Aneasthesia Burns Course

Anaesthesia for BurnsDr. Alex Kan

Senior ConsultantDept of Anaesthesia & SICUSingapore General Hospital

Introduction

• Survival from burns have steadily increased in the last 50 years.– 50% of adults (age <45) survive 75% burns

• Exception of the elderly (age > 64)– Still 50% mortality with 20% burns

• Multiple operations & anaesthetics required for initial injury and subsequent rehabilitation.

Improved Outcome

• Team approach• Early surgery• Improved understanding of pathophysiology

and prevention of Multi-Organ Failure•Aggressive resuscitation• Infection surveillance & routine line change•Directed antimicrobial therapy•Pulmonary toilet•Enteral feeding

Early Excision - advantages

• Wounds uncolonized - less tissue excision• Allows complete excision in one sitting• Blood loss minimised• Improved mortality

Pathophysiologic Response

• Thermal injury produces – predictable early and late pathophysiologic

responses – in all major organs of the body.

• These responses must be considered when formulating an anaesthetic plan.

Anaesthetic Plan

• Preoperative management• IV access and Monitoring• Blood loss• Airway• Drugs• Temperature regulation• Immunosuppression• Postoperative period

Preoperative Management

• Airway, breathing and circulation (ABC’s) should be assessed in the primary survey

• Secondary survey, a head-to-toe evaluation is done, while resuscitation is started

• Associated injuries must be stabilised ( eg cervical spine, pneumothorax ) prior to anaesthesia.


• Correct severe acid-base abnormalities• Correct electrolyte disturbances• Correct coagulopathies. • Order enough colloid and blood products


• Provide adequate analgesia and sedation• Ketamine prior to transfer may be useful• Ensure fluid resuscitation is adequate or• Limit period of fluid fasting.

Parkland’s Formula

• 4 ml /kg / %TBSA burn over 24h• Ringer’s Lactate• Half - within 8 h of time of burn• Half - next 16h• End point = haemodynamic stability and

Urine output of 0.5-1 ml/kg/h.• Inhalational injury increases fluid

requirements independently

Anaesthetic Plan


Monitoring

• Large-bore iv lines are mandatory• Rapid / Level 1 infusion system• ECG - staples or needle electrodes• Arterial lines are indispensable• Central venous pressure lines • Urine output• Pulmonary artery catheter (if indicated)

Anaesthetic Plan


Blood Loss

• 70kg man, BSA 1.8 m2 with 20% burns– Estimated blood volume = 5000ml– Day 1 ( 0.4 ml/cm2 ) = EBL of 1440 ml– Day 2-4 (0.7 ml/cm2 ) = EBL of 2520 ml– After day 4 (0.9 ml/cm2 ) = EBL of 3240

ml– Infected burns wounds (1.0-1.25 ml/cm2)– = EBL of 4500 ml

Anaesthetic Plan


Inhalational Injury

• Suspected in the presence of – closed space fires / noxious vapours– burns of the head or neck; singed nasal hairs;– swelling of the oropharyngeal mucosa– hoarseness; carbonaceous sputum or– unexplained hypoxaemia (24 - 36 h post burn)– Intra-op fibreoptic bronchoscopy to confirm

Techniques for difficult intubation

• Alternative laryngoscope blades• Awake / Fibreoptic intubation• Blind intubation (oral or nasal)• Bougie/Intubating stylet/Light wand• Non-surgical airway (LMA, Proseal)• Surgical airway access (last resort)

Anaesthetic Plan


Anaesthetic Agents• There is no single preferred agent.• Ketamine and etomidate

– if uncertain volume status. – May still decompensate if inadequately resuscitated

• Ketamine– reduce morphine requirements– less respiratory depression, early extubation– side effects, minimize with midazolam, atropine

• Volatile agents - Induction / maintenance.

Muscle Relaxant

• Rapid sequence induction and intubation– Indicated for full stomach e.g. ileus

• Succinylcholine - contraindicated – 24 hours to 2 years after major burns, – profound hyperkalemia and cardiac arrest.

• Rocuronium in dosage of 0.9 mg/kg– Can intubate in 45 sec– Must be confident of airway management

Muscle Relaxant

• Nondepolarizing relaxants. -“resistance”• increase extra-junctional cholinergic

receptors, • altered affinity of these receptors• Alpha-1 acid glycoprotein increased, which

binds basic drugs (muscle relaxants)

Pharmacokinetic

• Acute phase – reduced organ blood flow – (hypovolaemia, decreased cardiac output). – Delayed absorption if drug not given iv.

• Albumin is decreased

– reduced protein binding of acidic/neutral drugs (benzodiazepines) - increased free fraction

– increased renal and hepatic drug clearance.

Anaesthetic Plan


Temperature Control

• Patient comfort = 38 ‘C • Maintain normothermia - OT and transport• Thermoneutral = 28-32 ‘C , OT > 25 ‘C • Warm IV fluids and blood• Inspired gases heated and humidified or use

HME (artificial nose). • Paediatrics - radiant heater and warming

blanket.

