Transfusions Associated With Lower Hospital Mortality in ICU Patients With Cardiac Disease

Whether mortality is improved in critically ill patients with cardiac disease using a restrictive threshold vs a liberal threshold for hemoglobin levels for red blood cell transfusions has been  an ongoing debate.¹ A study in the December 2015 issue of Journal of the American College of Cardiology provides new data that may help guide physicians about when to transfuse patients in this category.²

Yew Y. Ding, MBBS, MPH of the Department of Geriatric Medicine and Institute of Geriatrics and Active Ageing at Tan Tock Seng Hospital in Singapore and colleagues, sought to estimate the hemoglobin level threshold below which transfusion in patients with key cardiac conditions (such as comorbid heart disease, acute myocardial infarction, unstable angina, and congestive heart failure) would be associated with reduced hospital mortality.

The investigators hypothesized that transfusion thresholds in critically ill patients with cardiac disease would be higher than the restrictive thresholds frequently advocated. The American Association of Blood Banks guidelines recommend that transfusions be provided to hospitalized patients with pre-existing cardiovascular disease only when hemoglobin (Hgb) levels are ≤8 g/dL. Using national Veterans Affairs patient databases for fiscal years 2001 through 2005, the investigators identified 258 826 first intensive care unit (ICU) episodes of each year for each unique patient. The outcome of interest was hospital death, while the treatment variable of interest was red blood cell transfusion within 30 days of ICU admission. Surgical ICU cases were excluded. Logistic regression was performed to build explanatory models for hospital mortality, with adjustments for nadir Hgb level, demographic characteristics, admission information, comorbid conditions, and ICU admission diagnoses.

Hospital death took place in 30 086 patients (11.6%). In 32 097 (12.4%) of episodes, transfusion was provided within the first 30 days of ICU admission. Lower hospital mortality was associated with transfusion at lower Hgb levels. In the entire group, each 1 g/dL increase in Hgb, transfusion was associated with a 22% increase in odds of hospital mortality. However, in patients with comorbid heart disease or an ICU admission diagnosis of acute myocardial infarction (AMI), transfusion was associated with lower hospital mortality (0.78 odds ratio; 95% confidence interval), suggesting that the benefit associated with transfusion was greater in this group of patients.

In the absence of comorbid heart disease, transfusion was associated with decreased adjusted hospital mortality when Hgb was approximately <7.7 g/dL, but transfusion increased mortality above this Hgb level. Corresponding Hgb level thresholds were approximately 8.7 g/dL when comorbid heart disease was present and approximately 10 g/dL when the ICU admission diagnosis was AMI.

Following a sensitivity analysis in which adjustments were made for the designated variables, transfusion during ICU admission was associated with fewer hospital deaths in patients with cardiac disease when pre-transfusion Hgb levels were <8 to 9 g/dL. The Hgb level threshold for transfusion was 9 to 10 g/dL when AMI was the ICU admission diagnosis.

The authors concluded, “Although transfusion decisions should be individualized based on clinical assessment, critically ill patients with comorbid heart disease may benefit from Hgb levels >8 to 9 g/dL, and patients with ACS may need levels >9 to 10 g/dL.”

References

1. Walsh TS, McClelland DBL. II. When should we transfuse critically ill and perioperative patients with known coronary artery disease?†. Br J Anaesth. 2003;90(6):719-722. doi:10.1093/bja/aeg109.
2. Ding YY, Kader B, Christiansen CL, Berlowitz DR. Hemoglobin Level and Hospital Mortality Among ICU Patients With Cardiac Disease Who Received Transfusions. J Am Coll Cardiol. 2015;66(22):2510-2518. doi:10.1016/j.jacc.2015.09.057.