i-Stat

Wired News, in an excellent story about miniaturized medical devices that are being developed for battlefield care of American soldiers, has the following passage:

… i-Stat, a handheld device that launches a series of tests on a single drop of blood. About 30,000 of the $8,500 machines have been sold since 1994, and the military has bought about 3,000 of them, said Dr. Greg Shipp, medical director at Abbott Point of Care, which manufactures the device.
Although it can’t determine blood type, the i-Stat can monitor kidney, lung and heart functions, among other things. The devices are commonly used in hospital emergency rooms where quick tests are crucial.

More info about the device is available from i-Stat:

The i-STAT System is at the cutting edge of diagnostic technology. With the revolutionary integration of biochemical and silicon chip technologies, the System achieves previously unattainable miniaturization of sophisticated components that provides clinicians a truly portable, nearly instantaneous blood analyzer with no sacrifice in accuracy and reliability. To meet the needs of the entire hospital, a variety of sensor configurations make it possible to perform a number of critical care assays: electrolytes, general chemistries, blood gases and hematology.
The solid-state chips contain biosensors configured to perform specific tests with chemically sensitive membranes and films containing reagent chemicals. Sensors perform other functions such as monitoring the quality of the sample being tested. Silicon-type microfabrication utilizing high quality materials that exhibit exceptional stability allows consistent reproducibility in a high-volume manufacturing environment. This well accepted technology ensures that each cartridge offers a high level of accuracy and reliability.

Some of the parameters measured by i-Stat are: sodium, potassium, chloride, ionized calcium, blood gas values (pH, pO2, PCO2, HCO3, TCO2, BE, SO2), as well as anion gap, hemoglobin/hematocrit, urea, and glucose.