83 BURNS

Detailed notes

Burns are among the most lethal mechanisms of trauma, killing not by the wound itself but by the systemic chaos that follows — massive fluid shifts, immune collapse, hypermetabolism and infection. For MRCS Part A you are expected to know the pathophysiology, how to estimate burn size and depth, how to resuscitate, when to escalate, and how to recognise the deceptive injuries (electrical, inhalational, chemical) that kill patients who look superficially well.

Pathophysiology — Jackson's burn zones

Jackson described three concentric zones around a burn. Understanding them tells you why early resuscitation matters.

➡ Zone of coagulation — central, point of maximum damage. Proteins are denatured and tissue is irreversibly necrotic. Nothing you do will save it.

➡ Zone of stasis — surrounds the coagulated core. Tissue here is hypoperfused but viable. With adequate resuscitation it recovers; with hypovolaemia, sepsis or oedema it converts to necrosis, deepening the burn over 24–48 hours. This is the zone you are resuscitating to save.

➡ Zone of hyperaemia — outermost. Vasodilated, inflamed, but fully reversible. Recovers spontaneously unless infection intervenes.

The systemic response is biphasic: an initial hypovolaemic "ebb" phase from massive capillary leak (peaking 6–12 h), followed after 24–48 h by a hypermetabolic "flow" phase with high cardiac output, catabolism and immune dysfunction.

Burn depth

Depth determines healing potential and whether grafting is needed. Examiners love asking you to match clinical signs to depth.

Depth	Layer	Appearance	Sensation	Capillary refill	Blisters	Healing
Epidermal (1st°)	Epidermis only	Dry, red (erythema)	Painful	Brisk	None	5–7 d, no scar (sunburn)
Superficial partial (2a)	Upper dermis	Pink, moist, blisters	Very painful	Brisk	Yes	7–14 d, minimal scar
Deep partial (2b)	Deep dermis	Waxy white/red, dry	Painful but reduced	Sluggish/absent	May be present	>3 weeks, scars — graft often needed
Full thickness (3rd°)	Through dermis	White, leathery, charred	Painless (nerves destroyed)	Absent	None	Will not heal — excision + graft

👩‍⚕️ The classic exam trap: a painless burn is deep, not mild. Loss of pain means the dermal nociceptors have been destroyed.

➡ Epidermal burns are not included in %TBSA calculations.

Estimating burn size (%TBSA)

Three methods — know all three.

➡ Wallace rule of 9s (adult): head 9%, each arm 9%, each leg 18%, anterior trunk 18%, posterior trunk 18%, perineum 1%. Quick but inaccurate in children (proportionally larger heads).

➡ Palmar method — the patient's palm including fingers is approximately 1% TBSA. Useful for small or scattered burns.

➡ Lund–Browder chart — adjusts for age. Most accurate, mandatory in paediatrics.

[Image: Wallace rule of 9s diagram showing adult and paediatric percentages]

Fluid resuscitation — the Parkland formula

Parkland: 4 mL × weight (kg) × %TBSA = total crystalloid in first 24 hours.

Half is given in the first 8 hours from the time of injury (not time of presentation — if they arrive 2 hours late, you have 6 hours left), and half over the next 16 hours.

➡ Fluid of choice: Hartmann's solution (lactated Ringer's).

➡ Only burns ≥15% in adults (≥10% in children) require formal Parkland resuscitation.

➡ Titrate to urine output: 0.5 mL/kg/h in adults, 1 mL/kg/h in children, 1–2 mL/kg/h in children under 30 kg or electrical burns with myoglobinuria.

👩‍⚕️ Urine output — not blood pressure, heart rate or CVP — is the single best bedside guide. Blood pressure can be preserved long after the kidneys have started to fail.

Over-resuscitation ("fluid creep") is now the bigger killer than under-resuscitation, causing pulmonary oedema, abdominal compartment syndrome and orbital compartment syndrome.

Primary survey — ATLS approach

Burns are trauma. Follow A–E.

A — Airway with C-spine control. This is where burns kill quickly. Look for:

- Singed nasal vibrissae or facial hair

- Soot in nostrils, mouth or sputum (carbonaceous sputum)

- Hoarseness, stridor or change in voice

- Facial or circumoral burns

- Burns sustained in an enclosed space

- Reduced GCS

Any of these warrants early intubation before airway oedema closes the larynx — within an hour it may be impossible to pass a tube.

