Cardiogenic shock

Background

• Leading cause of death in pts w/ MI who reach the hospital alive

Etiology

• Myocardial infarction
  • Pump failure
  • Mechanical complications
  • Acute MR (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

Clinical Presentation

Physical Exam

• Assess for signs of CHF
  • elevated JVD, pulmonary edema, S3
• Assess for valvular disease (MR, critical AS, or aortic regurgitation)
• Assess e/o end-organ hypoperfusion
  • cool/mottled extremities, weak pulses, AMS, decreased UOP
• Assess for pulsus paradoxus (cardiac tamponade)

Work-Up

• Labs
  • Troponin
  • Lactate
  • CBC
  • Chem
  • BNP
    • <100 may rule-out cardiogenic shock
• ECG
• CXR
• TTE

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)

Treatment

• General
  • Intubation
    • Decreases O2 demand BUT may worsen preload
• Coronary perfusion

1. Small Fluid challenge
2. Increase inotropy
   1. Titrate to clinical effect
      • Dobutamine or Milrinone:
      1. Use milrinone if pt is on BB
      2. CaCl 1gm
         1. Give if pt is hypocalcemic
3. Achieve MAP >65

Pressors

Pressor	Initial Dose	Max Dose	Cardiac Effect	BP Effect	Arrhythmias	Special Notes
Dobutamine	2.5mcg/kg/min	10-40 mcg/kg/min	mainly inotrope (ß1)	alpha effect minimal	Some HR(ß1) increase. Also Increase SA and AV node fx	Debut Research 1979 Isoproterenol has most Β2 vasodilatory and Β1 HR effects
Dopamine	2mcg/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
Norepinephrine	8-12mcg/min	30 mcg/min	β1 direct effect	β1 and α1,2 effects	Less arrhythmias than Dopamine	Increases MAP, coronary perfusion pressure, little β2 effects.
Milrinone	50mcg/kg x 10 min	0.375-75mcg/kg/min	Direct influx of Ca2+ channels	Smooth muscle vasodilator		PDE Inhibitor which increases Ca2+ uptake by sarcolemma. No venodilatory activity
Phenylephrine	100-180mcg/min then 40-60mcg/min	0.4-9 mcg/kg/min		Alpha agonist		Long half life
Vasopressin	Fixed Dose	0.4 U/min	unknown	increases via ADH peptide		should not be titrated due to ischemic effects

Other Therapies

• Transfusion
  • Consider if Hb < 10

Specific Situations

1. Mitral Regurg
   1. Need to increase forward flow
   2. Dobutamine (contractility)
   3. Nitroprusside (afterload reduction)
2. MI
   1. PCI or thrombolysis
3. Aortic Stenosis
   1. Do not give preload reducers such as Nitro
   2. Patients are flow dependent over stenotic value. Flow proportional to degree of stenosis and afterload.
   3. Maintain flow by decreasing afterload (use with extreme caution and in very small carefuly titrated doses)
      1. Nitropruside
      2. Dobutamine
      3. Hydralazine
4. Toxins
   1. Beta-Blocker Toxicity
   2. Calcium Channel Blocker
   3. Digoxin

See Also

• Shock
• Ultrasound in Shock and Hypotension