Hemoglobin trends and transfusion practices after cardiac arrest: a cohort study

Hemoglobin targets are absent from post-cardiac arrest guidelines. New trials suggest that patients with brain and myocardial injury, injuries common post-arrest, may benefit from higher hemoglobin targets. Trends in post-arrest hemoglobin and real-world practices remain poorly characterized.

We performed a retrospective cohort study of consecutive adult cardiac arrests at three academic hospitals. We screened in-hospital and out-of-hospital arrests with resuscitation efforts ongoing at hospital arrival for inclusion. Patients who survived the initial resuscitation and had a hemoglobin value measured were included. All post-arrest hemoglobin values and red blood cell transfusions were collected through 30 days; descriptive statistics and graphical visualization were used to present hemoglobin trends and transfusion practices. Exploratory analyses evaluated the association between hemoglobin and in-hospital mortality.

Of 2,634 cardiac arrests, 958 met inclusion criteria, with 152 (15.9%) out-of-hospital arrests and 806 (84.1%) in-hospital. The mean initial post-arrest hemoglobin was 9.75 g/dL (SD 2.60), with hemoglobin levels declining progressively over the first 20 days post-arrest. Red cell transfusions were delivered for 369 (38.5%) patients in the 30 days post-arrest, with 1,238 total transfusions. The mean pre-transfusion hemoglobin value was 6.96 g/dL (SD 1.06). Pre-transfusion hemoglobin levels were < 7 g/dL for 762 (61.6%) of transfusions, and ≥ 7 g/dL for 476 (38.4%) of transfusions. Over 30 days, the highest proportion of patients transfused was in the first 48 h. Patients with initial post-arrest hemoglobin ≥ 9 g/dL had lower in-hospital mortality (adjusted OR 0.62, 95% CI 0.46-0.84, p<0.01). In time-varying analysis, post-arrest hemoglobin through 30 days demonstrated an L-shaped association with mortality, with 95% of the total reduction in mortality hazard captured below 9.20 g/dL.

Anemia is common after cardiac arrest, worsening in initial survivors. There is substantial variation in pre-transfusion hemoglobin levels, reflecting clinical equipoise. Clinical trials are needed to disentangle anemia as a driver versus a marker of outcomes, and test whether the risk is modifiable.