Ceftazidime avitbatan sodium is a broad-spectrum antibiotic with an antimicrobial spectrum covering resistant gram-negative bacteria. Its use in pediatric intensive care for severe infections is not unusual. Pathophysiological changes in severe sepsis can lead to significant changes in pharmacokinetics and pharmacodynamics during continuous renal replacement therapy.This research aims to study change of pharmacokinetic and pharmacodynamic in severe infection children with extracorporeal life support, thus improve the treatment of severe sepsis and sepsis shock.