2021 article
Comparison of venous hemoglobin saturation measurements obtained by in vivo oximetry and calculated from blood gas analysis in critically ill dogs
Walton, R. A. L., & Hansen, B. (2021, July 16). JOURNAL OF VETERINARY EMERGENCY AND CRITICAL CARE.
Abstract Objective To compare in vivo central venous hemoglobin saturation measurement (ScvO 2 ) using a fiber optic catheter with saturation calculated from blood gas analysis in critically ill dogs. Design Prospective observational study. Setting University veterinary teaching hospital intensive care unit. Animals A convenience sample of 20 dogs with severe illness. Interventions Dogs were instrumented with either a central venous catheter with an integrated fiber optic cable or a conventional catheter with a fiber optic probe inserted through its distal port. Baseline saturation was measured with the fiber optic system (FSO 2 ), then monitored continuously. Central venous blood was collected for analysis and FSO 2 was recorded by the principal investigator (PI) or nursing staff participating in data collection (staff) at baseline and at 1, 2, 3, and 6 hours. Hemoglobin oxygen saturation (SO 2 ) values calculated using human Bohr coefficients were taken directly from the analyzer (GPSO 2 ), and were also calculated using temperature‐correction and canine Bohr coefficients (RSO 2 ). Measurements and Main Results Ninety‐seven paired measurements from 20 dogs were analyzed. FSO 2 obtained by the PI (n = 41) had better agreement with both GPSO 2 (concordance correlation coefficient ρc = 0.926 vs 0.5562) and RSO 2 (ρc = 0.75 for PI vs 0.54) than did staff (n = 56). RSO 2 values were always smaller than GPSO 2 . FSO2 ‐ GPSO 2 differences were smaller when measurements were collected by the PI versus Staff (mean difference 0.21 vs −6.6, respectively, P < 0.02). Thirty‐six of 41 FSO 2 values obtained by PI were within 5% of GPSO 2 . Conclusions Concordance between FSO 2 and either calculation method was low, but was better when performed by PI. The larger difference between methods when using RSO 2 suggests a positive bias by FSO 2 . Difficulty obtaining stable measurements may have contributed to the poor concordance between methods within Staff.