Overview
Clinical Meaning
Shock classification is based on the underlying mechanism and hemodynamic profile.
Shock classification is based on the underlying mechanism and hemodynamic profile. Understanding the hemodynamic parameters (cardiac output [CO], systemic vascular resistance [SVR], central venous pressure [CVP], and pulmonary artery occlusion pressure [PAOP/wedge]) guides treatment: (1) Hypovolemic shock: ↓CO, ↑SVR (compensatory vasoconstriction), ↓CVP, ↓PAOP — treatment: volume replacement. (2) Cardiogenic shock: ↓CO, ↑SVR (compensatory), ↑CVP, ↑PAOP (backup of blood behind failing ventricle) — treatment: inotropes, vasopressors, reduce afterload, reperfusion for MI. (3) Distributive shock (septic, anaphylactic, neurogenic): initially ↑CO (hyperdynamic), ↓SVR (vasodilation — the primary defect), ↓CVP (relative hypovolemia) — treatment: fluids + vasopressors. Late septic shock may have ↓CO from myocardial depression. (4) Obstructive shock: ↓CO (mechanical obstruction to filling or ejection), ↑SVR, variable CVP (↑ in tamponade/PE, ↓ in tension pneumothorax with mediastinal shift) — treatment: relieve the obstruction. Tissue oxygenation assessment: ScvO2 >70% in early septic shock (cells cannot extract O2 — cytopathic hypoxia) vs. ScvO2 <60% in cardiogenic/hypovolemic shock (increased O2 extraction from low cardiac output).
