Restrictive transfusion strategies supported by large randomized trials are resulting in decreased blood utilization in cardiac surgery. What remains to be determined, however, is the impact of lower discharge hemoglobin (Hb) levels on readmission rates. We assessed patients with higher versus lower Hb levels on discharge to compare 30-day readmission rates after coronary artery bypass grafting (CABG).
We retrospectively evaluated 1552 patients undergoing isolated CABG at our institution from January 2013 to May 2016. We evaluated 2 Hb cohorts: “high” (above) and “low” (below) the mean discharge Hb level of 9.4 g/dL, comparing patient characteristics, blood utilization, and clinical outcomes including 30-day readmission rates. We further evaluated the effects of the lowest (<8 g/dL) discharge Hb levels on 30-day readmission rates by dividing the patients into 4 anemia cohorts based on discharge Hb levels: “no anemia” (>12 g/dL), “mild anemia” (10–11.9 g/dL), “moderate anemia” (8–9.9 g/dL), and “severe anemia” (<8 g/dL). Risk adjustment accounted for age, sex, Charlson comorbidity index, preoperative comorbidities, revision sternotomy, and patient blood management program implementation.
The “high” and “low” groups had similar patient characteristics except for Hb levels (mean discharge Hb was 10.4 ± 0.9 vs 8.5 ± 0.6 g/dL, respectively). Notably, no evidence for a difference in 30-day readmission rates was noted between the “high” (76/746; 10.2%) and “low” (97/806; 12.0%) (P = .25) Hb cohorts. The 4 anemia cohorts had differences in age, revision sternotomy incidence, Hb levels, certain patient comorbidities, and time to readmission. On multivariable analysis, the risk-adjusted odds of readmission in the “low” Hb cohort (odds ratio, 1.16; 95% confidence interval, 0.84–1.61; P = .36) was not significant compared to the “high” Hb cohort. Compared to patients with discharge Hb ≥8 g/dL, patients with Hb <8 g/dL had a higher incidence of readmission (22/129; 17.1% vs 151/1423; 10.6%; P = .036). On multivariable analysis, Hb <8 g/dL on discharge was predictive of readmission (odds ratio, 1.77; 95% confidence interval, 1.05–2.88; P = .03). The most common reason for readmission was volume overload, followed by infection and arrhythmias.
A discharge Hb level below the institution mean for CABG patients does not provide evidence for an association with an increased 30-day readmission rate. In the small number of patients discharged with Hb <8 g/dL, there is a suggestion of increased risk for readmission and larger more controlled studies are needed to verify or refute this finding.
From the *Department of Anesthesiology/Critical Care Medicine
†Department of Cardiac Surgery, The Johns Hopkins Medical Institutions, Baltimore, Maryland
‡Department of Anesthesiology/Critical Care Medicine, Johns Hopkins Health System Blood Management Program, Faculty, Armstrong Institute for Patient Safety and Quality, The Johns Hopkins Medical Institutions, Baltimore, Maryland.
Published ahead of print 18 June 2018.
Accepted for publication June 18, 2018.
Funding: S.M.F. has received consulting fees from Haemonetics and Medtronic.
The authors declare no conflicts of interest.
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C.H.B. has consulted for and received grant support from Medtronic in areas unrelated to this study. Funding: 1 K76 AG057020.
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Address correspondence to Steven M. Frank, MD, Department of Anesthesiology/Critical Care Medicine, Johns Hopkins Hospital, Sheik Zayed Tower 6208, 1800 Orleans St, Baltimore, MD 21287. Address e-mail to firstname.lastname@example.org.