Can a Model Predict Blood Loss During Surgery for a Metastatic Spine Tumor?
In a recently published study, researchers identified factors associated with higher amounts of intraoperative blood loss during surgery for metastatic spine tumors and then used the data to develop a model to predict this blood loss.
Michael Dinizo, MD, and Timothy B. Rapp, MD
Gao X, Fan T, He S, et al. A useful model for predicting intraoperative blood loss in metastatic spine tumor surgery. Clin Spine Surg. 2019 Nov 5. doi: 10.1097/BSD.0000000000000911. [Epub ahead of print].
As spine surgery techniques and instrumentation continue to evolve, a larger spectrum of interventions becomes available to patients with spinal metastases, which can lead to improved quality of life.
Despite this, blood loss in metastatic spine tumor surgery remains a significant challenge due to the rich blood supply of vertebral tumors. Inadequately preparing for rapid and high-volume blood loss in this fragile patient population may result in poor clinical outcomes or death. Only a limited number of previous studies have analyzed factors influencing intraoperative blood loss in spine tumor surgery.
This study by Gao et al had 2 phases:
In phase 1, 318 surgeries performed between January 2011 and December 2015 were analyzed to identify risk factors for excessive blood loss in order to design a new model for predicting the amount of intraoperative blood loss in metastatic spine tumor surgery. The univariate model created to screen the risk factors for intraoperative blood loss was then subjected to multivariate linear regression analysis.
In phase 2, 105 surgeries performed between January 2016 and September 2017 were used to test the validity of the proposed model using correlation analysis between predicted and actual blood loss.
Patient selection was restricted to the following inclusive criteria:
- Patients who were diagnosed with metastatic spinal tumors by postoperative pathology
- Patients who received total or subtotal vertebrectomy with reconstruction rather than laminectomy alone
- Patients with hemoglobin level, platelet count, and blood coagulation parameters within normal ranges
- Patients with complete and accessible medical and surgical records
These patients were then stratified into groups according to:
- Primary tumor: Lung, liver, hematologic, colorectal, breast, prostate, renal, thyroid, or other
- Tumor site: Cervical, thoracic, lumbar, or sacral
- Surgical approach: Anterior, posterior, or combined anterior and posterior
- Level of instrumentation: 0–3, 4, or > 4
- Level of vertebrectomy: 1, 2, > 2, or sacrum
- Resection method: En bloc or piecemeal
Multivariate linear regression analysis showed that primary renal or thyroid tumor, lumbar tumor site, total sacrectomy, 4 or more levels of instrumentation, 2 or more levels of vertebrectomy, and piecemeal resection were independent risk factors associated with high blood loss. The final model for intraoperative blood loss has a correlation coefficient of 0.559 and a P value of < 0.001.
The model is available online here (requires a subscription to the journal Clinical Spine Surgery, institutional access, or 1-time payment).
Spinal metastasis is increasingly encountered in clinical practice due to the prolonged survival of the 5% to 30% of patients with systemic cancer who develop spinal metastasis. These patients may present with severe pain and/or neurologic dysfunction that adversely affects their quality of life. Surgical intervention plays an increasingly critical role in the management of metastatic spinal tumors due to improvements in surgical technology, allowing a broader spectrum of interventions and improved outcomes available to patients. However, massive blood loss in metastatic spine tumor surgery remains a huge challenge.
Accurately predicting intraoperative blood loss is a crucial part of preoperative planning, as it helps with intraoperative and postoperative management. Clinically, the estimation of intraoperative blood loss is usually based on the personal experience of the surgeon rather than on data. Mistakes in judgment could have serious consequences: Inadequate preparation for rapid and high-volume blood loss could result in failure of the operation and even threaten the life of the patient, while overestimation of blood loss could lead to wasting of blood products.
The study by Gao et al has several limitations. First, the retrospective nature, selection bias and confounding bias were difficult to avoid. Second, the model needs to be further validated by more data, especially data from other clinical centers. Moreover, personal surgical experience and surgeon skills play a vital role in the amount of intraoperative blood loss, which is difficult to analyze objectively. Therefore, the model could not predict intraoperative blood loss completely, with the coefficient of correlation of the regression equation being only 0.559.
Surgeons who perform metastatic spine tumor surgery need to be aware of the extent of operative blood loss in advance. According to the study by Gao et al, independent factors influencing blood loss include primary tumor, tumor site, level of instrumentation, level of vertebrectomy, and resection method. Identifying these factors allowed them to develop a useful model for predicting the amount of intraoperative blood loss for various metastatic spine tumor surgeries. This model provides a reliable – but not comprehensive – preoperative prediction of the amount of intraoperative blood loss.
Michael Dinizo, MD, is an orthopedic surgery resident at NYU Langone Orthopedic Hospital, New York, New York. Timothy B. Rapp, MD, is an Associate Professor of Orthopedic Surgery and Chief of the Division of Orthopedic Oncology at NYU Langone Orthopedic Hospital, New York, New York.
Disclosures: The authors have no disclosures relevant to this article.