Typical spinal tuberculosis usually presents with symptoms of tuberculosis poisoning such as pain, fatigue, night sweats, low fever, weight loss, and other symptoms of tuberculosis poisoning . Imaging exhibited bone destruction, and severe tuberculosis of the spine often results in kyphosis . The kyphotic deformity increases surgical difficulty and the risk of bleeding. However, the supply for blood products is inadequate to meet the growing demand for surgery . Therefore, a reasonable prediction of intraoperative blood transfusion in the perioperative period has become crucial.
The present study introduced perioperative parameters to develop the nomogram for predicting the blood transfusion risk. The C-index calculated by the nomogram was 0.787 and 0.763 in the training and validation sets, respectively, which indicated the highly accurate predictability of the nomogram . The C-index calculated in the present paper was higher than that obtained by the previous nomogram (0.734) . The combination and predictive efficacy of the nomogram increased with C-index . The present study used internal validation to calculate the C-index. Studies have shown that good discrimination and calibration ability could be obtained through internal validation in the cohort. The high C-index was especially suitable for wide use in large sample data . The nomogram in the present study achieved the best discriminatory ability with an AUC of 0.785, which was slightly higher than that of the previously established nomogram (AUC = 0.75) .
DCA is applied to estimate the clinical usefulness of the nomogram and is a superior tool to estimate the predicted net benefit of the model [25, 26]. Net benefit could be derived based on the threshold probability [27, 28]. The DCA of the nomogram to predict intraoperative red blood cell transfusions could benefit blood transfusions .
Blood transfusion risk could be assessed in the perioperative period by using the nomogram model, and the surgeon was well prepared with adequate blood to perform the surgery, which promoted a more reasonable allocation of blood resources . Huang exhibited the efficient development and validation of the nomogram to predict blood transfusion for surgery. This could effectively improve the utilisation of red blood cells for surgery . HGB was crucial to the total score of the nomogram as it contributed up to 50 points to the score. Dominique Engel predicted perioperative blood transfusion in patients undergoing surgery using the same nomogram and exhibited that preoperative HGB was a vital factor affecting blood transfusion . The preoperative low HGB may be closely related to the deficiency of iron, vitamin B12, and folic acid [11, 12].
Female patients were more likely to receive intraoperative blood transfusion than male patients. A study by Stammers involved 54,122 blood transfusion patients and exhibited that the rate of blood transfusion in female patients was almost three times higher than that in male patients, . This finding is concurrent with that of Cao et al. . This may due to the application of the same absolute transfusion strategy by clinicians and the performance of liberal transfusion strategy in clinical settings .
In the present study, internal fixation was a predictor of blood transfusion during spinal tuberculosis surgery. The increase in the surgical exposure range as the number of pedicle screws implanted leads to an increase in surgical bleeding. The study by Ding et al. found that the mean difference of incision length of fenestration discectomy was 3.74 cm longer than that of percutaneous transforaminal endoscopic discectomy, and the mean difference of amount of bleeding was 63.66 mL higher than that of the latter . In addition, the vertebrae are rich in blood, and blood flows out of the orifice when the pedicle is drilled and the internal fixation device is inserted. The haemorrhage increases with the number of pedicle screws implanted during surgery, making intraoperative blood transfusion necessary. Yang et al. observed that surgical bleeding increased with an increase in the number of internal fixations . Shi et al. observed that the bleeding volume of internal fixation during spinal tuberculosis surgery ranged from 467.7 to 2833.3 mL .
Age was a predictor of blood transfusion during spinal tuberculosis surgery in the present study, with elderly patients exhibiting a higher frequency of transfusion. The fragility of blood vessels in elderly patients increased, and the coagulation factor activity in these patients was lower than that in young patients, resulting in increased surgical bleeding. Nie et al. included 565 elderly people to construct a blood transfusion prediction model for spinal surgery and observed that age was a crucial influencing factor . These findings were concurrent with those of Liu et al. . Additionally, the present study exhibited that lower BMI was a predictor of the risk of spinal tuberculosis blood transfusion. These results were similar to those of Liu et al., who exhibited that although the BMI decreased from 44 to 14, the ability to predict the risk of blood transfusion gradually increased .
Although the association between analgesics and surgical bleeding has been rarely explored, the model constructed in the present study suggested that pain was a predictor of spinal tuberculosis surgical blood transfusion. It has been reported in the literature that spinal pain is closely related to inflammatory factors . Bacteria infect surrounding tissues leading to inflammatory edema, increasing vasculitis permeability and necrotic vasculitis . The study by Oehlers et al. showed that inflammatory granuloma induced an increase in vascular permeability and thus contributed to the spread of Mycobacterium tuberculosis . Therefore, patients with inflammatory pain tend to increase the amount of intraoperative blood loss.
The present study has some limitations. This article was a retrospective study and lacked validation from prospective studies. Additionally, the study spanned 10 years, and the results were influenced by changes in surgical procedures. A larger sample size is required to further validate the efficacy of the nomogram.