He, Yu-Kun MM; Li, Hui-Zi MD; Lu, Hua-Ding MD, PhD

Medicine: July 2019 – Volume 98 – Issue 28 – p e16287
doi: 10.1097/MD.0000000000016287

Summary by: Khoa Tran, BA

Intraoperative blood loss is a major concern in spine surgery due to the stripping of skeletal muscle and cancellous bone exposure. To avoid perioperative anemia, 8% to 36% of spine surgery patients are given blood transfusions according to Janssen et al. [1]. Allogenic blood transfusions are thought to be a risk factor for bacterial infections, ultimately resulting in higher morbidity and worse prognoses for patients. Many researchers argue that this observation is due to the immunosuppressive effects of allogeneic transfusions [2,3].

He et al. conducted a systematic review and meta-analysis on studies published up until July 2017 that examined blood transfusions and infection rates among spine surgery patients. The primary outcome was a comparison of infection rates between patients who received blood transfusions to those who did not; secondary outcomes compared length of hospital stay and morbid complications. Patients were divided into two groups, transfusion and non-transfusion, according to whether they received perioperative blood transfusion during spine surgery. Final analysis included 34,185 spine surgery patients, identified from 8 cohort studies.

There were 10,072 patients included in the transfusion group and 24,113 patients in the non-transfusion group. The pooled analysis suggested that blood transfusion increased the infection rate in spine surgery patients (8 studies; OR, 2.99; 95% CI, 1.95-4.59) with high heterogeneity (I² = 86%). Removing the two studies that were the source of the heterogeneity, however, did not substantially change the results (I²=0; OR, 1.93; 95% CI 1.65-2.26). Blood transfusion was also associated with longer hospital stays (4 studies; mean difference (MD), 3.55; 95% CI, 1.97–5.14) and a higher rate of morbid complications (5 studies; OR, 2.65; 95% CI, 1.23–5.71). The secondary outcomes results had high heterogeneity (I² = 73%, I² = 98%, for length of stay and complications, respectively); however, the results were consistent in the sensitivity analyses.

The authors concluded that perioperative blood transfusion was a risk factor for postoperative infection among spine surgery patients. The study also revealed the adverse effects of transfusions on patient prognoses, as seen in other outcomes including length of hospital stay and morbid complications, though the relationship among these factors remains unclear. These findings were limited by the observational nature and small number of included studies. The authors also could not identify specific causes of heterogeneity. Future studies can further assess these outcomes through more randomized, controlled studies that control for factors not included here, such as surgical approach, case complexity, or use of urinary catheter.

References

1. Janssen SJ, Braun Y, Wood KB, et al. Allogeneic blood transfusions and postoperative infections after lumbar spine surgery. Spine J 2015;15:901–9.
2. Dellinger EP, Miller SD, Wertz MJ, et al. Risk of infection after open fracture of the arm or leg. Arch Surg 1988;123:1320–7.
3. Jensen LS, Andersen AJ, Christiansen PM, et al. Postoperative infection and natural killer cell function following blood transfusion in patients undergoing elective colorectal surgery. Br J Surg 1992;79:513–6.