Postoperative anemia following posterior decompression surgery for lumbar spinal canal stenosis

The incidence of lumbar spinal canal stenosis (LSCS) is increasing in Japan. Posterior lumbar decompression surgery, wide fenestration and laminectomy, for LSCS is a common treatment modality. Compared with posterior fusion surgery, posterior decompression surgery has been considered as less invasive. However, no reports regarding postoperative anemia following posterior decompression surgery have been published. In this retrospective study, we evaluated changes in hemoglobin values following wide fenestration in 80 patients with LSCS based on the number of operated levels, and also analyzed the differences between intraoperative and postoperative bleeding volume. Two patients required allogenic transfusion. The mean preoperative hemoglobin values were 13.6 g/dL and the mean postoperative minimum hemoglobin values were 11.2 g/dL. The mean hemoglobin values decreased by 1.8 g/dL in patients with one operated level (n = 15); 2.2 g/dL in those with two operated levels (n = 31); 2.6 g/dL in those with three operated levels (n = 23); and 3 g/dL in those with four operated levels (n = 11). The mean decrease in hemoglobin values was calculated as follows: 1.8 + 0.4 × (X - 1), where X was the number of operated levels. The mean intraoperative bleeding volume was 94 ml and the mean postoperative bleeding volume was 418 ml. Postoperative bleeding volume was significantly larger than intraoperative bleeding volume. Accordingly, postoperative hemoglobin values can be predicted in patients undergoing wide fenestration. Effective management of postoperative bleeding is necessary to prevent postoperative anemia.