GC190 I Have A Scald Burn
A scald burn is a thermal injury to the skin and underlying tissues caused by contact with hot liquids or steam, commonly classified by depth as superficial, partial-thickness, or full-thickness.
I Have a Scald: Burn
This lecture (GC 190) is delivered by Dr. Velda Chow from the Division of Plastic and Reconstructive Surgery, HKU/QMH. It is a comprehensive surgical lecture covering the assessment and management of burn injuries — from initial assessment through fluid resuscitation, inhalational injury, electrical and chemical burns, paediatric burns, transfer criteria, and advances in burn management. [1]
The big idea: Burns are not just a "wound" — they are a systemic disease. A scald/burn triggers local tissue destruction AND a systemic inflammatory response. Your job is to (1) assess depth and extent accurately, (2) resuscitate appropriately, (3) identify life-threatening complications early (airway compromise, compartment syndrome, cardiac arrest in electrical burns), and (4) manage the wound definitively while coordinating multidisciplinary care.
How this fits into exams: Burns questions typically appear as SAQs (fluid resuscitation calculations, escharotomy indications, inhalational injury signs) or MCQs (burn depth classification, Rule of Nines, Parkland formula). The 2017 Fourth Summative SAQ Q9 tested crush syndrome — closely related to compartment syndrome and fasciotomy concepts taught here. Paediatric burns overlap with child abuse (GC 143) and paediatric surgery (GC 203). [2]
Before discussing burns, understand what you're losing when skin is destroyed: [1]
| Function of Skin | Consequence When Lost |
|---|---|
| Protection from infection and injury | Open portal for bacteria → burn wound sepsis |
| Prevent loss of body fluid | Massive evaporative water and protein loss → hypovolaemic shock |
| Regulation of body temperature | Hypothermia (especially paediatric patients) |
| Sensory contact with environment | Loss of pain/touch → risk of further unnoticed injury |
High Yield: The four functions of skin — infection barrier, fluid barrier, thermoregulation, sensation — are directly from the lecture slide and explain every systemic complication of burns. [1]
When heat is applied to tissue, the damage is not uniform. Jackson described three concentric zones: [1]
Why this matters clinically:
- Zone of Coagulation: Cells are dead — coagulation necrosis. Nothing you do saves this tissue. This is the centre of the burn. [1]
- Zone of Stasis: This is the critical zone. Cells are injured, blood flow is sluggish. If you under-resuscitate, allow infection, or let oedema compress vessels, this zone converts to irreversible necrosis (i.e., the burn gets deeper/wider). This is WHY aggressive early fluid resuscitation matters. [1]
- Zone of Hyperaemia: Peripheral zone with inflammatory vasodilation. Minimal cellular injury; will recover spontaneously unless complicated by sepsis or prolonged shock. [1]
Clinical Pearl
The zone of stasis is the therapeutic target. Everything you do in the first 24-48 hours — fluid resuscitation, wound care, avoiding infection, keeping the patient warm — is about preventing this zone from converting to coagulation necrosis.
Major burns (typically > 20% TBSA in adults, > 10% in children) trigger a systemic inflammatory response syndrome (SIRS) that goes far beyond the wound: [1]
- Massive capillary leak → oedema, hypovolaemia (even in non-burned tissues)
- Catecholamine surge → tachycardia, vasoconstriction
- Hypermetabolic state → increased oxygen consumption, muscle catabolism, negative nitrogen balance
- Immunosuppression → susceptibility to sepsis
- GI mucosal breakdown → stress ulceration (Curling's ulcer), bacterial translocation
- Haematological changes → haemoconcentration early, then anaemia later
This systemic response is why burn patients die from organ failure and sepsis, not just from the wound itself.
