Burn Phases & Fluid Resuscitation

A major burn patient can lose liters of plasma into interstitial spaces within hours — yet the fluid you give in the first 8 hours matters more than the next 16. Timing is everything.

Major burns trigger a massive systemic inflammatory response that produces three distinct phases. The emergent/resuscitative phase (0–48 hours) is defined by capillary leak: plasma shifts from intravascular to interstitial spaces, causing hypovolemia, hemoconcentration, and edema. Urine output — not blood pressure — is the primary indicator of adequate resuscitation, targeting 0.5–1 mL/kg/hr in adults (1 mL/kg/hr in children). The Parkland formula guides initial crystalloid replacement: 4 mL × body weight (kg) × %TBSA burned. Half of the calculated volume is infused in the first 8 hours from the time of injury (not from hospital arrival), and the remaining half over the next 16 hours using lactated Ringer's solution. During the acute/intermediate phase (beginning around 48 hours), capillary integrity begins to restore. Fluid shifts back into the vasculature, causing hemodilution and risk of fluid overload — watch for crackles, jugular vein distention, and rising CVP. The rehabilitative phase focuses on wound healing and functional recovery. Potassium is released from damaged cells during the emergent phase, creating hyperkalemia risk; as diuresis begins in the acute phase, hypokalemia becomes the concern.

Key Distinctions

The 8-hour window starts from time of burn injury, not ED arrival — students consistently get this wrong and miscalculate infusion rates. Don't confuse the emergent phase (hypovolemia, hemoconcentration, hyperkalemia) with the acute phase (hypervolemia, hemodilution, hypokalemia) — the electrolyte and fluid shifts reverse. Parkland uses lactated Ringer's, not normal saline — the formula is specific to crystalloid choice.

Clinical Pearl

Emergent phase = everything leaves the vessels (hypovolemia, edema, hyperkalemia). Acute phase = everything floods back in (hypervolemia, hemodilution, hypokalemia). The shift flips at 48 hours.