What is known?
Thresholds for red cell transfusion are currently under much scrutiny with a growing number of randomised controlled trials (RCTs) supporting the safety of restrictive transfusion practices in specified patient groups e.g. patients treated on the intensive care unit (TRICC) , following hip (FOCUS)  and cardiac surgery (TRACS) [3, 4], and patients with acute upper gastrointestinal bleeding  and sepsis (TRISS) . Patients with cancer who are anaemic have poorer outcomes than those who are not  but there are no previous RCTs examining risks and benefits of transfusion in surgical patients with malignancy.
What did this paper set out to examine?
This paper describes 198 critically ill patients following surgery for abdominal malignancy randomised to restrictive (threshold 7 g/dl) and liberal (9 g/dl) transfusion strategies . The primary outcome was a composite 30-day endpoint of all-cause mortality, cardiovascular complications, acute respiratory distress syndrome, acute kidney injury requiring renal replacement therapy, septic shock and reoperation.
What did they show?
This is the first RCT to demonstrate a worse outcome for patients assigned a restrictive threshold. There is an almost two-fold increase in the composite 30-day endpoint in the restrictive group (35.6% versus 19.6%, p=0.012). Thirty day mortality was 8.2% (liberal) versus 22.8% (restrictive), p= 0.005. The most common causes of death were septic shock and multisystem organ failure. Cardiovascular events and intra-abdominal sepsis were more frequent in the restrictive group.
The extent of the worse outcomes in the restrictive group is unexpected following larger RCTs supporting the safety of restrictive transfusion practice. The least supportive of this strategy was the recently published cardiac surgery RCT which concluded that a restrictive threshold was not superior to a liberal threshold ; they showed no difference in the primary outcome (serious infection or ischaemic event at 3 months). However, there was an increased mortality in the restrictive group (4.2% versus 2.6%, p=0.045).
There are significant differences in outcomes between the 2 groups in Almeida’s study and so we must consider whether these are attributable to differences in transfusion practice. Importantly, 57.7% of those even in the liberal group (79.2% in the restrictive group) were not transfused during the randomisation period. The reported difference in haemoglobin between the groups relates to the pre-transfusion haemoglobin and therefore does not include haemoglobins of those not transfused (68.9% of total study population).
Although the target thresholds were 7.0 and 9.0 g/dl, patients were transfused on average at 6.8 g/dl (restrictive group) and 7.9 g/dl (liberal). Compared to the preceding large RCTs there is a lack of separation in haemoglobin levels between groups [2, 6]. All 13 protocol deviations in the liberal group occurred when patients with haemoglobin <9.0 g/dl were not transfused; all 7 deviations in the restrictive group were for transfusions given with haemoglobin >7.0 g/dl.
The median duration for which patients remained randomised (i.e. length of ICU stay) was 4 days, compared to 11 days in the TRICC trial and until discharge or death in the Villanueva and FOCUS trials. In this study the small difference in haemoglobin between the groups only emerges at 4 days.
These factors together call into doubt whether the differences in outcomes can be attributed to differences in transfusion alone, and so an alternative explanation for the differences in outcomes must be sought. One possible reason is the small excess in major operations (oesophagectomy, gastroduodenopancreatectomy) as compared to cystectomy and hysterectomy in the restrictive group; this may also explain the excess of abdominal sepsis. There was a small, non-significant, excess of patients with diabetes, chronic obstructive pulmonary disease and congestive heart failure in the restrictive group.
The question addressed in the study is important and there are positive aspects to the trial which should be highlighted. This is the first randomised study specifically assessing post-operative patients with malignancy; the FOCUS study is the only other large RCT to include significant numbers of cancer patients (18.0 and 18.8% in the two arms) but the types, stage or remission status are not given. In the current study there were attempts to blind patients and investigators and the clinical practice described is deliverable on most ICUs. There were small numbers of protocol deviations and follow-up to the primary endpoint was complete.
What are the implications for practice and for future work?
It is important to consider the limitations of this study if its findings are to be used to inform practice. In the presence of multiple other RCT data supportive of restrictive transfusion practice we would caution against changing practice based on this research. Despite its unexpected findings, this study questions the safety of restrictive transfusion practice and it is important that future trials continue to address the safety this approach among different patient groups.
1. Hébert PC, et al., A multicenter, randomized, controlled clinical trial of transfusion requirements in critical care. Transfusion Requirements in Critical Care Investigators, Canadian Critical Care Trials Group. N Engl J Med, 1999. 340(6): 409-17.