Anaesthetic Management: Electrical Burn Patient Posted for Amputation

1. Preoperative Assessment

Understand the Injury Pattern

System-by-System Review

Fluid Status

Investigations

• ECG (cardiac monitoring for 24 hours minimum in high-voltage injury)
• ABG — measure HbCO directly (pulse oximetry is unreliable — falsely elevated due to inability to distinguish HbO₂ from HbCO)
• FBC, U&E, creatinine, LFTs
• Coagulation screen
• Urinalysis (myoglobinuria)
• Cervical spine imaging if altered consciousness or high-voltage mechanism

2. Airway Management

• Assess for airway burns: singed nasal vibrissae, facial burns, hoarse voice, stridor, oropharyngeal oedema
• Facial burns alone are not an indication for intubation; functional compromise is the trigger
• If airway oedema is present or anticipated (especially if surgery is delayed after initial injury), early elective intubation is safer than delayed emergency intubation into a swollen, distorted airway
• Consider awake fibreoptic intubation if significant oropharyngeal oedema, burns, or limited mouth opening from contracture is present
• Carbon monoxide poisoning: if HbCO >20%, intubate and ventilate with 100% FiO₂ to accelerate CO elimination (half-life on air ~5h; on 100% O₂ ~60–90 min)

3. Neuromuscular Blocking Agents — Critical Consideration

Succinylcholine

• Safe within 24–48 hours of initial burn injury for RSI/emergency intubation
• AVOID after 48 hours — burn injury causes upregulation of extrajunctional nicotinic acetylcholine receptors (nAChRs), causing massive K⁺ efflux on succinylcholine administration → potentially lethal hyperkalaemia
• Lethal hyperkalaemia has been documented with as little as 8% TBSA burn
• This risk persists for up to 2 years after the burn heals
• Conservative guideline: avoid succinylcholine from 24 hours post-burn until 1–2 years after healed skin is restored — Miller's Anaesthesia 10e

Rocuronium/Non-depolarising NMBDs

• Preferred for intubation after the 48-hour window
• Dose resistance: burn patients with ≥25% TBSA burns show significant resistance to non-depolarising NMBDs due to upregulation of nAChRs and increased acetylcholine quantal release — higher doses are required
• Use quantitative neuromuscular monitoring (TOF) — do not rely on clinical endpoints alone
• Recovery of normal neuromuscular function may take months to years — Miller's Anaesthesia 10e
• Atracurium/cisatracurium (organ-independent elimination) are useful if hepatic or renal function is compromised

4. Intraoperative Management

Positioning and Access

• IV access may be technically difficult — consider central venous access
• Interosseous access if peripheral access is impossible
• Avoid placing IV cannulae in the zone of electrical injury (unreliable absorption, thrombosis risk)
• High-voltage patients require spine immobilisation until imaging clears the cervical spine

Monitoring

• Standard monitoring + invasive arterial line (beat-to-beat BP monitoring, frequent ABG sampling)
• Continuous ECG (arrhythmia risk)
• Temperature monitoring — aim for normothermia
• Urinary catheter with hourly measurement
• If haemodynamically unstable or major surgery: consider CVC/cardiac output monitoring

Anaesthetic Technique for Amputation

• Avoidance of difficult airway manipulation
• Attenuation of catecholamine surges
• Superior postoperative analgesia
• Potential for reduced phantom limb pain

• TIVA (propofol/remifentanil) is a reasonable option
• Volatile agents are acceptable; avoid halothane (sensitises myocardium to arrhythmias)
• Maintain normothermia aggressively (forced-air warming, warm fluids, warm theatre)
• Use quantitative neuromuscular monitoring; higher doses of non-depolarising agents are likely needed
• Expect greater analgesic requirements (opioid tolerance develops rapidly in burn patients)

Fluid Management Intraoperatively

• Continue resuscitation to maintain UO targets
• Warm all IV fluids
• Blood products based on EBL and haematocrit — amputations can involve significant blood loss
• Tourniquet use is commonly employed for lower limb amputation to reduce blood loss

5. Analgesia

• Multimodal analgesia: opioids + paracetamol + NSAIDs (if renal function allows) + ketamine (sub-anaesthetic doses reduce opioid requirements and may reduce phantom limb pain)
• Regional techniques (peripheral nerve block, perineural catheter) where feasible — provides excellent surgical block and perioperative analgesia
• Early liaison with the acute pain/chronic pain team is important, particularly regarding phantom limb pain prophylaxis (consider continuous perineural local anaesthetic catheters, gabapentinoids)
• — Morgan & Mikhail's Clinical Anaesthesiology 7e

6. Postoperative Considerations

• HDU/ICU care is appropriate given the severity of electrical injury and major surgery
• Continue temperature management
• Monitor for evolving rhabdomyolysis, renal impairment, and hyperkalaemia
• Continue cardiac monitoring
• Optimise pain management including phantom limb pain protocol
• Early multidisciplinary involvement: burns team, physio/OT, rehabilitation, psychology

Summary of Key Points