UCSD Pediatrics Burn Pain Management Site

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Background Information
Although modern techniques such as early excision and the use of dermal substitutes have decrease the number of dressing changes which are necessary to treat a burn injury (1) , daily cleaning of the wound, topical aplication and closed dressings remain the "state of art" standard technique especially for the burns where enough epidermal living cells remain present to ensure some satisfactory spontaneous healing. Remember that a thermal injury is seldom homogeneous and that it is often necessary to wait for 8 to 10 days before deciding which tissues must be excised and grafted and which will heal by themselves.

Burn dressing changes can cause one of the most "excruciating" type of pain ever experienced by a patient. As first shown by M. Choinière (2), it must be clearly differentiated from the burn background continuous pain which, when it has been recognized and evaluated, can be well controlled by various pharmacological agents such as paracetamol, NSAI's and opioids: a "zero" background pain objective is perfectly realistic in burns !

Conversely, procedural burn pain remains "a formidable problem" (3) for which there is nowaydays no consensus among burn specialists. And a number of recent studies show that it is widely undertreated even in specialized burn care facilities (4,5) .

Physiopathology of burn pain : Hyperalgesia.

The imediate pain which follows a burn is due to the stimulation of the skin nociceptors. Nerve endings which are completely destroyed become silent. However, during the time-course of burn treatment, pain will quickly arise from the remaining viable nerve endings and from the regenerating nerves, still connected with intact afferent fibers (6).

"Primary Hyperalgesia" : a thermal injury is immediately followed by an intense inflammatory reaction and the liberation of now well-identified mediators which will sensitize the still active nociceptors. Thus the wound quickly becomes very sensitive to mechanical stimuli (such as contact, rubbing or debridement)as well as to chemical stimuli ( such as those due to antiseptics or topics) (7).

"Secondary hyperalgesia" : continuous or repeated peripheral stimulation of nociceptive afferent fibers is known to induce a significant increase of the dorsal horn excitability, partly via NMDA receptors) (8) . Recent studies by Pedersen and Kehlet shows that this "wind-up" phenomenon" (9) is a component of post-burn hyperalgesia (as well as after mechanical stimuli) .The very high levels of nociception reached during dressing changes, and the fact that they are inflicted repeatedly favor this enhancement; a mechanism which may be partly responsible for an increase in pain sensitivity and opioid requirements which are common during the course of burn management. (10). (It is anecdotic but significant to remember that ketamine, now known as a potent NMDA antagonist has been extensively used for burn dressings for more than 40 years (11).