Effect Of Fluid Therapy Guided By Different Stroke Variation On Tourniquet-related-hypotension In Elderly Patients Undergoing Total Knee Arthroplasty

Objective:To observe the effects of intraoperative fluid therapy guided by different stroke volume variation（SVV）on tourniquet-related hemodynamic fluctuations in elderly patients undergoing total knee arthroplasty.Method:Eighty-one elderly patients of both sexes,aged over 60 yr,of American Society of Anesthesiologists physical status Ⅱ or Ⅲ,scheduled for total knee arthroplasty under general anesthesia,were divided into 3 groups（n=27 each）using a random number table:low SVV group（group L）,medium SVV group（group L）and high SVV group（group L）.In group L,group M and group H,SVVs were maintained at 5%～7%,8%～10%and11%～13%,respectively.After tourniquet was inflated,appropriate volume expansion was performed to control the SVVs to meet the criterion.All the patients were continuously monitored the hemodynamic indexes such as invasive arterial pressure,SVV,CI by the LiDCO instrument during the operation.According to the image data collected by the LiDCO instrument,the area under the curve（AUT）of the part of MAP below 20%of the baseline 10min after tourniquet deflated was calculated.Meanwhile,the minimum MAP(MAP_min)and the maximum percentage of MAP decreasing from the baseline(MAP_%max)were calculated.Blood samples were taken to measure arterial gas analysis at three times:before the tourniquet was deflated（T₀）,5 minutes after the tourniquet was deflated（T₁）and 10 minutes after the tourniquet was deflated（T₂）.Compared the levels of the blood lactate concentration at these three times.The requirement for crystalloid and colloid solution,total volume of fluid infused,blood loss,urine volume and requirement for vasoactive agents were recorded during operation.Troponin T were recorded before operation,1 day and 3 days after operation.The early postoperative complications in the three groups were recorded.Results:AUT of hypotension showed a decreasing trend after tourniquet release in all three groups.Compared with group L,MAP_minwas significantly decreased and MAP_%maxwas significantly increased in group H（P<0.05）.Compared with group M,MAPmin was significantly decreased in group H（P<0.05）.Compared with group L,the blood lactate concentration was significantly increased in group M and group H at T₁（P<0.05）.Compared with group L,troponin T concentration in group M and group H was significantly increased on the first day after operation（P<0.05）.Conclusion:In elderly patients undergoing total knee arthroplasty,controlling SVV at5%～7%level before tourniquet was deflating can prevent tourniquet-related hypotension,improve tissue perfusion,and decrease postoperative myocardial injury.