Patients were recruited from 47 participating hospitals in the USA and Canada , and eligible participants were randomly allocated in a 1:1 ratio by a central telephone system to either liberal transfusion in which they received blood transfusion to maintain haemoglobin level at 100 g/L or higher , or restrictive transfusion in which they received blood transfusion when haemoglobin level was lower than 80 g/L or if they had symptoms of anaemia .