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Limitations of TCI models

In order to use TIVA safely, we must understand the limitations of TCI models.

Limitations of Any Models

  • Most pharmacokinetic models were developed in a small group of young, healthy, non-obese subjects
  • Large inter-individual and intra-individual differences exist
  • Plasma drug concentrations in any individual patient are unlikely to be identical to those predicted by the pharmacokinetic model but are generally within +/- 20%
  • The system does not consider drug interaction or concurrent drug therapy
  • Less accurate in patients with characteristics deviating from healthy young adults
    • Multimorbidity
    • Older patients
    • Obese patients
  • Less accurate in extreme clinical conditions
    • Critically unwell patients
    • Hypovolaemia
    • Severe hypothermia
    • Metabolic disturbances

Why bother using TCI if it is not accurate?

  • TCI pumps are a useful tool for titration to effect (clinical effect or the desired effect on the EEG as measured by a pEEG monitor)
  • The reliance on the accuracy of proportional changes (e.g. increasing or decreasing 10%) to allow titration of the drug concentration to the clinical effects in individual patients is more important than the predicted or actual measured values
  • TCI systems allow the determination of a relevant and effective decrement time so as to predict the offset of the drug

Join us in Week 6 to learn more about these special subsets of patients

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Introduction to Using Total Intravenous Anaesthesia (TIVA)

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