Rapid prognostic tools in disaster medicine: C-reactive protein-to-albumin ratio (CAR) and bicarbonate-to-lactate ratio (BILAR) in crush syndrome

Crush syndrome is a life-threatening complication frequently observed following earthquakes and other natural disasters, often leading to multi-organ failure and high mortality. Rapid and reliable prognostic tools are critical for early risk stratification and management of affected patients, particularly in resource-limited disaster settings. In this context, inflammatory and perfusion-based indices such as the C-reactive protein-to-albumin ratio (CAR) and the bicarbonate-to-lactate ratio (BILAR) have recently gained attention as potential predictors of adverse outcomes. The aim of this retrospective study was to evaluate the prognostic value of CAR and BILAR in patients with crush syndrome and to determine their role in predicting mortality and major clinical outcomes. This study included patients over 18 years of age who were diagnosed with crush syndrome following the February 6, 2023 Kahramanmaraş earthquakes. Demographic, clinical, and laboratory data were analyzed. The CAR was calculated using the formula CRP (mg/L)/Albumin (g/L), while the BILAR was derived as the ratio of HCO₃ (mmol/L) to lactate (mmol/L). The primary endpoint was defined as mortality, and the secondary endpoints included amputation, intensive care unit (ICU) admission, stage 3 acute kidney injury (AKI), and the need for renal replacement therapy. The prognostic impact of CAR and BILAR indices on mortality was assessed using statistical analyses. A total of 231 patients (mean age 36.63 ± 12.35 years, 51.1% female) were included, of whom 18 (7.8%) died. Mortality was significantly associated with elevated levels of BUN, creatinine, potassium, phosphorus, AST, ALT, creatine kinase, lactate, and the CAR index, as well as decreased albumin, calcium, HCO₃⁻, hemoglobin, and BILAR index values (p < 0.05). ROC analysis revealed that CAR showed moderate-to-good discriminative ability for mortality (AUC = 0.64), stage 3 AKI (AUC = 0.73), ICU admission (AUC = 0.75), amputation (AUC = 0.65), and the need for hemodialysis (AUC = 0.72). According to the Youden index, the optimal CAR cut-off for predicting mortality was 2.37 (sensitivity = 83%, specificity = 44%). Low BILAR values were inversely associated with all endpoints, with BILAR < 5 showing a particularly strong correlation with mortality (p < 0.001). Importantly, 71 patients (30.7%) required renal replacement therapy (RRT), with a significantly higher mortality rate compared to non-RRT patients (19.7% vs. 2.5%, p < 0.001). In multivariate logistic regression analysis including CAR, BILAR, age, gender, comorbidity, AKI, and RRT, low BILAR values, advanced age, and receipt of RRT were independently associated with increased mortality, whereas CAR, AKI, sex, and comorbidity did not retain independent significance. CAR and BILAR are rapid and easily calculated prognostic indices in crush syndrome. In this study, low BILAR values, advanced age, and the need for renal replacement therapy (RRT) were independently associated with increased mortality. These findings suggest that perfusion-based markers such as BILAR may be more reliable than inflammatory indices like CAR for early mortality risk prediction. Incorporating BILAR into clinical assessment could support timely risk stratification and treatment planning in disaster-related mass-casualty settings.