Surgeon-Estimated Blood Loss Is Discordant With Calculated Blood Loss in Acetabular and Pelvic Fracture Surgery

To compare blood loss as estimated by surgeon-estimated blood loss (EBL), the Gross formula, and the HB equation in open pelvic and acetabular surgery.Retrospective cohort study.Single Level I academic trauma center.We included 710 patients 18-89 years of age who underwent acetabular or pelvic surgery between 2008 and 2018 for the management of fracture.Surgical treatment for the management of acetabular or pelvic fracture and blood transfusion when deemed clinically appropriate in the perioperative setting.Surgeon EBL and calculated blood loss (using the Gross formula, a Gross formula derivative, and the HB equation with both Moore and Nadler blood volume estimations).One hundred ninety-two patients (27%) received intraoperative blood transfusions. Surgeon EBL significantly differed from all formulas except the Gross/Nadler and the modified Gross/Nadler calculations. Gross and HB calculation methods yielded similar results in the overall cohort but yielded significantly different results in the subgroup analysis. Use of a corrective transfusion factor mildly improved correlation of the Gross equation with EBL. At high levels of blood loss, surgeon EBL predictions became more discordant with calculated blood loss values. When assessing only patients who did not receive transfusions, concordance improved.Blood loss in pelvic and acetabular surgery is challenging to quantify, and this study demonstrates discordance between formula predictions and surgeon-estimated blood loss. At higher levels of blood loss, this discrepancy worsens. This exploratory study highlights the need for the development of improved methods of quantifying blood loss in orthopaedic trauma surgery.Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.