Burn Assessment
The two pillars of burn wound assessment are depth and extent (TBSA%). [1]
| Depth | Old Term | Structures Involved | Appearance | Sensation | Healing | Management |
|---|---|---|---|---|---|---|
| Superficial | 1st degree | Epidermis only | Red, dry, no blisters (like sunburn) | Painful | 3–7 days, no scar | Conservative (moisturiser) |
| Superficial partial thickness | Superficial 2nd degree | Epidermis + superficial dermis | Blisters, pink/red moist base, blanches with pressure | Very painful | 7–14 days, minimal scar | Conservative (dressing) |
| Deep partial thickness | Deep 2nd degree | Epidermis + deep dermis (adnexal structures partially destroyed) | Mottled pink/white, less blanching, may have blisters | Reduced sensation | 14–21+ days, significant scarring | Surgery — debridement ± skin graft |
| Full thickness | 3rd degree | Entire epidermis and dermis destroyed | White/waxy/leathery/charred, does not blanch | Insensate | Will not heal spontaneously (no remaining epithelial elements) | Surgery — excision and skin graft |
High Yield: The lecture slide groups management into Conservative (dressing) vs. Surgery (debridement + skin graft). The critical decision point is distinguishing superficial partial thickness (conservative) from deep partial thickness/full thickness (surgical). [1]
Why is deep partial thickness tricky?
- Adnexal structures (hair follicles, sweat glands) are partially preserved → some epithelialisation can occur but it takes > 3 weeks and produces poor-quality, hypertrophic scar
- If you wait too long, you get contractures and keloids; early surgery produces better functional and cosmetic outcomes
- Indocyanine green (ICG) angiography is an advance mentioned in the lecture to help distinguish superficial vs. deep dermal burns by assessing perfusion [1]
The lecture emphasises three methods: [1]
| Method | Description | Best Use |
|---|---|---|
| Rule of Nines (Wallace) | Body divided into regions of 9% (or multiples): Head 9%, each arm 9%, anterior trunk 18%, posterior trunk 18%, each leg 18%, perineum 1% | Quick adult estimation |
| Lund & Browder Chart | More accurate; accounts for age-related body proportion changes (especially head vs. legs in children) | Gold standard, especially paediatric |
| Patient's palm (including fingers) | ≈ 1% TBSA | Scattered/small burns |
Paediatric TBSA Adjustment
Children have proportionally larger heads and smaller legs than adults. A child's head = up to 18% TBSA (vs 9% in adults). The Lund & Browder chart MUST be used for accurate paediatric TBSA estimation. Using adult Rule of Nines in children will underestimate head burns and overestimate leg burns.
Important: Only count partial-thickness and full-thickness burns in the TBSA calculation. Superficial (first-degree/erythema-only) burns are NOT included in TBSA% for fluid resuscitation purposes.
Burn Wound Management
- Dressing — the mainstay for superficial and superficial partial-thickness burns [1]
- Aims: moist wound healing environment, prevent infection, absorb exudate, protect from mechanical trauma
- Common dressings: silver sulfadiazine cream, Aquacel Ag, paraffin gauze, biological dressings
- Daily or alternate-day dressing changes with wound inspection
- Debridement — removal of devitalized/necrotic tissue (eschar) [1]
- Skin graft — coverage of debrided wound bed [1]
- Split-thickness skin graft (STSG): most commonly used; epidermis + partial dermis from donor site; donor site re-epithelialises
- Full-thickness skin graft (FTSG): epidermis + full dermis; used for cosmetically/functionally important areas (face, hands); donor site needs primary closure
- Cryo-preserved cadaveric skin (from skin bank) — temporary biological dressing for large burns when autograft donor sites are limited [1]
Circumferential Burns and Escharotomy
High Yield: Circumferential full-thickness burns create a constricting, non-elastic eschar that acts like a tourniquet. [1]
| Feature | Detail |
|---|---|
| Indication | Circumferential full-thickness burn with signs of vascular/respiratory compromise |
| Where | Bedside (emergency; do NOT delay for operating theatre) |
| How | Incision through eschar down to subcutaneous fat; bloodless (full-thickness burn = thrombosed vessels) |
| Tool | Diathermy cautery |
| Anaesthesia | Often not needed for full-thickness eschar (insensate); may need sedation |
| Location | Along mid-lateral/mid-medial lines of limbs; along anterior axillary lines for chest |
Why is it "bloodless"? Because full-thickness burns have destroyed all dermal blood vessels. You are cutting through dead tissue. If there is significant bleeding, you may be cutting too deep or the burn may be less deep than estimated.
