Electronic health records reveal variations in the use of blood units by hour and medical specialty.

Background and objectives: Efficient blood supply chain requires accurate demand estimates. Blood demand is created by clinicians making transfusion decisions based on patient status. To better understand the use of blood units, we tracked their use hourly and across a large hospital organization.

Materials and methods: We analysed blood use in adult patients over 2021-2022 at HUS Helsinki University Hospital, serving a population of 1.7 million and consuming a third of blood units used in Finland. We utilized electronic health records (EHR) to map transfusions to patient demographics, diagnoses, medical specialties, treatment events, surgical procedures and laboratory values. Data were matched to transfusions of red blood cells, platelets and plasma using timestamps and treatment episodes.

Results: In total, 107,331 units were transfused to 19,637 unique patients in 50,978 transfusion episodes. Most transfusions occurred in emergency settings, with 61.5% of use driven by emergency department admissions. The most common diagnoses were malignant neoplasms, anaemia and cardiovascular diseases. In total, 47.9% of transfusions were associated with a surgical procedure. Of these, 72.9% were for urgent surgery. Blood use peaked in the early evening and was lowest during morning office hours.

Conclusion: The study offers a comprehensive picture of blood use in one of the largest European hospital organizations. In addition to elective use, a significant portion of blood demand is driven by urgent and emergency needs, which introduce some uncertainty in predicting blood use. Future studies should aim to understand both elective and emergency blood use to help improve demand estimates.