[A study of blood loss during surgery for scoliosis. Posterior approach in 319 adolescents].

A retrospective study including 319 patients was realized from 1984 to 1993 in order to evaluate during scoliosis surgery the incidence on bleeding of the type of scoliosis and the anesthetic procedure. Blood losses were below one litre thus reducing the homologous blood transfusions. The patient was in prone position on a modified Wilson frame which facilitates venous return from the dorsal region. A moderate controlled hypotension was realized by combination of halothane, intravenous nitroglycerin (NG) and beta-blocking drugs (when required). Somatosensory evoked potentials were continuously monitored during surgery. A compression of the dorsal region was realized postoperatively in order to reduce blood loss. The blood losses were compared using Student's t-test. The mean perioperative bleeding was 9.8 ml.kg-1 for idiopathic scoliosis (no transfusion required), 14.1 ml.kg-1 for secondary scoliosis (p < 0.05 vs idiopathic) and 29.3 ml.kg-1 for neuromyopathic scoliosis (p < 0.05 vs idiopathic), indicating a major influence of muscle atonia on bleeding. The moderate controlled hypotension by iterative injection of NG and beta-adrenergic blocking drugs provided a safe and reversible hypotension.