During operation on 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 potentially can be used for preoperative planning and also for risk stratification to evaluate outcomes.
Through autologous blood transfusion contributed to reduce perioperative blood loss, the fact that spinal tuberculosis or brucellosis is the 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 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.19 Similarly, Durand reported operative duration, surgical invasiveness, hematocrit, weight, and age as the most influential variables predicting blood transfusion.7 In addition, it is reported that preoperative hemoglobin level is an important predictor of allogenic blood transfusion in perioperative duration for patients underwent surgery. However, through our analysis, preoperative hemoglobin is not a predictor of perioperative blood transfusion for patients with spinal tuberculosis. Our data revealed that preoperative hemoglobin level had a significant correlation with intraoperative high blood loss . A previous study showed that preoperative low hemoglobin level increases the postoperative complications for patients with spinal tuberculosis.30 In addition, several studies showed that preoperative anemia is associated with poor outcomes after surgery and increased health care use.8,10 Therefore, correction of preoperative anemia may contribute to improve the outcome in spinal tuberculosis surgery.
Several clinical factors, including the higher number of involved discitis, higher levels of instrumentation and combined surgical approach, was found that corelated to the increased rate of blood transfusion and intraoperative blood loss However, after adjusting for interaction between covariates by multivariate analysis, the influence of these factors was not significant, and only the odds of transfusion increased by 4.5 times for the patients with pathological fracture or kyphosis. The choice of surgical approach was reported to be linked to the intraoperative blood loss.28,29 Previous studies reported that one-stage anterior operation had advantages when compared to posterior instrumentation, as both instrumentation and grafting are done as single-stage surgery through the same incision, which may minimize total blood loss.12,29 In contrast, other studies illustrated that posterior approach favors less intraoperative blood loss. This difference may be attributed to the preference and experience of the surgeons. Usually, combined approach often leads to prolonged operative time and more blood loss, which may be associated with significant kyphosis and multiple-level lesion.22 Furthermore, our investigation revealed that increased operative duration is strongly associated with higher likelihood of blood transfusion and higher amount of blood loss. Four or more levels of instrumentation is also a risk factor of intraoperative high 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.17,19 Kumar reported 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 factors predicting increased blood loss.17
Our results showed that female and lower BMI were risk factors for blood transfusion. The possible explanation for the relationship of gender and BMI to blood transfusion is that smaller body size may increases the intraoperative blood loss.14 In our cohort, the mean age is 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.24,26. It has been reported that advanced age did not increase the morbidity associated with spinal operation.23 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 cutoff in this study. Intraoperative cues indicative of intraoperative blood transfusion includes low hematocrit and hemoglobin (<70 g/L), higher heart rate (>120 beats/min), a weak peripheral pulse, cool extremities with pale or mottled skin and so on.2
There were several limitations to the study. This was a retrospective study and may have been limited sample size. A multicentered study is still warranted. Almost all the patients in this cohort were spondylodiscitis. Atypical form of spondylitis without disc involvement was not included in this study. There is also a lack of clinical information on commodities, medications, nutritional status and other variables. Tranexamic acid was not applied on patients in this cohort, therefore its effect on spinal tuberculosis surgery was not evaluated. It is reported that tranexamic acid could reduce both intraoperative-perioperative allogeneic transfusion rates and operative time in spinal surgeries.13 A recent study demonstrated that Tranexamic acid contributes to reduce the drainage and blood transfusion perioperative duration of tuberculosis patients, but it can’t decrease intraoperative blood loss.11 Additionally, the cause of transfusion was not collected, but patients typically get transfused when their hemoglobin is less than 70 g/L and they present a change of symptomatic or vital signs. However, despite such limitations, we believe that we collected several important clinical variables that allowed us to calculate relationships between the evaluated surgeries and blood loss and risk of blood transfusions.