Anaesthetic Plan


Infection and Immunity

• All aspects of immunity impaired• Delayed healing / graft taking• Endotoxaemia / septicaemia• Management

– Meticulous aseptic techniques– Early excision and coverage– Topical antimicrobial– Systemic antibiotics

Anaesthetic Plan


Burn Pain

• Postoperative and burn pain may be severe • Intravenous morphine infusion or PCA• Midazolam infusion supplement. • Paracetamol for background analgesia is

useful especially in children.• Nitrous oxide for change of dressing

Nitrous Oxide

• Demand valve - cylinder or wall supply• Mask or mouth-piece• Administered by Medical/Nursing Staff• Used in ward

NO Cook-book RecipesNeed to individualise and titrate drug effect

LA / RA Asleep AwakeMask LMA ETTLaryngoscope Bougie FiberopticEtomidate Propofol MidazolamKetamine Morphine FentanylAtracurium Rocuronium IsofluraneExtubated Ventilated Sevoflurane

Conclusion

• To maximise patient survival• Take full advantage of early excision• Providing meticulous Anaesthesia / Surgery

• Meticulous Preoperative management • Meticulous Intraoperative Care

– IV access and Monitoring– Keep up with Blood loss– Optimum Airway management– Optimum Temperature regulation– Contain Immunosuppression

• Meticulous Postoperative management

The End

Thank You

Respiratory System

• Direct Effects– Early (Airway obstruction, smoke inhalation)– Late ( Chest wall eschar)

• Indirect Effects– Early (inflammatory mediators)

• pulmonary oedema, ARDS

– Late complications• IPPV (O2 toxicity, barotrauma, pneumonia)• Intubation (tracheal stenosis, laryngeal damage)

Inhalational Injury

• closed space fires / noxious vapours • Suspected in the presence of

– burns of the head or neck; singed nasal hairs;– swelling of the oropharyngeal mucosa, – hoarseness; carbonaceous sputum or– unexplained hypoxaemia (24-36 h post burn)

• Mortality is increased up to two-fold.

Inhaled Toxic Chemicals

• Direct damage to tracheobronchial tree or produce other systemic effects.– Polyurethane products -> hydrogen cyanide

• inhibit mitochondrial cytochrome oxidase.– Cotton and synthetic fibres -> aldehydes

• damage mucosa and cilia– Wood -> carbon monoxide– Particulate matter (smoke, soot) -> obstruction

Carboxyhaemoglobin

• Diagnosis is difficult• absorbs light at the same wavelength (660nm)• normal or falsely high pulse oximetry readings• Partial oxygen pressure (PaO2) in the normal range• direct measurement with cooximetry

– <20% (headache, tinnitus, nausea), 20-40% (weakness, drowsiness), >40% (neurologic dysfunction and coma)

• Half-life is related to the inspired FiO2 • 4-6 h (room air); 40 to 60 min (100% oxygen)• 20 to 30 minutes (Hyperbaric oxygen at 3 atm)

Evaluation of Resp System

• Chest x-ray is done - insensitive.• Fibreoptic naspharyngoscopy/bronchoscopy

– diagnosis and also aid in difficult intubation• Endotracheal intubation - done early

– if upper airway injury (oedema onset is rapid)• Cricothyrotomy and tracheostomy

– reserved as last resort– high complication rate.

Indications for Intubation

• Respiratory insufficiency• Cardiovascular instability• CNS depression• Massive burns (60% TBSA)• Head and neck burns

Cardiovascular System

• Early– Burn shock, hypovolaemia– Impaired cardiac contractility

• Late– Hyperdynamic state

• hypermetabolism• decrease SVR

Metabolism & Nutrition

• Metabolic rate - initial decrease• Hypermetabolism from day 3 up to day 12• Offset this with

– early wound closure– early enteral feeding

• Impaired thermoregulation• low ambient temp increases BMR

Haematologic

• Early– Haemoconcentration– Haemolysis– Dilutional thrombocytopaenia (after resus)– Activation of thrombotic - fibrinolytic system

• Late– Anaemia– DIC in severe sepsis

Renal

• Early dysfunction due to– Decrease renal blood flow and function– Myoglobinuria / haemoglobinuria– Nephrotoxic drugs

• Late– Increased renal blood flow– Variable drug clearance

Gastro-intestinal

• Early– Ileus - nasogastric tube needed– Stress ulceration (Curling’s)– Impaired intestinal barrier function

• Late– Dysphagia– Oesophagitis, TOF, cholecystitis

Endocrine System

• Increases in these catabolic hormones – catecholamine, corticosteroid, and glucagon

• Insulin, growth hormone and testosterone levels are dercreased. – Testosterone - anabolic stimulus – Insulin can provide similar benefits, with

improved outcome.

Neuro-musculoskeletal System

• Circumferential burns of the extremities– Escharotomy is required

• Neuropathy found in 11% of patients.• Muscle and nerve injury in electrical burns,

– rhabdomyolysis and neuropathy.• A high incidence of encephalopathy

Aneasthesia Burns Course

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