Prospective Quantification of Blood Loss During Adult Spinal Deformity Surgery: Defining the Optimal Intraoperative Hemoglobin Target

Introduction: Adult spinal deformity (ASD) surgery results in significant blood loss especially when high-grade osteotomies are performed. Reports of estimated blood loss (EBL) vary widely and are proposed to range from 1-2L. Visual assessments of EBL are often inaccurate and there is no accepted hemoglobin (HGB) target. Under-resuscitation places patients at risk of neurological injury, hypotension, multiorgan injury, and even death. Here, we aim to define the actual magnitude of blood loss during ASD surgery using a standardized quantitative blood loss (QBL) protocol and establish an optimal intraoperative resuscitation target for ASD.

Methods: This is a prospective single-center study of patients undergoing ASD surgery following implementation of a QBL protocol between 1/7/2022-5/1/2024. Patients with >=5 levels fused and SVA >4.5cm and/or PI-LL mismatch >10 were included. QBL was calculated through volumetric/gravimetric analysis of blood in suction canisters, sponges, and irrigation. The cumulative incidence of postoperative pRBC transfusion was recorded to determine an ideal intraoperative HGB target.

Results: This study included 107 patients with a mean age of 68.5 years and mean of 10.8 levels fused. Mean QBL for the entire cohort was 2758.8mL (range 277-11963mL) or 59.3% (range 6.2-316%) of estimated total blood volume (TBV). Fifty-five (51.4%) patients underwent posterior column osteotomy (PCO), 37 (34.6%) underwent 3CO, and 66 (62.3%) underwent same-stage interbody fusion. 3CO was most frequently performed in the lumbar spine (64.8%). Mean QBL increased with number of levels fused: 1877.7mL for 5-9 levels, 3569.4mL for 10-14 levels, and 3899mL for ≥15 levels (p=0.002). Mean QBL for 3CO was 4709.9mL (range 2690.4-11963 ml), or 96.7% TBV (range 12.4-316%). PCO (p=0.034) and 3CO (p < 0.001) were associated with major blood loss. Eighty percent of transfusions occurred when immediate postoperative HGB was < 11.8g/dl.

Conclusion : EBL significantly underestimates blood loss during ASD surgery. Mean QBL was 2.75L for all ASD cases and 4.71L (97% TBV) for 3CO cases. Hence adequate and rapid resuscitation with blood products is essential to mitigate intraoperative and postoperative complications. Targeting HGB>11 may reduce postoperative transfusion requirements.