Clinical meaning
Shock is a life-threatening condition of inadequate tissue perfusion resulting in cellular hypoxia, anaerobic metabolism, lactic acid accumulation, and progressive organ dysfunction. If not reversed, shock progresses from compensated (vital signs maintained through sympathetic activation) to decompensated (falling blood pressure, altered mental status, organ failure) to irreversible (multi-organ failure and death). The four types of shock are: (1) Hypovolemic — decreased intravascular volume from hemorrhage (hemorrhagic) or fluid loss (non-hemorrhagic: dehydration, burns, third-spacing); treated with volume replacement. (2) Cardiogenic — pump failure from MI, cardiomyopathy, arrhythmias, or valve dysfunction; treated with inotropes, vasopressors, and reperfusion. (3) Distributive — inappropriate vasodilation causing relative hypovolemia: septic (most common), anaphylactic, or neurogenic; treated with volume and vasopressors. (4) Obstructive — mechanical obstruction to cardiac output: tension pneumothorax, cardiac tamponade, massive PE; treated by relieving the obstruction. The RN must recognize early shock (tachycardia, anxiety, cool/pale skin, decreased urine output) before decompensation occurs, and initiate emergency interventions while the cause is being determined.