P22. Identifying tranexamic acid dosing predictive of decreased risk of intraoperative transfusion accounting for body mass index and surgical invasiveness in complex adult spinal deformity surgery

BACKGROUND CONTEXT Prior studies have associated increased BMI with greater EBL. Yet, EBL in the context of complex adult spinal deformity (ASD) surgery may inherently be elevated, and the interaction between BMI, invasiveness, and EBL has yet to be studied. Additionally, there is a lack of literature assessing relative TXA dosing within these subsets of patients to minimize the risk for transfusion. PURPOSE To define a threshold of EBL based on patient-specific factors that is associated with increased risk of transfusion for complex adult spinal deformity patients, and identify TXA dosing associated with remaining below resulting thresholds. STUDY DESIGN/SETTING Retrospective multi-center. PATIENT SAMPLE A total of 439 complex ASD patients. OUTCOME MEASURES Complication, medication dosage, peri-op. METHODS Complex ASD patients with baseline (BL) and up perioperative (6W) data were isolated. Patients were grouped by BMI (Underweight [<18.5 kg/m2]), Healthy Weight [18.5-25 kg/m2], Overweight [25-30 kg/m2], and Obese [>30 kg/m2]), ISSG-Invasiveness (tertiles of low, moderate, high) and deformity correction per δ6W-BL C7S1 SVA, S1PT, max. kyphosis, and PI-LL (tertiles of low, moderate, high). ANOVA determined differences in EBL by BMI, invasiveness, and deformity correction. Logistic regressions and CIT analysis provided thresholds of EBL requiring intraoperative blood transfusion, along with TXA loading and maintenance dose associated with achievement of subsequent thresholds within invasiveness tertiles and controlling for relevant covariates. RESULTS A total of 302 complex ASD patients (average of 60.4±15.4 years, 69% female, BMI of 27.4±5.8 kg/m2) were isolated who underwent surgical correction with on average 12.5±3.8 levels fused, operative time 467.4±158.1 mins, length of stay 7.0±6.1 days, and EBL 1638.1±1321.3 mL. By BMI, 3.0% were underweight, 32.1% healthy weight, 36.4% overweight, and 28.5% obese. Patients with greater EBL had greater mean rates of post-op ICU admission or prolonged stay (p=.018) but not medical (p=.713), cardiac (p=.364), or neurologic (p=.110) complications. When controlled for levels fused and OR time, greater EBL was predictive of ICU admission or prolonged stay (OR: 1.000 (1.0-1.0), p=.034). CIT determined EBL thresholds associated with transfusion of 800 mL for Low (p=.029), 2100 mL for Moderate (p<.001), and 2600 mL (p12.3 mg/kg loading (p=.029)/≥3.0 mg/kg/hr (p=.019) maintenance for Low invasiveness, >23.5 mg loading (p=.037)/≥3.25 mg/kg/hr maintenance (p=.024) for Moderate invasiveness, and >25.9 mg/kg loading (p=.004)/≥4.7 mg/kg/hr maintenance (p=.002) for High invasiveness groups. CONCLUSIONS Prior research has demonstrated correlations between body mass index (BMI), surgical invasiveness, and estimated operative blood loss (EBL), but this had yet to be studied within complex adult spinal deformity surgery. The present study demonstrates that EBL thresholds predictive of transfusion risk differ based on the degree of surgical invasiveness and deformity correction required. Predictive analysis also reveals that with increasing invasiveness tertiles, incrementally increased dosage of tranexamic acid is associated with maintaining blood loss below said thresholds. FDA Device/Drug Status This abstract does not discuss or include any applicable devices or drugs. Prior studies have associated increased BMI with greater EBL. Yet, EBL in the context of complex adult spinal deformity (ASD) surgery may inherently be elevated, and the interaction between BMI, invasiveness, and EBL has yet to be studied. Additionally, there is a lack of literature assessing relative TXA dosing within these subsets of patients to minimize the risk for transfusion. To define a threshold of EBL based on patient-specific factors that is associated with increased risk of transfusion for complex adult spinal deformity patients, and identify TXA dosing associated with remaining below resulting thresholds. Retrospective multi-center. A total of 439 complex ASD patients. Complication, medication dosage, peri-op. Complex ASD patients with baseline (BL) and up perioperative (6W) data were isolated. Patients were grouped by BMI (Underweight [<18.5 kg/m2]), Healthy Weight [18.5-25 kg/m2], Overweight [25-30 kg/m2], and Obese [>30 kg/m2]), ISSG-Invasiveness (tertiles of low, moderate, high) and deformity correction per δ6W-BL C7S1 SVA, S1PT, max. kyphosis, and PI-LL (tertiles of low, moderate, high). ANOVA determined differences in EBL by BMI, invasiveness, and deformity correction. Logistic regressions and CIT analysis provided thresholds of EBL requiring intraoperative blood transfusion, along with TXA loading and maintenance dose associated with achievement of subsequent thresholds within invasiveness tertiles and controlling for relevant covariates. A total of 302 complex ASD patients (average of 60.4±15.4 years, 69% female, BMI of 27.4±5.8 kg/m2) were isolated who underwent surgical correction with on average 12.5±3.8 levels fused, operative time 467.4±158.1 mins, length of stay 7.0±6.1 days, and EBL 1638.1±1321.3 mL. By BMI, 3.0% were underweight, 32.1% healthy weight, 36.4% overweight, and 28.5% obese. Patients with greater EBL had greater mean rates of post-op ICU admission or prolonged stay (p=.018) but not medical (p=.713), cardiac (p=.364), or neurologic (p=.110) complications. When controlled for levels fused and OR time, greater EBL was predictive of ICU admission or prolonged stay (OR: 1.000 (1.0-1.0), p=.034). CIT determined EBL thresholds associated with transfusion of 800 mL for Low (p=.029), 2100 mL for Moderate (p<.001), and 2600 mL (p12.3 mg/kg loading (p=.029)/≥3.0 mg/kg/hr (p=.019) maintenance for Low invasiveness, >23.5 mg loading (p=.037)/≥3.25 mg/kg/hr maintenance (p=.024) for Moderate invasiveness, and >25.9 mg/kg loading (p=.004)/≥4.7 mg/kg/hr maintenance (p=.002) for High invasiveness groups. Prior research has demonstrated correlations between body mass index (BMI), surgical invasiveness, and estimated operative blood loss (EBL), but this had yet to be studied within complex adult spinal deformity surgery. The present study demonstrates that EBL thresholds predictive of transfusion risk differ based on the degree of surgical invasiveness and deformity correction required. Predictive analysis also reveals that with increasing invasiveness tertiles, incrementally increased dosage of tranexamic acid is associated with maintaining blood loss below said thresholds.