P(v-a)CO2/C(a-v)O2 as a red blood cell transfusion trigger and prognostic indicator for sepsis-related anaemia: protocol for a prospective cohort study

Introduction Red blood cell (RBC) transfusion primarily aims to improve oxygen transport and tissue oxygenation. The transfusion strategy based on haemoglobin concentration could not accurately reflect cellular metabolism. The ratio of venous-arterial carbon dioxide tension difference to arterial-venous oxygen content difference (P(v-a)CO2/C(a-v)O2) is a good indicator of cellular hypoxia. We aim to explore the influence of P(v-a)CO2/C(a-v)O2 as an RBC transfusion trigger on outcomes in septic shock patients.Methods and analysis The study is a single-centre prospective cohort study. We consecutively enrol adult septic shock patients requiring RBC transfusion at intensive care unit (ICU) admission or during ICU stay. P(v-a)CO2/C(a-v)O2 will be recorded before and 1 hour after each transfusion. The primary outcome is ICU mortality. Binary logistic regression analyses will be performed to detect the independent association between P(v-a)CO2/C(a-v)O2 and ICU mortality. A cut-off value for P(v-a)CO2/C(a-v)O2 will be obtained by maximising the Youden index with the receiver operator characteristic curve. According to this cut-off value, patients included will be divided into two groups: one with the P(v-a)CO2/C(a-v)O2 >cut-off and the other with the P(v-a)CO2/C(a-v)O2 ≤cut off. Differences in clinical outcomes between the two groups will be assessed after propensity matching.Ethics and dissemination The study has been approved by the Institutional Review Board of Affiliated Hospital of Weifang Medical University (wyfy-2021-ky-059). Findings will be disseminated through conference presentations and peer-reviewed journals.Trial registration number ChiCTR2100051748.