Postoperative anaemia frequently occurs after major vascular or general surgical procedures and has been linked to an increased risk of short-term complications, especially in patients with pre-existing cardiovascular disease. While restrictive transfusion thresholds (haemoglobin < 7 g/dL) are generally considered safe for most hospitalised patients, uncertainty persists regarding the optimal strategy for those at high cardiac risk following major surgery.
The Transfusion Trigger after Operations in High Cardiac Risk Patients (TOP) trial was conducted to determine whether a liberal transfusion strategy (initiating transfusion when haemoglobin falls below 10 g/dL) reduces death or major ischaemic events within 90 days compared with a restrictive threshold of 7 g/dL.
The trial included 1,428 adult veterans (≥ 18 years) at 16 US Veterans Affairs Medical Centres between February 2018 and March 2023. Participants were assigned either to a liberal or restrictive transfusion group and followed for 90 days; the primary outcome was a composite of all-cause death, myocardial infarction, coronary revascularisation, acute kidney failure, or ischaemic stroke. Secondary outcomes included other cardiac complications (arrhythmias, heart failure, non-fatal cardiac arrest) and infectious events.
Of 1,424 analysed participants (mean age 69.9 years; 97.8% men), 91% underwent vascular operations. Chronic comorbidities were common, with 72% having peripheral artery disease, 59% coronary artery disease, and nearly half diabetes. Mean haemoglobin at randomisation was 9.3 g/dL in the liberal group and 9.0 g/dL in the restrictive group, producing an average 2 g/dL difference by day 5 post-randomisation. Transfusion exposure varied widely: 94% of restrictive-group patients received no postoperative transfusion compared with only 6.5% in the liberal group.
The primary composite outcome occurred in 9.1% of patients in the liberal group (61 of 670) and 10.1% in the restrictive group (71 of 700). Mortality at 90 days was nearly identical (4.6% vs 4.7%). Secondary analysis showed a modest reduction in non-myocardial-infarction cardiac complications, principally new arrhythmias and worsening heart failure, among liberal-strategy patients (5.9% vs 9.9%). However, rates of myocardial infarction, stroke, acute kidney failure, and infection were similar between groups, and one-year mortality did not differ.
The authors note that the anticipated event rate was lower than expected, possibly reflecting improvements in peri-operative care that have reduced morbidity and mortality over time. Although the study was underpowered to detect small differences, its results align with prior trials in critical care, cardiac surgery, and orthopaedic populations showing no significant advantage for liberal transfusion thresholds. The TOP trial thus strengthens evidence that restrictive strategies remain appropriate even in patients at high cardiac risk undergoing major operations.
One secondary finding was the higher rate of cardiac complications other than myocardial infarction in the restrictive group. This may relate to sustained anaemia increasing myocardial workload and oxygen demand in patients with impaired coronary reserve. While this difference did not extend to major ischaemic outcomes or overall survival, it highlights the physiological stress imposed by anaemia and suggests clinicians should individualise transfusion decisions when symptoms or haemodynamic instability arise.
Overall, the study concludes that a liberal transfusion strategy did not reduce 90-day mortality or major ischaemic events compared with a restrictive approach in high-cardiac-risk postoperative patients. These results support the continued use of restrictive transfusion thresholds, in line with international guidelines recommending transfusion only when haemoglobin falls below 7 g/dL in stable patients. However, the observed increase in non-ischaemic cardiac complications with restrictive practice warrants further investigation, particularly to determine whether select subgroups, such as those with severe coronary disease or limited cardiac reserve, might benefit from more liberal thresholds.
Source: JAMA
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