[Blood Loss in Open Spine Surgeries - Preoperative Estimate vs Reality]

Intraoperative blood loss represents a critical challenge in spinal surgery, with the potential to increase morbidity, mortality, and healthcare costs. Significant blood loss is associated with postoperative complications such as respiratory failure, infections, and hematomas. This paper evaluates current methods of estimating blood loss and highlights the discrepancy between intraoperative clinical estimates and the actual total blood loss, with a specific focus on the phenomenon of hidden blood loss (HBL). The concept of Total Blood Loss (TBL) is analyzed as the sum of Visible Blood Loss (VBL), consisting of blood in suction canisters, sponges, and drains, and HBL, which results from hemolysis and sequestration of blood into tissues. Mathematical formulas, specifically the Gross equation and Nadler's formula for patient blood volume, are discussed as tools for calculating TBL based on hematocrit changes. Visual estimation is consistently shown to be inaccurate, often leading to significant underestimation, especially in losses exceeding 1,000 ml. Research indicates that in major spinal procedures, approximately 21% of the total intraoperative blood loss is captured in surgical sponges. For practical intraoperative monitoring, a "28% coefficient" should be added to the volume in the suction canister to provide a realistic estimate of the blood trapped in textiles. Furthermore, HBL accounts for at least 30% of the total perioperative loss. In extensive posterior thoracolumbar fusions, the visible blood in the suction canister may represent about half of the actual TBL only. Younger patients are paradoxically more susceptible to higher HBL due to more dynamic transcapillary refill and greater vascular compliance.