RESUMO
PURPOSE: The aim of this study was to quantify the reduction of perceived pain levels during lymphoscintigraphy for melanoma by altering the pH of the Tc-sulfur colloid to near the physiologic value of 7.40. PATIENTS AND METHODS: This is an institutional review board- and Food and Drug Administration-approved randomized, double-blinded, prospective crossover trial, registered with clinicaltrials.org. Before beginning the procedure and after signing informed consent, 60 serial enrollees presenting for sentinel lymph node imaging of melanoma of the thorax and appendicular structures completed a questionnaire addressing background information, administered by a research support nurse.An investigator (N.H.) prepared the injections to be used and labeled them such that no one else could discover which injections contained standard-of-care solution and which contained the pH-altered solution (buffered to near pH 7.40 using sodium bicarbonate).After each injection, the enrollee was asked by a research support nurse to quantify the pain of each injection using a scale of 0 to 10. The injection site location (head, thorax, appendicular structures, and other) was also recorded. RESULTS: Sixty subjects were enrolled in the study, of which 57 had complete data. On average, there was a significant mean (SD) decrease of 1.42 (2.17) points (95% confidence interval, 0.85-2.00) on a pain scale of 0 to 10 when the buffered injections were used as compared with the standard-of-care injections (P < 0.0001). Ordering of injections did not significantly affect perceived pain scores. CONCLUSIONS: The use of sodium bicarbonate to buffer the pH of Tc-sulfur colloid to near the physiologic value of 7.40 significantly reduced perceived pain levels during nonbreast lymphoscintigraphy.