This is a prospective observational multicentre study. The study is to obtain the real world data of the efficacy and safety of ceftazidime-avibactam(CAZ-AVI) in the treatment of critically ill patients with carbapenem-resistant organisms(CRO) infections (including dialysis patients and extracorporeal membrane oxygenation(ECMO) patients) by using therapeutic drug monitoring(TDM). A population-pharmacokinetic(PPK) model of CAZ-AV in these patients will be established in this study. The main question it aims to answer is the clinical success rate and microbiological success rate of CAZ-AVI based regimen in the treatment of critically ill patients with CRO infections. According to the clinical practice (symptoms, signs, imaging, culture and drug sensitivity, etc.), the doctor determines the combined regimen of CAZ-AVI, and the combined drugs are used routinely according to their instructions or clinical diagnosis and treatment.