An O2-based enzyme electrode for whole blood lactate measurement under continuous flow conditions

An enzyme electrode-continuous flow system for whole blood lactate measurement has been produced using ultrafiltration membrane-entrapped lactate oxidase retained over an O2 sensor housed in a measuring chamber. Linearity was to 0.8 mmol/l. Oxalate inhibition of the enzyme necessitated the use of lithium heparin-fluoride as anticoagulant for blood samples. A continuous flow system was devised which eliminated differences in sample PO2; analysis of serum and plasma specimens showed good correlation with a routine fluorimetric method (y = 1.097x -0.494, r = 0.959 and y = 0.978x + 0.085, r = 0.952, respectively). The correlation for the enzyme electrode between whole blood and plasma lactate concentrations was y = 0.801x + 0.142, r = 0.986. The flow system should, furthermore, allow reagentless continuous in vivo extracorporeal lactate monitoring.