Study: Relationship Between Storage Time of RBC and Postoperative Atrial Fibrillation (POAF) in Cardiac Surgery
For a very long period, postoperative atrial fibrillation (POAF) following cardiac surgery has been associated with allogeneic red blood cell transfusion. Many have observed that the risk may rise if red blood cells are stored for an extended period of time. A research was done to determine whether the amount of time that RBC is stored is actually related to the emergence of POAF in order to investigate this claim.
Pre-, intra-, and postoperative statistics were obtained for this purpose from the Western Denmark Heart Registry and nearby blood banks. All of this data was gathered from patients who received combined procedures, coronary artery bypass surgery, or valve surgery at Aarhus University Hospital. In order to analyze the data, multiple logistic regression was applied in order to determine the risk of POAF according to transfusion of RBC on the day of surgery. In addition to this, the study determined trends in storage time of RBC according to the risk of POAF by use of restricted cubic splines. The study included a total of 2978 patients with a mean age of 66.4 years with 609 patients receiving RBC transfusion on the day of the surgery. The study excluded patients who had a history of preoperative atrial fibrillation, those who received blood preoperative and those that died on the day of the surgery.
Results: Little to No Significant Link Between Storage Time of RBC and POAF
The results of the study showed that 752 patients developed POAF with transfused patients experiencing an increased risk compared to non-transfused patients. However, according to these results, RBC transfusion was not necessarily the cause of the POAF that was experienced and may be only a single factor in the development of POAF. Hence, the study concluded that there was little to no significant link between the storage time of RBC and the development of POAF in cardiac surgery. The results of this study were largely conclusive given that the two university hospitals serve a very large pool of consecutive patients in Denmark. This made acquiring information on blood transfusions and POAF relatively easy. However one thing that should have interfered with the process was the varying storage times of RBC varied across patients.
Limitations of the Study
The majority of patients received less than 5 RBC units however in some cases patients received more than ten units. Hence, some received mixed RBC units hence receiving both "old" and "new" blood. In addition to this, there have been different studies on how transfused blood is categorized as either "fresh" or "old" further complicating the issue. The study's conclusion is in accordance with several other studies that have noted RBC transfusion is only a predictor of the development of POAF but their cause. Hence only results from randomized studies can truly reflect on the intended results compared to observational studies which only lead to a hypothesis. In addition to this, the study did not use continuous ECG monitoring which would have been an optimal method of collecting data. This means that the incidence of POAF in the study may have been underestimated. In addition to this, the study failed in correlating the findings with the haemoglobin, haematocrit concentrations, and pH and potassium concentration in the blood that was transfused. This means that even though the study reached a conclusive conclusion, we cannot truly say that it achieved since the study was limited by the various weaknesses that can be used to challenge the results.
Bibliography
Gu, J., Skals, R.K., Torp-Pedersen, C., Lundbye-Christensen, S., Jakobsen, C.J., Bæch, J., Petersen, M.S. and Andreasen, J.J., 2017. Storage time of intraoperative transfused allogeneic red blood cells is not associated with new-onset postoperative atrial fibrillation in cardiac surgery. PloS one, 12(2), p.e0172726.
