Minimising the adverse effects and maximising the benefits of TIVA

Minimising adverse effects

• Caution is required to avoid adverse side effects
• pEEG can be used to help avoid excessively deep levels of anaesthesia
  • Allows drug titration based on PD response, particularly if paralysed
  • May improve safety
  • ↓ Postoperative neurobehavioral disease (PND)
• Which site to target?
  • Plasma or effect-site targeting can be used
  • Effect-site targeting will lead to higher initial plasma concentrations
    • ↑ Risk of hypotension post-induction
  • Plasma site targeting results in longer induction times
    • ↑ Haemodynamic stability
• Start LOW and go SLOW
  • Drug distribution from the plasma to the site of action is also delayed in elderly patients, hence the onset of action is slower
• Define V1 through the lean body
  • Actual weight is likely to be useful to define the other distribution volumes
  • Age-related drug elimination and age-adjusted Keo to reflect the delayed onset

Effect of ageing and suggested drug adjustments

• Metabolism and distribution of certain drugs (e.g. propofol) will be affected more than others (e.g. remifentanil)
• Polypharmacy (regular use of 5 or more medications) is seen in over 40% of elderly patients with implications for drug interactions
• Propofol
  • Pharmacokinetics
    • ↓ Vd
    • ↓ Protein Binding
    • ↓ Clearance
  • Pharmacodynamics
    • ↑ Hypotension (dose-dependent)
    • ↑ Brain sensitivity
  • Recommended dose adjustment
    • ↓ 20-50% (Bolus and Infusion)
• Remifentanil
  • Pharmacokinetics
    • ↓ Vd
    • ↓ Clearance ~30% (↓plasma esterase)
  • Pharmacodynamics
    • ↑ Respiratory and vasomotor centre depressant effect
    • ↑ Brain sensitivity (50% decrease in EC50)
  • Recommended dose adjustment
    • ↓ 50% (Bolus and Infusion) context insensitive

A delay in the emergence of elderly patients from anaesthesia may be partially due to their increased proportion of fat or inadvertent overdosing

Advantages of TIVA in the elderly

• Anaesthesia and analgesia components can be administered independently
• Titration of anaesthesia is easier than with inhalation anaesthesia (which is very difficult to titrate and usually guessed, based on MAC)
• Haemodynamic stability
• Smooth recovery profile
• ↓ Postoperative neurocognitive disorders
  • ↓Cognitive impairment, delirium and pain
  • Possible benefits in cancer surgery