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.