The concentration of lidocaine in follicular fluid when used for paracervical block in a human IVF-ET programme

Lidocaine is a well-documented local anaesthetic often usedfor paracervical block (PCB) in pregnant women. For this reason,the substance was used early on for PCB in connection with transvaginalfollicle aspiration. However, the concentration reached in follicularfluid after PCB or local infiltration of the vaginal wall hasnot been previously determined. Furthermore, if lidocaine reachesthe follicle, it seems important to determine if the concentrationreached influences fertilization and early cleavage of the embryoand the pregnancy rate. The study included 46 women who hadPCB with lidocaine (50 mg) and 46 women who had no PCB in connectionwith follicle aspiration. The mean concentration in follicularfluid was 0.36 ± 1.1 µg/ml. There was no significantdifference in lidocaine concentration between follicles containingoocytes that were fertilized and those that were not. Furthermore,the fertilization and cleavage rates did not differ significantlyin women with and without PCB with lidocaine. The pregnancyrate did not differ between the two groups. It thus seems thatthe concentration of lidocaine found in the follicular fluidafter PCB with 50 mg lidocaine does not negatively affect fertilizationof the human oocyte or early cleavage of the human embryo.