Effect Of Ischemic Preconditioning Combined With Dexmedetomidine On Lung Function After Limb Ischemia Reperfusion In Patients

Objective:To investigate the efficacy of remote ischemic preconditioning（RIPC）combined with dexmedetomidine on lung function in patients undergoing limb ischemia reperfusion.Methods:Seventy-five patients aged 50～89 years undergoing lower extremity surgery with tourniquet time of longer than 60 minutes and less than 150 minutes were enrolled for the study.All patients were American Society of Anesthesiologists（ASA）physical statusⅡorⅢ,who had a body mass index less than 40kg/m².Patients were randomly allocated into four groups:control group（Group C）,ischemic preconditioning group（Group IP）,dexmedetomidine group（Group D）,and ischemic preconditioning combined with dexmedetomidine group（Group IPD）.Spinal anesthesia was administered to all patients in the L_2-3or L_3-4interval with bupivacaine.The maximum upper levels of sensory block were Thoracal 8 at the beginning of the operation.In group IP,the patients was preconditioned by three 5-minute periods of upper cuff inflation to 200mmHg separated by 5 minutes at 24h before surgery.In the D group,a continuous infusion of dexmedetomidine 0.5μg?kg^-1for 15minutes,followed by 0.5μg?kg^-1?h^-1was used until the end of surgery.The equivalent volume of saline was infused in the C group and dexmedetomidine was combined with ischemic preconditioning in the IPD group whose methods were the same as those in the IP group and the D group.Mean arterial pressure（MAP）and heart rate（HR）were recorded before the upper tourniquet（T₀）,after the tourniquet released（T₁）and 24h after the operation（T₂）in the four groups.To observe the lung function and pulmonary oxygenation,the arterial blood samples were collected at T₀～T₁,p H value,arterial partial pressure of oxygen（Pa O₂）,arterial partial pressure of carbon dioxide（Pa CO₂）and lactate（Lac）were recorded in the four groups,Pa O₂/Fi O₂,respiratory index（RI）,alveolar-arterial oxygen partial pressure difference(P_A-aDO₂)were calculated.The serum levels of Clara cells secrete proteins 16（CC16）and malonyldialdehyde（MDA）were measured.The occurrences of perioperative adverse reaction and clinical events about postoperative lung injury were observed and recorded.Results1 There were not markedly different among the four groups in the general situation and intraoperative data of patients（P>0.05）.2 Comparison of hemodynamic parameters among the four groups at different time points:compared with group C,HR was decreased at T₁in group D and IPD（P<0.05）;there was no significant difference in MAP at T₁～T₂（P>0.05）.There was no significant difference in HR and MAP in group IP at T₀～T₂（P>0.05）.3 Comparison of blood gas analysis parameters at different time points within the four groups:Compared with T₀,p H value of the four groups was decreased and Lac was significantly increased at T₁（P<0.05）.Compared with group C,Pa CO₂of group D and IPD was significantly increased at T₁（P<0.05）.Pa O₂and Pa O₂/Fi O₂in group IP and group IPD were increased and RI was decreased at T₁（P<0.05）,and Lac was decreased in group IP（P<0.05）.Compared with group IP,Pa O₂and Pa O₂/Fi O₂were decreased in group D at T₁（P<0.05）.4 Comparison of serum CC16 and MDA concentrations in the four groups:Compared with T₀,CC16 and MDA in group C were increased at T₁,while MDA was decreased in group IP and IPD at T₁（P<0.05）.Compared with group C,CC16 and MDA in group IP,group D and group IPD were decreased at T₁（P<0.05）.5 Comparison of perioperative adverse reactions between the four groups:There was no statistical significance in the incidence of perioperative adverse reactions among the four groups（P>0.05）.6 No clinical manifestation of lung function injury was found in all patients after surgery.Conclusions:Both ischemic preconditioning and dexmedetomidine can reduce lipid peroxidation and inhibit the secretion of CC16.They have lung protective effects in patients with limb ischemia reperfusion.But there is not obvious between the combined effects of the two.