Validation of noninvasive hemoglobin measurements using co-oximetry in anesthetized dogs.

New technology allows noninvasive measurement of total hemoglobin (Hb) in humans through use of multiple wavelength co-oximetry. This monitor is now available to the veterinary market but no studies have been performed to validate its use in animals. This study investigated the use of co-oximetry to measure Hb in anesthetized dogs by comparing "gold standard" Hb measurements from a laboratory (LabHb) with those measured by the co-oximeter (SpHb). Bland-Altman analysis showed that the monitor had a bias of -3.01 (SpHb values were lower than LabHb values) and that 64.5% of measured SpHb values were greater than 20 g/L different from their associated LabHb values. Based on the results of this study, use of co-oximetry to measure Hb in anesthetized dogs is not accurate enough to direct treatment. Further studies are warranted in other animal species and under other clinical conditions.