An audit of the incidence of over-transfusion at a quaternary centre

Massive transfusion (MT) is a resource intensive event, associated with significant morbidity and mortality. Excessive transfusion of blood product is associated with harm and waste of a limited resource. Restrictive transfusion, when haemoglobin (Hb) is less than 70 g/l, has been demonstrated to reduce mortality and re-bleeding in patients with upper gastrointestinal (UGI) haemorrhage when compared with liberal transfusion (Hb <90 g/l). In cardiac surgery, the TRICS III trial demonstrated non-inferiority of restrictive transfusion (Hb <75 g/l) compared with liberal transfusion (Hb <95 g/l). At our institution, concern was raised regarding cases in which excessive blood product replacement was given as part of MT. To determine the veracity of this, we audited our incidence of over-transfusion. Our audit was granted ethics approval as a quality assurance activity (reference 21059). Data were from a record of massive transfusion protocols (MTPs) from January 2020 to May 2021 and patient medical records. Our definition of MT required transfusion of blood products totalling 50% or greater of patient blood volume within four hours, or 100% or greater of blood volume within 24 hours. Patient blood volume was calculated using a 70 ml/kg estimate up to 100 kg body weight. Cases of intraoperative mortality due to inability to control bleeding were not included. We categorised outcomes according to post-transfusion Hb: ‘mild over-transfusion’ (Hb 80–100 g/l) and ‘significant over-transfusion’ (Hb >100 g/l); ‘appropriate transfusion’ for post-transfusion Hb of 70–80 g/l and ‘under-transfusion’ for Hb less than 70 g/l. Preand post-transfusion Hb were defined, respectively, by the Hb concentration before the first unit of packed red blood cells (PRBCs), and two to four hours following MTP completion. Of 83 cases of MTP activation, 30 episodes occurring in 29 patients met the criteria for inclusion (Table 1). Forty-seven excluded cases received less than the defined blood products for MT. Four were excluded due to intraoperative or preoperative mortality. Two duplicates were removed. The median transfused volume was 9 units PRBCs, 5.5 units fresh frozen plasma (FFP) and 8 units platelets. Twenty-seven of 30 episodes met the definition of over-transfusion. The median (interquartile range) Hb post-transfusion was 98 (91.3–106.3) g/l. At discharge, median Hb was 96.5 (89.8–106.5) g/l. No included patients met the criteria for under-transfusion. However, under-transfusion may have occurred in patients who did not survive. Our audit demonstrated a pattern of overtransfusion associated with MT, with no cases of under-transfusion. A similar incidence of overtransfusion has been identified in other institutions. Our reported in-hospital mortality (Table 1), was slightly higher than in previous meta-analyses of MT (31% versus 24%). Over-transfusion occurred at similar rates regardless of subgroup, although appropriate transfusion was most common in those with UGI haemorrhage (Figure 1). All MTs involved anaesthetists at some stage and took place, at least partially, in the operating theatre; demonstrating the importance of anaesthetists in MT management. With critical intraoperative bleeding, anaesthetists are required to rely on estimates of volume loss, ongoing bleeding and haemodynamic parameters to calculate blood product replacement. There may be a delay in acquiring frozen products due to thawing time. These factors may risk excessive administration of PRBCs for volume resuscitation prior to control of bleeding.