ABSTRACT
Objective:To evaluate the effect of esketamine on extremity ischemia-reperfusion-induced lung injury in elderly patients undergoing total knee replacement.Methods:Sixty elderly patients of both sexes, aged 65-80 yr, with body mass index <35 kg/m 2, of American Society of Anesthesiologists Physical Status classification Ⅱ or Ⅲ, scheduled for elective unilateral total knee replacement under neuraxial anesthesia, were divided into 2 groups according to the random number table method: control group (C group) and esketamine group (S group), with 30 cases in each group. Esketamine 0.3 mg/kg was intravenously infused before tourniquet inflation in group S. Immediately after the end of operation, the two groups received adductor block with 0.5% ropivacaine 15 ml under ultrasound guidance. And then patient-controlled intravenous analgesia was performed, patient-controlled intravenous analgesia solution included sufentanil 1.5 μg/kg in 100 ml of normal saline in group C and sufentanil 1.5 μg/kg and esketamine 0.75 mg/kg in 100 ml of normal saline in group S. The background infusion rate was 1.5 ml/h, the patient-controlled analgesia dose was 1.5 ml, and the lockout interval was 15 min in the two groups. When the visual analogue scale score at rest≥ 4 points within 3 days after surgery, ketorolac tromethamine 30 mg was intravenously injected for rescue analgesia. Blood samples from the radial artery were collected for blood gas analysis at 30 min before tourniquet inflation(T 0), 30 min after tourniquet inflation(T 1), and 3 min, 30 min and 24 h (T 4) after tourniquet release (T 2-4), and PaO 2 and PaCO 2 were recorded. The alveola-arterial oxygen partial pressure difference, oxygenation index and respiratory index were calculated. Peripheral venous blood samples were collected at T 0, T 3 and T 4 for determination of serum endothelin-1 and malondialdehyde by enzyme-linked immunosorbent assay. The requirement for rescue analgesia and occurrence of dizziness, hallucinations and pulmonary complications within 3 days after surgery were recorded. Results:Compared with group C, alveola-arterial oxygen partial pressure difference was significantly decreased at T 1-3, respiratory index was decreased, oxygenation index was increased at T 2, 3, and serum endothelin-1 and malondialdehyde concentrations were decreased at T 3, 4, and the rate of postoperative rescue analgesia was decreased in group S( P<0.05). There was no significant difference in the incidence of postoperative dizziness, hallucinations, and pulmonary complications between the two groups ( P>0.05). Conclusions:Esketamine can reduce extremity ischemia-reperfusion-induced lung injury in elderly patients undergoing total knee replacement, and the mechanism may be related to regulating vascular endothelial function and reducing lipid peroxidation.