A single dose of aminophylline administration during therapeutic hypothermia; does it make a difference in glomerular filtration rate?

Aminophylline has been demonstrated to be effective in improving renal functions of the infants suffering from acute kidney injury (AKI) due to perinatal asphyxia. We aimed to evaluate the effect of a single-dose aminophylline on estimated glomerular filtration rate (eGFR), urine output (UO), and incidence and severity of AKI according to the pediatric-modified RIFLE and neonatal RIFLE criteria in newborns with perinatal asphyxia under therapeutic hypothermia. This was a single-center, retrospective cohort study including newborns (gestational age ≥36 weeks) who underwent therapeutic hypothermia due to hypoxic ischemic encephalopathy between 2016 and 2019. Demographic and clinical data were obtained from electronic medical records and patient files. Two patient groups were established: aminophylline group and control group which were only under therapeutic hypothermia. Twenty-one newborns were in the aminophylline group and 13 newborns were in the control group. Our study revealed that on the third day of life (DOL), eGFR was significantly higher in the control group (p=0.025), but UO was significantly higher in the aminophylline group (p=0.021). In the aminophylline group, eGFR on the first DOL was higher than the value on the second DOL (p=0.017) while UO was higher on the second and third DOL compared to the first DOL (1-2 DOL p=0.006, and 1-3 DOL p=0.004). However, in the control group, there was no statistically significant difference in UO over the four DOL. Both groups were similar in the presence, severity, and outcome of AKI.Conclusion: This study demonstrated that aminophylline increases UO even in the infants under therapeutic hypothermia. However, the eGFR did not significantly increase in the aminophylline group. Understanding how therapeutic hypothermia affects pharmacokinetics may help us improve our results in future studies. What is known: • Therapeutic hypothermia (TH) reduces the incidence of acute kidney injury in asphyxiated newborns. • Aminophylline is effective in improving renal functions in asphyxiated newborns. What is new: • This is the first study evaluating the effect of a single dose of aminophylline on renal functions in newborns under TH. • A single dose of aminophylline administration in newborns under TH was associated with increased urine output especially on the third day of life. However, no significant increase was detected in glomerular filtration rate associated with aminophylline administration.