Shock Defined
Shock = inadequate tissue perfusion → cellular hypoxia → organ dysfunction → death if untreated. Not the same as hypotension — shock can occur with normal BP early. Classic triad: hypotension, tachycardia, altered mental status. Elevated lactate (>2 mmol/L) = cellular hypoxia.
Hypovolemic Shock
Caused by volume loss: hemorrhage, burns, severe dehydration. Hemodynamics: low CO, high SVR. Clinical: tachycardia (first sign), pale/cool/clammy skin, decreased UO. Treatment: aggressive fluid resuscitation, stop the source.
Distributive Shock
Massive vasodilation → maldistribution. Types: Septic (norepinephrine first-line), Neurogenic (spinal cord injury — bradycardia + hypotension), Anaphylactic (epinephrine IM IMMEDIATELY). All share: low SVR, initially high/normal CO.
Cardiogenic Shock
Heart failure as pump → inadequate CO despite adequate volume. Causes: massive MI. Hemodynamics: low CO, high SVR, high PCWP. Clinical: cool/clammy skin, S3 gallop, crackles. Treatment: inotropes (dobutamine), avoid aggressive fluid.
Obstructive Shock
Mechanical obstruction. Tension pneumothorax: needle decompression. Cardiac tamponade: Beck's triad (JVD, muffled heart sounds, hypotension) — pericardiocentesis. Massive PE: anticoagulation, thrombolytics.
Important Notes
- Anaphylactic shock: epinephrine IM is FIRST-LINE, not second. Delayed epinephrine increases mortality.
- Tension pneumothorax: DO NOT wait for CXR — needle decompression is a clinical diagnosis.
Clinical Tips
- Skin temperature differentiates: WARM shock = distributive; COOL shock = hypovolemic or cardiogenic.
Summary
Rapid identification of shock type guides resuscitation strategy. Distributive requires vasopressors, hypovolemic requires volume, cardiogenic requires inotropes, obstructive requires removal of obstruction.
