FRCA Notes

Paediatric Pain

Resources

  • Pain is a common presenting symptom in paediatric patients
  • Owing to the emotional, cognitive and behavioural components of pain, it can impact on both health outcomes and on all areas of life
  • Inadequate pain management may have negative long-term sequelae on:
    • Pain sensitivity (hyperalgesia)
    • Immune function
    • Neurophysiology
    • Attitude and health care behaviour

Central

  • The excitatory neural pathways necessary to perceive pain are present at 25 weeks' gestation
    • Foetuses which undergo painful stimuli show behavioural and hormonal stress responses
  • The endogenous descending inhibitory pathways are not fully developed until mid-infancy

  • Opioid receptors, and other receptors, are more widely distributed in the foetus and neonate
    • Functional opioid receptors are expressed by C- and A-fibre cell bodies in the dorsal horn, reverting to the adult pattern of expression in predominantly small diameter neurons in the first few weeks of life
    • Mu-opioid receptors in the dorsal horn are spread diffusely, but become more localised to the substantia gelatinosa in the first few weeks

  • Depending on developmental age, there is variable expression of the neurotransmitters, receptor-mediated systems and other molecules involved in pain pathways
  • There's increased expression of ɑ2-receptors, which causes increased susceptibility to the sedative and cardiovascular effects of clonidine and dexmedetomidine

  • Overall, noxious stimuli may provoke different patterns of activity depending on CNS maturity

Peripheral

  • Peripheral nociceptors are responsive to chemical, mechanical and thermal stimuli from birth
  • Persistent stimuli (e.g. repeated heel lances) can lead to peripheral sensitisation

  • C-fibres themselves are mature in neonates, though their connection at the dorsal horn is immature
  • Aβ-fibres show extended spinal cord connections which may produce nociception in response to low-intensity stimuli
  • Inhibitory pathways are not fully developed either
  • As such:
    • There is far less discrimination between the perception of noxious and non-noxious stimuli
    • Patients will experience more pain in response to noxious stimuli

  • Alterations in activity in nociceptive pathways during the early post-natal period produce persistent structural and functional spinal cord changes
  • The chronicity of the insult influences the reversibility of the changes
  • Early injury may predispose to enhance responses to subsequent injuries at the same site i.e. consequent hyperalgesia

  • Altered volume of distribution of analgesics due to:
    • Higher TBW at birth (85% in pre-term infants, 75% in term infants and 60% at 5 months of age)
    • Changes to protein concentration and binding,

  • Altered elimination and clearance of drugs due to:
    • Hepatic immaturity, with fewer selective pathways to metabolise drugs
    • Renal immaturity, with GFR (30ml/min) and tubular reabsorption reduced until 6 months

  • The developing CNS is more sensitive to opioid-induced respiratory depression and apnoea, but has a higher MAC requirement than adults

  • These changing pharmacokinetics means dose requirements vary throughout childhood

  • The main causes of pain in paediatric patients are:
    • Procedural pain
    • Surgical/post-operative pain
    • Pain from traumatic injury
    • Pain arising from acute medical illness e.g. sickling crises
    • Chronic or recurrent pain

Procedural pain

  • Often involves a strong element of anticipation
  • Uncontrolled pain during a first procedure can adversely affect the levels of pain and distress experienced during subsequent procedures
  • The aim of management for procedure-related pain is to minimise not only pain, but also physical and psychological discomfort

  • Non-pharmacological strategies include:
    • Adequate preparation for both children and parent as to how the procedure will be conducted
    • Provision of age- and developmentally-appropriate information about what to expect
    • Facilitate question-asking
    • Allow younger children to act out the procedure with a toy medical kit
    • Use of a dedicated treatment room in a comfortable, calm and friendly environment
    • Use of staff trained in psychological techniques e.g. play therapists
    • Distraction techniques e.g. interactive books, toys, bubbles, (video) games

  • Use of pharmacological methods depends on factors including procedural factors and patient factors, although techniques include:
    • Topical anaesthesia e.g. EMLA cream for cannulation
    • LA infiltration
    • Nitrous oxide/entonox
    • Intra-nasal fentanyl
    • Ketamine
    • Peripheral nerve block ± IVRA

Post-operative pain

  • Pain should be discussed pre-operatively with parents and, if appropriate, child
  • The aim of pain management is to control pain as early as possible; early, preventative treatment is more effective
  • Multi-modal analgesia including regional anaesthesia/analgesia should be used
  • Analgesia should be properly dosed according to bodyweight and development

Traumatic pain

  • Should be addressed in ED as part of initial assessment/management
  • The dose, route, mode and choice of drug will depend on the clinical scenario and should be tailored to a patient's individual requirements
  • Options include, but are not limited to:
    • Morphine up to 0.1mg/kg
    • Intra-nasal fentanyl
    • Topical anaesthesia
    • Entonox
    • IVRA

Chronic or recurrent pain

  • Sickle cell disease
  • Inflammatory bowel disease
  • Cystic fibrosis
  • Neuropathic pain e.g. Fabry's disease, Charcot-Marie-Tooth disease, sodium channelopathies e.g. erythromelalgia
  • Nociplastic pain e.g. CRPS, centrally mediated abdominal pain syndrome