A Clinical Study on Remimazolam in Mitigating Lower Limb Ischemia-Reperfusion Lung Injury in Elderly Patients Undergoing Knee Arthroplasty

INTERVENTION: Control group (Group C):Administer propofol intravenously for anesthesia induction and maintenance;Experimental group (Group R):Give remimazolam intravenously for anesthesia induction and maintenance; CONDITION: Lung complications after knee replacement surgery under general anesthesia in the elderly PRIMARY OUTCOME: Postoperative lung complications; SECONDARY OUTCOME: Blood gas analysis indicators;Monitoring breathing during surgery;Blood gas analysis indicators; INCLUSION CRITERIA: 1.ASA II‐III, aged 65‐85 years, any gender; 2.Patients undergoing unilateral total knee replacement under general anesthesia, where a tourniquet is used during surgery for at least 60 minutes; 3.Arterial blood gas analysis indicators before surgery without oxygen: 65mmHg < PaO2 < 80mmHg.