Jw. Downing et al., THE PHARMACOKINETICS OF EPIDURAL LIDOCAINE AND BUPIVACAINE DURING CESAREAN-SECTION, Anesthesia and analgesia, 84(3), 1997, pp. 527-532
We studied the maternal pharmacokinetics of epidural lidocaine and bup
ivacaine in 20 healthy parturients with institutional review board app
roval and written, informed consent. Epidural anesthesia was induced u
sing either 2% lidocaine with epinephrine 1:200,000, n = 10, or 0.5% p
lain bupivacaine, n = 10. Maternal arterial (Ma) blood was sampled at
regular intervals and umbilical venous (Uv) blood at delivery. Results
for lidocaine and bupivacaine, respectively, were (mean +/- SEM): age
30.4 +/- 1.5 and 24.7 +/- 1.6 yr; weight 74.0 +/- 4.2 and 74.9 +/- 4.
5 kg; duration of surgery 55.5 +/- 4.3 and 53.1 +/- 3.5 min; epidural
dosage 6.1 +/- 0.6 and 1.5 +/- 0.2 mg/kg; elimination half-life 113.9
+/- 5.6 and 110.4 +/- 20.4 min; plasma clearance 6.1 +/- 0.4 and 13.6
+/- 1.3 mL . kg(-1). min(-1); volume of distribution 0.98 +/- 0.1 and
1.67 +/- 0.3 L/kg; time to peak concentration 31 +/- 2.3 and 40.5 +/-
1.7 min; peak Ma concentration 6.4 +/- 0.65 and 0.8 +/- 0.1 mu g/mL; a
nd Uv/Ma gradient 0.43 +/- 0.05 and 0.26 +/- 0.1. Peak Ma lidocaine co
ncentrations in 2 of 10 patients reached potentially toxic levels with
out producing clinical toxicity, whereas peak bupivacaine Ma concentra
tions never approached levels considered unsafe. The results suggest t
hat epidural bupivacaine reliably produces acceptable Ma concentration
s below the toxic range.