13.3 Acute Burns, Necrotizing Soft Tissue Infections & Severe Dermatologic Emergencies

13.3 Acute Burns, Necrotizing Soft Tissue Infections & Severe Dermatologic Emergencies

Clinical Scenario: A 44-year-old male is admitted to the burn intensive care unit following an enclosed structural fire. He sustained flame burns over his entire anterior chest and abdomen, both upper extremities, and circumferential full-thickness burns to his left thigh. Vital signs: BP 102/62 mmHg, HR 128 bpm, SpO2 96% on 100% non-rebreather. Physical exam reveals soot within the oral cavity, singed facial hair, carbonaceous sputum, and a raspy, hoarse voice. Weight is 80 kg. The acute care nurse practitioner must prioritize emergency airway stabilization, calculate total body surface area (TBSA) burns, initiate protocolized crystalloid resuscitation, and maintain vigilance for abdominal and extremity compartment syndromes.

Burn Depth Classification & Total Body Surface Area

Burn depth and total body surface area (TBSA) percentage dictate resuscitation volume and burn center referral:

Estimation of Burn Surface Area

• Adult Rule of Nines: Head: 9%; anterior torso: 18%; posterior torso: 18%; each upper extremity: 9%; each lower extremity: 18% (anterior 9%, posterior 9%); perineum: 1%.
• Palmar Surface Rule: The patient's palm and fingers equal approximately 1% TBSA, ideal for patchy burns.
• Lund-Browder Chart: Adjusts surface proportions for age, providing optimal accuracy in pediatric and adolescent patients.

Inhalation Injury & Airway Stabilization

Inhalation injury drastically increases mortality through supraglottic thermal edema, lower airway chemical irritation, and toxic asphyxiation.

Clinical Indicators & Proactive Intubation

• Supraglottic thermal injury causes rapid pharyngeal and laryngeal edema. Key signs: enclosed fire, facial burns, singed nasal hairs, soot in oral cavity, carbonaceous sputum, brassy cough, hoarseness, and stridor.
• Airway Decision: Obtain urgent experienced airway assessment. Intubate early for evolving obstruction (e.g., stridor/progressive hoarseness), respiratory failure, impaired protection or high risk of rapid deterioration; do not wait for profound hypoxia. Isolated singed hair or soot warrants assessment/monitoring rather than automatic intubation. When feasible, use a large-bore tube to facilitate bronchoscopy and secretion clearance.

Toxic Inhalants

• Carbon Monoxide (CO): Binds hemoglobin with $200\text{--}250\times$ oxygen's affinity, shifting dissociation curves leftward. Pulse oximetry ($\text{SpO}_2$) is falsely normal because sensors cannot differentiate carboxyhemoglobin from oxyhemoglobin. Confirm with co-oximetry blood gas. Treat with 100% oxygen (reduces half-life from 320 to 80 minutes). Seek hyperbaric consultation for severe clinical features or COHb above 25%–30%. Pregnancy warrants a lower threshold. Clinical severity and exposure history guide decisions.
• Cyanide Poisoning: From combustion of plastics. Blocks mitochondrial cytochrome c oxidase, causing severe lactic acidosis. Treat with IV hydroxocobalamin 5 g over 15 minutes.

Fluid Resuscitation Protocols & Physiological Titration

Severe burns (>20% TBSA) induce widespread capillary leakage, causing burn shock.

Classic Parkland Calculation and Current Initial Resuscitation

The classic Parkland calculation is shown below. Current ABA guidance favors an initial 2 mL/kg/%TBSA estimate for adults with burns ≥20% TBSA, followed by clinical titration.

$\text{24-Hour Crystalloid Volume (Lactated Ringer's)} = 4\text{ mL} \times \text{Weight (kg)} \times \%\text{TBSA (2nd and 3rd Degree)}$

• Schedule: Administer 50% of total volume in first 8 hours from TIME OF INJURY, and remaining 50% over subsequent 16 hours. (Example: 80 kg patient with 45% TBSA: $4 \times 80 \times 45 = 14,400\text{ mL}$; if 2 hours elapsed and no resuscitation fluid has been given, the Parkland starting estimate is 7,200 mL over the next 6 hours = $1,200\text{ mL/hr}$).
• Modified Brooke Formula: Uses $2\text{ mL} \times \text{kg} \times \%\text{TBSA}$, widely used to mitigate over-resuscitation.

