Shock

Shock is inadequate tissue perfusion that starves cells of oxygen, with types including hypovolemic, cardiogenic, distributive (septic, anaphylactic, neurogenic), and obstructive. Early shock shows tachycardia and restlessness as the body compensates; hypotension is a late and dangerous sign of decompensation. Restoring perfusion early — with fluids, oxygen, and treatment of the underlying cause — improves survival.