The Four Categories
- Hypovolemic — loss of intravascular volume (hemorrhage, GI losses, burns)
- Cardiogenic — pump failure (MI, arrhythmia, valve failure, cardiomyopathy)
- Distributive — pathological vasodilation (septic, anaphylactic, neurogenic)
- Obstructive — physical obstruction to flow (tension pneumothorax, cardiac tamponade, massive PE)
Hemodynamic Differences
| Type | Preload (JVP) | Cardiac output | Peripheries |
|---|---|---|---|
| Hypovolemic | Low | Low | Cold |
| Cardiogenic | High | Low | Cold |
| Distributive (early septic) | Low/normal | High | Warm |
| Obstructive | High | Low | Cold |
Bedside Clues
- Cold, clammy peripheries with low JVP → think hypovolemic
- Cold peripheries, raised JVP, pulmonary edema → think cardiogenic
- Warm peripheries with fever or recent infection → think septic (early/warm phase)
- Raised JVP, muffled heart sounds, hypotension (Beck's triad) → think tamponade
General Management Principle
Treat the underlying cause while supporting perfusion: fluids for hypovolemic and distributive shock, judicious fluids plus inotropes for cardiogenic shock, and immediate decompression (needle thoracostomy, pericardiocentesis) for obstructive causes.