Abstract SNACC-74

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A Comparison Of Hemoglobin Measured By Co-Oximetry And Central Laboratory During Major Spine Fusion Surgery

Carabini L, Navarre W, Ault M, Bebawy J, Gupta D
Northwestern University Feinberg School of Medicine, Chicago, IL, USA

Background: There are a multitude of factors affecting the accuracy of hemoglobin concentration values, including the type of measurement device and laboratory methodology. This study aims to evaluate if the hemoglobin concentration obtained by means of arterial blood gas co-oximetry and central laboratory techniques correlate within the stated resolution of 0.1 g/dL using simultaneous measurements of hemoglobin concentration obtained during complex spine procedures occurring at Northwestern Memorial Hospital.

Methods: 348 patients who underwent spinal fusion of greater than 3 bony levels between September 2006 and September 2010 with concurrent ABG and CBC samples were identified. The mean difference between pairs of measured hemoglobin values was determined using limits of agreement analysis. Error grid analysis was used to delineate correlation of samples in relation to hemoglobin values within the range considered for transfusion.

Results: The median difference (ABG-CBC) between the measured hemoglobin values was 0.4 g/dL (95% CI -0.3 to 1.1 g/dL, p <0.0001). Limits of agreement analysis correcting for repeated observations in multiple patients demonstrated the mean difference between measured hemoglobin values (i.e. bias) was 0.4 g/dL (95% CI 0.36 to 0.41 g/dL). However, 44.5% of paired samples were within 0.5 g/dL and there was only fair to moderate agreement between the CBC and ABG values within the clinically significant range of hemoglobins 7 to 10 g/dL (Cohen’s κ = 0.39, 99% CI 0.31 to 0.47) (Fig1).

Conclusions: The hemoglobin values obtained from ABG and CBC cannot be used interchangeably when verifying accuracy of novel point-of-care hemoglobin measurement modalities. Additionally, while a 0.4 g/dL bias between ABG and CBC hemoglobin values may be clinically inconsequential at higher hemoglobin values, when implementing a restrictive transfusion strategy this difference may alter transfusion management during acute blood loss.

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  • SNACC-74 Image 1

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