B — Breathing. 100% oxygen via non-rebreather. Check for circumferential chest burns restricting ventilation (need escharotomy).

C — Circulation. Two large-bore IV lines (through unburned skin if possible). Start Parkland.

D — Disability. GCS, pupils, glucose. Reduced consciousness suggests hypoxia, CO or cyanide.

E — Exposure. Remove all clothing and jewellery; estimate %TBSA; keep warm — burns patients lose heat catastrophically.

Inhalation injury

Three distinct pathologies, often combined:

➡ Thermal injury to upper airway — supraglottic oedema. The lower airway is protected by the heat-exchanging nasopharynx unless steam is inhaled.

➡ Carbon monoxide poisoning — CO binds haemoglobin with 240× the affinity of oxygen. Standard pulse oximetry reads falsely normal because it cannot distinguish carboxyhaemoglobin from oxyhaemoglobin. Classic "cherry-red" skin is a late sign. Treat with 100% oxygen (reduces CO half-life from ~4 hours to ~80 minutes); hyperbaric oxygen if levels >25%, neurological symptoms, or pregnancy.

➡ Cyanide toxicity — from combustion of synthetic materials (plastics, foam furniture). Inhibits cytochrome oxidase → high lactate with normal PaO₂. Treat with hydroxocobalamin.

👩‍⚕️ A patient pulled from a house fire with normal SpO₂ but obtunded and acidotic has CO ± cyanide until proven otherwise. SpO₂ lies in CO poisoning.

Referral to a specialist burns centre

Refer if any of the following:

- >10% TBSA in adults, >5% in children

- Deep partial-thickness (2b) or full-thickness

- Burns to face, hands, feet, perineum, genitalia or major joints

- Circumferential burns

- Electrical (including lightning) or chemical burns

- Inhalation injury

- Burns in extremes of age, pregnancy, significant comorbidity

- Suspected non-accidental injury

Escharotomy

Circumferential full-thickness burns form a rigid, inelastic eschar. As tissue oedema rises beneath it, the eschar acts like a constricting band, causing:

➡ Limb compartment syndrome → ischaemia distally (loss of pulses, pain, pallor)

➡ Chest eschar → restrictive ventilatory failure

➡ Neck eschar → airway and venous obstruction

Treatment is escharotomy — full-thickness longitudinal incision through the eschar down to subcutaneous fat (not fasciotomy unless compartments are also tight). Performed at the bedside; the eschar itself is insensate.

[Image: escharotomy incision lines on upper limb, chest and lower limb]

Wound management

➡ Cool with running water at 15–25°C for 20 minutes; effective up to 3 hours post-injury. Do not use ice — causes vasoconstriction and deepens the burn.

➡ Cover with cling film (laid on, not wrapped tightly) — analgesia, prevents contamination, transparent for assessment.

➡ Topical silver sulfadiazine (Flamazine) reduces colonisation; avoid on the face and in sulphonamide allergy.

➡ Early excision and grafting of deep burns within 5 days improves survival, reduces sepsis and shortens hospital stay.

➡ Tetanus prophylaxis as for any contaminated wound.

Special burn mechanisms

Chemical burns

- Brush off dry powder before irrigation (water activates some agents, e.g. elemental sodium).

- Irrigate copiously with water for at least 20 minutes (longer for alkali).

- Alkalis penetrate deeper than acids because they cause liquefactive necrosis; acids cause coagulative necrosis which forms a protective eschar. Counter-intuitive but heavily tested.

- Hydrofluoric acid — calcium gluconate gel.

Electrical burns

- The skin entry/exit wounds underestimate damage. Current travels through deep tissues (muscle, nerve, vessel) causing extensive necrosis.

- Cardiac arrhythmias — ECG and cardiac monitoring; AC current (domestic) is more arrhythmogenic than DC.

- Rhabdomyolysis → myoglobinuria → AKI. Target urine output 1–2 mL/kg/h; consider alkalinisation.

Non-accidental injury — suspect with: glove-and-stocking scald (forced immersion), sharply demarcated buttock/perineum burns, cigarette burns, burns inconsistent with history, delayed presentation.

Complications

➡ Hypothermia — large burns lose evaporative heat rapidly; warm the room and the fluids.

➡ Sepsis — leading cause of late death; burn wound is the commonest source (Pseudomonas, Staph aureus).

