ABSTRACT
OBJECTIVE: To determine the concentrations of lidocaine in maternal plasma and to establish the kinetic constants following absorption of a single dose of lidocaine in obstetric epidural anesthesia. PATIENTS AND METHOD: Epidural blockade was provided to 10 patients by a single injection of lidocaine at doses of 200 to 300 mg (265 +/- 35 mg). The plasma concentrations of lidocaine were determined 1, 5, 10, 15, 20, 40, 60, 120 and 180 min later and at the moment of birth, by way of polarized immunofluorescence (PIF) with a Tdx automatic analyzer (Abbott). RESULTS: Time until peak plasma concentration was 17.4 min. Peak concentrations ranged from 1.44 to 2.12 micrograms/ml. Plasma clearance took place at a rate of 10.1 +/- 1.7 ml/min/kg, more slowly than in surgical patients. Duration of anesthesia ranged from 40 to 80 min and was sufficient in all cases, even for women undergoing cesarean section. At birth (25 +/- 5 min after epidural injection), plasma concentration was 1.67 +/- 0.28 micrograms/ml. CONCLUSION: Injection of 200-300 mg of lidocaine provides good analgesia during childbirth, even when cesarean section is practiced, with no toxic effects for the mother.
Subject(s)
Analgesia, Epidural , Analgesia, Obstetrical , Anesthetics, Local/pharmacokinetics , Lidocaine/pharmacokinetics , Anesthetics, Local/administration & dosage , Anesthetics, Local/blood , Cesarean Section , Female , Humans , Injections, Epidural , Lidocaine/administration & dosage , Lidocaine/blood , PregnancyABSTRACT
We compare plasma concentrations of mepivacine (MPV) and lidocaine (LDC) after epidural injection in 20 patients. Samples were drawn at 1, 5, 10, 15, 20, 60, and 120 minutes after administration. Absorption from epidural space is equally fast for both anesthetic agents (t max 20 +/- 7 minutes for MPV and 25 +/- 12 minutes for LDC) resulting in high values of Cmax: 7.8 +/- 3.3 microg/ml for MPV and 2.6 +/- 0.7 microg/ml for LDC (p less than 0.001). Mean values of K and Vd were 0.0076 +/- 0.0020 minutes-1 for MPV versus 0.0087 +/- 0.0032 minutes-1 for LDC and 0.9 +/- 0.7 1/kg for MPV versus 1.8 +/- 0.6 1/kg for LDC (p less than 0.001).
Subject(s)
Anesthesia, Epidural , Lidocaine/pharmacokinetics , Mepivacaine/pharmacokinetics , Adult , Aged , Female , Humans , Lidocaine/administration & dosage , Lidocaine/blood , Male , Mepivacaine/administration & dosage , Mepivacaine/blood , Middle AgedABSTRACT
The curves of lidocaine (LDC) plasma levels versus time were evaluated in a group of 16 patients receiving single epidural injections of 2% LDC for each metamer to be anesthesized. LDC absorption from epidural space is fairly rapid (tmax = 17 +/- 4 min and t1/2a = 6.2 +/- 1.7 min). This results in very shape peak plasma levels (2.97 +/- 0.87 micrograms/ml with 2% LDC). The remaining pharmacokinetic parameters were: Ke = 0.0057 +/- 0.0022 min-1 and Vd = 1.5 +/- 0.5 l/kg. In all patients adequate levels for operation were obtained.
