Effects of volume and concentration of lidocaine on epidural anaesthesia in pregnant females

Background and objective: The effects of altering the concentration of a local anaesthetic on the development of epidural anaesthesia in pregnant females are unclear. We compared the anaesthetic effects of a constant dose of two different concentrations of epidural lidocaine for Caesarean section. Methods: After Institutional Review Board approval and informed consent, patients undergoing elective Caesarean section were randomized to receive either lidocaine 1% 30 mL (+ epinephrine 5 μg mL−1) or lidocaine 2% 15 mL (+ epinephrine 5 μg mL−1) (n = 20 each) for epidural anaesthesia at the L1-L2 interspace. The spread of the sensory block to pinprick and the degree of motor block (modified Bromage scale) were measured at 5, 10, 15, 20 and 30 min after injection. Results: No significant differences in the progression of analgesia and motor block were observed at any time between 1 and 2% lidocaine. The maximum cephalad spread was observed 30 min after injection; the median was at T4 (range T3-T5) and at T4 (range T3-T6) for lidocaine 1 and 2%, respectively. Conclusions: The same doses but different volumes of lidocaine 1 and 2% produced comparable anaesthetic effects in pregnant females. The effects of epidural anaesthesia depend primarily on the total dose of the local anaesthetic.