Biosensor technology in the treatment of cardiovascular disease - Biomaterials and Devices for the Circulatory System - page 285

prism-coupled SPR technique shown in Fig. 11.3 is the basis for many
current commercial systems, but more advanced materials and manufactur-
ing techniques, such as fi bre-optic and waveguide technology and microfl u-
idics, are being used to build miniaturised and integrated SPR devices.

11.3 Ex vivo sensors

11.3.1 Point-of-care testing

Point-of-care testing has become an important tool in patient monitoring
and diagnosis in various settings, including in-hospital, where its use is
widespread in applications from surgery and critical care to initial diagnosis
and routine monitoring, and at home (chiefl y glucose testing for manage-
ment of diabetes). The main advantage of point-of-care testing is that it is
performed at the site of patient care, which reduces the time taken to obtain
test results. This has been enabled by the biosensor technology employed
in the devices. The instruments used to perform the tests are generally small
enough to be portable, and the tests are self-contained and convenient to
use. Small amounts of the sample (whole blood, plasma, serum, urine) are
required, from which a large amount of information can be extracted.
Among the most common whole blood analysers in current use are the
i-STAT (Abbott Diagnostics, Illinois, USA) and the AVL OMNI and
OPTI (AVL Scientifi c, Georgia, USA). The i-STAT (Fig. 11.4) is a hand-
held device capable of analysing blood gas ( p O 2 , p CO 2 ), levels of various ions
(Na + , K + , Ca 2+ , Cl − ), haematocrit, haemoglobin, pH, glucose, creatinine,
lactate, urea nitrogen and also various cardiac markers (BNP, CK-MB,
troponin). Similar analyses are performed by the AVL instruments, and
other point-of-care devices. 15
The rapid availability of data from patient samples obtained via point-
of-care testing is particularly useful in critical care departments, where
information about the patient's condition needs to be quickly analysed and
responded to. Lactate is an important metabolite for monitoring in the
critical care setting. 16-18 Lactate levels indicate cellular oxygen deprivation,
and have prognostic value in relation to patient outcome in general, and
specifi cally in monitoring respiratory insuffi ciency, heart failure, shocks and
metabolic disorders. In addition to lactate, measurements of blood pH, base
excess and strong ion difference are also predictors of complications and
mortality in critically ill patients, especially when used together.
Biosensor-based instrumentation is available for the diagnosis of cardio-
vascular disease, including acute myocardial infarction (AMI) and heart
failure. The i-STAT device described above and the Biosite Triage Cardiac
Panel and BNP Test (Biosite Inc., California, USA) are among such com-
mercially available devices. Biomarkers for cardiovascular disease have

￿ ￿ ￿ ￿ ￿