Analysis of Predictors and Outcomes of Allogeneic Blood Transfusion After Shoulder Arthroplasty
In shoulder arthroplasty, patients often receive postoperative blood transfusions. Studies of predictors of allogeneic blood transfusion (ABT) in these patients have been limited by sample size.
We conducted a study to identify predictors of ABT in patients undergoing shoulder arthroplasty and to evaluate the effect of ABT on postoperative outcomes, including inpatient mortality, adverse events, prolonged hospital stay, and nonroutine discharge. Using the Nationwide Inpatient Sample, we stratified an estimated 422,371 patients who presented for shoulder arthroplasty between January 1, 2002, and December 31, 2011, into total shoulder arthroplasty (59.3%) and hemiarthroplasty (40.7%) cohorts, and then subdivided these cohorts into patients who received blood transfusions and those who did not.
Patients who received ABTs were older, female, and nonwhite and had Medicare or Medicaid insurance. Many had a primary diagnosis of proximal humerus fracture. Those who received ABT were more likely to experience adverse events or a prolonged hospital stay and were more often discharged to a nursing home or an extended-care facility. The 5 most significant predictors of ABT in a population of 422,371 patients who underwent shoulder arthroplasty were fracture, fracture nonunion, deficiency anemia, coagulopathy, and avascular necrosis.
Given these findings, it is important to identify at-risk patients before surgery in order to provide education and minimize risk.
Type of Arthroplasty
Bivariate analysis revealed that 55.6% of the patients who received ABT underwent HSA; the other 44.4% underwent TSA. The effect of primary diagnosis on procedure choice likely played a role in this finding. HSA indications include humerus fracture, which has been associated with increased ABT, whereas patients with osteoarthritis requiring TSA are significantly less likely to require ABT, as reflected in this analysis.7,32-34 Previous studies have failed to show a difference in blood transfusion rates between TSA and HSA.2,4-6,35 Conversely, with confounding factors controlled for, multivariate logistic regression analysis showed that TSA was 1.2 times more likely than HSA to require ABT, which could be explained by the increased operative time, case complexity, and blood loss that may be associated with the glenoid exposure.36,37 With analysis restricted to the year 2011, patients with reverse TSAs were 1.6 times more likely than patients with anatomical TSAs to receive a blood transfusion (OR, 1.63; 95% CI, 1.50-1.79). Although this finding differs from what was previously reported, it fits given that patients having reverse TSAs are often older and may present with a more significant comorbidity profile.3 In addition, there are the increased technical surgical aspects associated with “salvage surgery” for challenging indications such as cuff arthropathy and failed previous arthroplasty.38-41
Medical Comorbidities
Patients who received ABT were more likely to present with numerous medical comorbidities. Previous studies have indicated that the presence of multiple medical comorbidities significantly increased blood transfusion rates, possibly by working synergistically.42 All studies of blood transfusion in shoulder arthroplasty concluded that lower preoperative Hb was an independent predictor.1-6 Schumer and colleagues4 reported a 4-fold increase in likelihood of blood transfusion in patients with a preoperative Hb level less than 12.5 g/dL. In addition, Millett and colleagues6 showed a 20-fold increase in likelihood of transfusion in patients with a preoperative Hb level less than 11.0 g/dL compared with patients with a level higher than 13.0 g/dL. Patients with a Hb level between 11.0 and 13.0 g/dL showed a 5-fold increase in likelihood of transfusion.6 We should note that correction of preoperative anemia through various pharmacologic methods (eg, erythropoietin, intravenous iron supplementation) has been shown to decrease postoperative transfusion rates.43,44 Although we could not include preoperative Hb levels in the present study, given inherent limitations in using NIS, our multivariate analysis showed that preoperative deficiency anemia and coagulopathy were the most significant predictors of ABT.
In addition, the multivariate logistic regression model showed that both cardiac disease and diabetes were independent predictors of ABT, confirming data reported by Ahmadi and colleagues.1 Although not as well characterized in other studies, in the current analysis multiple other medical comorbidities, including fluid and electrolyte abnormalities, weight loss, liver disease, renal failure, and chronic lung disease, had significant predictive value. Contrarily, obesity significantly decreased the odds of ABT, likely because of higher baseline blood volume in obese patients.
Patient Outcomes
Patients who undergo shoulder arthroplasty with ABT are more likely to experience adverse events or a prolonged hospital stay and are more often discharged to a nursing home or an extended-care facility. In this population, however, deaths did not occur at a significantly higher rate—similar to what was found for patients who underwent hip or knee arthroplasty with blood transfusions.45
Little has been done to investigate the effect of pharmacologic agents on the need for perioperative ABT for orthopedic shoulder procedures. Aprotinin, tranexamic acid, epoetin-α, and aminocaproic acid have all been effective in limiting ABT during the perioperative period in various orthopedic hip, knee, and spine procedures.9,46-53 Given the increased morbidity associated with ABT, it may be beneficial to use similar methods to limit blood loss in high-risk patients undergoing shoulder arthroplasty.
Study Limitations
NIS has intrinsic limitations. Given its massive volume, it is subject to errors in both data entry and clinical coding. Moreover, the database lacks data that would have been useful in our study: preoperative Hb levels, intraoperative course, number of units transfused, total blood loss, use of blood conservation techniques, transfusion protocols, and severity of comorbidities. Reverse TSA was given a unique ICD-9-CM code in October 2010, so 2011 was the only year we were able to examine the relationship between reverse TSA and transfusions. Further, our analysis was unable to identify any medications, including chronic anticoagulants or postoperative prophylaxis, that have been shown to significantly affect blood transfusion rates.54 Yet, there are obvious advantages to using the NIS database, as previously outlined across the medical landscape.
