9.3 Thermal, Chemical & Electrical Burn Assessment & Fluid Resuscitation
Key Takeaways
- Total Body Surface Area (TBSA) estimations must exclude 1st-degree (superficial) burns; utilization of the Rule of Nines or Lund-Browder chart guides fluid requirements.
- The Consensus / Parkland Formula dictates fluid resuscitation using Lactated Ringer's (2–4 mL x kg x %TBSA), delivering 50% of total volume in the first 8 hours post-injury (calculated from time of burn occurrence) and 50% over the subsequent 16 hours.
- Resuscitation fluids must be continuously titrated to maintain target urine output: 0.5–1.0 mL/kg/hr in adults, 1.0–2.0 mL/kg/hr in pediatric patients (< 30 kg), and 1.0–1.5 mL/kg/hr in high-voltage electrical injuries with myoglobinuria.
- Inhalation injury requires early endotracheal intubation with an ETT size ≥ 7.5–8.0 mm prior to progressive upper airway glottic edema; high-flow oxygen and Hydroxocobalamin must be administered for suspected Cyanide toxicity.
- Hydrofluoric acid (HF) burns cause severe localized tissue destruction and systemic binding of calcium; management mandates topical/infiltrative Calcium Gluconate to neutralize fluoride ions and prevent fatal hypocalcemic ventricular dysrhythmias.
9.3 Thermal, Chemical & Electrical Burn Assessment & Fluid Resuscitation
Burn trauma represents a complex, multi-system insult characterized by massive capillary leak, intravascular fluid loss, profound systemic inflammatory response syndrome (SIRS), and high risk for acute airway failure.
Burn Depth Assessment & Total Body Surface Area (TBSA)
Accurate classification of burn depth and TBSA is vital to prevent under- or over-resuscitation.
Classification of Burn Depth
- Superficial (1st Degree): Involves epidermis only. Red, painful, dry, no blisters. EXCLUDED from TBSA calculation for fluid resuscitation.
- Superficial Partial-Thickness (2nd Degree): Epidermis and upper dermis. Intact blisters, weeping, blanches with pressure, excruciatingly painful.
- Deep Partial-Thickness (2nd Degree): Extends into deep reticular dermis. Mixed waxy white/red, dull to pressure, sluggish capillary refill.
- Full-Thickness (3rd Degree): Complete destruction of epidermis and dermis into subcutaneous fat. Leathery, charred, dry eschar, painless (destruction of cutaneous nerve endings).
- 4th Degree: Involves underlying muscle, fascia, tendon, or bone.
TBSA Estimation Methods
- Adult Rule of Nines:
- Head and Neck: $9%$
- Each Upper Extremity (Arm): $9%$ (Anterior 4.5%, Posterior 4.5%)
- Anterior Trunk (Chest/Abdomen): $18%$
- Posterior Trunk (Back/Buttocks): $18%$
- Each Lower Extremity (Leg): $18%$ (Anterior 9%, Posterior 9%)
- Perineum / Genitalia: $1%$
- Lund-Browder Chart: Preferred in pediatric patients and definitive burn centers due to age-related changes in head-to-body surface proportions.
- Palmar Method: The patient's palm (including fingers) represents approximately $1%$ TBSA, useful for scattered, patchy burns.
Fluid Resuscitation Formulas & Administration
Burn shock causes systemic capillary leak. Resuscitation requires Lactated Ringer's (LR) (isotonic balanced salt solution) to prevent hyperchloremic acidosis.
The Consensus / Parkland Resuscitation Formula
- Thermal Burns (Adults): $2 \text{ mL} imes \text{kg} imes % \text{TBSA}$
- Thermal Burns (Children $< 14$ years or $< 30$ kg): $3 \text{ mL} imes \text{kg} imes % \text{TBSA}$ (Plus maintenance IV fluids containing D5 1/4 NS to prevent pediatric hypoglycemia)
- Electrical / Myoglobinuric Burns: $4 \text{ mL} imes \text{kg} imes % \text{TBSA}$
Timing Distribution Rule
- First 8 Hours: Administer 50% of the total calculated 24-hour volume within the first 8 hours from the time of injury (NOT the time of medical arrival).
- Next 16 Hours: Administer the remaining 50% of total volume over the subsequent 16 hours.
Urine Output Titration & Fluid Creep
Calculated Parkland volumes serve merely as a starting point. Critical care transport clinicians must titrate hourly IV rates up or down by 10–20% per hour based strictly on target end-organ perfusion.
| Patient Category | Target Hourly Urine Output (UO) |
|---|---|
| Adult Thermal Burns | $0.5 - 1.0 \text{ mL/kg/hr}$ ($30 - 50 \text{ mL/hr}$) |
| Pediatric Thermal Burns ($< 30 \text{ kg}$) | $1.0 - 2.0 \text{ mL/kg/hr}$ |
| Electrical Burns with Myoglobinuria | $1.0 - 1.5 \text{ mL/kg/hr}$ ($100 - 150 \text{ mL/hr}$ in adults) |
Warning — Fluid Creep
Over-resuscitation causes "fluid creep," leading to pulmonary edema, orbital compartment syndrome, and Abdominal Compartment Syndrome (ACS) (defined by Intra-Abdominal Pressure $> 20 \text{ mmHg}$ with organ dysfunction). If UO exceeds targets, decrease fluid rate systematically.
