A new study published in the journal Transfusion suggests that chest tube drainage, but not transfusion, is independently associated with mortality.
Dr. Barry Dixon and colleagues retrospectively analyzed mortality among 2599 patients who had undergone cardiac surgery. Greater than 40% of patients received post-operative blood transfusion within 24 hours and mortality was defined as death in the hospital, before discharge.
Dr. Dixon explains, “It is believed that blood transfusion is an important cause of harm following cardiac surgery based on studies that demonstrated the risk of death increased by around 2 – 4 fold for every 2 units of blood given.”
“We wondered whether chest bleeding following cardiac surgery may in itself be harmful, in as much as the chest drains are inefficient at clearing blood and retained blood in the chest may compromise both cardiac and lung function.”
While previous studies had shown that blood transfusion appeared to increase mortality, Dr. Dixon’s analysis suggested that the observed effect of transfusion may have been confounded by other factors. His study found that after accounting for 24-hour chest tube drainage, blood transfusion was no longer a significant risk factor for mortality. The volume of chest tube drainage, however, was significantly associated with increased risk of death, and exhibited a dose-response relationship with mortality. Furthermore, the effect of chest tube drainage on mortality was evident regardless of whether or not the patient had been transfused.
In an accompanying editorial, Drs. Jonathan Waters and Mark Yazer discussed Dr. Dixon’s findings and their implications. They suggest that the relationship between chest tube drainage and mortality has a logical basis. Chest tube drainage can be inefficient, leaving behind some fluid, which can impair cardiac and lung function.
Here is Dr. Waters. “This paper suggests that it’s not the transfusion but rather the bleeding that causes the harm. This is an intuitive finding that has not previously been recognized and it should change how we approach the study of outcomes in major blood loss surgery.”
We’ll be back on January 30th with another edition of Transfusion News. Thanks for joining us.
1. Dixon B, Santamaria JD, Reid D, et al. The association of blood transfusion with mortality after cardiac surgery: cause or confounding? Transfusion 2013;53:19-27.
2. Waters JH, Yazer MH. Bleeding Causes Harm…Really?! Transfusion 2013;53:2-4.