A 28-year-old woman with a penetrating stab wound to the right upper quadrant is in the resuscitation bay. She is in Class II hemorrhagic shock (BP 95/60 mmHg, HR 110/min, anxious, normal urine output). Two large-bore IVs are running. The trauma surgeon is preparing for the operating room. Which fluid is the drug of choice for initial resuscitation in this hemorrhagic shock scenario?

## Crystalloid Choice in Hemorrhagic Shock Resuscitation **Key Point:** Lactated Ringer's (LR) solution is the preferred crystalloid for initial resuscitation in hemorrhagic shock because it is physiologically balanced, contains lactate (metabolized to bicarbonate), and does not cause hyperchloremic acidosis. ### Why Lactated Ringer's Over Normal Saline? **High-Yield:** The ATLS guideline recommends LR as the crystalloid of choice for trauma resuscitation. | Feature | Lactated Ringer's | Normal Saline (0.9%) | |---------|-------------------|---------------------| | **Sodium** | 130 mEq/L | 154 mEq/L (hypernatremic) | | **Chloride** | 109 mEq/L | 154 mEq/L (hyperchloremic) | | **Potassium** | 4 mEq/L | 0 (hypokalemic risk) | | **Calcium** | 3 mEq/L | 0 | | **Lactate** | 28 mEq/L (buffer) | None | | **pH** | 6.5 (physiologic) | 5.5 (acidic) | | **Osmolality** | 273 mOsm/L | 308 mOsm/L | | **Risk** | Minimal | Hyperchloremic acidosis, dilutional coagulopathy | ### Mechanism of Benefit 1. **Lactate metabolism:** Lactate is converted by the liver to bicarbonate, providing a physiologic buffer and correcting metabolic acidosis from shock. 2. **Electrolyte balance:** Sodium and chloride concentrations are closer to plasma, reducing hyperchloremic acidosis. 3. **Coagulation:** Hyperchloremia impairs platelet function and coagulation cascade; LR avoids this. **Clinical Pearl:** In prolonged resuscitation (>2 L crystalloid), normal saline causes hyperchloremic metabolic acidosis and dilutional coagulopathy, worsening outcomes. LR is superior for massive transfusion protocols. ### Resuscitation Principles **Mnemonic:** **CRASH** — **C**rystalloid first, **R**apid infusion (wide-bore IV), **A**ssess response, **S**urgery for control, **H**emostasis. **Warning:** Avoid over-resuscitation ("damage control resuscitation"). Target BP 90 mmHg systolic in penetrating trauma until bleeding is controlled—excessive fluids increase bleeding and dilute clotting factors. [cite:ATLS 10e; Harrison 21e Ch 296]