Anaesthetic Management of Post Burn Contracture Release and Split Skin Grafting (SSG)

Introduction

1. Preoperative Assessment

History

• Time elapsed since original burn (important for suxamethonium safety window)
• Site, extent and depth of original burn - TBSA involved
• History of inhalation injury - may cause internal airway fibrosis even without external deformity
• Prior anaesthetic records - previous intubation difficulties, tracheostomy
• Nutritional status, ongoing wound infections, sepsis
• Medications: analgesics, antiepileptics (for pain), topical antimicrobials

Airway Evaluation (Most Critical Step)

• Microstomia - restricted mouth opening due to perioral scar contractures; measure inter-incisor distance
• Neck contracture - mentosternal or mandibulo-clavicular bands restrict atlantooccipital extension and neck rotation, impairing laryngoscopy position
• Perinasal scar - fibrosis of nares causes restricted nasal access (important for nasal intubation or nasopharyngeal airway)
• Decreased submandibular compliance - impairs forward tongue displacement during laryngoscopy
• Trismus, restricted temporomandibular joint movement

Systemic Assessment

• Cardiovascular: Hypertrophic scar may limit chest wall movement; assess cardiac function in chronically ill patients
• Respiratory: Pulmonary fibrosis from inhalation injury; assess by PFTs and CXR/CT if indicated
• Haematological: Chronic anaemia (common due to repeated procedures, malnutrition, chronic infection) - optimise Hb preoperatively; cross-match blood
• Nutritional: Hypermetabolic state persists; hypoalbuminaemia affects drug protein binding and pharmacokinetics
• Renal/Hepatic: Evaluate for organ dysfunction secondary to severe burns or sepsis
• Psychological: High anxiety; consider preoperative counselling and sedative premedication with caution

Investigations

• CBC, renal/liver function, coagulation profile, serum electrolytes (check K+)
• ECG, CXR, PFTs if respiratory compromise suspected
• Blood grouping and crossmatch
• Fibreoptic evaluation of airway if nasopharyngeal/subglottic pathology suspected

2. Premedication

• Anxiolysis: Oral midazolam (with caution if airway concern) or tablet alprazolam night before
• Antacid prophylaxis: Ranitidine 150 mg oral night before + morning of surgery
• Antisialogue: Glycopyrrolate 0.2 mg IV/IM before awake fibreoptic intubation (preferred to atropine - no tachycardia, does not cross BBB)
• Topical airway anaesthesia preparation if awake intubation planned

3. Intraoperative Management

Monitoring

• Pulse oximetry (may be difficult to place on fingers - use ear, toe, forehead reflectance probe)
• ECG (electrodes may need to be placed on unburned areas)
• Non-invasive BP (use unburned limb; intra-arterial line if major surgery)
• Capnography (mandatory)
• Temperature monitoring (core - rectal, oesophageal, or bladder)
• Urinary catheter for urine output monitoring in longer cases
• Arterial line + central venous access for major cases

Vascular Access

• IV access can be extremely challenging: scarred veins, limited IV sites
• Large bore IV cannula in unaffected area
• Consider intraosseous access or central venous access if peripheral access fails
• Surgeon may help by inserting cannula into a surgically exposed vein

Positioning

• Carefully padded positioning - pressure ulcers are a serious risk
• Neck contracture may require surgeon to perform partial contracture release BEFORE definitive airway can be secured
• Prone positioning may be needed for posterior donor sites - plan airway accordingly
• Eyes must be protected; care for bony prominences

4. Airway Management - The Central Challenge

1. Awake vs. asleep intubation
2. Oral vs. nasal vs. surgical airway
3. Whether to maintain spontaneous ventilation

• Mouth opening < 2.5 cm (microstomia)
• Severe neck contracture preventing extension
• History of failed intubation
• Predicted cannot-intubate, cannot-ventilate scenario

• Adequate preoperative counselling and consent
• Glycopyrrolate for antisialogue effect
• Topical airway anaesthesia: nebulised or gargled 4% lignocaine; superior laryngeal nerve block or transtracheal injection of 2-3 mL 2% lignocaine
• Sedation: small doses IV ketamine 30 mg + propofol 30 mg in aliquots (maintaining spontaneous ventilation) - the "Belfast cocktail" or similar balanced approach
• Pass fibreoptic bronchoscope (FOB) via oral or nasal route, railroading the ETT over it
• Confirm position by visualising carina before advancing tube

• Videolaryngoscopy (McGrath, C-MAC) - useful when mouth opening is adequate but neck movement is limited; does not require neck extension
• Supraglottic airways (LMA) - only as rescue or for cases where contracture is distal (limb, trunk); contraindicated as primary airway in neck contractures
• Tracheostomy under local anaesthesia - last resort when all endoscopic methods fail; inform surgeon beforehand

5. Choice of Anaesthetic Agents

Induction

• Ketamine (1-2 mg/kg IV): Drug of choice especially when airway is borderline - preserves airway reflexes and spontaneous ventilation; also provides analgesia; useful in haemodynamically unstable patients
• Propofol (1.5-2.5 mg/kg): Can be used in haemodynamically stable patients
• Combination of ketamine + propofol ("ketofol") reduces side effects of each drug

