4.1 Fluid Resuscitation Formulas: Parkland (Baxter), Modified Brooke, and Consensus Protocols

4.1 Fluid Resuscitation Formulas: Parkland (Baxter), Modified Brooke, and Consensus Protocols

Core Knowledge: Severe thermal injury involving ≥20% of Total Body Surface Area (TBSA) triggers a profound systemic inflammatory cascade characterized by widespread microvascular hyperpermeability, rapid intravascular fluid extravasation, and burn shock. Resuscitation formulas establish a standardized starting estimate for crystalloid administration during the initial 24 hours. The American Burn Association (ABA) Consensus Guidelines emphasize starting with lower initial volumes (2 mL/kg/%TBSA in adults) to prevent fluid creep while titrating hourly infusions to physiological endpoints.

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1. Indications for Formal Crystalloid Resuscitation

Not every burn requires aggressive intravenous fluid resuscitation. The systemic inflammatory response and capillary leak syndrome are directly proportional to the total burn size and depth. Systemic burn shock typically manifests when the burn exceeds a critical physiological threshold:

                    INDICATIONS FOR FORMAL FLUID RESUSCITATION
  ┌─────────────────────────────────────────────────────────────────────────────┐
  │ • Adults: Partial-thickness (2nd°) and Full-thickness (3rd°) burns ≥ 20% TBSA │
  │ • Pediatric Patients: Partial- and Full-thickness burns ≥ 10% to 15% TBSA    │
  │ • Older Adults (>65 years) / Significant Comorbidities: ≥ 10% to 15% TBSA    │
  │ • High-Voltage Electrical Injuries (regardless of visible cutaneous TBSA)   │
  │ • Inhalation injury combined with cutaneous burns of any measurable size   │
  └─────────────────────────────────────────────────────────────────────────────┘

[!IMPORTANT] Superficial (First-Degree) Burns Exclusion: Erythematous, epidermal-only burns (such as standard sunburns) do NOT disrupt dermal microvasculature, do NOT cause plasma extravasation, and are STRICTLY EXCLUDED from TBSA calculations when estimating fluid resuscitation volumes. Only partial-thickness (second-degree) and full-thickness (third-degree) burns are included.

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2. Core Resuscitation Formulas & Consensus Guidelines

Over the past six decades, multiple resuscitation formulas have evolved. While historical formulas calculated higher initial volumes, modern practice utilizes lower baseline estimates to mitigate iatrogenic volume overload.

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3. The Resuscitation Clock and the 8-Hour Rule

A universal rule across all burn resuscitation formulas is the strict timeline governing fluid delivery:

                                THE 24-HOUR RESUSCITATION TIMELINE
  Time of Injury                                   8 Hours Post-Injury             24 Hours Post-Injury
        │                                                  │                                  │
        ▼◄────────────────── FIRST 8 HOURS ───────────────►▼◄──────── NEXT 16 HOURS ─────────►▼
        ┌──────────────────────────────────────────────────┬──────────────────────────────────┐
        │            50% OF TOTAL 24-HOUR VOLUME           │   50% OF TOTAL 24-HOUR VOLUME    │
        │             (Infused over First 8 Hours)         │   (Infused over Next 16 Hours)   │
        └──────────────────────────────────────────────────┴──────────────────────────────────┘

The Critical Rule: Time of Injury vs. Time of Arrival

The 8-hour clock begins at the EXACT MOMENT OF INJURY, not when the patient arrives in the emergency department, when the trauma team evaluates the patient, or when IV access is established.

If there is a delay between injury and initiation of intravenous therapy:

1. Calculate the total 24-hour requirement using the selected formula.
2. Determine the volume required for the first 8 hours (50% of total 24-hour volume).
3. Subtract any prehospital or emergency intravenous fluid already administered.
4. Divide the remaining first-8-hour volume by the REMAINING HOURS left in the first 8-hour window.

[!WARNING] If a patient arrives 4 hours post-burn with no prior fluids, the entire first 8-hour volume (50% of total 24-hour requirement) must be infused over the remaining 4 hours, resulting in a doubled hourly rate for that initial period.

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4. Resuscitation Fluid Selection: Crystalloids vs. Colloids

Why Lactated Ringer's (LR) is the Fluid of Choice

Lactated Ringer's (or a balanced crystalloid such as Plasma-Lyte) is the standard resuscitation fluid in modern burn care because its electrolyte composition closely mirrors human extracellular fluid:

• Osmolarity: 273 mOsm/L (physiologically balanced)
• Sodium: 130 mEq/L
• Chloride: 109 mEq/L
• Potassium: 4 mEq/L
• Calcium: 2.7 mEq/L
• Lactate Buffer: 28 mEq/L (metabolized by the liver into bicarbonate, helping buffer metabolic acidosis without exacerbating hyperchloremia)

The Danger of 0.9% Normal Saline (0.9% NaCl)

Resuscitation with large volumes of 0.9% Normal Saline is contraindicated in major burns. Normal Saline contains 154 mEq/L of sodium and 154 mEq/L of chloride (supraphysiologic chloride). Infusing massive volumes of 0.9% NaCl causes hyperchloremic metabolic acidosis, reduces renal cortical perfusion, worsens base deficit, and creates diagnostic confusion regarding whether worsening acidosis is due to shock or chloride load.

