Pain can be experience pain at various points during uterine aspiration.  Pain most commonly emanates from tenaculum placement, cervical dilation, stimulation of the uterine fundus, and uterine involution.  Evidence shows that local block of 200-300mg of lidocaine (20-30 mL of 1% solution) to the cervix and uterus decreases pain.  Local anesthetics primarily block sodium channels, preventing depolarization of the nerve.  The general principles of local anesthetic include (1) aiming to block all nerves possible that could transmit pain and (2) checking to see if the block is adequate and adding more if safe to do so before beginning a procedure.  These principals are often not routinely practiced in gynecology.  The following tips can help guide a practitioner to manage pain effectively for women undergoing uterine aspiration.

Key points summarizing local anesthesia for uterine aspiration:

• Use the equivalent of 200-300 mg of lidocaine, with buffer and vasopressin.  Consider diluting to 0.5% except for intrauterine instillation.
• Aim to block all nerves that could transmit pain.
• Minimize pain with the block.  Slow injections with smaller gauge needles (25-75 G) are less painful.  Using topical anesthetic such as 20% benzocaine spray prior to injection can help decrease pain.
• Wait.  Don’t rush.  Pharmacokinetics and neurobiology say local block needs a few minutes to work.
• Individualize – Add more block and wait longer if the patient feels any pain with dilation.

Resources

Pain Management with Uterine Aspiration (video lecture)

Innovating Education in Reproductive Health blog post

References

Renner RM, Nichols MD, Jensen JT, Li H, Edelman AB.  Paracervical block for pain control in first-trimester surgical abortion: a randomized controlled trial.  Obstet Gynecol. 2012 May: 119(5): 1030-7.

Edelman A, Nichols MD, Leclair C, Jensen JT.  Four percent intrauterine lidocaine infusion for pain management in first-trimester abortions.  Obstet Gynelcol.  2006 Feb: 107(2 Pt 1): 269-75.