Titration & Complications

• Urine Output Targets: Titrate IV fluids to an adult urine output of $0.5\text{ mL/kg/hr}$ ($30–50\text{ mL/hr}$). In high-voltage electrical burns with rhabdomyolysis, target $1.0–2.0\text{ mL/kg/hr}$ ($75–100\text{ mL/hr}$).
• Fluid Creep & Abdominal Compartment Syndrome (ACS): Over-resuscitation causes pulmonary edema and intra-abdominal hypertension. Check bladder pressure if fluids exceed $250\text{ mL/kg}$ in 24 hours. Sustained intra-abdominal pressure above 20 mmHg with new organ dysfunction defines ACS. Obtain urgent surgical assessment, optimize fluid balance and organ support, and decompress when indicated.
• Escharotomy: Obtain urgent burn-surgeon assessment for restrictive circumferential thoracic eschar or worsening limb perfusion. Release constrictive eschar when clinically indicated. Do not wait for absent pulses if progressive vascular compromise is evident.

Local Anesthetic Administration and Toxicity

Before local infiltration, check allergies, formulation, concentration, total dose from all sites and patient factors requiring dose reduction. Lidocaine 1% contains 10 mg/mL. For a normal healthy adult, the labeled maximum without epinephrine is 4.5 mg/kg, not exceeding 300 mg: at 50 kg, 225 mg equals 22.5 mL of 1% solution. This is a ceiling, not a target; use the lowest effective dose. Aspirate and inject incrementally while monitoring for intravascular injection and toxicity. Circumoral symptoms, tinnitus, seizures or cardiovascular instability can signal local-anesthetic systemic toxicity. Stop administration, summon help and use airway/seizure support and the ASRA lipid-emulsion rescue protocol.

Necrotizing Soft Tissue Infections (NSTI)

Necrotizing fasciitis involves rapid bacterial destruction of fascia and subcutaneous fat:

• Type I (Polymicrobial, 70–80%): Mixed anaerobes (Bacteroides, Peptostreptococcus) and aerobes (Enterobacteriaceae). Typical in elderly, diabetics, and Fournier gangrene.
• Type II (Monomicrobial, 20–30%): Group A Streptococcus (Streptococcus pyogenes [GAS]) alone or with MRSA. Affects healthy individuals after minor trauma or IV drug use; pyrogenic exotoxins trigger toxic shock syndrome.
• Clinical Hallmarks: Severe pain out of proportion to exam, spreading erythema, tense edema, bullae with hemorrhagic fluid, cutaneous anesthesia, and crepitus.
• LRINEC Score: Evaluates CRP ($\ge 150\text{ mg/L} = 4$), WBC (15–25 = 1; $>25\text{ k} = 2$), Hemoglobin (11–13.5 = 1; $<11\text{ g/dL} = 2$), Sodium ($<135\text{ mEq/L} = 2$), Creatinine ($>1.6\text{ mg/dL} = 2$), and Glucose ($>180\text{ mg/dL} = 1$). Higher scores increase concern, but performance varies. A low score cannot rule out necrotizing infection, and surgical assessment must not wait for the score.
• Emergency Management: Immediate radical operative debridement is mandatory; never delay surgery for imaging. Empiric IV antibiotics: vancomycin ($15–20\text{ mg/kg}$), piperacillin-tazobactam ($4.5\text{ g}$ q6h), and clindamycin ($900\text{ mg}$ q8h). Clindamycin binds the 50S ribosome, halting pyrogenic exotoxin and M-protein synthesis to overcome the penicillin "Eagle effect."

Exfoliative Dermatologic Emergencies: SJS & TEN

Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) are cell-mediated cytotoxic type IV hypersensitivity disorders characterized by keratinocyte apoptosis:

• Classification: SJS involves <10% TBSA detachment; SJS/TEN overlap involves 10%–30%; TEN involves >30% TBSA.
• Culprit Drugs (SATAN): Sulfonamides, Allopurinol, Tetracyclines, Anticonvulsants (carbamazepine, phenytoin, lamotrigine), and NSAIDs.
• Exam Findings: Dusky macules, flaccid blisters, positive Nikolsky sign (epidermal detachment with gentle lateral pressure), and erosive mucositis in $\ge 2$ sites (oral mucosal sloughing, purulent conjunctivitis, urogenital ulceration).
• SCORTEN Mortality Predictor: Calculated within 24 hours (1 point each: age $>40$, HR $>120$, malignancy, detached BSA $>10\%$, BUN $>28\text{ mg/dL}$, glucose $>252\text{ mg/dL}$, bicarbonate $<20\text{ mEq/L}$). Score $\ge 5$ indicates $>90\%$ mortality.
• ICU Management: Immediate drug cessation (most critical prognostic step), burn ICU admission, ambient warming ($30\text{--}32^\circ\text{C}$), non-adherent silicone dressings, urgent ophthalmology assessment, with early amniotic membrane treatment when indicated for severe ocular involvement. Dermatology and critical care teams select systemic immunomodulatory therapy according to disease severity, contraindications and current evidence.