During surgery for spinal tuberculosis infection, patients can lose a significant amount of blood, which may result in the patient receiving a blood transfusion. Therefore, it is important to evaluate the different risk factors for increased intraoperative blood loss and perioperative blood transfusion, which can potentially be used for preoperative planning and risk stratification to evaluate outcomes.
Through autologous blood transfusion contributing to reducing perioperative blood loss, the fact that spinal tuberculosis or brucellosis is a complication of a systematic disease makes it impossible to perform preoperative autologous blood donation and intraoperative autologous blood transfusion. Several previous studies have investigated risk factors associated with the risk of transfusion in spine surgical patient populations. In lumbar fusion surgery, ASA > 1, prolonged operative time, multilevel fusion, sacrum involvement, and open posterior approach are predictors of transfusion. Similarly, Durand reported that operative duration, surgical invasiveness, hematocrit, weight, and age were the most influential variables for predicting blood transfusion. In addition, it has been reported that preoperative hemoglobin levels are an important predictor of allogenic blood transfusion in the perioperative period for patients who underwent surgery. However, in our analysis, preoperative hemoglobin levels did not predict the need for a perioperative blood transfusion among patients with spinal tuberculosis. Our data also revealed that the preoperative hemoglobin levels were significantly correlated with high intraoperative blood loss. Preoperative low hemoglobin levels may increase postoperative complications for patients with spinal tuberculosis. In addition, several studies have shown that preoperative anemia is associated with poor outcomes after surgery and increased health care use.[19, 20] Therefore, the correction of preoperative anemia may improve the outcome of spinal tuberculosis surgery.
Several clinical factors, including the higher number of involved discitis, higher levels of instrumentation and combined surgical approach, were found to be correlated with the increased rate of blood transfusion and intraoperative blood loss. However, after adjusting for interactions between covariates in the multivariate analysis, the influence of these factors was revealed to be nonsignificant, and the odds of transfusion increased by 4.5 times when patients had a pathological fracture or kyphosis. The choice of surgical approach has been reported to be linked to intraoperative blood loss.[21, 22] Previous studies reported that one-stage anterior operation had advantages when compared to posterior instrumentation, as both instrumentation and grafting are performed as single-stage surgery through the same incision, which may minimize total blood loss.[21, 23] In contrast, other studies illustrated that the posterior approach favors less intraoperative blood loss. This difference may be attributed to the preference and experience of surgeons. Usually, the combined approach often leads to prolonged operative time and more blood loss, which may be associated with significant kyphosis and multiple-level lesions. Furthermore, our investigation revealed that increased operative time is strongly associated with a higher likelihood of blood transfusion and a higher amount of blood loss. Four or more levels of instrumentation are also a risk factor for high intraoperative blood loss. In fact, operating time and blood loss are associated with an increase in the number of levels fused or instrumentation in spine surgery.[13, 25] Kumar reported the results of their review of 243 patients undergoing surgery for metastatic spinal tumors and identified primary tumor, type of surgery, and prolonged surgery time as predictors of increased blood loss.
Our results showed that female sex and lower BMI were risk factors for blood transfusion. A possible explanation for the relationships between blood transfusion and gender and BMI is that a smaller body size may increase intraoperative blood loss. In our cohort, the mean age was 49.5 ± 15.6 years old. In North America, Europe and China, tuberculous spondylodiscitis is more commonly seen in adult patients with a mean age of 40 years[1, 27]. It has been reported that advanced age did not increase the morbidity associated with spinal operation. For most patients, robust compensatory mechanisms render hypotension an insensitive indicator of shock until more than 30% of the patient’s blood volume has been lost; therefore, intraoperative blood loss over 30% of the total blood volume was set as the cutoff in this study. Intraoperative cues indicative of intraoperative blood transfusion include low hematocrit and hemoglobin levels (< 70 g/L), a higher heart rate (> 120 beats/min), a weak peripheral pulse, and cool extremities with pale or mottled skin, among others.
Several factors probably contribute to reducing the risk of bleeding during spinal tuberculosis surgery. Proper surgical approaches, the discontinuation of anticoagulant medications, the correction of preoperative anemia and the preoperative estimation of blood loss are essential in minimizing blood loss in surgery. Intraoperative methods to control blood loss include positioning to reduce intraabdominal pressure, the use of tranexamic acid and the use of topical antifibrinolytic agents. Moreover, modified anesthesia techniques such as core temperature control and hypotensive anesthesia have shown promising results in safely reducing blood loss[30–32].
There were several limitations in this study. This was a retrospective study with a small sample size. A multicenter study should be conducted. Almost all the patients in this cohort had spondylodiscitis. Patients with atypical forms of spondylitis without disc involvement were not included in this study. There was also a lack of clinical information on commodities, medications, nutritional status and other variables. Tranexamic acid was not given to patients in this cohort; therefore, its effect on spinal tuberculosis surgery was not evaluated. It has been reported that tranexamic acid could reduce both intraoperative-perioperative allogeneic transfusion rates and operative time in spinal surgeries. A recent study demonstrated that tranexamic acid contributes to reducing the drainage and blood transfusion perioperative duration of tuberculosis patients, but it cannot decrease intraoperative blood loss. The cause of transfusion was also not collected, but patients typically get transfused when their hemoglobin level less than 70 g/L, and they present changes in symptomatic or vital signs. Additionally, the risk of bleeding with regards to other causes of spine surgery was not investigated and a such comparation would be further analyzed in future work. However, despite such limitations, we believe that we assessed several important clinical variables that allowed us to determine the relationships between the evaluated surgeries and blood loss and the risk of blood transfusions.