| Feature | Escharotomy | Fasciotomy |
|---|---|---|
| Depth of incision | Through eschar to subcutaneous fat | Through fascia into muscle compartments |
| Indication | Circumferential burn constriction | Compartment syndrome (especially electrical burns) |
| Setting | Bedside | General anaesthesia (in OT) |
| Cause | Tight eschar | Elevated compartment pressure from muscle oedema/necrosis |
Compartment syndrome signs (5 Ps): Paresthesia, Pain (on passive stretch), Pallor, Pulselessness, Paralysis [1]
- Compartment pressure measurement confirms diagnosis
- Fasciotomy must be done urgently to prevent irreversible muscle/nerve damage
- Last resort for non-viable, unsalvageable limbs (typically severe electrical burns or very extensive full-thickness burns with tissue mummification)
Fluid Resuscitation
Burns > 20% TBSA (adults) or > 10% TBSA (children) cause massive capillary leak → intravascular volume depletion → hypovolaemic shock → organ failure if untreated. The zone of stasis converts to coagulation necrosis without adequate perfusion.
| Component | Detail |
|---|---|
| Fluid type | Crystalloid — Lactated Ringer's (Hartmann's) solution |
| Total volume in first 24 hours | 2–4 mL × body weight (kg) × TBSA (%) |
| Distribution | ½ given in the first 8 hours post-injury |
| ½ given in the next 16 hours post-injury |
Key points to understand:
- The "first 8 hours" is counted from the time of injury, NOT from the time of arrival at hospital. If a patient arrives 3 hours after the burn, you have only 5 hours left to give the first half.
- Lactated Ringer's is preferred over normal saline because it is more physiological (lower chloride content → less hyperchloraemic metabolic acidosis).
- The formula is a starting guide — actual fluid rate must be titrated to urine output.
Under- vs Over-Resuscitation
Under-resuscitation: Organ hypoperfusion → acute kidney injury, conversion of zone of stasis, multi-organ failure. [1]
Over-resuscitation (Fluid Creep): Abdominal compartment syndrome, pulmonary oedema, cerebral oedema, worsened extremity oedema compromising perfusion. This is a real and dangerous iatrogenic complication. The Parkland formula is a GUIDE, not a rigid prescription. Titrate to urine output. [1]
Worked example:
- 70 kg man with 40% TBSA burn
- Parkland: 4 mL × 70 × 40 = 11,200 mL in 24 hours
- First 8 hours: 5,600 mL → rate ~700 mL/hr
- Next 16 hours: 5,600 mL → rate ~350 mL/hr
- Monitor urine output → target 0.5 mL/kg/hr = 35 mL/hr
Inhalational Injury
High Yield: "Dysfunction within the respiratory tract during the first 5 days after inhaling smoke and irritating products of incomplete combustion." [1]
- It is the leading cause of death in fire-related injuries
- It increases fluid requirements by 40-50% above the Parkland formula estimate
- It dramatically increases mortality at any given TBSA
| Clue | Why It Matters |
|---|---|
| Conscious level | Decreased consciousness → unable to protect airway; also suggests CO/cyanide poisoning |
| Noxious chemicals | Burning plastics → HCN, HCl, phosgene; specific toxicities |
| Closed space | Enclosed environment → higher concentration of smoke/toxins; much higher risk than open-air burns |
High Yield:
- Singed facial hairs (eyebrows, nasal vibrissae)
- Carbonaceous sputum
- Hoarseness
- Elevated carboxyhaemoglobin (COHb) levels
Why hoarseness? Supraglottic structures (epiglottis, aryepiglottic folds) are highly vascular and swell rapidly when exposed to heat → airway narrows → stridor and hoarseness are LATE signs (if present, intubation is urgent).
Why COHb? CO binds haemoglobin with 240× the affinity of O₂ → left-shifts the oxyhaemoglobin dissociation curve → tissue hypoxia. Pulse oximetry is UNRELIABLE (reads COHb as oxyHb → falsely normal SpO₂). Must use co-oximetry on ABG.
| Step | Rationale |
|---|---|
| Early intubation | Airway oedema progresses rapidly; if you wait for obstruction, it may be too late to intubate. Preventive intubation when clinical suspicion is high. |
| Humidified high-flow oxygen (100%) | Treats CO poisoning — reduces CO half-life from 4-5 hours (on room air) to ~60-90 minutes (on 100% O₂). Also maintains oxygenation. |
CO Poisoning — Don't Trust SpO2
Standard pulse oximetry cannot distinguish COHb from OxyHb. A patient with severe CO poisoning can have SpO₂ reading 99% while actually being profoundly hypoxic. Always use co-oximetry (ABG) to measure COHb directly.
