Burn Analgesia James Huffman, R-2 Emergency Medicine March 19, 2007

Willie Sutton Depression era bank robber When asked why he robbed banks – simply replied: “Because that’s where the money is”

Outline 1. Pathophysiology 2. Treatment Surgical Pharmacological Behavioural 3. Special Circumstances (if time) Pediatric patients Ventilated patients

Introduction 37% response rate Only 55% of responding Ontario emergency physicians included analgesia in their treatment plan!

Introduction Studies on the characteristics of burn pain show the one constant factor is the unpredictable and variable intensity of the pain Burn pain is multifactorial: Nocioception – nerve pain Hyperalgesia – secondary to inflammatory markers Neuropathy – nerve damage and regeneration Components of burn pain: Injury / background Procedures

Introduction Several studies have shown physicians do a poor job assessing and treating pain (both general and burns) Reasons for inadequate analgesia:  Fear of opiod side-effects  Fear of opiod addiction  Lack of pain evaluation  Differences in physician practices

Pathology of burn injury pain Full thickness burns completely destroy the network of nerve endings  Leads to an initially completely anesthetic wound to sharp stimulus  Yet, dull or pressure type pain in these areas  Neuropathic component (insect walking on skin with spikes on its feet) Neural reorganization takes approx 5-6 months Burn size may correlate with pain on VAS Psychological factors (anxiety and depression) Grafting vs. Granulation

Measuring burn pain Why?  Improved control of pain  Assessment of pain management / protocols  Improved communication with patients No gold standard Ideal tool VAS / numeric scales McGill Pain Questionnaire

Other Considerations Anxiety Itching  Both poorly researched and utilized but preliminary studies and anecdotal reports tend to emphasize the importance of these factors in burn analgesia

Treatment of Burn Pain 1. Surgical 2. Pharmacological 3. Behavioural

Treatment - Surgical Much pain is produced by the open wound – once closed, this is relieved Resection and grafting both significantly reduce pain For 2 nd ° burns, OpSite® or Tegaderm® applications can provide nearly immediate relief

Treatment – Pharmacological Tenets of pain medication: 1. A pt’s reports of pain are accurate and should be acted upon 2. Analgesics are most effective when given regularly, NOT PRN 3. Analgesics should rarely be given IM Adjust dosing for pt condition and concurrent illness

Treatment – Pharmacological Review articles have typically found three distinct stages: 1. Emergency / resuscitative phase (0-72h) 2. Acute phase – until wounds closed (72h – 3/52) 3. Rehab phase – until scar maturity (months to years) Emergency Phase  IV is preferred route of admin  Opiods excellent for both background and procedural pain  (Ketamine, NO) and anxiolytics good adjuncts

Treatment - Pharmacologic Acute Phase:  Backgroud pain: PCA and non-pain contingent administration of opioids (IV / PCA / PO)  Procedural pain: opiods, anxiolytics, Nitrous oxide  Neuropathic pain: Neuroleptics and TCAs Rehabilitative Phase:  Oral routes preferred for obvious reasons  Opiods, Acetaminophen, NSAIDs (*GI effects)  Continue treatment of neuropathic pain

Treatment - Pharmacologic Lidocaine and relatives  Nerve blocks shown to be effective in several studies Opioid analgesics  Mainstay in all three phases for both procedural and background pain  Methadone may be an underutilized option (NMDA action) α 2 Adrenergic agonists  Clonidine, dexmedotomidine: sedative, anxiolytic, analgesic and sympatholytic properties  Requires intense, invasive monitoring – probably better suited for an ICU setting

Treatment - Pharmacologic NSAIDs Acetaminophen  Dose is 10-15mg/kg Anxiolytics: Lorazepam: (T ½ = 13h) Diazepam (36h) Midazolam (2.5h)

Treatment - Pharmacological Itch Medications: 85% of burn injury patients (Field et al.) Poorly understood mechanism (histamine, kinins, proteases, prostaglandins, substance P, 5-HT) Moisturizing body shampoos / lotions (non-steroid) Anti-histamines Topical TCAs Gabapentin Cyproheptadine (anti 5-HT) 0.1mg/kg q6h

Treatment - Behavioural Pain experience is strongly influenced by psychological factors – esp. anxiety Non-pharm Tx can play an impt role in addressing these factors

Treatment - Behavioural Classical conditioning  Prevent negative associations and promote positive ones Operant conditioning  Reinforcement of behaviours

Treatment – Behavioural Cognitive Interventions  Control  Distraction Hypnosis  At least a dozen case reports and one small controlled study of burn patients

Summary Vigilance is key to good analgesia Phases or burn pain:  Emergent/Resuscitative  Acute  Rehab Components of burn pain:  Background pain  Procedural pain  Neuropathic pain Multi-faceted approach to treating burn pain:  Surgical  Pharmacological  Behavioural

Questions?

Infants and Children For many years, it was thought infants did not feel pain d/t incomplete myelination of sensory nerves Research by Anand et al has shown via a number of metabolic and physiologic parameters that pain is experienced Noxious stimuli is likely transmitted by C fibers, unlike in adults as a result of immature status of A fibers Children may be more sensitive to the respiratory depressive effects of opiates

Ventilated Patients Will need increased analgesia for the ETT