Overview
This lecture covers the types, causes, recognition, and emergency treatment of shock, including definitions, the perfusion triangle, and specific care for various shock types.
Introduction to Shock and Perfusion
- Shock (hypoperfusion) is inadequate cellular perfusion, causing cellular injury or death.
- Early body response to shock aims to maintain homeostasis.
- Diffusion allows oxygen and COâ‚‚ exchange across the alveoli; oxygen binds hemoglobin, COâ‚‚ is transported as plasma, bicarbonate, or hemoglobin-bound.
- Poor perfusion impairs COâ‚‚ removal, causing toxic buildup and cellular damage.
- Shock is a failure of the cardiovascular system, leading to inadequate circulation; blood is shunted to vital organs (heart, brain, lungs).
The Perfusion Triangle & Blood Pressure
- The cardiovascular system (pump, container, contents) = heart, vessels, blood; called the perfusion triangle.
- Blood pressure: systolic (heart contraction), diastolic (rest), pulse pressure (systolic minus diastolic).
- Capillary sphincters regulate blood flow, controlled by the autonomic nervous system.
- Adequate perfusion requires enough oxygen, nutrients, and waste removal.
- Sympathetic nervous system releases epinephrine/norepinephrine in shock, increasing heart rate and vasoconstriction.
Types & Causes of Shock
- Shock arises from: pump failure (heart), poor vessel function, or low fluid volume.
- Pump failure: Cardiogenic shock (heart can't pump) and obstructive shock (mechanical obstruction like cardiac tamponade, tension pneumothorax, pulmonary embolism).
- Vessel problem: Distributive shock (widespread vessel dilation) includes septic, neurogenic, anaphylactic, and psychogenic shock.
- Fluid problem: Hypovolemic shock divides into hemorrhagic (blood loss) and non-hemorrhagic.
Recognition and Stages of Shock
- Stages: Compensated (body compensates), decompensated (compensation fails), irreversible (no recovery).
- Blood pressure drops late in shock, especially critical in infants and children.
- Suspect shock in trauma, severe infection, heart attack, or anaphylaxis.
Assessment & Emergency Care
- Rapid scene size-up, primary assessment, and control life-threatening bleeding before airway management.
- Assess LOC, airway, breathing, circulation, pulses, skin, cap refill.
- High-flow oxygen, keep patient warm, rapid transport, consider advanced life support.
- Secondary assessment: focused physical exam, detailed history, reassess interventions.
Management by Shock Type
- Cardiogenic: Position for comfort, high-flow oxygen, prompt transport—no nitro if hypotensive.
- Obstructive: High-flow oxygen, rapid transport, ALS for interventions (e.g., chest decompression).
- Septic: High-flow oxygen, preserve heat, rapid transport, notify sepsis team.
- Neurogenic: High-flow oxygen, spinal immobilization, rapid transport.
- Anaphylactic: Administer epinephrine IM, high-flow oxygen, rapid transport, ALS backup.
- Psychogenic: Reassess for injuries, transport all with LOC loss for evaluation.
- Hypovolemic: Stop bleeding (direct pressure/tourniquet), support airway, high-flow oxygen, rapid transport, gentle handling.
Special Populations
- Elderly: More complications, medications may mask signs.
- Pediatric and geriatric shock care is similar to adults; maintain airway, oxygen, control bleeding, warmth, and prompt transport.
Key Terms & Definitions
- Shock (Hypoperfusion) — State of inadequate tissue perfusion and oxygenation.
- Perfusion triangle — Heart (pump), blood vessels (container), blood (contents).
- Cardiogenic shock — Pump failure due to poor heart function.
- Obstructive shock — Pump failure from physical obstruction (e.g., tamponade, pneumothorax, embolism).
- Distributive shock — Poor vessel function with widespread dilation.
- Hypovolemic shock — Shock from low blood volume (hemorrhagic or non-hemorrhagic).
- Compensated shock — Early, body maintains perfusion.
- Decompensated shock — Body can no longer compensate; perfusion fails.
Action Items / Next Steps
- Review signs and symptoms of different shock types.
- Memorize the perfusion triangle and stages of shock.
- Practice shock assessment and management steps.
- Complete related readings and chapter questions.