Blood Samples and Pharmacokinetic Analysis
Blood samples (2 mL) were then obtained at 0,2,6,12,24,48 and 56 hours
after the block injection. The blood samples were centrifuged within 60
minutes after collection. The plasma samples were stored at –20 °C
until the assays were performed. The total plasma concentration of
ropivacaine was measured by ultra-performance liquid
chromatography-tandem mass spectrometry (UPLC‒MS/MS, Waters, American)
after direct injection of diluted serum without further cleanup
pretreatment. The method and validation characteristics have been
described elsewhere [14].