Preoperative Detection of Low Von Willebrand Factor Activity and Operative Blood Loss in Pediatric Scoliosis Patients Undergoing Posterior Spinal Fusion

Purpose: Patients with von Willebrand disease (VWD), typically have von Willebrand Ristocetin cofactor activity (VWF: RCo) levels ≤30%. Patients with marginal levels 30-70 % don’t receive replacement therapy unless there is a bleeding history. Our program screens for VWF: RCo activity in advance of posterior spinal fusion (PSF) surgery. We hypothesized all patients with levels <70% are at higher bleeding risk when undergoing scoliosis repair. Design: this is a retrospective review of prospectively gathered data from a dedicated patient blood management program database. Methods: 169 scoliosis patients with preoperative VWF: RCo >70% were initially matched to 59 patients with activity ≤70%. Stratification was done at VWF: RCo levels >70 %, 61-70%, 51-60% and ≤50%, to examine blood loss. Matching was done by scoliosis type (idiopathic, neuromuscular, others), and operative difficulty. Both logistic regression and multivariate regression were used to examine the various levels. Results: Patients with VWF: RCo >70 % compared to those with ≤70% had similar demographics, blood loss, and transfusion rates. On stratification, blood loss/segment fused with VWF: RCo levels <50% was significant compared to other levels; 51-60%, 61-70% or >70%, p = 0.044. Multivariate regression revealed compared to other levels, those patients with VWF: RCo levels ≤60 % were most likely to have higher blood loss even on controlling for potential confounders (p < 0.005). Sixteen patients with levels <50% had significant bleeding despite factor replacement in 15. Conclusion: Layered multivariate analysis showed that patients with VWF: RCo levels ≤ 60% carried higher risk of operative bleeding/ level fused. Prospective therapeutic studies are much needed.Purpose: Patients with von Willebrand disease (VWD), typically have von Willebrand Ristocetin cofactor activity (VWF: RCo) levels ≤30%. Patients with marginal levels 30-70 % don’t receive replacement therapy unless there is a bleeding history. Our program screens for VWF: RCo activity in advance of posterior spinal fusion (PSF) surgery. We hypothesized all patients with levels <70% are at higher bleeding risk when undergoing scoliosis repair. Design: this is a retrospective review of prospectively gathered data from a dedicated patient blood management program database. Methods: 169 scoliosis patients with preoperative VWF: RCo >70% were initially matched to 59 patients with activity ≤70%. Stratification was done at VWF: RCo levels >70 %, 61-70%, 51-60% and ≤50%, to examine blood loss. Matching was done by scoliosis type (idiopathic, neuromuscular, others), and operative difficulty. Both logistic regression and multivariate regression were used to examine the various levels. Results: Patients with VWF: RCo >70 % compared to those with ≤70% had similar demographics, blood loss, and transfusion rates. On stratification, blood loss/segment fused with VWF: RCo levels <50% was significant compared to other levels; 51-60%, 61-70% or >70%, p = 0.044. Multivariate regression revealed compared to other levels, those patients with VWF: RCo levels ≤60 % were most likely to have higher blood loss even on controlling for potential confounders (p < 0.005). Sixteen patients with levels <50% had significant bleeding despite factor replacement in 15. Conclusion: Layered multivariate analysis showed that patients with VWF: RCo levels ≤ 60% carried higher risk of operative bleeding/ level fused. Prospective therapeutic studies are much needed.