Electrical Burns
High Yield: "The grand masquerader" — surface appearance dramatically underestimates the depth and extent of tissue destruction. [1]
Electricity flows through tissues of least resistance (nerves > blood vessels > muscle > skin > bone > fat). Deep tissues (muscle) sustain massive damage while the skin wound may look deceptively small (entry and exit wounds only).
| Factor | Detail |
|---|---|
| High vs. low voltage | High voltage (> 1000V) → more severe deep tissue injury |
| Type of current | AC (alternating current) vs DC (direct current) — AC causes tetanic muscle contraction → victim cannot let go → prolonged contact → more damage; AC also more likely to cause cardiac arrhythmias |
| Pathway of flow | Transthoracic pathway → cardiac arrest; Arcing/Flash burns = external thermal injury without current passing through body |
| Duration of contact | Longer contact → more energy transfer → more tissue destruction |
| Local tissue resistance | Wet skin has lower resistance → more current penetrates; bone has high resistance → generates heat at bone-muscle interface → deep muscle necrosis |
- Loss of consciousness (brain injury from current flow)
- Cardiac/pulmonary arrest at scene (ventricular fibrillation from AC; asystole from DC)
- Paralysis/mummification of extremity (irreversible tissue destruction)
- Flexor surface burns (tetanic contraction causes flexion → current entry on palm/flexor surface)
- Compartment syndrome (massive muscle oedema)
- Myoglobinuria (rhabdomyolysis from muscle necrosis → dark "tea/cola-coloured" urine)
| Step | Rationale |
|---|---|
| Airway protection | May have facial/neck burns; oedema |
| Cardiac monitoring | ECG monitoring for arrhythmia/asystole — all high-voltage electrical burn patients need continuous cardiac monitoring for at least 24 hours |
| Fluid resuscitation | Needs MORE fluid than the Parkland formula predicts (because surface TBSA underestimates true tissue damage). Target urine output 1-2 mL/kg/hr (double the standard adult target) to prevent myoglobin-induced AKI |
| Forced diuresis / Sodium bicarbonate and mannitol | Myoglobin is nephrotoxic (precipitates in renal tubules, especially in acidic urine). NaHCO₃ alkalinises urine → keeps myoglobin soluble. Mannitol → osmotic diuresis → flushes myoglobin through tubules faster |
| Compartment syndrome → Fasciotomy | Under GA; decompress muscle compartments |
Electrical Burns vs Thermal Burns - Key Differences
- Surface area grossly underestimates injury
- Parkland formula underestimates fluid needs
- Myoglobinuria/rhabdomyolysis is a major concern (not typical in thermal burns)
- Cardiac monitoring is mandatory
- Fasciotomy (not just escharotomy) is often needed
Chemical Burns
| Agent | Mechanism |
|---|---|
| Alkalis | Liquefaction necrosis and protein denaturation — alkalis penetrate DEEPER because liquefaction allows continued penetration into tissues (worse than acids!) |
| Acids | Coagulation necrosis and protein precipitation — the coagulum acts as a barrier limiting further penetration (self-limiting to some degree) |
| Organic compounds | Fat solvent action + systemic renal and hepato-toxicity (e.g., phenol, petroleum products) |
Clinical pearl: Alkali burns are generally MORE dangerous than acid burns of equivalent concentration because they penetrate deeper.
- Agent (type of chemical)
- Concentration
- Volume
- Duration of contact
| Step | Rationale |
|---|---|
| Removal of contaminated clothing | Stops ongoing exposure; clothing traps and holds chemical against skin |
| Immediate continuous irrigation with water | Dilution is the solution — copious water irrigation for at least 20-30 minutes (some sources say until pH normalises). Do NOT try to neutralise (exothermic reaction → thermal injury on top of chemical injury) |
| Early surgical debridement | Chemical burns often deeper than initially apparent; necrotic tissue must be removed |
Never Neutralise a Chemical Burn
Do NOT apply acid to an alkali burn or vice versa. The neutralisation reaction is exothermic and will cause additional thermal injury. The correct treatment is always copious water irrigation.
