## Causes of Death in Acute Burn Injury — Timeline **Key Point:** The cause of death in burn patients varies significantly with the phase of injury. In the **immediate and early phase (0–48 hours)**, hypovolemic shock is the leading cause; later, infection and sepsis dominate. ### Timeline of Burn Mortality | Phase | Timeframe | Primary Cause of Death | Mechanism | |---|---|---|---| | **Immediate/Early** | 0–48 hours | Hypovolemic shock | Massive fluid loss from capillary leak and evaporation | | **Intermediate** | 2–7 days | Inhalation injury complications | Airway obstruction, ARDS, pulmonary edema | | **Late** | >7 days | Sepsis and multi-organ failure | Bacterial translocation, wound infection, immunosuppression | ### Pathophysiology of Early Hypovolemic Shock in Burns 1. **Thermal injury** → denaturation of proteins and cell membrane disruption 2. **Increased capillary permeability** → massive fluid extravasation into interstitium ("capillary leak") 3. **Plasma volume depletion** → relative hypovolemia despite normal total body water 4. **Inadequate fluid resuscitation** → tissue hypoperfusion, organ dysfunction, shock 5. **Death** from cardiovascular collapse if fluids not replaced promptly **High-Yield:** The **Parkland formula** (4 mL × %TBSA × body weight in kg) was developed specifically to prevent early hypovolemic death by providing aggressive fluid resuscitation in the first 24 hours. **Clinical Pearl:** Inhalation injury (present in ~20–30% of hospitalized burn patients) accelerates mortality but is NOT the most common cause of death in the first 48 hours; it becomes more significant if the patient survives the initial shock phase. **Warning:** Electrolyte imbalances (hyperkalemia from cell lysis, hyponatremia from free water shifts) occur but are secondary complications; they do not cause the majority of early deaths — hypovolemic shock does.
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