Microprocessor-based near real-time bedside blood chemistry monitor.

A microprocessor-based instrument which integrates the function of a volumetric infusion pump with a blood chemistry analyzer has been developed. Presently, the instrument is capable of measuring Na+, K+, Ca++ and pH within approximately 40 sec at a frequency of up to every 2 min. The system is set up as an intravenous (IV) infusion pump with the addition of an array of disposable sensors placed at the distal end of the IV set. An isotonic IV solution is used to keep the site patent while also serving as a calibrant for the sensors. The instrument first calibrates the sensors, then withdraws approximately 0.6 ml of blood to come in contact with the sensors. Within approximately 15 sec, it displays the results, flushes the blood back into the patient and resumes normal infusion. There is no blood loss to the patient and no need to handle blood. The system was first validated with known aqueous controls and then used on-line in a variety of animal studies where dynamic fluctuation of electrolytes and pH occurred. Excellent correlation was found with off-line samples tested on conventional STAT analyzers. Some preliminary patient data is also presented.