RESUMEN
Objective To evaluate the effects of age factors on the pharmacokinetics of ropivacaine during combined lumbar plexus-sciatic nerve block in patients.Methods Twenty patients of both sexes,aged ≥ 18 yr,weighing 50-75 kg,of American Society of Anesthesiology physical status Ⅰ or Ⅱ,scheduled for elective lower extremity surgery,were divided into 2 groups (n=10 each) according to age:young and middle-aged group (18-59 yr) and elderly group (≥ 60 yr).Combined lumbar plexus-sciatic never block was performed using an ultrasonic instrument and a nerve stimulator.Lumbar plexus block was performed with 0.5% ropivacaine 30 ml.Sciatic never block was performed with 2% lidocaine 10 ml plus 0.75% ropivacaine 10 ml.Before administration and at 5,10,15,20,30,45,60,120,180 and 360 min after administration,blood samples were collected from the radial artery for determination of the blood concentration of ropivacaine by high-performance liquid chromatography.The area under the concentrationtime curve,maximum concentration (Cmax),time to C terminal elimination half-life and clearance were calculated.Results Compared with young and middle-aged group,the blood concentration of ropivacaine was significantly decreased at 5-45 min after administration,the Cmax was significantly decreased,terminal elimination half-life was significantly prolonged (P<0.05),and no significant change was found in area under the concentration-time curve,the time to C and clearance in elderly group (P> 0.05).Conclusion Age factors can affect the pharmacokinetics of ropivacaine during combined lumbar plexus-sciatic nerve block,and both absorption and metabolism of ropivacaine are slower in elderly patients than in young and middle-aged patients.