Transfusion intensity in the ICU: Reasons and triggers

Background: The reasons and physiological triggers for blood transfusion in critically ill patients are not well characterized. Beyond hemoglobin levels, hemodynamic instability is frequently cited, but its role across clinical contexts remains unclear. Aims: (1) To determine whether reasons and triggers for RBC transfusion differ across intensive care unit (ICU) days with varying transfusion intensity. (2) To describe reasons for non-RBC transfusions across these intensity groups. Methods: This sub-study of the prospective International Point Prevalence Study of Intensive Care Unit Transfusion Practices (InPUT) classified ICU days by transfusion intensity: nonmajor (1 RBC unit), major (≥2 units), and massive (≥6 units in a single event, ≥10 per day, or Massive Transfusion Protocol activation). ICU days without transfusion for active bleeding were classified as no bleeding. Results: Significant differences in the multivariate composition of reasons for RBC transfusion were observed across intensity groups on permutational analysis of variance (PERMANOVA). Hypotension was the most frequently cited physiological trigger in nonmajor (54%, n = 80/148) and major transfusions (68%, n = 196/288), but less frequent in massive transfusions (30%, n = 14/64). Tachycardia was the second most common trigger in nonmajor (37%, n = 80/148), major (40%, n = 116/288), and massive transfusions (22%, n = 19/64). Conclusion: RBC transfusions are administered for distinct, intensity-dependent combinations of reasons and triggers. Transfusion intensity and clinical context are therefore key factors in evaluating transfusion practices. Among bleeding critically ill patients, hypotension and tachycardia are the most frequently cited physiological triggers.