Variability of Target-controlled Infusion Is Less Than the Variability after Bolus Injection

Abstract

TCI devices neither create nor eliminate biologic variability. For any drug described by linear pharmacokinetic models, no infusion regimen, including TCI, can have higher variability than that observed after bolus injection. The median performance of TCI devices should be reasonably close to the prediction of the device. However, the overall spread of the observations is an intrinsic property of the drug, not the TCI delivery system.

A dexmedetomidina para sedação, por via venosa, não interfere com a duração dos bloqueios sensitivo e motor da raquianestesia

“…A utilização de dose única ou repetida em anestesia pode ser uma alternativa inadequada para a mensuração dos efeitos de uma droga. Hu e col., por intermédio de simulações matemáticas, previram o dobro do coeficiente de variação na concentração plasmática de um fármaco, quando administrado por dose única comparada à técnica de infusão contínua 12 . Isto pode acarretar elevadas concentrações plasmáticas de fármacos e a ocorrência de efeitos adversos.…”

“…Single or repeated dose in anesthesia could be an inadequate alternative to measure the effects of a drug. Hu et al, using mathematical simulations, have forecasted twice the variation coefficient in plasma concentration of a drug in bolus as compared to continuous infusion 12 . This may promote high plasma concentrations of drugs and the presence of adverse effects.…”

Influence of real-time Bayesian forecasting of pharmacokinetic parameters on the precision of a rocuronium target-controlled infusion

“…In this relationship, the blood concentration is usually linked to the dose by a two-or three-compartment model, and the pharmacological effect is linked to the effect compartment concentration by a linear or sigmoidal E-max model [19]. These models, available in the literature for all anesthetic drugs administered IV allow predicting the effect induced by a known dose but also choosing the dose to achieve a desired effect or driving an infusion in order to maintain a chosen level of concentration and effect, as in target-controlled infusion (TCI) [4] However, for a particular patient, the observed effects of a drug may differ markedly from the predicted, because the patient differs from the population used to establish the model (by age; cardiac, hepatic, or renal function; drug interactions) [9] or because some factors influence the dose-effect relationship over time. Using the population model to adjust drug delivery may then induce detrimental underdosage, overdosage, or delayed recovery [2,13].…”

Use of a target-controlled infusion system for propofol does not improve subjective assessment of anaesthetic depth by inexperienced anaesthesiologists*

“…anaesthetics. There is evidence that TCI outperforms manually controlled infusion (MCI) regarding safety and clinical performance [2][3][4][5][6], probably by limiting the variability of the infusion regimen [7]. Since 'depth of anaesthesia' is a function of anaesthetic concentration, the calculated plasma concentrations supplied by TCI systems may also help in the assessment of anaesthetic depth by anaesthesiologists.…”