Shock

Background

• Shock is a life threatening circulatory disorder that leads to tissue hypoxia and ischemia
• The several causes of shock are classified into hypovolemic, cardiogenic, obstructive, and distributive shock
• Distributive shock is further classified into septic, anaphylactic and neurogenic shock
• Diagnosis is mostly clinical but measurements of functional parameters (eg, cardiac output, systemic vascular resistance) can help distinguish between the different types of shock
• Management of shock involves circulatory support and treatment of the underlying cause

Hemodynamic measurements of undifferentiated shock

Hypovolemic shock

Background

• Loss of intravascular fluid volume would lead to decreased preload and stroke volume (this would lead to decreased cardiac output and compensatory increase in systemic vascular resistance)

Hemorrhage

• Postpartum hemorrhage
• Upper GI bleeding (eg, variceal bleeding, PUD)
• Blunt/penetrating trauma
• Ruptured aneurysm or hematoma
• Arteriovenous fistula

Nonhemorrhagic shock

• GI loss (Eg, diarrhea, vomiting)
• Increased sensitive fluid loss (eg, burns)
• Third space fluid loss (eg, bowel obstruction, pancreatitis)
• Renal fluid loss (eg, adrenal insufficiency, drug induced diuretics)

Clinical presentation

• Physical examination include hypotension, tachycardia, reduced skin turgor, nondistended jugular veins, dry mucous membranes and cold clammy skin

Diagnosis

• Most cases are clinically diagnosed

Treatment

• The priority is aggressive fluid resuscitation (further treatment depends on the etiologic category of hypovolemia (hemorrhagic vs. nonhemorrhagic)
• If hemorrhagic shock is suspected, perform blood grouping and cross matching and have packed RBCs at hand for transfusion (uncrossmatched RBC type O negative units can be transfused if the hemorrhage is severe)
• Treat the underlying etiology
• Supportive care (electrolyte abnormalities should be corrected)
• Once hemodynamically stable, replacement of fluid loss should be continued and oral rehydration therapy should be attempted

Complications

• Acute renal failure

Cardiogenic shock

Background

• Cardiogenic shock is a shock secondary to dysfunction of the heart (pump failure)
• The heart is unable to generate adequate cardiac output to maintain tissue perfusion
• Coronary artery disease is a major risk factor

Clinical presentation

• Symptoms include myocardial infarction (chest pain and dyspnea) or arrhythmias (palpitations and syncope)
• Physical examination findings include hypotension, tachycardia, pulmonary edema (diffuse lung crackles, distended jugular veins), cool extremities, and decreased urine output

Diagnosis

• Most cases are clinically diagnosed

Treatment

• Supportive (fluid resuscitation and oxygen)
• Medical intervention (intravenous inotropic drugs like dopamine, dobutamine, norepinephrine)

Complications

• Pulmonary edema
• Acute renal failure

Obstructive shock

Background

• A type of shock secondary to extra-cardiac causes of pump failure
• There are several etiologies to obstructive shock; subclassified into pulmonary vascular and mechanical etiologies
• Pulmonary vascular etiologies are associated with right ventricular failure. These include pulmonary embolism and severe pulmonary hypertension
• Mechanical etiologies include tension pneumothorax, pericardial tamponade, constrictive pericarditis, and restrictive cardiomyopathy

Clinical presentation

• Physical examination findings include hypotension, tachycardia, jugular venous distention, and cold clammy skin

Diagnosis

• Echocardiography (to detect underlying causes, such as pericardial tamponade)
• Most cases are clinically diagnosed

Treatment

• Manage underlying cause

Complications

• Death
• Acute renal failure

Distributive shock

Distributive shock

• A shock secondary to severe peripheral vasodilation
• Risk factors include infection, exposure to allergens, or trauma

Septic shock (most common type)

• Background
  • Septic shock is a type of distributive shock
  • This condition is a potentially fatal medical condition that occurs when sepsis leads to hypotension (this condition is the most severe complication of sepsis)
  • There is a decreased systemic vascular resistance due to peripheral vasodilation and increased cardiac output
• Clinical presentation
  • Bounding pulse seen in early septic shock due to hyperdynamic circulation
  • Late septic shock presents with decreased cardiac output
• Diagnosis
  • Most cases are clinically diagnosed
• Treatment
  • Fluid resuscitation
  • Identifying the underlying infection and treating it properly
  • Vasopressors
• Complications
  • Death
  • Acute renal failure

Non-septic shock (Anaphylactic and Neurogenic shock)

• Anaphylactic shock
  • Background
    • Anaphylactic shock is a potentially life threatening systemic allergic reason (can results in airway obstruction and cardiovascular collapse)
    • Anaphylactic shock is very rapid (minutes to hours)
    • Assess and secure the airway as needed
    • Remove allergen when possible (e.g., stop medication or IV contrast)
    • Administer epinephrine IM 1:1,000 as soon as possible and repeat as needed
    • Provide immediate hemodynamic support with fluid resuscitation
    • Differential diagnosis includes vasovagal syncope and other diseases associated with flushing (alcohol-induced, rosacea, or carcinoid tumor)

    • Causes of anaphylaxis
      Immunologic mechanism
      IgE-mediated	Medications Food Insect stings/bites Latex
      Nonimmunologic mechanisms
      Direct activation of mast cells and basophils	Exercise Cold air Iodinated contrast medium Medications (eg, opioids, NSAIDs)
      Idiopathic	Mast cell activation syndrome

  • Clinical presentation

    • Anaphylaxis
      Category	Details
      Triggers	Food (e.g., nuts, shellfish) Medications (e.g., beta-lactam antibiotics) Insect stings
      Clinical Manifestation	Cardiovascular (vasodilation, hypotension, edema, and tachycardia) Respiratory (stridor, hoarseness, and wheezing) Cutaneous (urticaria, pruritus, flushing) Gastrointestinal (nausea, vomiting, and abdominal pain)
      Treatment	Intramuscular epinephrine Airway management and volume resuscitation Adjunctive therapy (e.g., antihistamines, glucocorticoids)

    • Clinical Features of Anaphylaxis
      Category	Details
      Cutaneous/Mucosal	Ocular: periorbital swelling, injected conjunctiva, tearing Oral mucosa: swelling, tingling, or itching of tongue and lips Skin: urticaria, flushing, pruritus
      Respiratory	Nose: congestion, rhinorrhea Upper airway: edema (hoarseness and stridor) Lower airway: bronchospasm (wheezing)
      Cardiovascular	Vasodilation (hypotension and syncope) Cardiac dysfunction, cardiac arrest
      Gastrointestinal	Nausea, vomiting, abdominal pain, diarrhea
      Neurological	Headache, confusion, anxiety, feeling of impending doom

  • Treatment

    • Management of Anaphylaxis
      Category	Details
      Immediate Management	Epinephrine (most common) IM is preferred, may be repeated (e.g., 3 doses) IV crystalloids and Trendelenburg positioning for hypotension Albuterol for bronchospasm Early intubation for upper airway obstruction
      Adjunct Management	Antihistamines Glucocorticoids Glucagon for patients on beta blockers (reversal) Hospital admission for severe initial presentation (e.g., shock) or ongoing symptoms despite treatment

Neurogenic shock

• Background
  • A type of distributive shock that is secondary to a traumatic brain injury
• Clinical presentation
  • Physical examination include hypotension, warm/dry skin, may have fever
• Diagnosis
  • Most cases are clinically diagnosed
• Treatment
  • Fluid resuscitation
  • Vasopressors
• Complications
  • Death
  • Acute renal failure

Shock Management