Patent ID: 8130369

Claim:
In a hemodialysis system, a method for monitoring at least one blood constituent, the method comprising the steps of: providing a blood chamber in extracorporeal tubing through which a patient's blood flows for hemodialysis; providing a ratiometric model within a controller for an optical monitoring device that determines a hematocrit value as a function of at least a detected value of light intensity having a first wavelength and a detected value of light intensity having a second wavelength, wherein the ratiometric model is calibrated at least in part by testing the ratiometric model by using the optical monitoring device with whole blood from a supply of blood preserved in a first anticoagulant, measuring the hematocrit value of whole blood from the same supply of blood preserved in the first anticoagulant using an in vitro method, and calibrating the ratiometric model to the measured hematocrit value taken using the in vitro method; emitting light at a first wavelength through the extracorporeal blood chamber and the patient's blood flowing through the blood chamber; emitting light at the second wavelength through the extracorporeal blood chamber and the patient's blood flowing through the blood chamber; detecting the intensity of the light at the first wavelength after it has passed through the extracorporeal blood chamber and the patient's blood flowing therethrough; detecting the intensity of the light at the second wavelength after it passes through the extracorporeal blood chamber and the blood flowing therethrough; calculating a hematocrit value using the ratiometric model from at least the detected light intensity at the first wavelength and the detected light intensity at the second wavelength; and scaling the hematocrit value calculated by the ratiometric model by a scaling factor to result in a scaled hematocrit value that accounts for a second anticoagulant in the patient's blood.