A-379 Frequency of Reassignment of Blood Gas Sample Source at a Large Tertiary Care Hospital

Abstract

Abstract Introduction Arterial blood gases analysis are central to the assessment and management of the critical patient acid-base status and its collection requires expertise and is often collected by trained respiratory therapists, nursing, and medical staff. Venous blood gases, arterialized venous blood gases, and capillary samples are however easier to collect. In this retrospective, study we examined the frequency of reassignment of blood gases results to a different sample type. Method Retrospective review of blood gases results requiring sample type reassignment collected during the last three years from January 2020 to December 2022 were obtained. Results were analyzed for concordance with sampling site and workflow analysis. Results Over the three years study period (2020 to 2022), a total of 196 samples for blood gases analysis required reassignment to a different collection site representing 0.12% of all blood gases testing. Among the 123 initial arterial collections, 72 were reassigned as venous, 40 reassigned to mixed venous sample, and one to capillary collection. Whereas, among the initial 24 venous samples collections 16 were reassigned as arterial and 8 to mixed venous collections. Additionally, among the 25 initial mixed venous collections, 16 were reassigned as arterial, 9 reassigned as venous and 3 were reassigned as capillary collections. The frequency of reassignment from arterial to venous was significantly higher compared to venous to arterial (P < 0.05) or for the reassignment in the mixed venous collections. Although a smaller number of samples were amended to capillary, capillary blood gases reflect arterial samples.There was no significant difference in the frequency of sample type reassignment between the three years of collection with the exception of a slight drop in year 2020 where the majorly of patients were of COVID-19 infection and that collections were likely performed by the same assigned medical personnel. Conclusion Common errors in blood gases collection are failure to obtain an arterial sample and accidental collection of venous samples instead often due to close proximity is common. In this retrospective review, the common reassignment is that of arterial to venous followed by arterial to mixed venous and venous to arterial sample types. Artifactual causes that may lead to misclassification of sample type include sample integrity as exposure to room air falsely reduces pCO2 and elevates pO2 giving a false impression of an arterial collection, similarly, dilution of arterial blood samples by heparin is common (inadequate blood fill of syringe) falsely lowers pCO2 both raising doubt as to the sample type.The impact of reassignment of change of sample type on outcomes and on interpretation requires analysis.