➡ Curling's ulcer — acute gastric/duodenal stress ulcer post-burn. Give PPI prophylaxis. (Contrast: Cushing's ulcer = post-head injury, vagally driven hyperacidity.)

➡ AKI — early from hypovolaemia; later from myoglobinuria (electrical, full-thickness) or sepsis.

➡ Pulmonary oedema / ARDS — over-resuscitation or inhalation injury.

➡ Abdominal compartment syndrome — over-resuscitation in large burns.

➡ Contractures and hypertrophic scarring — long-term; require physiotherapy, splinting, reconstruction.

👩‍⚕️ Curling = burns. Cushing = brain. Both stress ulcers, both Cs — but very different mechanisms.

[Image: MCQs banner]

Test yourself

A burn patient of 80 kg has burns over both forearms and both anterior thighs. How much fluid is required in the first 24 hours?

• ((4 L::Underestimate — recheck the TBSA total.))
• ((5 L::Underestimate — both forearms plus both anterior thighs total 18%.))
• ((6 L::☑️ 4 × 80 × 18 = 5760 mL ≈ 6 L. Each forearm 4.5%, each anterior thigh 4.5%.))
• ((8 L::Overestimate — would correspond to ~25% TBSA.))
• ((10 L::Overestimate — would correspond to >30% TBSA.))

👩‍⚕️ Forearm = 4.5% (half an arm); anterior thigh = 4.5% (quarter of a leg).

A 90 kg man has burns over one lower limb and the perineum. How much fluid is required in the first 24 hours?

• ((5 L::Underestimate — TBSA is 19% (18% + 1%).))
• ((7 L::☑️ 4 × 90 × 19 = 6840 mL ≈ 7 L. Lower limb 18%, perineum 1%.))
• ((9 L::Overestimate.))
• ((10 L::Overestimate — that figure would imply ~28% TBSA.))

A 70 kg patient arrives 2 hours after a 40% TBSA burn. Over what period must the first half of Parkland fluid be delivered?

• ((Next 8 hours from arrival::Parkland is timed from injury, not from arrival.))
• ((Next 6 hours from arrival::☑️ Half (5600 mL) must be delivered by 8 h post-injury — 2 h have elapsed.))
• ((Next 4 hours from arrival::Too fast — risks fluid overload.))
• ((Next 16 hours::This is the schedule for the second half.))
• ((Next 24 hours::This would deliver only the full 24 h total, not the first half.))

👩‍⚕️ Classic exam trap — the 8-hour clock starts at the burn, not at the door.

In burn resuscitation, fluid therapy is primarily titrated to which parameter?

• ((Heart rate::Useful trend but tachycardia persists from pain and catecholamines.))
• ((Blood pressure::Preserved late by vasoconstriction — falls only when shock is advanced.))
• ((Central venous pressure::Invasive, poor correlation with volume status in burns.))
• ((Urine output::☑️ Target 0.5–1 mL/kg/h adult, 1 mL/kg/h paediatric — best end-organ marker.))
• ((Serum lactate::Useful adjunct but lags behind and is confounded by cyanide toxicity.))

A patient pulled from a house fire has no visible burns, SpO₂ 99% on air, GCS 7. What is the most appropriate immediate management?

• ((Observe with serial GCS::Inadequate — airway is at imminent risk.))
• ((High-flow oxygen alone::Necessary but insufficient if GCS ≤8.))
• ((Intubate and ventilate with 100% oxygen::☑️ GCS ≤8 mandates intubation; 100% O₂ also reduces CO half-life from ~4 h to ~80 min.))
• ((Hyperbaric oxygen first::Airway must be secured before transfer.))
• ((Nebulised salbutamol::Treats bronchospasm, not the underlying problem.))

👩‍⚕️ SpO₂ is falsely reassuring in CO poisoning — the oximeter cannot distinguish carboxyhaemoglobin from oxyhaemoglobin.

Which feature most reliably indicates a full-thickness burn?

• ((Blister formation::Typical of superficial partial-thickness.))
• ((Brisk capillary refill::Suggests superficial burn with preserved dermal circulation.))
• ((Bright erythema::Feature of epidermal burns (e.g. sunburn).))
• ((Painless, leathery white skin::☑️ Nerve endings destroyed → no pain; coagulated dermis → leathery white/charred.))
• ((Severe pain on light touch::Hallmark of superficial partial-thickness.))

A patient with 45% TBSA burns develops rising airway pressures and falling tidal volumes 12 hours into resuscitation. Examination shows a circumferential full-thickness chest burn. Best management?

