Neutrophil gelatinase-associated lipocalin as an early indicator for postoperative renal failure

Introduction

Neutrophil gelatinase-associated lipocalin plasma (pNGAL) and urine (uNGAL) concentrations can be used as early indicators for the development of acute kidney injury (AKI) [1]. As AKI is associated with higher risk of morbidity and mortality in ICU patients [2], higher pNGAL and uNGAL on admission might be relevant to the clinical course. No data on pNGAL and uNGAL as early indicators of postoperative AKI have been published.

Methods

We collected plasma and urine samples from patients admitted postoperatively following noncardiopulmonary bypass-related surgery. NGAL concentrations were measured using an immunofluorescence assay. Subsequently we compared the time points of maximum pNGAL, uNGAL and SCr concentrations in the group of patients developing postoperative AKI (Mann-Whitney U test). Data are presented as mean ± SD.

Results

One hundred and ninety-five consecutive patients (age: 58 ± 16 years; APACHE II 15 ± 6) were included. Twenty-two patients (age 63 ± 17; APACHE II 20 ± 7) developed AKI (AKI 1 n = 14; AKI 2 n = 3; AKI 3 n = 5). Time to reach peak (T_max) concentrations for pNGAL, uNGAL and SCr are respectively 21 (21), 20 (22), 31 (32) for AKI 1, 39 (32), 24 (31), 54 (12) for AKI 2, and 17 (18), 26 (24), 34 (27) for AKI 3. Maximum concentrations of pNGAL (ng/ml), uNGAL (ng/ml) and SCr (mmol/l) are respectively 1,348 (1,569), 364 (220), 147 (38) for AKI 1, 424 (309), 949 (389), 175 (28) for AKI 2, and 2,375 (1,731), 726 (398), 265 (81). Figure 1 shows time course of pNGAL and uNGAL in patients developing AKI. T_max of pNGAL and uNGAL was significantly earlier than T_max of SCr (both α <0.001).

Figure 1

Conclusions

In postoperative patients developing AKI, pNGAL and uNGAL reach peak concentrations 1 day earlier than SCr. This might be of clinical importance as it provides us with an opportunity to prevent further deterioration of renal function at an earlier stage.