Shock Fundamentals - The Lowdown Low Flow
- Definition: Critical, life-threatening state of circulatory failure. Results in inadequate oxygen delivery ($DO_2$) to meet cellular oxygen consumption ($VO_2$) and metabolic demands.
- Core Issue: Global tissue hypoperfusion leading to cellular dysoxia (impaired oxygen use).
- Pathophysiology: ↓Perfusion → cellular hypoxia → anaerobic metabolism → ↑lactic acid → metabolic acidosis → cellular injury, organ dysfunction, and ultimately death if uncorrected.
⭐ Lactate is a key marker of tissue hypoperfusion and shock severity.
Shock Types - The Nasty Quartet
Meet the 'Nasty Quartet' of shock: four primary types, each defined by unique underlying causes and distinct hemodynamic profiles. Quick differentiation is absolutely vital.
| Type | CO | PCWP/CVP | SVR | Key Examples |
|---|---|---|---|---|
| Hypovolemic | ↓ | ↓ | ↑ | Hemorrhage, severe dehydration, burns |
| Cardiogenic | ↓↓↓ | ↑ | ↑ | MI, heart failure, valve rupture |
| Obstructive | ↓ | CVP ↑ (PCWP var.) | ↑ | PE, cardiac tamponade, tension pneumothorax |
| Distributive | ||||
| - Septic | ↑/N/↓ | ↓/N | ↓↓↓ | Infection (early: warm; late: cold) |
| - Anaphylactic | ↓ | ↓ | ↓↓↓ | Allergic reaction |
| - Neurogenic | ↓ | ↓ | ↓↓↓ | Spinal injury, regional anesthesia |
Shock Sleuthing - Spotting the Signs
Prompt recognition is key. Look for:
- Core Indicators: Hypotension (SBP <90 mmHg or MAP <65 mmHg), tachycardia (>100 bpm), tachypnea (>20/min).
- Perfusion Deficits: Altered mental status, oliguria (<0.5 mL/kg/hr), cool/clammy skin (warm in distributive), delayed capillary refill (>2s), ↑lactate (>2 mmol/L).
⭐ Pulsus paradoxus >10 mmHg is a key finding in cardiac tamponade (obstructive shock).
Shock Solutions - The Rescue Mission
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High‑Yield Points - ⚡ Biggest Takeaways
- Shock is inadequate tissue perfusion; key signs: hypotension, tachycardia, oliguria, altered mental status.
- Initial management: ABCDEs, IV crystalloids, oxygen; target MAP ≥65 mmHg.
- Hypovolemic shock: Aggressive fluid resuscitation and source control.
- Cardiogenic shock: Inotropes (dobutamine) and vasopressors (norepinephrine) for pump failure.
- Septic shock: Early antibiotics, fluids, and norepinephrine. Anaphylactic shock: IM epinephrine.
- Obstructive shock: Relieve obstruction. Monitor lactate clearance and urine output.
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