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Chronic Pain
"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).

Children aged between birth and four years old represent approximately 20% of all hospitalised burn patients [34]. Several studies show that procedural burn pain in children is largely underestimated and under treated [4],[5]. However, these shortcomings can be overcome by adhering to protocols similar to those used for adults, since the pharmacokinetic and pharmacodynamic differences between children and adults are minimal. For infants less than three months old, the adult opioid dosages must be divided by three because of hepatic and renal immaturity [35]. In children older than three months, the pharmacokinetic effects are similar to those in an adult. In preschool-age children, the half-lives of morphine and alfentanyl are 50% those in adults, which explains the need for higher dosages [36]. Despite some clinicians` preconceptions, the pharmacodynamics of opioids, especially the effects of respiratory depression, are no different in infants than in adults [37]. Accidental over dosage mostly occurs because of the difficulties of pain evaluation (overestimation) in children rather than the actual pharmacodynamic specificity of a drug. In addition, special attention should be paid to the child`s environmental conditions. For instance, a parent`s presence and participation in the procedure can have a highly beneficial effect [38].