Haematocrit differences modify the association of cardiopulmonary bypass reoxygenation with acute kidney injury after paediatric Tetralogy of Fallot repair

Abstract

Background:

Little is known regarding the potential impact of haematocrit differences in the association between cardiopulmonary bypass reoxygenation and acute kidney injury following Tetralogy of Fallot repair.

Methods:

We investigated the association of perfusate oxygenation during aortic occlusion associated with acute kidney injury between 204 normal and 248 higher haematocrit children with Tetralogy of Fallot, aged 1 month-18 years, who were surgically repaired in 2012-2018. Normal and higher haematocrit children were defined as having a preoperative haematocrit within and above age- and sex-specific reference intervals, respectively. Acute kidney injury was determined as a binary variable according to the Kidney Disease Improving Global Outcomes criteria.

Results:

After adjusting for baseline and clinical covariates, a significant interaction between the haematocrit and continuous perfusate oxygenation on acute kidney injury was found (p_interaction = 0.049): a higher perfusate oxygenation was associated with a greater acute kidney injury risk among higher haematocrit children (adjusted odds ratio = 1.50, 95% confidence interval = [1.02, 2.22] per SD, p = 0.038) but not among normal haematocrit children (adjusted odds ratio = 0.91, 95% confidence interval = [0.51, 1.63] per SD, p = 0.73). After a similar adjustment, there was a marginal interaction between tertiles of perfusate oxygenation and haematocrit on acute kidney injury (p_interaction = 0.09): the middle and top tertiles of perfusate oxygenation were associated with a trend towards increased acute kidney injury risks among higher haematocrit children (adjusted odds ratio = 1.69, 95% confidence interval = [0.61, 4.66]; adjusted odds ratio = 2.25, 95% confidence interval = [0.84, 5.99], respectively) but not among normal haematocrit children (adjusted odds ratio = 1.16, 95% confidence interval = [0.46, 2.94]; adjusted odds ratio = 0.45, 95% confidence interval = [0.15, 1.36], respectively) compared with the bottom tertile.

Conclusion:

Preoperative haematocrit differences significantly modify the association of perfusate oxygenation with acute kidney injury, highlighting differential control of reoxygenation for different haematocrit children with Tetralogy of Fallot in the management of cardiopulmonary bypass.