The use of biapenem,meropenem,piperacillin and tazobactam,tigecycline,levofloxacin.etc in elderly ICU patients during clinical treatment depended mostly on experience. Besides, there was no recommended dose for elderly patients in drug instruction, Therefore, we aim to study the pharmacokinetics and pharmacodynamics in elderly ICU patients and provide a tailormade regimen.
The investigator's purpose is to study the pharmacokinetics and pharmacodynamics of biapenem,meropenem,piperacillin and tazobactam,tigecycline,levofloxacin.etc in elderly ICU patients and recommend an individual dosage regimen of those antibiotics.