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 used for paracervical block (PCB) in pregnant women. For this reason, the substance was used early on for PCB in connection with transvaginal follicle aspiration. However, the concentration reached in follicular fluid after PCB or local infiltration of the vaginal wall has not been previously determined. Furthermore, if lidocaine reaches the follicle, it seems important to determine if the concentration reached influences fertilization and early cleavage of the embryo and the pregnancy rate. The study included 46 women who had PCB with lidocaine (50 mg) and 46 women who had no PCB in connection with follicle aspiration. The mean concentration in follicular fluid was 0.36 +/- 1.1 micrograms/ml. There was no significant difference in lidocaine concentration between follicles containing oocytes that were fertilized and those that were not. Furthermore, the fertilization and cleavage rates did not differ significantly in women with and without PCB with lidocaine. The pregnancy rate did not differ between the two groups. It thus seems that the concentration of lidocaine found in the follicular fluid after PCB with 50 mg lidocaine does not negatively affect fertilization of the human oocyte or early cleavage of the human embryo.