Special cases:
- Hydrofluoric acid (HF): Penetrates deeply; sequesters calcium → systemic hypocalcaemia → cardiac arrest. Treat with topical/injected calcium gluconate.
- Elemental metals (sodium, potassium, lithium): React violently with water. Brush off dry particles first, then irrigate.
- Cement: Alkali burn; prolonged contact through clothing/boots.
Paediatric Burns
- Scald injuries are the most common burn type in children (hot water, hot drinks, cooking oil)
- Flame burns — less common but often more severe
- Electric burns — especially toddlers biting electrical cords
- Child abuse/neglect — a critical consideration in every paediatric burn
| Feature | Clinical Implication |
|---|---|
| Relatively greater surface area per unit of body weight | Faster heat loss → hypothermia; higher fluid requirements per kg |
| Thinner dermal layer | Same thermal exposure produces DEEPER burns than in adults |
| Impaired capacity for thermal regulation | Greater risk of hypothermia |
| Less metabolic reserve | Faster depletion of glycogen stores → hypoglycaemia |
High Yield: Paediatric burn management priorities:
- Airway (smaller airway → obstructs faster with oedema)
- Hypothermia (wrap exposed areas, warm fluids, warm room)
- Hypoglycaemia (check blood glucose frequently; provide dextrose-containing maintenance fluids)
- Fluid resuscitation — Urine output target: 1 mL/kg/hr (double the adult target of 0.5 mL/kg/hr)
Children need BOTH resuscitative fluid AND maintenance fluid (unlike adults who usually get resuscitation fluid only):
Resuscitative fluid:
3–4 mL × weight (kg) × TBSA (%) — Lactated Ringer's
Maintenance fluid (D5LR — dextrose 5% in Lactated Ringer's): [1]
| Weight | Rate |
|---|---|
| First 10 kg body weight | 100 mL/kg/day |
| Second 10 kg (11–20 kg) | 50 mL/kg/day |
| Each kg above 20 kg | 20 mL/kg/day |
This is the Holliday-Segar formula for maintenance fluids. It is added ON TOP of the resuscitative fluid.
Why D5LR for maintenance? Children have low glycogen reserves → prone to hypoglycaemia during the stress of a major burn. The dextrose provides a glucose source.
Always consider non-accidental injury (NAI) in paediatric burns. Red flags include:
- Delay in presentation — brought to hospital hours or days after injury
- Inconsistent history — mechanism doesn't match burn pattern
- "Stocking/glove" distribution — symmetrical, well-demarcated burns on feet/hands (forced immersion)
- Contact burns — circular cigarette burns, iron-shaped burns
- Perineal/buttock burns — forced sitting in hot water ("toilet training punishment")
- Multiple burns of different ages
- Other signs of abuse — bruises, fractures, failure to thrive, frightened child
Cross-reference with GC 143 (A child with multiple bruises — child abuse) for detailed NAI assessment [3].
The lecture emphasises initial assessment follows "ABCDE" for burn patients AND assessment of associated injuries. [1]
| Step | Burns-Specific Considerations |
|---|---|
| A — Airway | Inhalational injury? Facial burns? Singed nasal hairs? Hoarseness? → Early intubation |
| B — Breathing | Circumferential chest burn → escharotomy; CO/cyanide poisoning → 100% O₂; blast lung injury |
| C — Circulation | Large bore IV access (through burnt skin if necessary); fluid resuscitation per Parkland; circumferential limb burns → escharotomy |
| D — Disability | Neurological status; CO poisoning → confusion, LOC; electrical injury → altered consciousness |
| E — Exposure/Environment | Full exposure to assess TBSA; then COVER → prevent hypothermia (especially children) |
Transfer and Burn Services in Hong Kong
| Level | Hospitals |
|---|---|
| Burn Facility | KWH (Kwong Wah Hospital) / QEH (Queen Elizabeth Hospital) / TMH (Tuen Mun Hospital) |
| Burn Unit | QMH (Queen Mary Hospital) / PWH (Prince of Wales Hospital) |
High Yield: QMH Burn Ward is one of two designated burn units in Hong Kong. Catchment areas include Hong Kong West Cluster, Hong Kong East Cluster, and Kowloon West Cluster. [1]
Burn unit resources include: [1]
- Surgical baths (for wound debridement and hydrotherapy)
- Skin bank (cryo-preserved cadaveric skin for temporary biological coverage)
Patients who should be referred to a burn unit:
-
10% TBSA partial-thickness burns
-
5% full-thickness burns
- Burns of face, hands, feet, genitalia, perineum, major joints
- Circumferential burns
- Electrical burns (including lightning)
- Chemical burns
- Inhalational injury
- Burns with pre-existing medical conditions
- Burns with associated trauma
- Paediatric burns
- Burns with suspected child abuse
High Yield: The lecture explicitly lists the multidisciplinary team: [1]
- Physiotherapists (prevent contractures, maintain ROM)
- Occupational therapists (splinting, functional rehabilitation, pressure garments)
- Psychologists (PTSD, body image, coping)
- Psychiatrists (depression, anxiety disorders, acute stress disorder)
- Social worker (housing, financial support, child protection if NAI suspected)
- Nurses specialized in burn care (wound management, dressing changes, pain management)
Why multidisciplinary care is emphasised: Burns affect every aspect of a patient's life — physical function, appearance, mental health, social functioning. Isolated surgical management without rehabilitation leads to contractures, poor functional outcomes, and psychological morbidity.
