Allogeneic blood transfusions and postoperative infections after lumbar spine surgery

Background context: Allogeneic blood transfusions have an immunomodulating effect, and the previous studies in other fields of medicine demonstrated an increased risk of infections after administration of allogeneic blood transfusions.

Purpose: Our primary null hypothesis is that exposure to allogeneic blood transfusion in patients undergoing lumbar spine surgery is not associated with postoperative infections after controlling for patient and treatment characteristics. Second, we assessed if there was a dose-response relationship per unit of blood transfused.

Study design/setting: This is a retrospective cohort study from a tertiary care spine referral center.

Patient sample: A total of 3,721 patients underwent laminectomy and/or arthrodesis of the lumbar spine.

Outcomes measures: Postoperative infections, pneumonia, endocarditis, meningitis, urinary tract infection, central venous line infection, surgical site infection, and sepsis, within 90 days after lumbar spine surgery were included.

Methods: Multivariable logistic regression analyses were used to assess the relationship of perioperative allogeneic blood transfusion with specific and overall postoperative infections accounting for age, duration of surgery, duration of hospital stay, comorbidity status, preoperative hemoglobin, sex, type of operation, multilevel treatment, operative approach, and year of surgery.

Results: The adjusted odds ratio for exposure to allogeneic blood transfusion from multivariable logistic regression analysis was 2.6 for any postoperative infection (95% confidence interval [CI]: 1.7-3.9, p<.001); 2.2 for urinary tract infections (95% CI: 1.3-3.9, p=.004); 2.3 for pneumonia (95% CI: 0.96-5.3, p=.062); and 2.6 for surgical site infection requiring incision and drainage (95% CI: 1.3-5.3, p=.007). Secondary analyses demonstrated no dose-response relationship between the number of blood units transfused and any of the postoperative infections. Because of the low number of endocarditis (1 case, 0.031%), meningitis (1 case, 0.031%), central venous line infection (1 case, 0.031%), and sepsis (14 cases, 0.43%), we abstained from multivariable analysis.

Conclusions: Conscious of the limitations of this retrospective study, our data suggest an increased risk of surgical site infection, urinary tract infection, and overall postoperative infections, but not pneumonia, after exposure to allogeneic blood transfusion in patients undergoing lumbar spine surgery. These findings should be taken into account when considering blood transfusion and developing transfusion policies for patients undergoing lumbar spine procedures.