CareFusion Alaris PK Plus MK4 8005PK201 Directions For Use Manual page 6

Knowledge of the k for various agents has made targeting of the effect-site possible. With effect-site targeting the TCI system first
eo
calculates the necessary plasma concentration profile required to achieve the effect-site target as rapidly as possible, and then calculates
the infusion rates required to achieve that plasma concentration profile (Fig 3). Effect Site vs Plasma Concentration will generate a larger
induction dose followed by a pause in the infusion to allow plasma to equilibrate with effect site concentration.
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 Plus 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
TCI Precautions
When first starting the infusion the pharmacokinetic / pharmacodynamic models within the Alaris PK Plus 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.
Input
cl2
k
V2 V1
21
Peripheral Central
k
Compartment Compartment
12
k
Effect eo
Compartment
Clearance cl1
Fig. 3: Schematic representation of the concentration-effect relationship.
1000DF00741 Issue 5
cl3
k
V3
13
Peripheral
k
Compartment
31
k
10
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Alaris™ PK Plus Syringe Pump
TCI Overview