According to ATLS classification, Class III hemorrhagic shock corresponds to blood loss of approximately what percentage of total blood volume?

Explanation

## ATLS Classification of Hemorrhagic Shock **Key Point:** The American College of Surgeons ATLS protocol stratifies hemorrhagic shock into four classes based on the percentage of circulating blood volume lost and the corresponding physiologic response. ### Class III Hemorrhagic Shock Class III hemorrhagic shock is defined by blood loss of **30–40% of total blood volume**. At this stage, the patient exhibits significant physiologic derangement: - **Systolic BP:** Decreased (hypotensive) - **Heart rate:** >120 bpm (severe tachycardia) - **Respiratory rate:** 30–40 bpm (marked tachypnea) - **Urine output:** 5–15 mL/hr (oliguria) - **Mental status:** Confused, anxious, restless - **Skin perfusion:** Cool, pale, clammy ### ATLS Hemorrhagic Shock Classification Table | Class | Blood Loss (%) | HR (bpm) | SBP | RR (bpm) | Urine Output (mL/hr) | Mental Status | | --- | --- | --- | --- | --- | --- | --- | | I | Up to 15% | <100 | Normal | 14–20 | >30 | Alert | | II | 15–30% | 100–120 | Normal | 20–30 | 20–30 | Anxious | | III | 30–40% | >120 | Decreased | 30–40 | 5–15 | Confused | | IV | >40% | >140 | Decreased | >35 | Minimal/absent | Lethargic/unresponsive | **High-Yield:** Class III shock requires immediate aggressive resuscitation with blood products (PRBC and FFP in 1:1 ratio) and definitive hemorrhage control. This is the threshold at which crystalloid alone is typically insufficient. **Clinical Pearl:** The progression from Class II to Class III represents the transition from **compensated shock** (normal BP maintained by sympathetic drive) to **decompensated shock** (BP begins to fall despite maximal compensation). Class III is the first class in which blood pressure typically drops. **Mnemonic:** Think of the four classes as roughly 15%, 15–30%, 30–40%, and >40% — each step escalating in severity. Class III = **30–40%** loss with overt hypotension and confusion. *Reference: ATLS Student Course Manual, 10th Edition, American College of Surgeons.*