Clinical management of the child with chronic pain

Introduction Chronic pain services for children have evolved along differing models depending on the specialists involved. There is, however, a consensus opinion that a multidisciplinary approach is required for effective management (1). Three main elements, Medicine, Psychology and Rehabilitation, need to be integrated in a multidisciplinary fashion to avoid the psychogenic/organic dichotomy commonly encountered when dealing with children with chronic painful conditions. Frequently, the main medical role is to provide a focus that will engage the child and family in a multidisciplinary approach. Medical Perspective I will be confining the rest of this presentation to the medical aspects of the management of the child with chronic pain. These will be considered under the headings of Diagnosis, Simple Analgesics, Strong Opioids, Other Drugs and Local Anaesthetic Blocks. The presentation will reflect my personal opinions, is not intended to be particularly balanced, and will use case histories and video sequences to illustrate particular points. Diagnosis 1 The International Association for the Study of Pain defines pain as ‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage’. Note: The inability to communicate in no way negates the possibility that an individual is experiencing pain and is in need of appropriate pain relieving treatment. I believe it is salutary to periodically remind oneself of this definition, particularly the emotional aspect. It is also helpful to consider the emotional effect upon parents of caring for a child with unrelieved pain. 2 The causes of chronic pain in childhood are varied; for most children it is possible to make a diagnosis, but not in all cases. As a paediatric anaesthetist, I find it most useful to manage chronic pain in children with the knowledge that consultant colleagues remain responsible for diagnosis of underlying conditions. Simple Analgesics Paracetamol, Ibuprofen, Diclofenac and Codeine Phosphate remain the basic pharmacological management of chronic pain in a child. Many children will have tried some or all of these drugs; nonetheless, a review of these drugs and a rationalisation of dose and timing is always appropriate. Cox 2 inhibitors can be useful in patients who are intolerant of traditional NSAIDs. It is important to always have a rescue medication available for exacerbations of pain. Some families are resistant to taking regular analgesia for a prolonged period of time, particularly if this has been ineffective in the past. Strong Opioids Tramadol will often fill a useful gap between Codeine and Morphine. I commonly use it when weaning children from patient controlled analgesia, and as an as required rescue medication. It is well tolerated by most children. Whether the adrenergic and serotoninergic mechanisms are important is not known. Morphine and Methadone are also used, usually in a weaning mode after prolonged administration. Other Drugs There is little or no evidence to support the use of adjuvant pharmacotherapy in the treatment of chronic pain in children. Adult findings for tricyclic antidepressants and anticonvulsants are applied to the paediatric population. I have found Amitriptyline to be very useful for all types of pain, and usually prescribe a twice-daily dose increasing slowly to about 1 mg·kg−1·day−1. If pain is neuropathic, I will try Gabapentin in adolescents. Baclofen is undoubtedly of use if muscle tone is increased. I have tried, and been persuaded by children and parents to try, many other drugs. Local Anaesthetic Blocks Local anaesthetic administered by subcutaneous infiltration or directly to specific nerves can produce long lasting pain relief for a variety of chronic painful conditions (2). Post appendectomy scar pain is a good example. Pain relief will often fast for months and can be permanent. The exact mechanism by which analgesia is produced is not known. Laboratory and clinical studies have demonstrated increased spontaneous activity, mechanosensitivity and chemosensitivity in damaged peripheral nerves. The consequent increased neural activity effects changes in both the dorsal root ganglion and the dorsal horn of the spinal cord (3). Intravenous lignocaine. at a concentration that does not block nerve conduction, can abolish spontaneous afferent activity in neuromas and the dorsal root ganglion. Abolition of spontaneous activity from damaged nociceptors or nerves may allow remodelling of the dorsal horn, and other areas of the central nervous system, resulting in prolonged pain relief. (a) Pleural block Pleural blockade has been described in adults in the management of several chronic painful conditions, notably pancreatitis (4) and reflex sympathetic dystrophy of the upper limb (5). It is a relatively simple alternative to coeliac plexus or stellate ganglion block, with a low complication rate. Local anaesthetic in the pleural cavity can undoubtedly diffuse through the parietal pleura to block the sympathetic chain, and perhaps intercostal nerves as well. A major advantage is that the indwelling catheter can be used for top-up injections. (b) Intravenous guanethidine block Evidence based medicine does not support the use of intravenous regional sympathetic block for the treatment of reflex sympathetic dystrophy (6). In my experience in paediatric practice it can be very beneficial, particularly in early or non-severe disease. Side effects are usually minor; hypotension is not a problem. (c) Lumbar plexus block Hip pain is common in childhood, most notably resulting from joint dislocation secondary to neurological disease. The lumbar plexus is reached in the psoas compartment by a needle passing paravertebrally through the mass of quadratus lumborum. The technique was initially described by Winnie (7) in adults, and subsequently by Chayen (8), again in adults, but using a more infero-medial approach. Dalens (9) reported a comparison of Winnie's technique with a modification of Chayen's technique in 50 children aged 7 months to 16 years. He found the Winnie approach to be technically easier; it also produced consistent ipsilateral block of the lumbar plexus, whereas the modified Chayen approach frequently produced bilateral epidural block.