Lidocaine buffered with sodium bicarbonate is significantly more comfortable than plain lidocaine when administered for pain control to women undergoing ultrasound-guided core-needle breast biopsies.

The combination is also less painful than lidocaine alone for women experiencing preprocedural breast pain ahead of intradermal anesthesia injections as well as certain patients receiving anesthesia injections in parenchymal (function-essential) breast tissues.

So report Duke University researchers in a study published online May 17 in the Journal of the American College of Radiology.

The combo is used quite widely in dentistry and surgery, as lidocaine is highly acidic and so causes pain upon initial introduction to tissue. The “baking soda buffer” can bring its pH to levels closer to human body pH.

However, prior to the present study, little had been published on anesthetizing deeper parenchymal organs as required during core-needle breast biopsy (CNBB). “Adding sodium bicarbonate to lidocaine during CNBB also adds time and expense to procedures, yet the benefits are unknown,” the authors write in their introduction.

For the study, Alison Vasan, MD, JD, and colleagues prospectively assigned 85 women undergoing ultrasound- or stereotactic-guided core-needle breast biopsies to receive intradermally and intraparenchymally either 1% lidocaine buffered with sodium bicarbonate (9:1 ratio)—the bicarbonate study group—or 1% lidocaine alone, the control group.

The researchers evaluated pain using a Likert scale (0 = painless, 10 = excruciating) during both intradermal and intraparenchymal anesthesia injections as well as during tissue sampling.

They recorded prebiopsy breast pain, anxiety, medical history, demographics, biopsy type, radiologist level of training, breast density and lesion histology.

Their key findings included:

• During ultrasound-guided biopsies, patients in the bicarbonate group experienced less tissue-sampling pain (0.23 ± 0.63) than the control group (1.79 ± 3.05).
• Among patients with preprocedural pain, those in the bicarbonate group experienced less intradermal injection pain (0.85 ± 1.23 Likert) than patients in the control group (2.50 ± 2.09).
• Among patients with fatty or scattered fibroglandular tissue, those in the bicarbonate group (1.35 ± 1.95) experienced less intraparenchymal injection pain than the control group (3.52 ± 3.13).  

The authors acknowledge their small sample size as one of their study’s limitations.

Other factors during the study, such as frequent questioning about pain levels, radiologists’ conversations and rapport with patients and other distractions “may also have had an effect on perceived and reported pain; these issues warrant further investigation during a larger study controlling for these issues and to assess applicability in varied settings,” they write.

“Nevertheless, our results demonstrated that bicarbonate buffering led to less pain experienced during intraparenchymal injections, and additional pain reduction was found in certain patient subgroups during intradermal injections, intraparenchymal injections, and tissue sampling.”

Vasan et al. also note that patients’ experiences with pain during clinical engagements affect their performance evaluations of clinicians and facilities, which in turn are increasingly tied to reimbursement.

“[E]fforts to manage patient pain during interventional radiology procedures such as breast biopsies are important issues to be addressed in the radiology community,” they write.