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Anaesthesiology

Pain Relief in Childhood

Dr Dilip Pawar, Professor of Anaesthesiology AIIMS

Key Points - The majority of the world’s children receive inadequate pain relief. - Quantifying pain in children is the first step to treating it. - Regional blocks are gaining in popularity as a method of paediatric pain relief.

Most children undergoing surgery around the world do not receive adequate pain relief, writes Dr Dilip Pawar, professor of anaesthesiology,All India Institute of Medical Sciences.

To make a uniform level of pain relief available around the world may not be possible. In most parts of the developing world, there is a scarcity of adequate skilled personnel, and even in developed countries this is true for more aggressive techniques of pain relief, such as regional blocks. However, we must attempt to provide the best care available with whatever drugs, equipment and manpower are available. Research is essential to developing effective techniques with simple drugs and equipment: techniques where high-level postoperative monitoring may not be necessary;techniques that can be performed by less skilled individuals such as nurses and technicians. There is also a need to develop longer-acting safer drugs. Only when we have done this can we contemplate being able to provide adequate pain relief to all the children in the world.

Raising Awareness

Anaesthetists primarily provide postoperative pain relief intra-operatively. In the post-operative period pain relief is usually administered by nurses on instructions from the surgeon or the intensivist (depending on whether the child goes to a ward or an intensive care unit). However, the anaesthetist has to convince himself of the need for direct involvement and availability for advice if required, until such time as the children are pain free.

Education on the role of the anaesthetist in paediatric pain relief at residency level would make a difference. But to get committed people into the profession, we need committed role models at senior levels. Regular continuing medical education (CME) programmes and workshops are useful for qualified caregivers.

Quantifying Pain and Relief

If we cannot assess pain or pain relief, how do we treat it and how do we know it has been relieved? Children above six or seven years can assess their own pain with the help of a visual analogue scale (VAS). This is a 10cm scale marked with ‘no pain’ at one end and ‘excruciating pain’ at the other. The patient is asked to score on this scale their level (0 to 10) of pain. For ease of children’s comprehension, VAS has been modified to incorporate facial expression or a ten-step ladder scale, where a child is asked to identify the number of steps a toy monkey or koala can climb with the same degree of pain as that of the patient.

Assessing the pain of children below five years, especially infants, is more difficult. A plethora of scales has been designed using facial scales, physiological parameters and behavioural responses or a combination of these parameters. Most of these scales are not validated (multi-centric) for universal application. An observer rating scale (which could be used by physicians, nurses or parents) has been found to be simple and as good as other multi-parameter scales.

The various methods by which one can provide postoperative analgesia can be classified primarily by their route of administration.

Non-Parenteral Route

The most commonly used non-opioid analgesic in children is paracetamol (acetaminophen). The traditionally recommended dose has been the antipyretic dose, which is too conservative for pain relief. The current recommendation is an oral dose of 20–30mg followed by 20mg/kg every six to eight hours, or a rectal dose of 30–40mg/kg followed by 15–20mg/kg every six hours. The total daily dose for either route should not exceed 100mg/ kg/day in children and 60mg/kg/day in neonates.

Non-steroidal anti-inflammatory (NSAID) drugs like ibuprofen and ketorolac have been used in children. Ibuprofen at a dose of 10–20mg/kg orally, provides effective relief of mild pain. Ketorolac rectal suppositories have been found to be useful in children with a narrow therapeutic margin for opioids. NSAIDS can affect bleeding time when carefully used in adenotonsilectomy. Combination therapy with paracetamol and NSAID has been found to be superior to paracetamol alone.

Parenteral Route

Opioids are the first line of systemic therapy in moderate to severe pain, morphine being the most frequently used one. It has been intensively studied in children. Serum levels of 10–25ug/kg have been found to be analgesic in postoperative cardiac surgery in children. Total body morphine clearance is 80 per cent that of the adult value by six months. Morphine clearance in children, from infancy through to adolescence, is actually higher than it is in adults primarily because of higher hepatic blood flow and active alternate sulfation pathways.

Fentanyl has been used as a substitute for morphine in children who have haemodynamic instability and who cannot tolerate histamine release. In neonates, fentanyl has a prolonged elimination half-life compared with that of morphine (almost twice that of adults). Children older than one year have a similar clearance to adults. An infusion rate of 1–4ug/kg/hr usually provides adequate analgesia in children. Remifentanyl provides adequate analgesia with a loading dose of 1ug/ kg/hr followed by maintenance infusion of 0.25ug/kg/min. There has been a resurgence of interest in ketamine, the NMDA antagonist, for its analgesic property. A dose of 0.1–0.5mg/kg (i.v.) has been found to provide effective intra-operative pain relief.

The traditional route of parenteral administration is intramuscular. This should be avoided in children because of the fear, anxiety and distress it produces. The subcutaneous route might be an alternative in those cases where venous access is difficult.

Regional Blocks

In recent years there has been an increase in the popularity of the use of regional blocks in children because of their efficacy in providing good pain relief. Almost all the blocks used in adults have been used in children. The most commonly used block is the caudal epidural. Other blocks used in children include the lumbar epidural, ileoinguinal, ileohypogastric and penile. Bupivacaine (0.125–0.25 per cent) is the most commonly used local anaesthetic drug. Levobupivacaine and Ropivacaine have been shown to be equianalgic and less toxic. The efficacy of caudal block can be increased by the addition of adjuvants like tramadol, clonidine, morphine and ketamine. Morphine, when administered through the caudal route, is effective even for upper abdominal and thoracic surgery because of its hydrophilc property.

Lumbar epidural can be used,especially where caudal block is contraindicated or the volume needed through caudal block is high (near toxic dose). A catheter placed in the epidural space can provide continuous analgesia for a long period of time. It can safely be left for three to seven days. It can be placed through lumbar, caudal or thoracic route. Catheters can be advanced through the caudal route even up to the thoracic segment in infants up to age six. Fentanyl, being lipophilic, when it is added to local anaesthetic has to be deposited closer to the dermatome of the expected block, hence the need to administer it through a catheter advanced from the caudal or lumbar epidural route.

Peripheral nerve blocks have the fewest complications compared with neuraxial blocks, and have gained popularity in recent years, especially femoral and axillary blocks.

Patient-Controlled Analgesia

Patient-controlled analgesia (PCA)devices are infusion pumps with the facility to deliver a top-up dose whenever the patient feels the need for it. They can be programmed to prevent delivery of toxic doses by lockout interval and hourly maximum dose. Morphine is the usual drug of choice.

The patient bolus delivers 10–25ug/kg. A basal rate of continuous infusion of 10–20ug/kg might be administered with a lockout interval of six to 12 minutes. In children, a background infusion might be helpful during sleep and it does not seem to increase the total dose. Fear of respiratory depression and addiction has led to the underutilisation of opioids, even in adults, but the pharmacokinetics and pharmacodynamics of these drugs in children are well understood now. Administered in proper dosage,they are safe.

Patient-controlled regional analgesia,such as poplitial or fascia iliaca blocks have been found to be effective. Patientcontrolled epidural analgesia has also been used. One should remember that the lockout interval in these cases is longer than 30 minutes because the time needed for the bolus dose to be effective is longer.

An Achievable Goal

Management of pain can be achieved in most patients by simple drugs and techniques. Only a small percentage of children need aggressive pain relief measures. Children undergoing minor to moderate surgery can receive a regional block in the intraoperative period, followed by oral/rectal analgesics such as paracetamol in adequate dose. Following major surgery, measures such as continuous epidural, intravenous opioid infusion or patient-controlled analgesia (in older children) can be provided.

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