Vancomycin pharmacokinetics in PICU using scavenged samples
Research type
Research Study
Full title
The use of scavenged blood samples to better understand vancomycin therapy in children in intensive care
IRAS ID
137966
Contact name
Rhian Isaac
Contact email
Research summary
Vancomycin is an antibiotic often used in a paediatric intensive care setting for life threatening gram positive infections. Vancomycin therapy is particularly challenging as the drug has a narrow therapeutic window, meaning that all patients have blood samples taken to measure the vancomycin concentration during therapy to ensure and that levels are not toxic but are also above the minimum inhibitory concentration; so the medication is effective and does not potentially lead to antibiotic resistance.
Although a trough level indicates the presence or absence of potentially toxic levels, it is not fully informative as these levels may have been reached several hours before the level was obtained. Modern methods of pharmacokinetic (PK) analysis allow a more sophisticated approach by taking account of variables affecting drug levels including renal function and by performing an estimate of drug exposure on the basis of a population model and a single measurement in the individual taken before the trough is reached. This raises the possibility that samples for TDM can be obtained at clinically more flexible times. Currently, trough levels are obtained at formal pre-set intervals, usually require a separate blood test and are often performed at inconvenient times for babies, parents and staff.
This blood sampling is usually done at dose 5 of therapy or sooner if renal impairment is suspected. However, computer simulations can predict the concentration of vancomycin over time, if these predictions are accurate then it may be possible to measure vancomycin concentrations sooner than dose 5 to ensure therapy is optimised as soon as possible. Optimisation of these models requires several vancomycin concentrations over time; this is unlikely to be acceptable to paediatric patients in intensive care. However, many children in intensive care have routine blood samples taken where the entire sample is not always required for analysis therefore there is “spare” blood. This project aims to use these “spare” scavenged blood samples to measure vancomycin levels, rather than taking a dedicated sample. These scavenged samples can be used to validate the computer simulation; then in future a simple scavenged measurement may be used rather than taking a dedicated sample at day 5.
As part of this project we will develop a vancomycin PK model through analysis of clinical datasets. This model will incorporate the effects of a number of important variables such as age, weight, current serum creatinine and will enable individualised TDM based on levels obtained at times of convenience.REC name
North East - Newcastle & North Tyneside 2 Research Ethics Committee
REC reference
14/NE/0040
Date of REC Opinion
5 Feb 2014
REC opinion
Favourable Opinion