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Pain in patients with burns

Created: 30/6/2017
Updated: 7/9/2017
 
In general:
  • Around 13,000 people (45% children) are admitted to hospital 
  • Mechanisms for pain are nociception, primary and secondary hyperalgesia, and neuropathy 
  • Can be broken down into acute initial pain, background pain and pain due to therapeutic procedures.

Features of burn pain

  • Long-lasting course, longer than healing time
  • Repetition of painful procedures leading to severe psychological disturbances (especially if pain control is inadequate)
  • Opioids are the mainstay for analgesia
  • Non-pharmacological techniques may be useful adjuncts
  • Pain referral is essential for efficient and safe analgesia
  • Pain in burned children remains underestimated and undertreated.

Functions of the skin include protection, immunocompetence, sensation, thermoregulation and metabolism. Sensory structures are contained within the dermis:

  • Free nerve endings (for pain, temperature and touch) 
  • Meissner’s corpuscles (light discriminatory touch) 
  • Pacinian corpuscles (pressure) 
  • If nerve endings are entirely destroyed --> don’t transmit pain.

Primary hyperalgesia

Pain induces a potent response, releasing inflammatory mediators, causing the wound and surrounding skin to become sensitive to touch, debridement or antiseptics.

Secondary hyperalgesia

Repeated painful stimuli lead to increased sensitivity in surrounding unburned areas, mediated by the spinal cord – occurs as a result of frequent dressings changes.

In reality, burn injuries consist of a combination of deep dermal or full-thickness wounds intermingled with more shallow areas. All burn victims experience pain. Psychological factors play an important part.

Initial acute pain

The stress response triggers an initial neural component – the sympathetic nervous system, which releases norepinephrine. This is followed by a slower hormonal response, in which cortisol, epinephrine and aldosterone are released.

First aid: Cooling. Beware hypothermia from environment.

Initial pain management in emergency department

  • Assess the patient – A, B, C 
  • May require general anaesthesia to control pain, particularly if there are other injuries/inhalation injury or if surgery/transfer is required
  • Intravenous morphine is the gold standard. Watch for over-sedation and respiratory depression. Avoid intramuscular opioids as absorption can be unpredictable
  • Non-steroidal anti-inflammatory drugs (NSAIDs) are useful in smaller burns but avoid them if you are suspicious of hypovolaemia or there is a risk of gastric ulcers. Critically ill patients may also be at risk of coagulopathy.

Pain after admission

Following the acute injury, pain can be classified as follows: 

  • Procedural pain (short to medium duration) – high intensity from skin grafting and physiotherapy of affected joints 
  • Resting pain, dull in nature and constant 
  • Breakthrough pain exacerbations.

Procedures in theatre – pain options

  • Opioids 
  • NSAIDS – may be contraindicated originally because of coagulopathy or risk of haematoma but useful in the longer term 
  • Regional anaesthesia – risk of infection/ haematoma/extent of burn often eliminates these. Epidurals for lower limb/abdominal procedures sometimes used. Regional blocks ± catheter insertion may be useful for postoperative pain. 
  • Local anaesthetics – can be applied directly in theatre to large raw areas (e.g. donor sites, theoretical toxic doses).

Pain control is essential to allow further wound management, to stabilize the sleep/wake cycle and to improve morale.

Dressings changes: No single technique is better than any other.

General anaesthesia is recommended for longer procedures (>1–2 hours).

For shorter procedures, options include: 

  • Entonox 
  • Local anaesthesia 
  • Opioid bolus pre-procedure 
  • Ketamine ± benzodiazepine (helps with hallucinations) 
  • Sedation with propofol infusion ± short-acting opioids – alfentanil/remifentanil.

Physiotherapy: Predictable pain, therefore amenable to multimodal oral medication.

Background pain: Consider long-acting analgesia; low-dose slow-release opioids + NSAIDs(if tolerated) work well together. Impaired sleep and depression can inhibit rehabilitation.

Pruritus

  • Mechanism is not well understood but involves histamine/prostaglandins
  • Antihistamines + NSAIDS can be used
  • Possibly triggered by heat; therefore, cold compresses may help.

Chronic pain

  • Damaged and regenerating nerve tissues can lead to complex neuropathic pain syndromes that outlive their expected duration 
  • Hyperalgesia and allodynia can be treated with antidepressants (amitriptyline), anticonvulsants (gabapentin and sodium valproate), regional nerve block and cognitive behavioural therapy.

 

Adjuncts and alternative techniques

Non-pharmacological techniques have been investigated for managing pain associated with dressing changes. Hypnosis, cognitive behavioural therapy, relaxation techniques and virtual reality scenarios have all been trialled.



Children

  • Severe burns are especially distressing for children
  • More difficult to assess in terms of pain
  • Behavioural assessments are important
  • Paediatric pain scores “smiley faces” (CHEOPS)
  • Children as young as 4 years old can be shown how to use a patient-controlled analgesia device
  • Evidence for psychological strategies – utilize the “play” therapist
  • Propofol is not licensed for younger children
  • Ketamine is still widely used for children, in whom side effects seem to be less of a problem. A small dose of benzodiazepine can be added.

 

Other sources of pain

  • Ensure that no fractures or abdominal injuries have been missed 
  • Compartment syndrome in a limb with a circumferential burn or in association with a fracture – exacerbated by fluid resuscitation
  • Infection, if not in keeping with previous pain levels.

Major burns are associated with a multitude of complications, including abdominal viscus perforation, colonic pseudo-obstruction, abdominal compartment syndrome and heterotopic bone deposition.

Author: Dr Katharine Francis

Further reading

Laterjet J, Choinère M. Burns 1995; 21(5): 344–8. 

Norman AT, Judkins KC. Pain in the patient with burns. Contin Educ Anaesth Crit Care Pain 2004; 4(2): 57–61.


ArticleDate:20170630
SiteSection: Article
 
   
    
                                            
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