Bleeding and coagulation changes during spinal fusion surgery: a comparison of neuromuscular and idiopathic scoliosis patients.
OBJECTIVE
Major blood loss is common during spinal fusion surgery. We have previously demonstrated that patients with neuromuscular scoliosis have more blood loss and greater transfusion requirement than those with idiopathic scoliosis. Our objective is to study the relationships between etiology of scoliosis, blood loss, and coagulation changes in children and adolescents undergoing spinal fusion surgery.


DESIGN
Prospective, observational study.


SETTING
University teaching hospital.


PATIENTS
A total of 25 patients, 11 with neuromuscular and 14 with idiopathic scoliosis, undergoing spinal fusion surgery.


INTERVENTIONS
Blood was obtained preoperatively, 2 and 4 hrs intraoperatively, and 2 and 24 hrs postoperatively for prothrombin time, partial thromboplastin time, thrombin time, platelet count, D-dimer, factor VII and VIII activity, thrombin-antithrombin III complex, and protein induced by vitamin K absence. Changes in coagulation over time were analyzed by repeated-measures analysis of variance. Comparisons between groups were made using independent t-tests.


RESULTS
Neuromuscular scoliosis patients had significantly greater blood loss than idiopathic scoliosis patients (median blood loss, 78% of total blood volume; range, 25-127% vs. 20%, 2-82%; p < .001). Prothrombin time increased over time in both groups and was higher in the neuromuscular than the idiopathic group both preoperatively and postoperatively (p < .05). Factor VII activity decreased over time in both groups (p < .001) and was lower in the neuromuscular than the idiopathic group during surgery (p < .05). No changes in partial thromboplastin time, thrombin time, or factor VIII activity were observed. D-dimers were present in both groups by 4 hrs intraoperatively. Protein induced by vitamin K absence was not detected in any patient.


CONCLUSIONS
Neuromuscular scoliosis patients have more blood loss during spinal fusion surgery than idiopathic scoliosis patients. The prolongation of prothrombin time and decrease in Factor VII activity suggest activation of the extrinsic coagulation pathway. Depletion of clotting factors during scoliosis surgery occurs to a greater extent in patients with underlying neuromuscular disease.