Renal Functions in Preeclamptic Pregnant Women Using Neutrophil Gelatinase-associated Lipocalin (NGAL) and Standard Renal Function Tests

Overview

Acute kidney injury (AKI) is a significant postoperative complication. Risk factors for AKI include impaired renal perfusion, decreased functional renal reserve, as well as advanced age, peripheral arterial disease, diabetes mellitus, renovascular disease and congestive heart failure. Mean arterial pressure (MAP) below 55-60 mmHg has been associated with postoperative AKI. Traditional diagnostic criteria for AKI include increased serum creatinine levels and oliguria. However, creatinine levels do not rise until more than half of renal function is lost. Serum and urine NGAL levels rise earlier-within 24-48 hours-making it a promising early biomarker. In our study, hypotension is defined as systolic blood pressure \<100 mmHg or a \>30% decrease in MAP. Patients requiring ephedrine under these conditions will be evaluated as the hypotension group and compared with non-hypotensive patients in terms of NGAL, BUN (blood urea nitrogen), creatinine, and GFR (Glomerular Filtration Rate) values at baseline and at the 4th postoperative hour.

All patients were informed about the study in the preoperative period and written informed consent was obtained before the procedure. The following data were recorded: age, sex, weight, height, BMI (Body Mass Index), comorbidities, regular medications, ASA (American Society of Anesthesiologists) classification, gestational age, history of preeclampsia in previous pregnancies, hemodynamic values and laboratory results. After being admitted to the cesarean operating room, patients were monitored according to the ASA guidelines using standard monitoring methods (non-invasive arterial blood pressure measurements at 2-minute intervals, 3-lead ECG (Electrocardiogram) and pulse oximetry). A peripheral intravenous line was established via the dorsum of the hand and Ringer's lactate was infused at a rate of 10 mL/kg/h. All patients received oxygen via nasal cannula at a rate of 3-4 L/min. Blood samples were collected from the patients before spinal anesthesia and at the 4th postoperative hour. The samples were centrifuged at 4000×g for 10 minutes in the biochemistry laboratory and then transferred into Eppendorf tubes and stored at -80°C in a deep freezer until the day of analysis. NGAL levels were measured using an ELISA (Enzyme-Linked ImmunoSorbent Assay) method with a commercial kit (USCN, China) at the Biochemistry Laboratory of Ankara Bilkent City Hospital. Each sample was measured in duplicate, and the mean values were used for evaluation. The intra-assay and inter-assay coefficients of variation (CV%) for the kit were determined to be \<10% and \<12%, respectively. At the 4th postoperative hour, blood samples were also analyzed for BUN, creatinine, and GFR levels, which were recorded accordingly.