TIVA and target-controlled infusion: the compartment model

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Target exams

Red flags

• A TCI pump is only as accurate as its model; the displayed concentration is a prediction, not a measurement — confirm depth with a processed-EEG monitor, especially when physiology distorts the model.
• Deep hypothermia and cardiopulmonary bypass markedly reduce the predictive accuracy of standard propofol models — do not trust the displayed target during cardiac cooling and rewarming.
• Context-sensitive half-time lengthens with infusion duration; long remifentanil or propofol infusions do not wear off promptly simply because the pump is stopped.
• Mixing models (a Marsh propofol target with a Schnider effect-site, or an adult model in a child) produces unpredictable concentrations — use the matched, weight- and age-appropriate model.
• The elderly, frail and haemodynamically compromised patient needs a lower target and titration; a standard young-adult target causes hypotension.
• TCI failure (disconnection, empty syringe, occluded line) delivers no drug and lightens anaesthesia silently — monitor depth and the infusion line.