When Does Intraoperative Blood Loss Occur During Pediatric Scoliosis Correction?

The purpose of our study was to assess the relationship between amount of blood loss and surgical stage in pediatric patients undergoing posterior spinal fusion for deformity correction to determine: (1) when the highest rate of blood loss occurred; (2) what percentage of total blood loss occurred during deformity correction and closure; and (3) how to predict remaining blood loss during a procedure. Blood loss following exposure and placement of the final pedicle screw is often underestimated, which may result in lack of sufficient blood product availability. Knowledge of the rate of blood loss plays an important role in intraoperative decision making, facilitating communication with the anesthesia team, and improving patient safety.

Clinical records were reviewed for all patients 9 to 18 years of age who underwent index spinal fusion surgery with pedicle screw constructs for deformity correction of greater than 4 levels by a single surgeon from April 2013 to July 2015. All patients received tranexamic acid prophylactically. Exclusion criteria included vertebral column resections, cell saver use, cases complicated by signal loss on monitoring, and incomplete records. Sixty-two of 99 patients met criteria and were included in data analysis. The surgery was divided into four stages: exposure, screw/anchor placement, corrective procedures (reduction, osteotomies), and closure. Normalized blood loss (NBL) was calculated by adjusting actual blood loss for patient weight and number of levels fused. Demographic factors of age, sex, weight/BMI, diagnosis, preoperative Cobb angle, and number of levels fused were accounted for and autoregressive moving average was used to assess whether NBL varied significantly at different stages of the procedure.

NBL during reduction and closure (1.69) was significantly greater than NBL during exposure and screw placement (1.49) (p < .040). The rate of blood loss was also highest during reduction/deformity correction procedures than exposure (p < .001), anchor placement (p = .010), and closure (p < .010). At the time of placement of the final pedicle screw, 47% of the total blood loss for the case had occurred.

Rate of blood loss varies during pediatric posterior spinal deformity correction surgery, with the highest rates occurring during the reduction portion of the operation. Just over half of the total EBL occurs during the reduction and closure stages of surgery requiring the surgical team to plan accordingly. Additional studies investigating modifiable factors affecting blood loss during the later stages of scoliosis surgery are warranted.