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TCI infusion pumps can provide optimal control of anaesthesia when the three elements mentioned above have been accurately modelled
and described. Firstly, the model that controls the pump has to work accurately (The models used in the Alaris® PK Syringe Pump are well-
validated and accepted). Secondly, the pharmacokinetic parameter set of a particular drug used by the computer model should match the
pharmacokinetics of the patient (it should be remembered that the models described in the literature are based on "population" data, and
apply to an "average" patient. They do not take account of the inter-patient pharmacokinetic variability). Thirdly, the pharmacodynamics
of the administered drug should be well understood to enable the user to select the plasma or effect-site concentration needed for the
required effect (with most anaesthetic agents there is broad inter-patient pharmacodynamic variability, and so the user needs to match
knowledge of the general population pharmacodynamic data with careful observation of the individual patient to ascertain that individual's
sensitivity to the drug, to enable titration to effect if necessary).
Note: Specific model parameters are available in the " TCI Overview" section or directly on the pump via the information key
when selecting drugs. Users should refer to the drug- prescribing information to verify that TCI mode is authorised in their
respective countries.
References :
1. Danhof M: Does variability explain (all) variability in drug effects ?, Topics in pharmaceutical science. Edited by Breimer DD, Crommelin DJA, Midha KK. Noordwijk, Amsterdam
Med. Press BV, 1989, pp 573-586
2. Kruger-Theimer E: Continuous intravenous infusion and multicompartment accumulation. Eur J Pharmacol 1968; 4: 317-324
3. Schwilden H: A general method for calculating the dosage scheme in linear pharmacokinetics. Eur J Clin Pharmacol 1981; 20: 379-86
4. Shafer SL: Towards optimal intravenous dosing strategies. Seminars in Anesthesia 1993; 12: 222-234
5. Ausems ME, Hug CC, Jr., Stanski DR, Burm AG: Plasma concentrations of alfentanil required to supplement nitrous oxide anesthesia for general surgery. Anesthesiology 1986;
65: 362-73
6. Schnider TW, Minto CF, Stanski DR: The effect compartment concept in pharmacodynamic modelling. Anaesthetic Pharmacology Review 1994; 2: 204-213
7. Shafer SL: Principles of pharmacokinetics and pharmacodynamics., Principles and practice of anesthesiology. 2nd Edition. Edited by Longnecker DE, Tinker JH, Morgan GE. New
York, Mosby-Year Book, 1998, pp 1159- 1210
8. Shafer SL, Gregg KM: Algorithms to rapidly achieve and maintain stable drug concentrations at the site of drug effect with a computer-controlled infusion pump. J Pharmacokinet
Biopharm 1992; 20: 147-69
When first starting the infusion the pharmacokinetic / pharmacodynamic models within the Alaris® PK Syringe Pump are reset to zero.
Therefore, for any reason, if the pump is switched off during the surgical procedure all current pharmacokinetic / pharmacodynamic model
information will be lost. Under such circumstances switching the pump off and on and restarting the infusion whilst the patient contains a
significant residual drug dose could result in an over-infusion and, therefore, the pump should not be restarted in TCI mode.
TCI Overview (continued)
TCI Precautions
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