A 38-year-old woman with massive hemorrhage (2 L blood loss) is in hypovolemic shock. A 55-year-old man with acute pancreatitis and systemic inflammatory response is in distributive shock. Which finding best distinguishes hypovolemic shock from distributive (septic/anaphylactic) shock?

Explanation

## Distinguishing Hypovolemic from Distributive Shock ### Pathophysiologic Basis **Key Point:** Hypovolemic shock is characterized by absolute loss of intravascular volume with compensatory vasoconstriction (cold shock). Distributive shock involves maldistribution of blood volume with vasodilation and capillary leak (warm shock initially). ### Comparative Table | Feature | Hypovolemic Shock | Distributive Shock (Septic/Anaphylactic) | | --- | --- | --- | | **Capillary Refill** | ↑ Prolonged (>2 sec) | Normal (<2 sec) | | **Skin Temperature** | Cold, clammy | Warm, flushed (early) | | **CVP** | Low | Normal or low (early); high if fluid overloaded | | **SVR** | ↑ Elevated | ↓ Decreased | | **Cardiac Output** | ↓ Reduced | ↑ High (early) or ↓ Low (late) | | **Urine Output** | ↓ Oliguria | Variable; may be normal initially | | **Peripheral Perfusion** | Poor (vasoconstricted) | Good (vasodilated) initially | ### Clinical Pearl **High-Yield:** Capillary refill time is the single most practical bedside discriminator. In hypovolemic shock, intense peripheral vasoconstriction (sympathetic response to volume loss) causes slow capillary refill. In distributive shock, vasodilation and capillary leak cause normal or brisk capillary refill despite hypotension. This reflects the fundamental difference: hypovolemic = "cold shock," distributive = "warm shock." ### Why Capillary Refill Matters **Mnemonic:** **HYPO** = **H**ypotension, **Y**agged (slow) capillary refill, **P**eripheral vasoconstriction, **O**liguria. **DIST** = **D**ilation of vessels, **I**ncreased capillary refill, **S**wollen tissues (edema), **T**emperature warm. 1. **Hypovolemic shock:** Sympathetic activation → arteriolar and capillary bed vasoconstriction → prolonged capillary refill (>2 sec) 2. **Distributive shock:** Endotoxin/mediators → vasodilation + capillary leak → normal/brisk capillary refill (<2 sec) despite hypotension ### Bedside Assessment Press fingernail bed for 3 seconds, release, and time color return: - **Normal:** <2 seconds - **Prolonged:** >2 seconds (hypovolemic, cardiogenic, or late distributive shock) - **Brisk:** <1 second (early distributive shock, hyperthermia, or anxiety)