There are several Cochrane Reviews of methods to ensure that blood transfusions are used effectively and efficiently, and that donated blood remains available for use in emergency situations. One of the first of these reviews looked at the evidence on a technique called cell salvage. It was first published in October 2003 and the fourth update appeared in September 2023. We asked new lead author, Louise Geneen from NHS Blood and Transplant based in Oxford UK, to tell us more about the technique and the latest findings of the review.
Mike: Hello, I'm Mike Clarke, podcast editor for the Cochrane Library. There are several Cochrane Reviews of methods to ensure that blood transfusions are used effectively and efficiently, and that donated blood remains available for use in emergency situations. One of the first of these reviews looked at the evidence on a technique called cell salvage. It was first published in October 2003 and the fourth update appeared in September 2023. We asked new lead author, Louise Geneen from NHS Blood and Transplant based in Oxford UK, to tell us more about the technique and the latest findings of the review.
Louise: Cell salvage is the process of re-infusing blood that was lost during an operation. The blood is usually suctioned from the wound, processed, and returned to the same patient either during the surgery or in the hours afterwards. Our review focuses on elective surgery, so no trauma or emergency surgeries, and has allowed us to identify procedures for which cell salvage reduces the need for a transfusion of donated blood (known as allogeneic blood), and whether there are any safety issues, such as more adverse events, as a result of using cell salvage.
We have now included 106 randomised trials, from across 24 countries, with a total of nearly 15,000 adults. We split the evidence into different surgical specialties to determine if some populations saw a different effect to others. So: cancer surgeries, obstetrics (which ended up being elective caesarean sections only), orthopaedics (as hip, knee, or spinal surgeries), and cardiovascular surgeries focusing on vascular, on-bypass procedures, and off-bypass procedures separately.
There were differences between these patient groups in the volume of the data, and the effect of cell salvage.
For caesarean sections, there was no evidence of a difference in the need for a donated blood transfusion whether they received cell salvage, or not, but the evidence was low certainty due to wide confidence intervals. Whereas, we had low to moderate certainty evidence that there may be a benefit of using cell salvage (i.e. a reduction in the need for donated blood transfusion) for the cardiovascular procedures, both on and off bypass, and for spinal surgeries.
There was very low certainty evidence (or no evidence at all) for cancer, vascular surgeries, and the other orthopaedic surgeries (including hip and knee). So, we can't say either way whether cell salvage has any impact in these patient groups.
We did consistently see no difference in adverse events in all the surgical groups, whether patients received cell salvage, or not. The certainty of this evidence varied from very low to moderate, but it suggests there may be no additional harms from using cell salvage, and some patient groups may benefit by needing less donated blood.
However, there is a lot of variation across the more than 100 trials and different surgical areas, and we still need more well-conducted randomised trials, especially in cancer surgeries, vascular surgeries, and orthopaedics, where the evidence was often very low certainty, particularly around safety outcomes.
One hypothesis for the difference in effect is that those surgeries that expect to have low blood loss (such as the elective caesarean section, where we saw no clear benefit or detriment), may be less impacted by the use of cell salvage, compared to those with higher expected blood loss (such as heart surgeries), which may find it beneficial.
We therefore concluded that secondary analysis of the existing data, as well as future trials that focus on factors like expected blood loss (perhaps based on surgery type, or whether it is a primary or revision procedure), and other indications for surgery, may help identify people or surgeries where cell salvage would be beneficial to both the outcomes of the patients, and to maintaining donated blood stocks.
Mike: If you would like to read the current version of Louise's review and watch for the next update if more evidence becomes available, it's available online. A simple search for 'cell salvage and surgery' on Cochrane Library dot com will show you a link to the full version.