Advances in Burn Management
High Yield: Amniotic membrane used especially across joints and in paediatric patients. [1]
Why amniotic membrane?
- Natural biological dressing with anti-inflammatory, anti-microbial, and anti-fibrotic properties
- Reduces pain (covers exposed nerve endings)
- Promotes re-epithelialisation
- Particularly useful across joints (flexible, conforms to contours) and in children (reduces dressing change frequency → less distress)
High Yield: ICG used to assess second-degree burns — distinguishing superficial vs. deep dermal burns. This guides the decision between conservative management (superficial) vs. surgical debridement (deep). [1]
How it works: ICG is an intravenous fluorescent dye that binds albumin. Near-infrared camera visualises perfusion. Well-perfused tissue (superficial partial thickness) fluoresces brightly. Poorly perfused tissue (deep partial thickness) shows reduced/absent fluorescence → needs surgery.
- Emergency Management of Severe Burns Course (EMSB)
- Advanced Burn Life Support Course (ABLS)
Exam Intelligence
-
Calculate fluid resuscitation using Parkland formula — They give you weight, TBSA%, and time of injury. You must calculate volume AND rate, remembering to adjust for time already elapsed.
-
Identify signs of inhalational injury — Singed facial hair, carbonaceous sputum, hoarseness, elevated COHb, closed-space exposure.
-
When to perform escharotomy vs. fasciotomy — Escharotomy for circumferential burn constriction (bedside, bloodless, diathermy); fasciotomy for compartment syndrome (GA, operating theatre).
-
Paediatric burn TBSA estimation — Use Lund & Browder chart, NOT Rule of Nines.
-
Chemical burn management — Copious water irrigation, NOT neutralisation.
-
Electrical burn — "grand masquerader" — Surface appearance underestimates injury; check for myoglobinuria, cardiac arrhythmia, compartment syndrome.
| Trap | Correct Answer |
|---|---|
| Using SpO₂ to assess oxygenation in CO poisoning | SpO₂ is falsely normal; use co-oximetry on ABG |
| Including superficial (1st degree) burns in TBSA% | Only partial-thickness and full-thickness are counted |
| Starting the 8-hour clock from hospital arrival | Clock starts from time of injury |
| Giving normal saline for resuscitation | Lactated Ringer's is preferred |
| Applying neutralising agent to chemical burn | Always use copious water irrigation only |
| Adult urine output target in children | Adult = 0.5 mL/kg/hr; Child = 1 mL/kg/hr |
| Using Rule of Nines for a 2-year-old | Use Lund & Browder chart |
2017 Fourth Summative SAQ Q9 [2]
Question stem (faithfully reproduced): "A 28-year-old man is trapped under rubbles from waist down after an earthquake. When he is found by the rescue team, he has already been trapped for around six hours. He is alert and only complains of pain in the lower limbs. No open wounds are noted. Vitals: BP 130/90 mmHg, pulse 80/min, RR 15/min."
(a) Apart from pain control, what treatment will you start during the extrication process? (1 mark)
- Answer: Intravenous fluid resuscitation (aggressive IV normal saline/Lactated Ringer's) — to prevent washout of potassium and myoglobin causing cardiac arrest and AKI upon release of compression.
