The Effect of Buffered Lidocaine Versus Nonbuffered Lidocaine on Pain Scores During Infiltration for Vulvar Biopsies

BACKGROUND/INTRODUCTION:

Certain procedures, particularly those involving the skin, can cause pain and distress in patients. Often , a local anesthetic is used to dull the sensation and improve patient experience and satisfaction. The procedure at hand dictates the mode of delivery of the anesthetic, but typically immediate and fast acting analgesia requires infiltration. Lidocaine is in the amide class of local anesthetics and is the most commonly used agent for infiltration. Lidocaine is usually given as a 1 percent solution and can be combined with epinephrine in order to prolong the duration of action, decrease local bleeding via local vasoconstriction and decrease systemic absorption of the lidocaine.

It is well known that lidocaine injection can be painful, likely secondary to the acidity. A meta analysis published in the Cochrane Database of 23 trials that compared pain during infiltration of buffered or non-buffered lidocaine found that patients receiving buffered lidocaine reported significantly less pain than those who received non-buffered lidocaine. The decrease in pain was greater for patients who received lidocaine with epinephrine but was also present for those who received lidocaine without epinephrine. The authors' conclusion was that "increasing the pH of lidocaine decreased pain on injection and augmented patient comfort and satisfaction". The studies included in this review however were mainly focused on lacerations, carpal tunnel decompression and "outpatient procedures". There were two studies that specifically involved OB/GYN patients; one investigated buffered lidocaine during epidural catheter removal and the other investigated buffered lidocaine during Norplant insertion. Since the Cochrane Review was published, one further gynecologic study investigating buffered lidocaine has been published involving cervical loop excision.

To date, there are no studies investigating the efficacy of buffered lidocaine during procedures on the vulva. The vulva is a particularly sensitive region to have a biopsy performed because it has extensive innervation, a large blood supply and it involves a pelvic exam which can be associated with increased anxiety. As many OBGYNs know, the vulva can be affected by a variety of conditions both benign and malignant. A crucial aspect of caring for women with vulvar complaints is conducting biopsies of lesions to ensure no occult malignancy and/or to further classify a diagnosis with histology. Use of local anesthetic is standard of care during biopsy but can add to the pain and discomfort of an already painful procedure. Some sources recommend use of topical anesthetic prior to infiltration of lidocaine, particularly in the pediatric patient. However, this technique requires the topical anesthetic be applied 20-60 minutes prior to the biopsy, which may not be feasible in a busy outpatient practice. Currently, the American Board of Obstetrics and Gynecology suggests 8.4% sodium bicarbonate can be added to lidocaine to minimize discomfort. However, there is currently no standard anesthesia recommendations and this is often not being done in clinical practice.

Given the obstacles to topical anesthetic usage, the fact that it does not address the pain involved with lidocaine infiltration and the lack of published literature on use of buffered lidocaine on the vulva, this study aims to investigate the use of buffered lidocaine versus non-buffered lidocaine in the setting of vulvar biopsy using a visual analog scale.