Exploring urinary biomarkers of early acute kidney injury in a clinical model of canine intraoperative hypotension: an observational cohort study.

OBJECTIVE

To explore changes in urinary biomarkers of acute kidney injury (AKI) in healthy dogs experiencing intraoperative hypotension and explore the relationship between blood pressure and urinary biomarkers.

STUDY

DESIGN

Observational cohort study.

ANIMALS: A group of 50 client-owned dogs.

METHODS

Urine and blood samples were collected prior to anaesthesia (T0), within 24 hours after anaesthesia (T1) and 10 days post-surgery (T10). During anaesthesia, the lowest mean arterial pressure (MAP) in each dog was identified. Impact of duration was explored by categorizing according to arbitrary thresholds of MAP < 50, < 60, < 70 and < 80 mmHg and calculating duration (minutes) within each category. Serum creatinine (Cr) and validated biomarkers of AKI including urinary gamma-glutamyl transferase (uGGT), urinary neutrophil gelatinase-associated lipocalin (uNGAL) and urinary cystatin C (uCystatin C) were measured. Biomarker measurements were standardized to urinary Cr. The frequency of dogs with proportional increases between T1 and T0 and between T10 and T0 was recorded. Multiple regression analysis determined the simplest subset of independent variables (lowest MAP, duration with each MAP category) to best explain the variance in the proportional change of each biomarker.

RESULTS

Hypotension, defined as MAP < 60 mmHg, was observed in 38/50 (76%) of the dogs. Between T1 and T0, increases in uGGT/Cr, uCystatin C/Cr and uNGAL/Cr were observed in 37 (82%), 17 (41 %) and 19 (35%) of 50 dogs, respectively. Of the variance observed in uGGT/Cr at T1/T0, 62% could be explained by the lowest MAP recorded when combined with duration MAP < 50 mmHg (adjusted R2 0.62).

CONCLUSIONS AND CLINICAL RELEVANCE: In this clinical model of intraoperative hypotension, uGGT/Cr demonstrated potential for diagnosis of early AKI. The use of other validated biomarkers of AKI requires further investigation to establish their clinical relevance in diagnosis of post-anaesthetic kidney injury.