Central nervous system symptoms after intravenous lignocaine: dose-response during pregnancy

There is continuing controversy over what dose of what drug should be used to identify an accidental intravascular or subarachnoid catheter placement in obstetric epidural anaesthesia. The purpose of this randomized, double-blind study was to evaluate the dose-effect relationship for the production of central nervous system (CNS) symptoms by intravenous lignocaine. Sixty first-trimester, pregnant patients divided into groups of 10 received saline or one of five doses of lignocaine (0.39, 0.5, 0.63, 0.79, and 1.0 mg kg-1) i.v. An ED95 of 1.12 mg kg-1 was calculated to produce reliable CNS symptoms when injected intravascularly. Lignocaine is an effective and reliable marker for intravenous injection in pregnant women.