FRCA Notes

Acute Pain in the Elderly

Resources

  • Pain management in the elderly is more challenging, on account of:
    • A higher prevalence of comorbidities
    • Polypharmacy, which increases the risk of drug interactions
    • Age-related physiological changes, which impact on drug pharmacokinetics and pharmacodynamics
    • Altered responses to pain (although NB elderly patients do not 'have a higher pain threshold')
    • Difficulty assessing pain due to cognitive or communication impairment

Physiological change Pharmacological effect Adjustment to analgesia
↓ cardiac output by up to 20% ↓ volume of central compartment
↑ peak plasma concentration		 Smaller doses
Slower rate of injection
↓ CBF (20%) and brain mass (20%)
↑ CSF volume (10%)		 ↓ CNS distribution
↑ Response to opioids		 ↓ opioid bolus
& maintenance doses
↓ renal mass (30%), blood flow (10%) & GFR (30-50%) ↓ clearance of drugs & active metabolites ↓ maintenance dose for renally-cleared drugs
Monitor for toxic metabolite accumulation
↓ liver mass & blood flow
↓ phase I reactions (25%)		 ↓ hepatic clearance of drugs with high hepatic ER ↓ maintenance dose
May affect oral bioavailability
↓ body water (10%)
↑ body fat (10-50%)
↓ albumin levels (20%)		 ↓ VD for water-soluble drugs ↑ VD for lipophilic drugs ↑ free drug concentrations Smaller doses


Assessment

  • Diseases which impair cognition can impact on pain assessment
  • Common pain assessment tools are validated in those with mild-moderate cognitive impairment:
    • Numeric rating scale
    • Verbal descriptor scale
    • Faces pain scale

  • Other tools are validated in those with severe cognitive impairment:
    • Doloplus-2
    • Pain assessment in advanced dementia (Painad) scale
    • Abbey pain scale
    • Pain assessment checklist for seniors with limited ability to communicate (PACSLAC Checklist)

Analgesic choices

  • NSAIDs are associated with an increased frequency of side-effects in the elderly
  • Should avoid, or only use for short time periods with appropriate antacid cover

  • Opioids
    • Reduce doses and titrate appropriately
    • Ensure laxatives and anti-emetics are prescribed; constipation may contribute to delirium

  • Regional and neuraxial techniques are effective analgesic options in the elderly and reduce the risk of opioid-induced side-effects
  • Need to be mindful of the increased prevalence of anti-platelet and anti-coagulant use in these patients