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Alaris™ PK Plus Syringe Pump
Profiles from TCI Mode
Profiles from TCI Mode
When targeting in TCI Mode the Alaris PK Plus Syringe Pump will automatically calculate the flow rate profile from the specific
pharmacokinetic/pharmacodynamic model for the selected drug. This section of the Directions For Use is intended to help users
understand the profiled infusion and the performance accuracy attained from the TCI Pump.
Induction Bolus and maintenance rates are displayed before starting the titration. When initially starting the infusion or after increasing
the target (plasma or effect) concentration by titration, the Pump will first deliver a bolus dose through a typically short, high rate
infusion. On completion of this bolus, the Pump will immediately switch to a lower maintenance rate (when plasma target mode is used)
or will pause for a period of time before switching to a lower maintenance rate (when effect site targeting mode is used). Once the
maintenance phase is reached, any reduction made to the target (plasma or effect) concentration will typically result in the infusion rate
reducing to zero until the predicted plasma (or effect) concentration reduces the new target value.
The Alaris PK Plus Syringe Pump updates the pharmacokinetic model driving the plasma (or effect) concentration prediction and the
infusion rate every 10 seconds. The infusion rate graph, shown in the Infusion Rate vs Target concentration graphs was measured in
accordance with the protocol described in the IEC60601-2-24
1
Standard, with the data sample period reduced from 30 to 10 seconds.
The Pump solves the pharmacokinetic/pharmacodynamic algorithms so that the target (plasma or effect) concentration is attained as
rapidly and as accurately as possible. However, the User may need to take into consideration the limitations of the physical system in
attaining the target (plasma or effect) concentration; this includes:
• The limit on the flow rate permitted by the infusion pump mechanism;
• The limit on the flow rate permitted by the syringe size;
• The patient / drug dose limitation from the prescribing information to insure the safety of the administration;
• The variation in individual patient response to reach the plasma (or effect) concentration;
• The model specific cap rate.
A true assessment of the performance of the Alaris PK Plus Syringe Pump can be made if the volumetric error, that is the difference
between the actual volume infused and the predicted volume infused, is calculated. For the Infusion Rate vs Target concentration
graphs, over a one hour period, the Alaris PK Plus Syringe Pump has a mean volumetric accuracy in TCI Mode better than ±5%
2
.
By measuring the volume from the flow rate profile delivered from the Alaris PK Plus Syringe Pump and then introducing this into a
reverse pharmacokinetic model the predicted plasma (or effect) concentration can be calculated from the flow rate. These are illustrated
in the Predicted vs Ideal Concentration graphs, showing the typical performance of the system against changes in the target plasma (or
effect) concentration for a typical, idealised profile. For the same targeted profile, the deviation of the predicted plasmatic (or effect)
concentration (back calculated from the volume collected) from the expected Ideal plasma (or effect) concentration, results from the
volumetric inaccuracy of the system (Pump and syringe). The Alaris PK Plus Syringe Pump will track the predicted plasma (or effect)
concentration to within ±5%
2
of that calculated by pharmacokinetic model over a one hour period. Flow rate inaccuracies and start-up
delays may decrease the accuracy of the predicted plasma (or effect) concentration particularly where high syringe drug concentrations
are used in conjunction with large sizes of syringes and low target plasma (or effect) concentrations as the syringe plunger motion over
time (proportional to the flow rate accuracy) will be significantly reduced.
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For a given drug concentration, the volumetric error is proportional to the dose rate error. Knowledge of the system
accuracy over different time intervals may be of interest when assessing the impact of administering short-half
life drugs. In these circumstances, short-term fluctuation in the infusion rate could have a clinical impact that
cannot be determined from the performance profiles shown in Figures below. In general, the volumetric error
will increase with small induction and maintenance rates, which may occur when with large volume syringes, high
syringe concentrations, low patient weights and low target (plasma or effect) concentrations. For applications
where system accuracy is important, maintenance rates less than 1.0 ml/h are not recommended; syringe sizes, drug
concentrations / dilutions and target (plasma or effect) concentrations should be selected accordingly to ensure the
maintenance rate exceeds this lower limit.
The graphs illustrated in this section are for a Diprivan (1% Concentration); Diprivan (2% concentration), Remifentenil (50µg/ml
concentration), and Sufentanil (5µg/ml concentration) are given for comparison. As an illustration of the effect the syringe size has on
system performance, Remifentenil (50µg/ml concentration) is shown with a 50ml and 5ml syringe respectively.
The target (plasma or effect) concentrations shown are for illustrative purposes only.
Note:
1
IEC60601-2-24: Particular Requirements for the Safety of Infusion Devices;
2
95% Confidence / 95% Population.
