Plasma Ropivacaine Concentrations After Sciatic Nerve Block in Patients With Chronic Kidney Disease

Inclusion Criteria: * Patients scheduled for foot and ankle surgery * Patients with chronic kidney disease (glomerular filtration rate \< 60 ml/min/1.73m2) (changed from 30 ml/min/1.73m2 to facilitate patient recruitment) * Patients who are thought to be clinically helpful to receive sciatic nerve block rather than general anesthesia because of comorbidities such as cardiopulmonary dysfunction and cerebral dysfunction Exclusion Criteria: * Patients who need to renal replacement therapy, such as hemodialysis * Patients with liver disease (aspartate transaminase OR alanine transaminase \> 80 IU/L) * Patients with allergic disease * Patients with previous history of drug allery * Patients with chronic pain persisting 3 months