الفهرس 
PHYSIOLOGY OF PAINOnly 14 pages are availabe for public view
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Abstract
Pain is a complex interaction involving sensory, emotional and behavioural factors, so its definition and treatment must include these aspects. Stimuli may activate the nociceptive system, but they can be perceived as painful only in the conscious brain. Pain is a core component of the stress response to injury, and therefore should be managed appropriately to optimize recovery and minimize complication.
Modern pain research has uncovered important neuronal mechanisms that are underlying clinically relevant pain states, and research goes on to define different types of pains on the basis of their neuronal and molecular mechanisms. It has been advocated that pain is the sensation that is specifically evoked by potential or actual noxious (i.e. tissue damaging) stimuli or by tissue injury. Pain research has not only explored the neuronal and molecular basis of the “pain system” of the healthy subject but has also provided insights into the function and plasticity of the “pain system” during clinically relevant pain such as post-injury pain, and postoperative pain.
Pediatric pain assessment is a simple task that opens up communication and trust among clinicians, the child, and their family. Important steps involve evaluating pain in infants and non-verbal children using reliable behavioral tools, asking older children and adolescents for their selfreported pain scores using age-appropriate tools, and taking the appropriate action to decrease pain based on the scores obtained. Without assessment, there is no way to institute appropriate pain management.
A large number of measurement techniques have been devised to measure pain in children. These include observational checklists, physiological responses, self-report questionnaires, selections from lists of descriptors, selection from interval scales (such as face-scales and pain thermometers), visual analogue scales (VAS), and projective techniques.
Face-scales have been developed including the Oucher Scale, the Smiley Five Face Scale, the Affective Facial Scale, and the Faces Pain Scale (FPS). These scales comprise pictures of faces depicting expressions showing various levels of a pain response. They are generally appealing to children and they are popular with clinical staff, as they are relatively quick and easy to administer. Following procedures that are likely to produce pain, Oddler Preschooler Postoperative Pain Scale (TPPS), the face, legs, activity, crying, consolability (FLACC), and the COMFORT scale, modified as a purely behavioral tool, can be recommended for postoperative assessment of patients aged 1 to 5 years.
Mild non opioid analgesics are safe and effective for minor surgery. Opioids should be added when indicated. Proper dosing and monitoring are essential to ensure safety. A combination of paracetamol, NSAIDs, opioids and local anesthetics is usually effective in this respect. In more severe cases a number of adjuvant analgesics can be added
Local anesthetics are useful for a range of applications in infants and children. Recent research has elucidated developmental pharmacology of local anesthetics and has suggested approaches to safer and more effective use of these drugs. Bupivacaine, a long-acting well-studied local anesthetic, is used most commonly in children. The extreme rarity of major toxicity from local anesthetics suggests that widespread replacement of bupivacaine with the newer drugs ropivacaine or levobupivacaine is probably not necessary for routine practice. These newer drugs, however, may be specifically indicated in situations where prolonged infusions are planned, in neonates, in patients with impaired hepatic function, and for anesthetic techniques requiring a large mass of a local anesthetic drug.
Regional analgesia must be considered for pediatric postoperative pain releif unless contraindicated. Epidural analgesia is an important analgesic option in the control of postoperative pain. The analgesic and physiologic benefits conferred by epidural analgesia may potentially result in an improvement in many outcomes including reduced morbidity (eg, coagulation, cardiovascular, pulmonary, and gastrointestinal).
Epidural analgesia should not be used as a generic technique because multiple factors (eg, catheter-incision congruent analgesia, duration of use, and analgesic regimen) may influence the efficacy of this technique on patient outcomes, especially in the high-risk patient population. The use of postoperative epidural analgesia as part of a multimodal approach may result in early patient convalescence and improvement in outcomes. Despite the benefits of perioperative epidural analgesia, there are risks (some of which can be devastating) associated with use of epidural analgesia, and clinicians should weigh the risks and benefits of epidural analgesia for each patient on an individual basis.
Caudal epidural blockade remains the cornerstone of pediatric regional anesthesia. The addition of ketamine or clonidine to a caudal local anesthetic prolong the duration of the block. However, a preservative-free preparation of ketamine that is suitable for neuraxial use is not widely available. Although complications associated with caudal block are rare, the risks and benefits must be carefully considered on an individual basis.