Anemia before in-hospital cardiac arrest and survival from cardio-pulmonary resuscitation—a retrospective cohort study

Background: Multiple patient-related variables have been associated with reduced rates of survival to hospital discharge (SHD) after in-hospital cardiac arrest (IHCA). As opposed to most of these, anemia may be reversible. This retrospective single-center study aims to examine the relationship between prearrest hemoglobin levels, comorbidities, and survival after cardiopulmonary resuscitation (CPR) among patients with non-traumatic IHCA. Patients were classified as anemic (hemoglobin < 10 g/dL) or non-anemic (hemoglobin ≥ 10 g/dL) based on their lowest hemoglobin measurement in the 48 h preceding the arrest. The primary outcome was SHD. The secondary outcome was return of spontaneous circulation (ROSC). Results: Of 1515 CPR reports screened, 773 patients were included. Half of the patients (50.5%, 390) were classified as anemic. Anemic patients had higher Charlson Comorbidity Indices (CCIs), less cardiac causes, and more metabolic causes for the arrest. An inverse association was found between CCI and lowest hemoglobin. Overall, 9.1% (70 patients) achieved SHD and 49.5% (383) achieved ROSC. Similar rates of SHD (7.3 vs. 10.7%, p = 0.118) and ROSC (49.5 vs. 51.0%, p = 0.688) were observed in anemic and non-anemic patients. These findings remained consistent after adjustment for comorbidities, in sensitivity analyses on the independent variable (i.e., hemoglobin) and on potential confounders and in subgroups based on sex or blood transfusion in the 72 h preceding the arrest. Conclusions: Prearrest hemoglobin levels lower than 10 g/dL were not associated with lower rates of SHD or ROSC in IHCA patients after controlling for comorbidities. Further studies are required to confirm our findings and to establish whether post-arrest hemoglobin levels reflect the severity of the inflammatory post-resuscitation processes. © The Author(s) 2022.