Age-Related Differences in Early Laboratory Trajectories During Intravenous Colistin Therapy in Critically Ill Neonates and Children

Background: Colistin has reemerged as a last-line treatment for multidrug-resistant (MDR) gram-negative infections in neonatal and pediatric intensive care units, but age-specific data on early laboratory changes during therapy remain limited. This study evaluated early renal, hepatic, and hematologic laboratory trajectories during intravenous colistin treatment in critically ill neonates and children. Materials and Methods: In this retrospective cohort study, patients who received intravenous colistin for ≥7 consecutive days in the neonatal intensive care unit (NICU) and pediatric intensive care unit (PICU) of a tertiary-care university hospital between January 2011 and March 2014 were included. Hematologic, renal, and hepatic parameters were compared between baseline and day 7. Microbiological findings were summarized. Results: Seventy-five patients were included: 25 neonates and 50 children. Klebsiella pneumoniae and Acinetobacter baumannii were the predominant pathogens in both cohorts. In neonates, no significant changes were observed in hematologic, renal, or hepatic parameters between baseline and day 7 (all P > 0.05). In the pediatric cohort, serum creatinine ( P = 0.044) and AST ( P = 0.044) increased significantly by day 7. Patients demonstrating these increases already had abnormal baseline values. Conclusions: Intravenous colistin was not associated with a significant early laboratory toxicity signal in neonates. In PICU patients, increases in serum creatinine and AST were observed, primarily among children with preexisting laboratory abnormalities, suggesting that underlying organ dysfunction may have contributed to these changes. These findings indicate age-related differences in laboratory trajectories during colistin exposure and require confirmation in prospective studies using standardized acute kidney injury definitions.