The impact on allogenic blood transfusion rates
Correspondingly, allogenic blood transfusion rates also showed a predictable pattern with the incidence of transfusion being significantly less in non-anaemic patients than compared with anaemic patients (2.2 vs 26.1%, P < 0.001). However, there was no significance identified for transfusion rates between the 2 groups of anaemic patients (those treated pre-operatively vs those who did not receive pre-operative treatment). Similarly to the possible theory behind the LOS in both of these groups, questions may be asked of whether the use of erythropoietin injections to help stimulate growth of red blood cells as well as patient compliance to oral iron therapy contribute to these results. However, there are other significant factors that have not been taken into consideration when examining the transfusion rates. For instance, we did not account for the blood loss recorded for each patient. Primary knee replacement surgery commonly makes use of a tourniquet to reduce blood loss and assist in the visualisation of the surgical field – a surgical technique not possible with hip arthroplasties. It may be worth in the future considering the difference between the 2 sites of surgery and looking at each individual’s outcomes. The guideline illustrated in figure 2 above, also advocates the use of tranexamic acid, another factor we have not included in our analysis.
It is worth considering in this section transfusion threshold. The decision to give allogenic blood transfusions often rests on checking Hb levels, and considering a patient’s existing medical co-morbidities. When authorising blood transfusions, a risk versus benefit model must be considered as there are potential clinical incentives as well as cost benefits to be gained from avoiding it if it is not necessary[14], with each unit of packed red cell costing the Trust £133.22. There have been a variety of studies looking at strategies of liberal versus restrictive blood transfusions, and their outcome[24, 25]. The TRICC trial suggested that there was an equivalent benefit of using a restrictive strategy in ABTs within the elderly, but possibly a superior benefit in the under 55s[26]. Another study involving elderly patients with hip fractures suggested that liberal use of ABTs in patients with pre-existing risk factors for cardiac disease also showed no evidence of differences between the 2 groups[27].
Guidelines for anaesthetists within the UK were first published in 2008, followed by an update in 2016 which are more suggestive of using a restrictive ABT strategy to treat the anaemia in perspective to the surgery as opposed to their pre-operative haemoglobin level[28]. However, there is a loop hole to this guideline in which it suggests that transfusions maybe considered in patients who are symptomatic. This margin inevitably leads to a grey area in which patients and clinicians perceive the need for ABTs. This inconsistency in clinical management is one factor that may explain the unexpected results when analysing the 2 groups within the anaemia arm of the study. Another factor to also consider is that within the data reviewed, there was no specific mention of whether autologous blood transfusions were given via use of a cell salvage machine, thus reducing the possible need for allogenic blood transfusions.