Current designs of instruments providing blood gas and electrolyte results make them suitable for use in a point of care (POC) setting. Such instruments may be found away from the main laboratory, in accident and emergency departments, intensive care, coronary care and special baby care units.

The Radiometer ABL500 measures carbon dioxide partial pressure, oxygen partial pressure, and hydrogen ion concentration, reported as pH, in whole blood, and gas partial pressures in expired gas. The Radiometer KNA2 determines sodium and potassium in whole blood, serum, and urine. The two instruments work independently of each other, requiring individual blood samples. However they can be interfaced electronically so that patient results from the KNA2 are transmitted to the ABL500 and are printed out either separately or as part of a combined blood gas and electrolyte report. Blood gas partial pressures, hydrogen ion concentration and electrolytes are measured using electrode technology. Twenty eight other parameters are derived mathematically from the measured parameters.

The measurement of all available analytes was evaluated using whole blood samples; in addition the measurement of sodium and potassium was assessed using plasma samples. The evaluation included assessment of the analytical performance, carryover, ease of use, safety and reliability of the analyser.

The accuracy, imprecision and linearity of analysis were good for all the analytes. Instrument maintenance was straightforward but regular technical support is required for continuing satisfactory performance of the instrument. The instrument combination was reliable during normal use but the KNA2 had the potential for problems if misused. Field studies showed that a majority of non-technical volunteers found the instrument easy to use and drew attention to some potential problems in its design and use.