Lactic acid levels are associated with morbidity, length of stay, and total treatment costs in urban trauma patients with lower extremity long bone fractures

Introduction: Lactic acid is well studied in the trauma population and is frequently used as a laboratory indicator that correlates with resuscitation status and has thus been associated with patient outcomes. There is limited literature that assesses the association of initial lactic acid with post-operative morbidity and hospitalization costs in the orthopedic literature. The purpose of this study was to assess the association of lactic acid levels and alcohol levels post-operative morbidity, length of stay and admission costs in a cohort of operative lower extremity long bone fractures, and to compare these effects in the ballistic and blunt trauma sub-population. Methods: Patients presenting as trauma activations who underwent tibial and/or femoral fixation at a single institution from May 2018 to August 2020 were divided based on initial lactate level into normal, (< 2.5) intermediate (2.5–4.0), and high (> 4.0). Mechanism of trauma (blunt vs. ballistic) was also stratified for analysis. Data on other injuries, surgical timing, level of care, direct hospitalization costs, length of stay, and discharge disposition were collected from the electronic medical record. The primary outcome assessed was post-operative morbidity defined as in-hospital mortality or unanticipated escalation of care. Secondary outcomes included hospital costs, lengths of stay, and discharge disposition. Data were analyzed using ANOVA and multivariate regression. Results: A total of 401 patients met inclusions criteria. Average age was 34.1 ± 13.0 years old, with patients remaining hospitalized for 8.8 ± 9.5 days, and 35.2% requiring ICU care during their hospitalization. Patients in the ballistic cohort were younger, had fewer other injuries and had higher lactate levels (4.0 ± 2.4) than in the blunt trauma cohort (3.4 ± 1.9) (p = 0.004). On multivariate regression, higher lactate was associated with post-operative morbidity (p = 0.015), as was age (p < 0.001) and BMI (p = 0.033). ISS, ballistic versus blunt injury mechanism, and other included laboratory markers were not. Lactate was also associated with longer lengths of stay, and higher associated direct hospitalization cost (p < 0.001) and lower rates of home disposition (p = 0.008). Conclusion: High initial lactate levels are independently associated with post-operative morbidity as well as higher direct hospitalization costs and longer lengths of stay in orthopedic trauma patients who underwent fixation for fractures of the lower extremity long bones. Ballistic trauma patients had significantly higher lactate levels compared to the blunt cohort, and lactate was not independently associated with increased rates of post-operative morbidity in the ballistic cohort alone. Level of evidence: III.