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 2nd ° 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)

α2 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