DOES PERIOPERATIVE SERUM LACTATE PREDICT ACUTE KIDNEY INJURY IN ON-PUMP CABG PATIENTS

Abstract

BACKGROUND: AKI is a serious complication following the on-pump CABG which contributes to increased morbidity and mortality. Perioperative serum lactate has gained attention as an early of adverse outcomes. Raised lactate levels during and after the cardiopulmonary bypass may reflect the systemic hypoxia and impaired organ perfusion which predisposing patients to renal injury. Assessing perioperative serum lactate might provide a simple and timely tool for predicting the AKI within the CABG patients. OBJECTIVE: To determine the diagnostic accuracy of serum lactate to predict acute kidney injury in patients undergoing on-pump coronary artery bypass grafting, with serum creatinine as the gold standard. METHODOLOGY: This cross sectional validation study included two hundred sixty one patients aged 20 to 80 years from October 2025 to March 2026, who underwent elective on-pump CABG were enrolled at department of cardiac surgery and intensive care unit, armed forces institute of cardiology and national institute of heart diseases Rawalpindi. Patients with emergency surgery, re-do surgery, valvular procedures, left ventricular ejection fraction < 25%, or history of kidney disease were excluded. Serum lactate was measured at four hours postoperatively, and level > 4 mmol/L was considered the threshold/cut off. Acute kidney injury was diagnosed according to KDIGO guidelines based on serum creatinine. Diagnostic accuracy were calculated using 2x2 contingency tables. Data were analysed using with SPSS 27. Chi square/Fisher exact test was used with p value ≤ 0.05 considered significant. RESULTS: Acute kidney injury was diagnosed in 56 patients (21.5%). At four hours postoperatively 78 patients (29.9%) had serum lactate > 4 mmol/L. The sensitivity of serum lactate > mmol/L for predicting AKI was 78.57%, specificity 83.41% and the diagnostic accuracy was 82.38%. Significant associations of AKI were observed for age ≥ 65 years, male gender, diabetes, hypertension, and obesity. CONCLUSION: Serum lactate is an accurate and efficient marker to predict acute kidney injury in on-pump CABG patients with diagnostic accuracy of 82.38%