The 'transfusion trigger' in three large West of Scotland hospitals: medical staff questionnaire survey.

Efficient use of blood is desirable due to increased demand for blood, shortfall in donations, and the risk of mismatch transfusion accidents and transfusion-transmitted infections. We surveyed transfusion practice in three hospitals. Low haemoglobin was a feature in 91% of transfusion requests and is the commonest 'trigger' for transfusion.