for valvular disease (mitral regurgitation, critical aortic stenosis, or aortic regurgitation)
• Assess for end-organ hypoperfusion
  • cool/mottled extremities, weak pulses, altered mental status, decreased UOP
• Assess for pulsus paradoxus (cardiac tamponade)

Differential Diagnosis

Shock

• Cardiogenic
  • Acute valvular Regurgitation/VSD
  • CHF
  • Dysrhythmia
  • ACS
  • Myocardial Contusion
  • Myocarditis
  • Drug toxicity (e.g. beta blocker, CCB, or bupropion OD)
• Obstructive
  • Air embolism
  • Aortic Stenosis
  • Cardiac Tamponade
  • PE
  • Tension pneumothorax
• Distributive
  • Adrenal crisis
  • Anaphylaxis
  • Neurogenic shock
  • Sepsis
  • Toxicologic
• Hypovolemic
  • Severe dehydration
  • Hemorrhagic shock (traumatic and non-traumatic)

Evaluation

Workup

• Labs
  • Troponin
  • Lactate
  • CBC
    • WBC elevated with a left shift
  • Chem
  • LFTs
    • elevated due to liver hypoperfusion
  • ABG
    • anion gap acidosis
  • BNP
• ECG
• CXR
• TTE

Brain natriuretic peptide (BNP)

• Measurement
  • <100 pg/mL: Negative for acute CHF (Sn 90%, NPV 89%)
  • 100-500 pg/mL: Indeterminate (Consider differential diagnosis and pre-test probability)
  • >500 pg/mL: Positive for acute CHF (Sp 87%, PPV 90%)
  • Combination of BNP with clinician judgment 94% sensitive 70% specific (compared to 49% sn and 96% spec clinical judgement alone)

NT-proBNP

• <300 pg/mL → CHF unlikely
• CHF likely in:
  • >450 pg/mL in age < 50 years old
  • >900 pg/mL in 50-75 years old
  • >1800 pg/mL in > 75 years old

Management

General

Aim for MAP >65

• Consider etiologies (see above) and treat specific one, if present
• Consider small fluid challenge (250-500cc normal saline IV) or fluid removal, depending on estimation of patient's point on Starling curve
• Increase inotropy
  • Dobutamine +/- norepinephrine OR dopamine
    • Dobutamine may initially drop pressures, so may need to use second agent to maintain BP
  • Consider milrinone or beta-blocker reversal if patient is on a beta-blocker
  • Consider calcium chloride 1 g if hypocalcemic or normocalcemic through good PIV or central line
• Consider transfusion if hemoglobin < 10 (be aware of added fluid)
• Consider intubation
  • Decreases O2 demand BUT may worsen preload

Specific Situations

Mitral Regurgitation

Increase forward flow

• Dobutamine (contractility) + nitroprusside (afterload reduction)

ACS

• PCI or thrombolysis

Aortic stenosis

Decrease afterload (with extreme caution in very small, carefully-titrated doses)

• Agents:
  • Nitroprusside
  • Dobutamine
  • Hydralazine
• Do not give preload reducers such as nitro
• Patients are flow dependent over stenotic value. Flow proportional to degree of stenosis and afterload.

Toxins

• Beta-Blocker Toxicity
• Calcium Channel Blocker
• Digoxin

Vasopressors

Pressor	Initial Dose	Max Dose	Cardiac Effect	BP Effect	Arrhythmias	Special Notes
Dobutamine	3-5 mcg/kg/min	5-15 mcg/kg/min (as high as 200)	Strong ß1 agonist +inotrope +chronotrope, Weak ß2 agonist +weak vasodilatation )	alpha effect minimal	HR variable effects.	indicated in decompensated systolic HF, Debut Research 1979 Isoproterenol has most Β2 vasodilatory and Β1 HR effects
Dopamine	2 mcg/kg/min	20-50 mcg/kg/min	β1 and NorEpi release	α effects if > 20mcg/kg/min	Arrhythmogenic from β1 effects	More adverse events when used in shock compared to Norepi
Epinepherine	0.1-1 mcg/kg/min		+ inotropy, + chronotropy
Norepinephrine	0.2 mcg/kg/min	0.2-1.3 mcg/kg/min (5mcg/kg/min)	mild β1 direct effect	β1 and strong α1,2 effects	Less arrhythmias than Dopamine	First line for sepsis. Increases MAP with vasoconstriction, increases coronary perfusion pressure, little β2 effects.
Milrinone	50 mcg/kg x 10 min	0.375-75 mcg/kg/min	Direct influx of Ca2+ channels	Smooth muscle vasodilator		PDE Inhibitor which increases Ca2+ uptake by sarcolemma. No venodilatory activity
Phenylephrine	100-180 mcg/min then 40-60 mcg/min	0.4-9 mcg/kg/min		Alpha agonist		Long half life
Vasopressin	Fixed Dose	0.01 to 0.04 U/min	unknown	increases via ADH peptide		should not be titrated due to ischemic effects
Methylene blue	IV bolus 2 mg/kg over 15 min	1-2 mg/kg/hour	Possible increased inotropy, cardiac use of ATP	Inhibits NO mediated peripheral vasodilation		Don't use in G6PD deficiency, ARDS, pulmonary hypertension

Medication	IV Dose (mcg/kg/min)	Concentration
Norepinephrine (Levophed)	0.1-2 mcg/kg/min	8mg in 500mL D5W
Dopamine	2-20 mcg/kg/min	400mg in 250 D5W
Dobutamine	2-20 mcg/kg/min	250mg in 250 mg D5W
Epinephrine	0.1-1 mcg/kg/min	1mg in 250 D5W

Disposition

• Admission, frequently to intensive or higher-level of care

See Also

• Shock
• Ultrasound in Shock and Hypotension

External Links

• EMCrit Podcast – Cardiogenic Shock
• emDocs - Diagnosing Cardiogenic Shock in the ED