Effects of Peridural Block: V. Properties Circulatory Effects, and Blood Levels of Etidocaine and Lidocaine

Ten healthy, unpremedieated, male volunteers, aged 21–33 years, were given 20 ml 1 per cent etidocaine with 5 μ/ml epinephrine for peridural analgesia via a catheter placed at L2. On a different occasion they were given 20 ml 2 per cent lidocaine with 5 μg/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 ± 24 SE min vs. 114 ± 8 min) and total duration (379 ± 22 min vs. 190 ± 8 min). Onset of maximal motor blockade was significantly faster with etidocaine (15.4 ± 2.5 min) than with lidocaine (31.7 ± 3.3 min); blockade lasted longer with etidocaine (331 ± 25 min vs. 167 ± 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 ± 0.05 SE μg/ml (plasma) and 0.55 ± 0.03 μg/ml (whole blood), achieved at 17 ± 2 min. Mean maximum arterial concentrations of lidocaine were 2.22 ± 0.09 μg/ml (plasma) and 1.85 ± 0.01 μg/ml (whole blood), achieved at 24 ± 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.