Abstract
Objective:
To explore changes in urinary biomarkers of acute kidney injury (AKI) in healthy dogs experiencing intra-operative 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. Impact of duration was explored by categorising 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 standardised to urinary Cr. The frequency of dogs with proportional increases between T1 and T0 and between T10 and T0 was recorded. Multiple regression analysis was performed to determine 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 < 50mmHg (adjusted R2 0.62).
Conclusion and clinical relevance:
In this clinical model of intra-operative hypotension uGGT/Cr demonstrated potential for diagnosis of early AKI in healthy dogs. Increases in validated biomarkers uCystatin C/Cr, and uNGAL/Cr support their use in future studies investigating different causes or severity of AKI.
