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
• S_CVO₂ (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