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Local Anesthetics

There are five anesthetics that we can currently test for in our laboratory: Bupivacaine, Lidocaine, Mepivacaine, Prilocaine and Ropivacaine. These local anesthetics act to block the conduction of impulses in the peripheral nervous system, and therefore, are widely used for local and regional treatments. The structural differences within these five anesthetics allows for easy detection by gas chromatograph.

The method we employ is modeled after the one developed by Björk1. Using Waters Millennium32® chromatography software, a calibration curve is derived by using the concentration and peak areas obtained from each standard injection. The concentration values (ng/ml) of each patient sample are then determined mathematically by the software. This one-extraction assay to determine the free-fraction of drug with the use of a capillary column and nitrogen phosphorous detector has shown to be reproducible. If several anesthetics are administered simultaneously, this method can detect each drug by their retention times. We have recently performed Ropivacaine levels for the Anesthesia Department at Yale University and Ropivacaine levels for Duke University's Anesthesia Department. The limit of detection in our lab for Ropivacaine is 25ng/ml.