• ((Increase PEEP::Treats the symptom, not the constricting eschar.))
• ((Bronchoscopy::Useful for inhalation injury but won't relieve external restriction.))
• ((Bedside escharotomy::☑️ Longitudinal incisions through the eschar relieve restriction immediately.))
• ((Fasciotomy::Eschar is superficial to fascia — escharotomy first.))
• ((Emergency thoracotomy::Inappropriate — the problem is the chest wall, not intrathoracic.))

👩‍⚕️ Eschar is insensate — escharotomy is done at the bedside without anaesthesia.

Two days after a 50% TBSA burn, a patient develops haematemesis. The most likely cause is:

• ((Mallory–Weiss tear::Possible but uncommon without forceful vomiting.))
• ((Curling's ulcer::☑️ Stress-induced gastroduodenal ulceration following major burns. PPI prophylaxis is standard.))
• ((Cushing's ulcer::Associated with raised intracranial pressure, not burns.))
• ((Oesophageal varices::No suggestive history.))
• ((Dieulafoy lesion::Rare; not specifically associated with burns.))

Which chemical burn typically causes the deepest tissue damage?

• ((Hydrochloric acid::Coagulative necrosis forms a protective eschar limiting depth.))
• ((Sulphuric acid::Same mechanism — coagulative.))
• ((Sodium hydroxide (alkali)::☑️ Alkalis cause liquefactive necrosis and penetrate deeply through saponification of fats.))
• ((Acetic acid::Weak acid — minimal injury.))
• ((Phenol::Significant but not as deep as strong alkalis.))

👩‍⚕️ Counter-intuitive but heavily tested: alkali burns penetrate deeper than acid burns.

A man sustains a 15% TBSA flash burn while working on a domestic electrical panel. Entry wound on the right hand, exit on the left foot. Urine is dark brown. Most important early intervention?

• ((Topical silver sulfadiazine::Useful for wound care but not the priority.))
• ((Aggressive IV fluids targeting urine output 1–2 mL/kg/h::☑️ Rhabdomyolysis from current passing through deep muscle — prevent AKI from myoglobinuria.))
• ((Urgent fasciotomy of all four limbs::Reserved for evidence of compartment syndrome.))
• ((Hyperbaric oxygen::No role in electrical injury.))
• ((Immediate dialysis::Premature — preventive fluids first.))

Which of the following burns can be excluded from the %TBSA calculation when prescribing Parkland fluid?

• ((Simple erythema (epidermal)::☑️ Epidermal (first-degree) burns are not counted in TBSA.))
• ((Blistering on the forearm::Superficial partial-thickness — counts.))
• ((Waxy white burn on the thigh::Deep partial-thickness — counts.))
• ((Charred area on the chest::Full-thickness — counts.))
• ((Circumferential burn of the wrist::Counts and may need escharotomy.))

Revision summary

➡ Zones: coagulation (dead) → stasis (salvageable, the resus target) → hyperaemia (reversible).

➡ Depths: epidermal (red, painful) | 2a (blisters, painful, blanches) | 2b (waxy, reduced sensation) | 3rd (white/leathery, painless).

➡ TBSA: rule of 9s (adult), palm = 1%, Lund–Browder (paeds, most accurate). Don't count epidermal burns.

➡ Parkland: 4 mL × kg × %TBSA Hartmann's; half in first 8 h from injury; titrate to urine output 0.5–1 mL/kg/h (1–2 in paeds/electrical).

➡ Airway: intubate early for facial burns, hoarseness, soot, stridor, enclosed-space, GCS ≤8.

➡ CO poisoning: SpO₂ falsely normal; treat 100% O₂ → hyperbaric if severe. Cyanide: hydroxocobalamin.

➡ Refer: >10% adult / >5% paeds, ≥2b, face/hands/feet/perineum/joints, circumferential, electrical, chemical, inhalation, NAI.

➡ Escharotomy for circumferential full-thickness causing limb ischaemia or ventilatory restriction — bedside, insensate.

➡ Chemical: alkali > acid in depth (liquefactive necrosis).

➡ Electrical: deep > superficial damage; arrhythmias; rhabdomyolysis → AKI.

➡ Complications: Curling's ulcer, sepsis, AKI, ARDS, hypothermia, contractures.

➡ Cool 20 min within 3 h; cling film; early excision and graft.