Heterogenous treatment effects of transfusion thresholds by patient age: Post-hoc analysis of the TRISS trial.

BACKGROUND: Use of a lower haemoglobin (Hb) threshold to guide red blood cell (RBC) transfusion is now generally recommended in critically ill patients, but uncertainty remains regarding the optimal Hb threshold for RBC transfusion in patients of different ages. METHODS: We conducted a post-hoc analysis of 998 patients with septic shock and anaemia randomised to RBC transfusion at a Hb threshold of 7 g/dl [4.3 mmol/l] vs 9 g/dl [5.6 mmol/l] in the Transfusion Requirements in Septic Shock (TRISS) trial. We assessed if there were heterogeneous effects between the allocated Hb threshold and patient age categorised and on the continuous scale. The primary outcome was 1-year mortality; the secondary outcome was 90-day mortality. Both outcomes were analysed using logistic regression models and in sensitivity analyses with additional adjusting for site of enrolment, presence of haematological malignancy and the Sequential Organ Failure Assessment (SOFA) score. The secondary analyses were Kaplan-Meier curves with corresponding log-rank tests. RESULTS: We found no heterogeneity between patient age and the allocated Hb thresholds for RBC transfusion for 1-year mortality or 90-day mortality in the primary analyses. The sensitivity analyses suggested heterogeneity between age groups regarding 90-day mortality, however, this was not consistent for 1-year mortality or when assessing age on the continuous scale. CONCLUSION: In this post-hoc study of ICU patients with septic shock, we found no reliable heterogeneous effects of transfusion at a Hb threshold of 7 vs 9 g/dl according to patient age on mortality. However, due to low power, this study should only be considered as hypothesis generating.

Storage time of red blood cells among ICU patients with septic shock.

BACKGROUND: We aimed to describe the exposure to blood transfusions and mortality among patients with septic shock. METHODS: We did a retrospective cohort study of two cohorts-patients with septic shock registered in a Danish ICU database (2008-2010) and patients from the Transfusion Requirements in Septic Shock (TRISS) trial (2011-2013). We extracted information on blood transfusions issued to all patients. We investigated the number of patients receiving very fresh blood (less than 7 days), very old blood (more than 24 days) and blood with a mixture of storage time. RESULTS: In the Danish cohort, 1637 patients were included of whom 1394 (85%) received 20,239 blood units from 14 days prior the ICU admission to 90 days after; 33% were transfused before, 77% in the ICU and 36% after ICU. The exposure to exclusively very fresh or very old blood was 3% and 4%, respectively. In the TRISS cohort, 77% of the 937 patients received 5047 RBC units; 3% received exclusively very fresh and 13% very old blood. The point estimate of mortality was higher among patients receiving large amounts of exclusively very fresh and very old blood, but the number of patients were very small. CONCLUSIONS: Patients with septic shock were transfused both before and after ICU. Exposure to blood of less than 7 days or more than 24 days old were limited. We were not able to detect higher mortality among the limited number of patients with septic shock transfused with very fresh or very old blood.