Photo courtesy of UAB Hospital
Results of a large, randomized trial suggest a liberal transfusion strategy may benefit patients undergoing cardiac surgery.
Patients who received blood transfusions when their hemoglobin (Hb) levels were below 9 g/dL fared better than patients who only received transfusions once their Hb levels were below 7.5 g/dL.
The “low” Hb group had a slightly higher incidence of serious complications and a significantly higher rate of 90-day mortality than the “high” Hb group.
However, the researchers noted that the latter finding, while important, is difficult to interpret because the trial was not primarily designed to compare the difference in the number of deaths.
“Although only a hypothesis, the suggestion that it might be better rather than worse to transfuse patients who are only mildly anemic goes against the evidence about when to transfuse in non-cardiac surgery settings,” said Barnaby Reeves, DPhil, of the University of Bristol in the UK.
“Transfusing more rather than fewer patients would create a challenge for hospitals. With an aging population and possibly an increase in heart disease, obesity, and diabetes, it can only become more difficult in the future to maintain the national blood supply in the UK and in other developed countries around the world. Our findings emphasize the importance of interventions to reduce blood loss in the first place.”
Dr Reeves and his colleagues reported their findings in NEJM.
The team conducted their randomized, controlled trial to determine whether transfusing cardiac surgery patients at a lower Hb level would be safer or more cost-effective, as has been shown in other patient groups.
Individuals older than 16 who were undergoing non-emergency cardiac surgery were recruited to the trial at 17 UK hospitals. Patients with an Hb level of less than 9 g/dL after their operations were randomized to have a transfusion either when they became substantially anemic—with an Hb level of less than 7.5 g/dL—or right away, when they were mildly anemic—with an Hb level of less than 9 g/dL.
To compare the two transfusion strategies, the researchers assessed the incidence of serious infection, ischemic event, heart attack, infarction of the gut, and acute kidney injury in the first 3 months after the operation.
The team analyzed data for 2003 patients. Nearly all of the patients in the high Hb group received a transfusion (92.2%), compared to just over half of patients in the low Hb group (53.4%).
Slightly more patients in the low Hb group than the high Hb group had one or more of the aforementioned serious complications—35.1% and 33%, respectively (P=0.30). And significantly more patients had died at 90 days in the low Hb group than the high group—4.2% and 2.6%, respectively (P=0.045).
The researchers found no significant differences between the high and low Hb groups with respect to other information measured to assess recovery, but some of the other findings in the trial showed a trend in the same direction.
In addition, healthcare costs up to 3 months after surgery were similar in the high and low Hb groups.
“Even though the high group were given more blood, it was interesting that this did not lead to them costing more once the costs of treating complications were added to the analysis,” said Sarah Wordsworth, PhD, of the University of Oxford in the UK.
Based on the overall pattern of findings, the researchers proposed that a high or liberal transfusion threshold may be better after cardiac surgery. This challenges most prevailing guidelines and current health policy.
“Existing national and international transfusion guidelines recommend that blood transfusions only be given to patients who develop very low hemoglobin concentrations,” said Gavin Murphy, FRCS, of the University of Leicester in the UK.
“We have shown that this strategy may increase the number of deaths in cardiac surgery. This was the largest randomized trial ever conducted in the UK in a surgical or cardiac surgery population. It was the largest trial ever conducted that has considered indications for transfusion in cardiac surgery, and recruited over twice the number of patients recruited in all the previous trials put together. It . . . recruited patients from the majority of [National Health Service] cardiac surgery centers in the UK and therefore reflects current UK practice and is relevant to UK patients.”
