O'Connor, J.M., Helmer, S.D., Osland, J.S., Cusick, T.E., & Tenofsky, P.L. (2011). Do topical anesthetics reduce periareolar injectional pain before sentinel lymph node biopsy? American Journal of Surgery, 202(6), 707–711; discussion 711–122.

 To determine whether lidocaine-prilocaine cream decreases injection pain related to sentinel lymph node biopsy

Eligible subjects were randomized to either the treatment or control group, then provided with a syringe that contained either the study medication (lidocaine-prilocaine cream) or a placebo cream that looked identical to it. Subjects also received instructions on how to apply the cream and a copy of the postprocedure survey, which asked patients to evaluate ease of application as well as level of pain. The subjects were to apply the given cream and then a barrier dressing to the area. Patients went to one of three radiology departments to receive an injection of the Tc sulfur colloid for the sentinel lymph node biopsy. Postoperatively, over the telephone, the patients completed the survey with help from a researcher. 

• The sample was composed of 39 patients.
• All patients were older than 18 years.
• All the patients were female.
• All the patients had breast cancer
   

• Multisite
• Inpatient and outpatient settings
   

Phase of care: active treatment

Triple-blinded prospective randomized placebo-controlled trial

• Scale measuring ease of cream and dressing application, a five-point Likert-type scale    
• 10-point pain scale, to measure pain
• A tool that recorded whether patient would recommend cream (yes/no)
   

Thirty-nine subjects completed the study. Subjects from both groups rated the cream as easy to apply, and both groups responded similarly in regard to dressing retention. Authors reported no significant difference in median injectional pain scores between the treatment and control groups. Authors noted two trends: The treatment group was more likely than the control group to recommend the cream, and the control group was more likely to rate the injection as painful or extremely painful.

The pain scores of subjects who received the lidocaine-prilocaine cream were not significantly lower than those of the control group.

• The study had a small sample size, with fewer than 100 patients.
• The study comprised variability in injection techniques and volumes.
• Study design was based on the prediction of a large difference (4) between the two groups on a 10-point Likert scale.  
   

This study does not indicate that a topical anesthetic, lidocaine-prilocaine cream, had a significant effect on injectional pain; however, the finding may be a consequence of the study design. Further studies, with larger sample sizes and smaller predicted differences in the study groups, may produce a different result.