The Effect Of Tourniquet Deflation On Hemodynamics And Regional Cerebral Oxygen Saturation In Aged Patients Undergoing Total Knee Replacement Surgery With Combined Spinal Epidural Anesthesia

Purpose:This study aimed to observe the effect of tourniquet deflation on hemodynamics and regional cerebral oxygen saturation in aged patients undergoing total knee replacement surgery with combined spinal epidural anesthesia and to explore underlying mechanism.Method:37 elderly patients from May 2016 to December 2016 in Qilu Hospital of Shandong University?Qingdao?who would undergoing total knee replacement surgury with combined spinal epidural anesthesia,those patients?aged 65-80 years;ASA grade I-III?were excluded if they had a history of hypertension,stroke,heart failure,arrhythmia,chronic obstructive pulmonary disease or chronic kidney disease.Patients were opened venous access after they get in the room,and monitoring of life signs including heart rate,blood pressure,pulse oxygen saturation were put on them.Radial artery puncture tube and peripheral pulse oximetry were performed in each patients so that the Mostcare and Casmed instrument can monitoring the pressure and cardiac output of patients continuously.After that all the patients were put on an oxygen mask?3L/min?.Using combined spinal epidural anesthesia,patients with lateral position,using L3-4 for epidural puncture and cephalad catheter after epidural puncture,with spinal anesthesia needle into the subarachnoid space,when the cerebrospinal fluid outflow,given 0.5%ropivacaine 2.5ml.According to the operation time,2%lidocaine was injected to the epidural space.The mean arterial pressure?MAP?,heart rate?HR?,cardiac output?CO?,stroke volume?SV?and cerebral oxygen saturation?rSO₂?of those patients were recorded after their vital signs remain stable before surgury and every two minutes during the 20min after the tourniquet deflation.And the arterial blood gas analysis were recorded 5min before tourniquet deflation,5min and 10min after tourniquet deflation.Result:The decrease of cerebral oxygen saturation?rSO₂?was significantly after tourniquet deflation during 2min to 12min?P<0.05?,and the mean arterial pressure?MAP?,cardiac output?CO?,stroke volume?SV?decreased significantly during 4-10min,2-10min after tourniquet release,compared with the baseline before the deflation?P<0.05?,the change value of the lowest CO and rSO₂ is positive related?R=0.4,P<0.05?.The arterial blood gas analysis showed that the PH value and hemoglobin decreased significantly and the value of PaCO₂ and lactate increased significantly?P<0.05?campared with the value before the deflation.Conclusions:For elderly patients undergoing total knee replacement surgury?TKA?with combined spinal epidural anesthesia,the hemodynamic,metabolic state and rSO₂ will be significantly changed after tourniquet deflation.