Understanding Shock
Shock is inadequate tissue perfusion resulting in cellular hypoxia and metabolic dysfunction. If not corrected, shock progresses to organ failure and death. The cardiovascular system maintains perfusion through three components: the pump (heart), the pipes (blood vessels), and the fluid (blood volume). Failure of any of these components produces shock, and the type of shock determines the appropriate treatment. Recognizing shock early, identifying the type, and initiating appropriate treatment are among the most critical skills for EMS providers.
Shock progresses through three stages. Compensated shock occurs when the body's compensatory mechanisms (tachycardia, vasoconstriction, increased respiratory rate) maintain blood pressure and perfusion. The patient may have subtle findings such as anxiety, mild tachycardia, and slightly delayed capillary refill. Decompensated shock occurs when compensatory mechanisms fail, producing hypotension, altered mental status, and obvious signs of poor perfusion. Irreversible shock occurs when cellular damage is so extensive that death is inevitable regardless of treatment.
Types of Shock
Hypovolemic Shock
Caused by loss of blood volume (hemorrhage) or body fluids (dehydration, burns). The most common type of shock in trauma. Findings include tachycardia, hypotension, pale and cool skin, weak thready pulse, delayed capillary refill, and anxiety progressing to confusion. Treatment: control external bleeding, splint fractures to reduce internal bleeding, administer IV fluids (isotonic crystalloid), position flat or in Trendelenburg, and transport rapidly. For hemorrhagic shock, the goal is to get the patient to surgical intervention quickly; IV fluids are a temporizing measure, not a definitive treatment.
Cardiogenic Shock
Caused by pump failure, usually from acute myocardial infarction, severe heart failure, or cardiac tamponade. The heart cannot generate adequate cardiac output. Findings include hypotension, tachycardia (or bradycardia), pulmonary edema (crackles, dyspnea), jugular venous distension, and altered mental status. Treatment differs from hypovolemic shock: avoid excessive IV fluids (the heart is already failing as a pump, and additional fluid worsens pulmonary edema), administer vasopressors if available per protocol, and transport to a cardiac center.
Distributive Shock
Caused by inappropriate vasodilation that enlarges the vascular container, reducing effective circulating volume. Subtypes include septic shock (from severe infection), anaphylactic shock (from allergic reaction), and neurogenic shock (from spinal cord injury). Each subtype has characteristic findings: septic shock presents with fever, warm flushed skin initially, and a known or suspected infection source; anaphylactic shock presents with hives, wheezing, and facial swelling after allergen exposure; neurogenic shock presents with hypotension and bradycardia (warm, dry skin below the injury level) after spinal cord injury.
Obstructive Shock
Caused by mechanical obstruction of blood flow. The most common causes are tension pneumothorax (air trapping in the pleural space compressing the heart and great vessels), cardiac tamponade (fluid in the pericardial sac compressing the heart), and massive pulmonary embolism (blood clot blocking pulmonary blood flow). Treatment requires addressing the obstruction: needle decompression for tension pneumothorax, pericardiocentesis for tamponade (hospital procedure), and supportive care with rapid transport for pulmonary embolism.