Retrospective evaluation of anemia incidence and blood transfusion indications in anesthesia intensive care unit

Introduction: Anemia is very common in patients during intensive care unit (ICU) follow-up and treatment. Approximately 60% of patients have anemia on admission. The majority of the remaining patients may develop anemia related to the duration of hospitalization. For these reasons, blood and blood products transfusions are frequently administered in the ICU. Anemia may develop in the majority of the remaining patients in relation to the length of hospitalization. The etiology of anemia in ICU patients is usually multifactorial and it is difficult to distinguish between these causes. The aim of this study was to determine the frequency of anemia and blood product transfusions in ICU patients, to determine the hemoglobin (Hb) threshold value used for transfusion, to reveal the risks associated with transfusion and to evaluate the relationship between transfusion and clinical outcomes. Materials and Methods: This study was designed as a retrospective cohort study including patients who were followed up in the ICU between June 01, 2024 and December 01, 2024. Data of the patients were obtained from patient follow-up files and hospital information system database. Data recorded during ICU admission were; demographic information, disease severity scores during ICU admission, comorbidities, admission diagnosis, duration of ICU admission, history of surgical operation, need for supportive therapies (invasive/non-invasive mechanical ventilation, need for vasoactive drugs, RRT), the records included drug use that may affect coagulation, whether blood product replacement was performed before ICU admission, hemodynamic parameters and laboratory results, Hb values before transfusion, indications for transfusion, and transfusion-related complications. The duration of ICU and hospital stay and mortality status of the patients were also recorded. Same number of patients with the group of patients who were administered blood transfusion in the ICU within the period defined for the study were randomly selected from the group of patients who did not received blood product transfusion during the same period of time. Results: During the study period, a total of 1228 patients were admitted to the ICU and 160 of the 1000 patients who met the inclusion criteria received blood product transfusion and 160 patients were randomly selected from 840 patients who did not receive blood product transfusion and the data of a total of 320 patients were analyzed. Of the patients included in the study, 74.4% had comorbidities and the median CCI was 2 (0-10). The median age of the patients was 65 (min-max 18-96). 66% of the patients were anemic during ICU admission and mean Hb value of the patients at ICU admission was 11.1±2.3 g/dL. Of the 1000 patients admitted to the ICU, 160 (16%) received blood product transfusions. The most common indications for blood product transfusion were low Hb level (61.9%), need for vasopressors (46.2%), hemodynamic instability (37.5%) and active bleeding (21.2%). The mean age of patients with and without blood product transfusion was 60.5 ± 20.1 and 61.4 ± 19.5 years, respectively, and the distribution in terms of age, gender, smoking and CCI score was similar between both groups (p=0.789, p=0.061, p=0.307, p=0.125). The mean APACHE II and SOFA scores of patients who received blood product transfusion during ICU hospitalization were higher than those who did not (p<0.001, p<0.001). The Hb cut-off value ICU admission was ≤10.85 g/dL (sensitivity: 70%, selectivity: 69.4%). The mean threshold Hb level before RBC transfusion was 8.2±1.87 g/dL. In patients who received RBC transfusion due to low Hb level, the lowest pre-transfusion Hb level was 5.6 g/dL with a mean of 6.8±0.2 g/dL. Univariate logistic regression analysis showed that low Hb level at the time of hospitalization was associated with mortality (p<0.001). Increases in APACHE-II score (p=0.039) and ICU length of stay (p<0.001) had a significant effect profile on mortality. Mortality was 3.46 times (p<0.001) higher in patients who received blood transfusion, 1.999 times (p=0.005) higher in patients who needed vasopressor during ICU follow-up, 1.918 times (p=0.021) higher in patients with cardiac arrest and 2.818 times (p=0.02) higher in patients with major bleeding. After adjustment in the multivariable model, the most dominant and significant condition associated with mortality was blood transfusion (2.55-fold increase; p=0.002). Since there may be confounding variables between blood product transfusion and mortality, subgroup analysis showed that blood transfusion increased ICU mortality 4.29-fold in ICU patients without shock who received blood transfusion for an indication other than vasopressor/hemodynamic instability, but RBC transfusion had no adverse effect on mortality in patients with shock who received blood transfusion for vasopressor/hemodynamic instability indication (p=0.768). Conclusion: In our study, the most common indication for RBC transfusion was low Hb level (61.9%) and the Hb threshold value before transfusion was 8.2±1.87 g/dl. An Hb level ≤10.85 g/dl at ICU admission was an important finding in terms of predicting the need for blood product transfusion for any reason during ICU follow-up (70% sensitivity and 69.4% selectivity). The findings of our study support that blood product transfusion increases ICU mortality 2.55-fold when all ICU patients are analyzed, but has no adverse effect on ICU mortality in patients with shock status who receive blood transfusion with the indication of vasopressor need/hemodynamic instability, although it provides a decrease in the need for vasopressors and improves shock status. Keywords: Anemia, intensive care unit, transfusion, mortality