Structural equation modelling exploration of the key pathophysiological processes involved in cardiac surgery-related acute kidney injury in infants.
BACKGROUND
Uncertainties about the pathophysiological processes resulting in cardiac surgery-related acute kidney injury (AKI) in infants concern the relative impact of the most prominent risk factors, the clinical relevance of changes in glomerular filtration rate vs tubular injury, and the usefulness of available diagnostic tools. Structural equation modelling could allow for the assessment of these complex relationships.


METHODS
A structural model was specified using data from a prospective observational cohort of 200 patients <1 year of age undergoing cardiopulmonary bypass surgery. It included four latent variables: AKI, modelled as a construct of perioperative creatinine variation, of oliguria and of urine neutrophil gelatinase-associated lipocalin (uNGAL) concentrations; the cardiopulmonary bypass characteristics; the occurrence of a post-operative low cardiac output syndrome and the post-operative outcome.


RESULTS
The model showed a good fit, and all path coefficients were statistically significant. The bypass was the most prominent risk factor, with a path coefficient of 0.820 (95 % CI 0.527-0.979), translating to a 67.2 % explanation for the risk of AKI. A strong relationships was found between AKI and early uNGAL excretion, and between AKI and the post-operative outcome, with path coefficients of 0.611 (95 % CI 0.347-0.777) and 0.741 (95 % CI 0.610-0.988), respectively. The path coefficient between AKI and a >50 % increase in serum creatinine was smaller, with a path coefficient of 0.443 (95 % CI 0.273-0.596), and was intermediate for oliguria, defined as urine output <0.5 ml kg(-1) h(-1), with a path coefficient of 0.495 (95 % CI 0.250-0.864). A path coefficient of -0.229 (95 % CI -0.319 to 0.060) suggested that the risk of AKI during the first year of life did not increase with younger age at surgery.


CONCLUSIONS
These findings suggest that cardiac surgery-related AKI in infants is a translation of tubular injury, predominately driven by the cardiopulmonary bypass, and linked to early uNGAL excretion and to post-operative outcome.


TRIAL REGISTRATION
ClinicalTrials.gov identifier NCT01219998 . Registered 11 October 2010.
['Bojan|Mirela|M|', 'Basto Duarte|Maria Constanza|MC|', 'Ermak|Natalia|N|', 'Lopez-Lopez|Vanessa|V|', 'Mogenet|Agnès|A|', 'Froissart|Marc|M|']
D058186:Acute Kidney Injury D015415:Biomarkers D006348:Cardiac Surgical Procedures D002315:Cardiopulmonary Bypass D003404:Creatinine D015199:Extracorporeal Membrane Oxygenation D005260:Female D005602:France D006801:Humans D007231:Infant, Newborn D000071068:Lipocalin-2 D008297:Male D010372:Pediatrics D010530:Peritoneal Dialysis D011183:Postoperative Complications D012307:Risk Factors
Acute kidney injury Cardiopulmonary bypass Paediatric cardiac surgery