Effects of peridural block: V. Properties, circulatory effects, and blood levels of etidocaine and lidocaine.

Ten healthy, unpremedicated, male volunteers, aged 21-33 years, were given 20 ml 1 per cent etidocaine with 5 mug/ml epinephrine for peridural analgesia via a catheter placed L2. On a different occasion they were given 20 ml 2 per cent lidocaine with 5 mug/ml epinephrine in the same manner. Initial onset of sensory analgesia to pin prick was faster for etidocaine (7 min) than for lidocaine (9 min). Analgesia lasted significantly longer after etidocaine with respect to both two-segment regression (177 plus or minus SE min vs. 114 plus or minus 8 min) and total duration (379 plus or minus 22 min vs. 190 plus or minus 8 min). Onset of maximal motor blockade was significantly faster with etidocaine (15.4 plus or minus 2.5 min) than with lidocaine (31.7 plus or minus 3.3 min); blockade lasted longer with etidocaine (331 plus or minus 25 min vs. 167 plus or minus 13 min). Changes in mean arterial pressure cardiac output, central venous pressure, limb blood flows, total peripheral resistance, and stroke volume were similar with the two drugs, although those after etidocaine were more prolonged as a result of the longer blockade. Mean maximum arterial concentrations of etidocaine were 0.96 plus or minus 0.05 SE mug/ml (plasma) and 0.55 plus or minus 0.03 mug/ml (whold blood), achieved at 17 plus or minus 2 min. Mean maximum arterial concentrations of lidocaine were 2.22 plus or minus 0.09 mug/ml (plasma) and 1.85 plus or minus mug/ml (whold blood), achieved at 24 plus or minus 2 min. No sign of central toxicity was observed with either drug, although subjects receiving lidocaine tended to sleep, which was not the case with etidocaine. Hematologic screening, blood chemistries, and urinalyses performed 24 hours before and after each study showed no abnormality.