Shock

Shock is defined as circulatory failure resulting in systemic hypoperfusion. Most commonly as a result of low blood pressure.

Approach to the hypotensive patient

4 factors play a role in hypotension (see figure below)

  • Preload
  • Cardiac Contractility
  • Heart Rate
  • Systemic Vascular Resistance

Low Preload

  • Poor volume intake
    • Treatment: Volume resuscitation
  • Volume loss
    • Diarrhea
    • Diuretics
    • Hemorrhage
    • Treatment: Volume resuscitation
  • Obstruction (inability of blood to get back to Left Atrium)
    • Tension Pneumothorax
    • Pulmonary Embolism
    • Cardiac Tamponade
    • Treatment: Volume resuscitation and alleviation of obstruction (needle thoracostomy, fibrinolytic administration, or pericardiocentesis)
  • Tachyarrhythmias (inability of the ventricles to properly fill)
    • i.e. Atrial Fibrillation with Rapid Ventricular Response, Ventricular Tachycardia, Paroxysmal Supraventricular Tachycardia
    • Treatment: Synchronized Cardioversion

Low Cardiac Contractility

  • Infarction
  • Heart Failure
  • Thiamine Deficiency (“wet beriberi”)
  • Treatment: Inotropes, ACS management if applicable, high-dose IV thiamine supplementation if suspicious

Low Heart Rate

  • Sick Sinus Syndrome
  • AV node block (1st degree – 3rd degree)
  • Medications (Beta-Blockers, Calcium Channel Blockers)
  • Treatment: Atropine followed by transcutaneous pacing

Low Systemic Vascular Resistance

  • Sepsis
  • Anaphylaxis
  • “Neurogenic Shock”: Anesthetics or spinal trauma
  • Adrenal Insufficiency
  • Liver Failure
  • Medications
  • Treatment: Vasoconstrictors
    • Antibiotics if in sepsis
    • IM epinephrine and IV steroids if in anaphylaxis
    • Glucocorticoid and mineralocorticoid replacement if in adrenal crisis
    • Liver transplant if in liver failure

Evaluation of Shock

Pulse Pressure (SBP – DBP)

  • High Pulse Pressure: Think distributive
  • Low Pulse Pressure: Think cardiogenic

Extremities

  • Warm: Think Distributive
  • Cold: Think cardiogenic

Point-of-Care-Ultrasound (POCUS)

  • See “POCUS” as its own topic, but in short, can evaluate for volume status, pulmonary embolism, pneumothorax, tamponade, and cardiac function
  • Can also assist us in evaluating for fluid responsiveness – can calculate cardiac output as a function of stroke volume before and after fluid administration

Labs

  • Lactic Acid
    • Elevated in shock due to reversion of cellular metabolism to anaerobic metabolism in the absence of adequate tissue oxygen perfusion
    • Can trend as part of evaluation for improved tissue perfusion
  • SCVO2 (Central Venous Oxygen Saturation)
    • High: Distributive
    • Low: Cardiogenic/Hypovolemic
  • CVP (Central Venous Pressure)
    • High: Cardiogenic
    • Low: Distributive/Hypovolemic
  • Troponin
  • BNP
  • EKG
  • Infectious workup (blood cultures, urinalysis and culture, chest x-ray)
  • AM Cortisol if concerned for adrenal insufficiency

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