“Risk Factors for Lower Extremity Deep Vein Thrombosis by Spinal Cord Injury Level: A Population-Based Analysis” by Alejandro Pando et al

To the editor:

Recently, we had the privilege of reading the article titled “Risk Factors for Lower Extremity Deep Vein Thrombosis by Spinal Cord Injury Level: A Population-Based Analysis” by Alejandro Pando et al ¹ This study involved a retrospective analysis of data from the National Inpatient Sample (NIS) in the United States, covering the period from 2016 to 2021. The primary objective was to investigate the incidence of deep vein thrombosis (DVT) among patients with varying levels of spinal cord injury (SCI)—specifically, cervical, thoracic, and lumbar segments—and to identify independent risk factors. The study found a 2.8% overall incidence of DVT in SCI patients, with the highest incidence in the thoracic segment (3.2%) and the lowest in the cervical segment (2.6%). Pulmonary embolism (PE) was identified as a significant risk factor for DVT across all segments. We are very grateful to the authors for their contribution; however, there are still some issues in this article that require further exploration.

Firstly, there is a significant association between preoperative anemia and the incidence of postoperative DVT. The research conducted by Zhang et al indicates that preoperative anemia may be a contributing factor to the development of DVT in patients experiencing bone trauma during the perioperative period. ² A preoperative hemoglobin concentration threshold of 125 g/L has been identified as having predictive value for DVT. Failure to address anemia prior to surgery may exacerbate ischemia and hypoxia in cells, tissues, and organs during the surgical procedure, thereby increasing the risk of complications such as DVT. The authors did not account for anemia indicators, such as hemoglobin levels, nor did they consider the variability in hemoglobin levels among patients with different levels of SCI at admission or during hospitalization. This oversight could introduce bias into the statistical analysis of the sample.

Secondly, obstructive sleep apnea (OSA) is recognized as an independent risk factor for venous thromboembolism, encompassing both DVT and PE. The study by Lippi et al found that in OSA patients, platelet activation, inhibition of fibrinolysis, and thrombin generation were significantly enhanced. ³ The risk of DVT or PE in patients with obstructive sleep apnea was 2 to 3 times higher than that in those without obstructive sleep apnea. However, the authors did not account for this critical factor of obstructive sleep apnea, which may compromise the accuracy of their experimental findings.

Moreover, the author did not investigate the potential impact of intestinal microecological imbalance and associated inflammatory responses on the coagulation system. Research conducted by Cheng et al indicates a significant correlation between small intestinal bacterial overgrowth (SIBO) and the occurrence of early post-hospital DVT, thereby identifying SIBO as an independent risk factor for DVT. ⁴ SCI can lead to neurogenic intestinal dysfunction, intestinal flora imbalance, or SIBO, which may induce systemic inflammation and correlate with an elevated risk of DVT. The author did not address the potential influence of intestinal inflammation or SIBO on DVT risk in patients with SCI. It is recommended that the author incorporate indicators related to intestinal inflammation in future analyses to enhance the rigor of the study.

In conclusion, we extend our appreciation to the author for their research, which has elucidated the relationship between SCI segments and the risk of DVT, along with the identification of specific risk factors. This work offers novel insights for the clinical application of stratified prevention strategies, thereby contributing to the optimization of high-risk patient management and the reduction of thromboembolic event incidence, ultimately enhancing the prognosis of patients with SCI.