SUDDEN DECREASES IN MIXED VENOUS OXYGEN-SATURATION DURING POSTERIOR SPINAL-FUSION

Systemic hemodynamic instability during posterior spinal fusion rarely has been investigated. Most reports have focused on the relationship between prone position, venous pressure, and excessive bleeding by backflow into extradural veins (1-3). Others have considered the cardiac and pulmonary effects of pooling of blood in the lower body in the prone position (4,5). Case reports have implicated hypotension as a possible cause of compromised spinal cord perfusion during correction of kyphoscoliosis (6,7). This retrospective study describes the occurrence of sudden decreases in mixed venous oxygen saturation (Svo(2)) in response to surgical manipulations of vertebrae during posterior spinal fusion under general anesthesia.