(b) Name four important signs of a limb-threatening injury when you examine the limbs after extrication. (4 marks)
- Answer: Pain (especially on passive stretch), Paresthesia, Pallor, Pulselessness — these are the 5 Ps of compartment syndrome (also Paralysis). Directly correlates with the compartment syndrome content in GC 190.
(c) If a crush syndrome is suspected after extrication, what finding in your urine test will suggest the diagnosis? (1 mark)
- Answer: Myoglobinuria (dark/cola-coloured urine, positive for "blood" on dipstick but no RBCs on microscopy).
(d) If the patient goes into cardiac arrest five minutes after extrication, what is the likely cause? (1 mark) What drug will you give to try to treat the cause? (1 mark)
- Answer: Hyperkalaemia (sudden release of intracellular potassium from crushed muscle into circulation → cardiac arrest). Give intravenous calcium gluconate (cardioprotective — stabilises myocardial membrane).
(e) What can be done to prevent this in the prehospital phase? (2 marks)
- Answer: IV fluid resuscitation before extrication; sodium bicarbonate to alkalinise urine (prevents myoglobin precipitation in renal tubules).
Relevance to GC 190: This question tests compartment syndrome (5 Ps), myoglobinuria, forced diuresis with sodium bicarbonate — all directly covered in the electrical burn and fasciotomy sections of this lecture. [1] [2]
No other past paper questions in the indexed context directly test GC 190 burn content. However, the 2017 SAQ Q9 on crush injury is highly relevant as noted above.
| Parameter | Value |
|---|---|
| Adult urine output target | 0.5 mL/kg/hr |
| Paediatric urine output target | 1 mL/kg/hr |
| Parkland formula (adults) | 2-4 mL × kg × TBSA% |
| Parkland formula (paediatric resuscitative) | 3-4 mL × kg × TBSA% |
| First half of fluid | First 8 hours post-injury |
| Second half of fluid | Next 16 hours post-injury |
| CO half-life on room air | ~4-5 hours |
| CO half-life on 100% O₂ | ~60-90 minutes |
| CO affinity for Hb vs O₂ | ~240× greater |
| Rule of Nines: Head (adult) | 9% |
| Rule of Nines: Each arm (adult) | 9% |
| Rule of Nines: Each leg (adult) | 18% |
| Rule of Nines: Anterior trunk | 18% |
| Rule of Nines: Posterior trunk | 18% |
| Rule of Nines: Perineum | 1% |
| Patient's palm | ~1% TBSA |
High Yield Summary
Burns are a systemic disease, not just a wound.
-
Assess depth (superficial/partial/full thickness) and extent (TBSA% — Rule of Nines for adults, Lund & Browder for children; only count partial and full thickness).
-
Resuscitate with Lactated Ringer's using Parkland formula (2-4 mL × kg × TBSA%). Give half in first 8 hours from TIME OF INJURY. Target urine output 0.5 mL/kg/hr (adult) or 1 mL/kg/hr (child). Avoid both under- and over-resuscitation.
-
Inhalational injury: Suspect in closed-space burns. Look for singed facial hair, carbonaceous sputum, hoarseness, elevated COHb. Early intubation + 100% O₂. Do NOT trust SpO₂.
-
Circumferential burns → Escharotomy (bedside, bloodless, diathermy). Compartment syndrome → Fasciotomy (GA, operating theatre).
-
Electrical burns = "Grand masquerader." Surface underestimates depth. Watch for cardiac arrhythmia, myoglobinuria, compartment syndrome. Forced diuresis + NaHCO₃ + mannitol.
-
Chemical burns: Alkalis worse than acids (liquefaction necrosis penetrates deeper). Copious water irrigation. NEVER neutralise.
-
Paediatric burns: Greater surface area/weight ratio → hypothermia, hypoglycaemia. Thinner dermis → deeper burns. Need maintenance fluid ON TOP of resuscitative fluid. Always consider child abuse.
-
Hong Kong: Burn units at QMH and PWH. Burn facilities at KWH, QEH, TMH.
-
Multidisciplinary care is essential: physio, OT, psychology, psychiatry, social work, specialised nursing.
-
Advances: Amniotic membrane dressing (joints, paediatric); ICG angiography (distinguishing superficial vs deep partial thickness).
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