Do postoperative drain volumes correlate with intraoperative blood loss and postoperative transfusion requirements in posterior spinal fusion for adolescent idiopathic scoliosis?

Most studies have excluded postoperative drain volumes in analyzing blood loss associated with scoliosis surgery. We sought to analyze patient and surgical factors that influenced postoperative drain outputs. A retrospective review was conducted on 50 consecutive patients who had undergone posterior spinal fusion with pedicle screw instrumentation and subfascial drain placement over a 6-year period at a single institution for adolescent idiopathic scoliosis. Postoperative drain volumes were correlated to patient factors, surgical variables, and change in postoperative hemoglobin values. The association between drain output volumes and the need for allogeneic blood transfusion was also analyzed using univariate and multivariate analysis. Total postoperative drain volume positively correlated with Cell Saver volume (r=0.28, P=0.049), units of packed red blood cells transfused intraoperatively (r=0.31, P=0.03), and a number of Ponte osteotomies (r=0.43, P=0.002). On the basis of multiple linear regression analysis, only the number of osteotomies performed was associated with increasing total drain volume (R=0.25, P=0.003). Total drain output did not correlate with postoperative change in hemoglobin (P=0.85), the need for postoperative blood transfusion (P=0.22), or the total volume of blood transfused perioperatively (P=0.06). Patients with large intraoperative blood loss or multiple osteotomies are more likely to have higher postoperative drain volumes. Drain volume alone, however, should not be used as a trigger for recommending a postoperative blood transfusion.