Inhalation Injury & Airway Management
Inhalation trauma dramatically increases burn mortality. Thermal injury causes immediate supraglottic laryngeal edema, while chemical soot inhalation causes lower airway tracheobronchitis, bronchospasm, and mucociliary arrest.
Clinical Indicators of Inhalation Injury
- History of enclosed-space fire exposure.
- Facial burns, singed nasal/facial hairs, carbonaceous sputum, soot in the oropharynx.
- Voice alteration, hoarseness, brassy cough, or audible inspiratory stridor.
Airway Intervention
- Early Intubation: Perform early endotracheal intubation before progressive glottic swelling prevents visualization. Use a large endotracheal tube ($\ge 7.5 - 8.0 \text{ mm}$ ID) in adults to permit subsequent diagnostic bronchoscopy and toilet.
- Carbon Monoxide (CO) Poisoning: Pulse oximetry ($\text{SpO}_2$) cannot distinguish carboxyhemoglobin from oxyhemoglobin. Administer $100%$ High-Flow Oxygen (reduces CO half-life from 320 minutes to 60 minutes).
- Cyanide (CN) Toxicity: Suspect in closed-space smoke inhalation presenting with persistent, unexplained severe lactic acidosis ($\text{lactate} > 8 - 10 \text{ mmol/L}$). Administer Hydroxocobalamin ($5 \text{ g}$ IV over 15 minutes), which binds cyanide to form non-toxic cyanocobalamin (Vitamin B12).
Electrical Burns & Rhabdomyolysis
High-voltage electrical injuries ($> 1000 \text{ V}$) act as deep thermal heat conductors. Internal tissue destruction (especially in deep periosteal muscle beds) far exceeds cutaneous skin entry/exit wounds.
Electrical Current Flow:
Current Entrance ---> Deep Muscle Thermal Necrosis ---> Rhabdomyolysis ---> Free Myoglobin Release
|
Acute Tubular Necrosis <--- Renal Tubular Casts
Complications & Protocol
- Myoglobinuria & Acute Kidney Injury: Massive rhabdomyolysis releases toxic myoglobin into circulation, producing dark red/brown ("tea-colored") urine. Myoglobin precipitates in renal tubules under acidic conditions.
- Resuscitation Target: Increase LR infusion rate to maintain urine output at $1.0 - 1.5 \text{ mL/kg/hr}$ ($100 - 150 \text{ mL/hr}$) until urine clears.
- Urine Alkalinization: Add $50 \text{ mEq}$ Sodium Bicarbonate per liter of IV fluid to keep urine $\text{pH} > 6.5$.
- Extremity Compartment Syndrome: Deep muscle swelling under rigid fascia requires serial neurovascular checks and early surgical escharotomy/fasciotomy.
- Cardiac Monitoring: Continuous ECG monitoring for high-voltage exposure due to risk of immediate or delayed ventricular dysrhythmias.
Chemical Burns & Hydrofluoric Acid (HF)
Decontamination Principles
- Brush Dry Powders: Dry chemicals (e.g., lime) must be brushed off completely before water lavage.
- Copious Low-Pressure Flushing: Irrigate with warm water for at least 20–30 minutes (up to 1–2 hours for alkali burns due to liquefactive necrosis).
Hydrofluoric Acid (HF) Protocol
- Mechanism: Fluoride ions penetrate deep tissue, causing intense pain out of proportion and aggressively binding systemic cations ($\text{Ca}^{2+}$ and $\text{Mg}^{2+}$).
- Lethal Complication: Severe hypocalcemia triggering refractory Ventricular Fibrillation.
- Treatment: Apply topical 2.5% Calcium Gluconate Gel (or subcutaneous infiltration of 10% Calcium Gluconate). Administer IV Calcium Chloride/Gluconate for systemic toxicity.
An 80 kg adult male patient sustained partial- and full-thickness burns to his entire anterior trunk (18%) and both anterior upper extremities (9% total) in a structure fire 2 hours ago. Using the ABA Consensus / Parkland formula (2 mL x kg x %TBSA), what is the correct hourly IV fluid infusion rate for the remaining 6 hours of the first 8-hour window?
A 35-year-old utility worker suffers a high-voltage electrical burn with deep arm swelling and dark brown, tea-colored urine. What is the primary urine output target for titrating resuscitation fluids in this patient?
A chemical worker sustains a hydrofluoric acid (HF) splash burn to both hands and presents with excruciating, deep throbbing pain out of proportion to visible skin lesions. Which therapy is specifically indicated to neutralize the chemical agent?