The Role and Timing of Colloids (Albumin)

During the first 8 to 12 hours post-injury, microvascular endothelial gaps are open widely throughout burned and unburned tissues (generalized capillary leak). If colloids (such as 5% human serum albumin) are infused during this hyperpermeable phase, large protein molecules leak into the interstitial space, increasing interstitial oncotic pressure and exacerbating tissue edema.

• Colloid Rescue Window (12 to 24 Hours): Between 12 and 24 hours post-injury, endothelial capillary integrity begins to reconstitute. In patients requiring fluid volumes significantly exceeding predicted formula rates (or when fluid creep is anticipated), an infusion of 5% Albumin (0.5 to 1.0 mL/kg/%TBSA/day) or fresh frozen plasma (FFP) can be initiated to expand intravascular volume, restore intravascular oncotic pressure, and reduce overall crystalloid volume requirements.

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5. Worked Clinical Calculations & Nursing Timeline Scenarios

Scenario 1: Standard Adult Thermal Burn (Parkland vs. ABA Consensus)

• Patient: 35-year-old male, body weight = 80 kg.
• Injury: Flame burn to anterior torso (18%), entire right arm (9%), and anterior right leg (9%) = 36% TBSA partial- and full-thickness burns.
• Timing: Burn occurred at 14:00; arrives at the burn center at 16:00 (2 hours elapsed). Received 400 mL LR in prehospital transit.

                                CALCULATION BREAKDOWN (SCENARIO 1)
  1. Parkland Formula (4 mL/kg/%TBSA):
     • Total 24h Volume = 4 mL × 80 kg × 36% = 11,520 mL LR
     • First 8 Hours (50%) = 5,760 mL (covers 14:00 to 22:00)
     • Next 16 Hours (50%) = 5,760 mL (covers 22:00 to 14:00 next day)

  2. Timeline & Rate Adjustment for First 8 Hours:
     • Volume needed in first 8h: 5,760 mL
     • Volume already received: 400 mL
     • Remaining volume to deliver: 5,760 mL - 400 mL = 5,360 mL
     • Time remaining in first 8h block: 8 hours - 2 hours elapsed = 6 hours
     • Adjusted Initial Pump Rate: 5,360 mL ÷ 6 hours = 893.3 mL/hr (round to 893 mL/hr)

  3. Base Rate for Hours 8 to 24 (Next 16 Hours):
     • 5,760 mL ÷ 16 hours = 360 mL/hr (titrated hourly based on UOP)

  4. ABA Consensus Starting Rate (2 mL/kg/%TBSA):
     • Total 24h Volume = 2 mL × 80 kg × 36% = 5,760 mL LR
     • First 8h (50%) = 2,880 mL; remaining after 400 mL prehospital = 2,480 mL over 6h = 413 mL/hr
     • Next 16h (50%) = 2,880 mL over 16h = 180 mL/hr

Scenario 2: Pediatric Scald Burn (ABA Consensus + Maintenance Fluids)

• Patient: 3-year-old female, body weight = 15 kg.
• Injury: Scald burn to buttocks (4.5%), perineum (1%), and both lower legs (14.5%) = 20% TBSA partial-thickness.
• Timing: Burn occurred at 08:00; arrives at ED at 09:00 (1 hour elapsed). No prior IV fluid.

                                CALCULATION BREAKDOWN (SCENARIO 2)
  1. ABA Pediatric Resuscitation (3 mL/kg/%TBSA):
     • Total 24h Resuscitation Volume = 3 mL × 15 kg × 20% = 900 mL LR
     • First 8 Hours (50%) = 450 mL (from 08:00 to 16:00)
     • Next 16 Hours (50%) = 450 mL (from 16:00 to 08:00 next day)
     • Adjusted First 8h Rate (7 hours remaining): 450 mL ÷ 7 hours = 64.3 mL/hr of LR
     • Next 16h Rate: 450 mL ÷ 16 hours = 28.1 mL/hr of LR

  2. Pediatric Maintenance Fluid (Holliday-Segar / 4-2-1 Rule):
     • Weight = 15 kg
     • First 10 kg: 10 kg × 4 mL/kg/hr = 40 mL/hr
     • Remaining 5 kg: 5 kg × 2 mL/kg/hr = 10 mL/hr
     • Maintenance Fluid Rate = 40 + 10 = 50 mL/hr of D5 LR or D5 0.45% NS

  3. Combined Hourly Infusion (Initial 7 Hours):
     • Total IV Rate = 64.3 mL/hr (Resuscitation LR) + 50 mL/hr (Maintenance D5LR) = 114.3 mL/hr

[!NOTE] Pediatric patients <30 kg MUST receive two separate IV infusions: (1) balanced crystalloid for burn shock resuscitation titrated to urine output, and (2) dextrose-containing maintenance fluid running at a fixed hourly rate to prevent severe hypoglycemia and cerebral edema.