Muscle Relaxants - Critical Pharmacological Consideration

• Rocuronium: Use higher dose 1.2-1.5 mg/kg for RSI; duration of action is reduced
• Atracurium: Useful as its metabolism (Hofmann elimination) is independent of organ function
• Vecuronium, cisatracurium: Can be used; titrate with nerve stimulator

Maintenance

• Volatile anaesthesia: Sevoflurane or isoflurane in O2/air mixture
• TIVA with propofol + remifentanil infusion - advantageous for temperature conservation (avoids circuit breathing)
• Nitrous oxide: Avoid if significant inhalation injury or concern for pneumothorax/intestinal distension

6. Temperature Management

• Hypothermia is a major risk: Skin is the primary thermoregulatory organ; its compromise dramatically accelerates heat loss
• Pre-warm the OR to 28-32°C before the patient enters
• Forced air warming blankets (Bair Hugger) over unexposed areas
• Warm IV fluids (to 37°C)
• Warm surgical irrigation fluids
• Reflective foil/thermal blankets over uninvolved body parts
• Core temperature monitoring is mandatory

7. Fluid and Blood Management

• PBC surgery is associated with significant blood loss (SSG harvesting and wound bed preparation are highly vascular)
• Establish baseline Hb; transfuse to maintain Hb > 8-10 g/dL (10 g/dL preferred in children)
• Intraoperative losses can be rapid - maintain at least 2 large-bore IV cannulae
• Blood loss estimation: weighing surgical swabs, suction volume monitoring
• Balanced crystalloid (Ringer's Lactate) for maintenance and replacement; colloid as needed
• Avoid over-hydration - risk of pulmonary oedema and graft failure
• Tranexamic acid may be used to reduce blood loss intraoperatively

8. Analgesia - Multimodal Approach

• Opioids: IV morphine, fentanyl, or patient-controlled analgesia (PCA) in cooperative adults
• Ketamine: Sub-anaesthetic doses (0.1-0.3 mg/kg/h infusion) during and after surgery - excellent for burn pain; reduces opioid consumption; prevents opioid-induced hyperalgesia
• Paracetamol IV/oral: Regular scheduled dosing
• NSAIDs: Ketorolac (with caution - avoid if renal impairment or GI risk)
• Regional/Local anaesthesia:
  • Tumescent anaesthesia (dilute LA infiltration under skin) for donor site harvesting - reduces blood loss and provides postoperative analgesia; CONTRAINDICATED if raw area >10% TBSA or age <18 years due to LA toxicity risk
  • Peripheral nerve blocks where anatomy permits (e.g., femoral nerve block for thigh donor site)
  • Wound infiltration with bupivacaine at donor and recipient sites
• Dexmedetomidine: Alpha-2 agonist; useful as adjunct - reduces opioid requirements, provides sedation and analgesia without respiratory depression
• Gabapentin/Pregabalin: Useful for neuropathic component of chronic burn pain; can continue perioperatively

9. Postoperative Management

• Extubation: Only when fully awake, cooperative, with return of all protective airway reflexes and adequate reversal of neuromuscular blockade (confirmed with nerve stimulator)
• Extubation over an airway exchange catheter (AEC) is recommended - allows re-intubation if the airway deteriorates postoperatively (especially after neck/face contracture release where re-intubation may be even more difficult)
• Post-extubation airway obstruction can occur due to oedema after contracture release - have re-intubation/emergency airway equipment at bedside
• Analgesia: Continue multimodal regimen; PCA if suitable
• Monitoring in PACU/ICU depending on extent of surgery and patient status
• Prevent hypothermia in recovery room
• SSG care: Immobilise graft site; pressure dressings; avoid shearing forces; nurse in appropriate position to prevent graft displacement
• Physiotherapy early mobilisation planning

10. Special Considerations

Summary for Quick Recall (Exam Points)

1. Preop: Thorough airway assessment - microstomia, neck flexion, nasal fibrosis, internal airway changes; check K+, Hb; cross-match blood
2. Airway: AFOI is gold standard for predicted difficult airway; partial contracture release before intubation if microstomia; video laryngoscopy as alternative; surgeon on standby for emergency tracheostomy
3. Suxamethonium CONTRAINDICATED beyond 48h post-burn (upregulated extrajunctional AChRs - fatal hyperkalaemia); use high-dose rocuronium 1.2-1.5 mg/kg instead
4. Non-depolarising NMBAs: Patient is RESISTANT - need higher doses; use nerve stimulator
5. Ketamine is the induction agent/analgesic of choice
6. Temperature: Warm OR, warm fluids, warming blankets - hypothermia is a major risk
7. Blood loss: Large bore IV access; blood products ready; tranexamic acid
8. Analgesia: Multimodal - opioids + ketamine infusion + paracetamol + regional blocks + dexmedetomidine
9. Extubation: Over airway exchange catheter when fully awake; re-intubation equipment at bedside
10. Postop: PACU/ICU care; SSG immobilisation; early physiotherapy planning