Transfusion medicine

Age increases transfusion Hb threshold

Most recipients of blood transfusions are over 65 years of age yet patient blood management guidelines do not consider whether older patients should be treated differently to younger patients.

Speaking at the Blood 2018 symposium on Haematology at Extremes of Age, transfusion medicine researcher Geoff Simon said restrictive haemoglobin thresholds of 70-80 g/L might not be appropriate for older patients.

As reported in the limbic last year, his 2017 meta-analysis of restrictive versus liberal transfusion practice in older adults found higher haemoglobin thresholds were associated with lower mortality and few cardiac complications.

Mr Simon told the meeting that both the 30- and 90-day mortality rates favoured a more liberal approach.

Acknowledging that restrictive practice had the benefit of minimising the cost of potential harms of unnecessary exposure to blood products, he argued that it was not a case of one-size fits all.

Mr Simon, a lecturer in Blood Banking and Transfusion Sciences in the University of the Sunshine Coast’s School of Health and Sports Sciences, presented physiologic evidence that the impact of anaemia and subsequent need for transfusion were different in younger versus older adults.

Using cardiac output data from a study of 500 healthy adults, the study modelled the potential oxygen delivery (DO2) at normal and anaemic haemoglobin levels.

“Ageing impacts the capacity to maintain DO2 at lower haemoglobin levels,” he told the meeting.

The data showed that a male over 60 years with a haemoglobin of 70g/L would only deliver a peak 1100ml/min of oxygen. To match the peak DO2 of a younger adult male, they would need a haemoglobin of 100 g/L.

The physiologic modelling supported the evidence from trials that older adults benefited from higher haemoglobin thresholds for transfusion.

He added that evidence regarding optimal haemoglobin levels for transfusion was muddied by the use of different definitions and cut-offs.

For example, in some studies restrictive haemoglobin thresholds were higher than the lowest thresholds considered to represent liberal practice.

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