shock

Introduction

Hypoperfusion of vital organs associated with hypotension. Shock is a medical emergency.

Classification

• distributive shock (generalized systemic vasodilation)
  • septic shock
• cardiogenic shock (low cardiac output due to left-sided heart failure or right-sided heart failure
• hypovolemic shock (loss of preload)
• obstructive shock (massive increase in afterload)
  • cardiac tamponade, pulmonary embolism, tension pneumothorax
• anaphylactic shock

Pathology

• hypoperfusion of vital organs with tissue hypoxia
• acidemia
• distributive shock (generalized systemic vasodilation)
  • high cardiac output, low systemic vascular resistance
• cardiogenic shock (left-sided heart failure or right-sided heart failure)
  • low cardiac output, high PCWP, high systemic vascular resistance
• hypovolemic shock (loss of preload)
  • low cardiac output, low PCWP, high systemic vascular resistance
• obstructive shock (massive increase in afterload)
  • low cardiac output, variable PCWP, high systemic vascular resistance
  • cardiac tamponade, pulmonary embolism, tension pneumothorax
• anaphylactic shock
  • high cardiac output, normal PCWP, low systemic vascular resistance

Clinical manifestations

• onset is typically acute, but may be gradual
• systemic hypotension
• tachycardia occurs with:
  • pain, fever, hypoxia, hyperthyroidism, stress, myocarditis'
• bradycardia occurs with:
  • sick sinus syndrome, heart block, increased vagal tone
• fever - sepsis, anaphylaxis, adrenal insufficiency
• cool extremities & delayed capillary refill, known as 'cold shock*
• warm shock manifests as vasodilation with flash capillary refill*
• jugular venous flattening or distention
• pulmonary rales with heart failure, ARDS, pneumonia
• heart sounds
  • distant with cardiac tamponade
  • loud P2 with pulmonary hypertension
  • delayed A2 with aortic stenosis
  • S3 & diffuse impulse with cardiogenic shock
  • S4 & prominent impulse with obstructive shock
  • murmurs
    • mitral regurgitation
    • hypertrophic cardiomyopathy
    • aortic stenosis
    • aortic insufficiency
    • ventricular septal defect
  • pericardial rub with pericarditis
  • pericardial knock with pericardial constriction
  • diastolic plop with myxoma
  • muffling of metallic prosthetic valve clicks may occur

* it is not clear if these classifications are reserved for pediatric patients

Laboratory

• complete blood count (CBC)
  • hematocrit drops after hydration with acute blood loss
  • hemoconcentration with dehydration
  • leukocytosis, left shift & toxic granulation suggests sepsis
  • thrombocytopenia may be seen with bleeding diatheses
  • schistocytes may be seen with DIC
• coagulation studies
  • prothrombin time
  • partial thromboplastin time
  • D-dimer or other fibrin-split products
  • plasma fibrinogen
• arterial blood gas (ABG)
  • acidemia
  • hypoxia
• blood cultures
  • aerobic
  • anaerobic
  • fungal
  • acid-fast organisms
• urinalysis
• serum chemistries
  • electrolytes
  • serum Ca+2
  • serum Mg+2
  • serum glucose
  • markers of myocardial infarction
    • serum creatine kinase MB (CKMB)
    • serum lactate dehydrogenase
    • serum troponin-I
  • serum amylase
  • serum lipase
  • renal function tests
  • liver function test
  • serum phosphorus
  • serum cortisol
• drug levels

Diagnostic procedures

• electrocardiogram
• echocardiogram
  • transthoracic echocardiogram
    • pericardial effusion
    • generalized hypokinesis with cardiomyopathy
    • focal wall motion abnormalities with MI
    • cardiac valve function
    • cardiac output
    • septal defects
    • left ventricular ejection fraction
  • transesophageal echocardiogram
    • pulmonary artery thromboembolism
    • aortic dissection
    • cardiac valve function
    • septal defects
    • congenital heart disease
• cardiac catheterization
  • Swan-Ganz (right heart) catheterization
    • pulmonary artery & wedge pressure
    • cardiac output
      • thermodilution
      • Fick method
    • calculation of systemic vascular resistance
    • pulmonary angiography
    • of no benefit in management of shock
  • left heart catheterization
    • coronary artery catheterization
    • left ventriculography
    • aortography

Radiology

• chest X-ray
  • evaluate for cardiomegaly
  • progressive enlargement with cardiac tamponade
  • evidence of pulmonary congestion
  • dilated aortic arch with dissecting aortic aneurysm
  • prominent pulmonary vasculature with septal defects
  • pulmonary effusions
    • heart failure
    • pulmonary embolism
    • other conditions
• ventilation perfusion scan for pulmonary embolism

Management

• hemodynamic stabilization, restore perfusion of vital organs
  • intravenous (IV) fluids
    • avoid hydroxyethyl starch (hetastarch)
  • vasopressors
    • epinephrine, dopamine, dobutamine for cardiogenic shock
      • epinephrine is 1st line therapy for cold shock with hypotension
    • norepinephrine for warm shock & septic shock
  • central line to measure central venous pressure (CVP)
  • arterial line to measure arterial blood pressure
    • a mean arterial pressure of 65 mm Hg is the theshold at which there is sufficient pressure for organ perfusion (most humans)
  • pulmonary artery catheter for hemodynamic monitoring
  • continuous monitoring of:
    • vital signs
    • blood pressure
    • oxygen saturation
    • ECG for arrhythmias
  • glucagon: 1 mg in 1 L of D5W at 5-15 mL (5-15 ug)/min for refractory hypotension
• treatment of underlying pathology
• consider administration of
  • naloxone (Narcan) for opioid overdose
  • flumazenil (Romazicon) for benzodiazepine overdose
• low-calorie, low-protein enteral nutrition may reduce ICU stay in ventilated patients (see intensive care unit)

More general terms

• hypotension
• syndrome

More specific terms

• cardiogenic shock
• distributive shock; vasodilatory shock (multiple organ dysfunction syndrome)
• hypovolemic shock
• obstructive shock

Additional terms

• anaphylaxis