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Comparative Study
. 2018 Jul;156(1):66-74.e2.
doi: 10.1016/j.jtcvs.2018.03.109. Epub 2018 Apr 4.

Preoperative anemia versus blood transfusion: Which is the culprit for worse outcomes in cardiac surgery?

Damien J LaPar  1 , Robert B Hawkins  1 , Timothy L McMurry  1 , James M Isbell  1 , Jeffrey B Rich  2 , Alan M Speir  3 , Mohammed A Quader  4 , Irving L Kron  1 , John A Kern  1 , Gorav Ailawadi  5 ; Investigators for the Virginia Cardiac Services Quality Initiative
Affiliations
Comparative Study

Preoperative anemia versus blood transfusion: Which is the culprit for worse outcomes in cardiac surgery?

Damien J LaPar et al. J Thorac Cardiovasc Surg. 2018 Jul.

Abstract

Background: Reducing blood product utilization after cardiac surgery has become a focus of perioperative care as studies have suggested improved outcomes. The relative impact of preoperative anemia versus packed red blood cells (PRBC) transfusion on outcomes remains poorly understood, however. In this study, we investigated the relative association between preoperative hematocrit (Hct) level and PRBC transfusion on postoperative outcomes after coronary artery bypass grafting (CABG) surgery.

Methods: Patient records for primary, isolated CABG operations performed between January 2007 and December 2017 at 19 cardiac surgery centers were evaluated. Hierarchical logistic regression modeling was used to estimate the relationship between baseline preoperative Hct level as well as PRBC transfusion and the likelihoods of postoperative mortality and morbidity, adjusted for baseline patient risk. Variable and model performance characteristics were compared to determine the relative strength of association between Hct level and PRBC transfusion and primary outcomes.

Results: A total of 33,411 patients (median patient age, 65 years; interquartile range [IQR], 57-72 years; 26% females) were evaluated. The median preoperative Hct value was 39% (IQR, 36%-42%), and the mean Society of Thoracic Surgeons (STS) predicted risk of mortality was 1.8 ± 3.1%. Complications included PRBC transfusion in 31% of patients, renal failure in 2.8%, stroke in 1.3%, and operative mortality in 2.0%. A strong association was observed between preoperative Hct value and the likelihood of PRBC transfusion (P < .001). After risk adjustment, PRBC transfusion, but not Hct value, demonstrated stronger associations with postoperative mortality (odds ratio [OR], 4.3; P < .0001), renal failure (OR 6.3; P < .0001), and stroke (OR, 2.4; P < .0001). A 1-point increase in preoperative Hct was associated with decreased probabilities of mortality (OR, 0.97; P = .0001) and renal failure (OR, 0.94; P < .0001). The models with PRBC had superior predictive power, with a larger area under the curve, compared with Hct for all outcomes (all P < .01). Preoperative anemia was associated with up to a 4-fold increase in the probability of PRBC transfusion, a 3-fold increase in renal failure, and almost double the mortality.

Conclusions: PRBC transfusion appears to be more closely associated with risk-adjusted morbidity and mortality compared with preoperative Hct level alone, supporting efforts to reduce unnecessary PRBC transfusions. Preoperative anemia independently increases the risk of postoperative morbidity and mortality. These data suggest that preoperative Hct should be included in the STS risk calculators. Finally, efforts to optimize preoperative hematocrit should be investigated as a potentially modifiable risk factor for mortality and morbidity.

Keywords: CABG; anemia; cardiac; hematocrit; transfusion.

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Conflict of interest statement

Author Conflicts of Interest: There are no potential author conflicts of interest

Figures

Figure 1
Figure 1
Histogram displaying the distribution of preoperative hematocrit levels.
Figure 2
Figure 2
Figure 2a. Risk-adjusted model of the impact of preoperative hematocrit versus the probability of mortality following primary, isolated CABG. The 95% confidence interval is represented in orange. Figure 2b. Risk-adjusted model of the impact of preoperative hematocrit versus the probability of packed red blood cell (PRBC) transfusion following primary, isolated CABG. Figure 2c. Risk-adjusted model of the impact of preoperative hematocrit versus the probability of postoperative renal failure following primary, isolated CABG.
Figure 2
Figure 2
Figure 2a. Risk-adjusted model of the impact of preoperative hematocrit versus the probability of mortality following primary, isolated CABG. The 95% confidence interval is represented in orange. Figure 2b. Risk-adjusted model of the impact of preoperative hematocrit versus the probability of packed red blood cell (PRBC) transfusion following primary, isolated CABG. Figure 2c. Risk-adjusted model of the impact of preoperative hematocrit versus the probability of postoperative renal failure following primary, isolated CABG.
Figure 2
Figure 2
Figure 2a. Risk-adjusted model of the impact of preoperative hematocrit versus the probability of mortality following primary, isolated CABG. The 95% confidence interval is represented in orange. Figure 2b. Risk-adjusted model of the impact of preoperative hematocrit versus the probability of packed red blood cell (PRBC) transfusion following primary, isolated CABG. Figure 2c. Risk-adjusted model of the impact of preoperative hematocrit versus the probability of postoperative renal failure following primary, isolated CABG.
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