Hypovolemic Shock
The patient's blood pressure looks fine at 118/80 — but the heart rate is already 112. Hypovolemic shock announces itself through compensation long before the pressure drops.
Core Concept
Hypovolemic shock results from a critical loss of intravascular volume — either blood (hemorrhagic) or fluid (non-hemorrhagic: burns, vomiting, diarrhea, third-spacing). The body compensates early through sympathetic activation: tachycardia, vasoconstriction, and shunting blood to vital organs. This is why blood pressure is a late sign — by the time it falls, the patient has lost roughly 30% of circulating volume (Class III hemorrhage, ~1500-2000 mL in an adult). Staging matters: Class I (<15% loss) may show only mild tachycardia; Class II (15-30%) brings tachycardia above 100, narrowed pulse pressure, and anxiety; Class III (30-40%) produces hypotension, confusion, and tachycardia over 120; Class IV (>40%) presents with lethal hemodynamic collapse. Nursing priorities center on rapid isotonic crystalloid resuscitation — typically 1-2 L of 0.9% NS or lactated Ringer's via large-bore IV (16-18 gauge, two sites). Monitor urine output as the most reliable end-organ perfusion marker: the target is at least 0.5 mL/kg/hr. Trendelenburg or passive leg raise can temporarily augment preload. Ongoing assessment includes serial vital signs, level of consciousness, skin color and temperature, and capillary refill.
Watch Out For
Don't confuse hypovolemic shock (low preload, tachycardia, flat neck veins) with cardiogenic shock (high preload, distended neck veins, pulmonary crackles) — both cause hypotension, but fluid resuscitation helps one and worsens the other. Students often mistake a normal BP for hemodynamic stability — tachycardia with narrowed pulse pressure is the earlier alarm. Pulse pressure narrows in hypovolemia but widens in septic shock's warm phase.
Clinical Pearl
Flat veins, fast heart, falling urine output — that's the hypovolemic triad. The BP is the last domino to fall, not the first.
Test Your Knowledge
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