PLACENTAL-TRANSFER OF LIDOCAINE HYDROCHLORIDE AFTER PROLONGED CONTINUOUS MATERNAL INTRAVENOUS ADMINISTRATION

We treated a patient with arrhythmia during pregnancy with prolonged intravenous administration of lidocaine hydrochloride. This was a case of twin-to-twin transfusion syndrome and the arrhythmia was caused by ritodrine therapy. In total, 14.1 g lidocaine (50 mg . hr(-1) for 282 hr) were used. Since there are no descriptions of human placental transfer of lidocaine after such a prolonged continuous intravenous administration, we measured lidocaine concentrations in maternal and fetal serum, and in the amniotic fluid (AF) at delivery. Fetal serum lidocaine concentrations (donor: 0.83 mu g . ml(-1); recipient: 0.82 mu g . ml(-1)) were lower than in the maternal serum (1.6 mu g . ml(-1), while the AF lidocaine concentrations (donor: 1.05 mu g . ml(-1) recipient: 1.04 mu g . ml(-1)) were higher than those of the fetal sera. The fetal/maternal concentration ratios of lidocaine were 0.52 for the donor and 0.51 for the recipient, which were similar to those described previously after administration of lidocaine in labour.