Restrictive red blood cell transfusion strategies in critical care: does one size really fit all?
Many intensive care patients receive red blood cell transfusions. International clinical practice has recently changed, with a decrease in the "trigger" haemoglobin concentration used for red blood cell transfusions in critically ill patients. This change has been driven by increasing awareness of the infectious and non-infectious complications of allogeneic red blood cell transfusion, the perennial blood supply shortages, and most importantly by the Transfusion Requirements in Critical Care (TRICC) study, which suggested that a restrictive transfusion strategy (a transfusion trigger of 70 g/L and a post-transfusion goal of 70-90 g/L) may be equivalent to a liberal transfusion strategy (a transfusion trigger of 100 g/L and a posttransfusion goal of 100-120 g/L) in non-shocked ICU patients. However, patients with ischaemic heart disease may benefit from red blood cell transfusion at a haemoglobin trigger level higher than advocated by such a restrictive transfusion strategy. This assertion is supported by animal studies, retrospective clinical studies and a post-hoc subgroup analysis of the patients with ischaemic heart disease in the TRICC trial. Despite this, and a number of important methodological issues that limit the generalisation of the TRICC results to patients with ischaemic heart disease, the TRICC authors, subsequent guidelines and recent reviews have recommended a restrictive strategy in ICU patients with ischaemic heart disease. This conclusion and the change in clinical practice that followed these publications are premature. In determining the appropriate trigger for transfusion of allogeneic blood, the physician should ideally weigh the risk-benefit profile for each individual patient, for each unit of blood administered.