The efficacy of pectoral nerve blocks for acute pain management following modified radical mastectomy for breast cancer at the Kenyatta National Hospital : a randomised control trial

Abstract

Background: Management of acute pain following breast surgery remains a challenge to both the surgeon and the anesthesiologist. There are various recommendations from anesthesia and surgical groups on multimodal anesthesia regimens; however there remains no consensus specific for patients who have undergone modified radical mastectomy for breast cancer. Some studies have indicated modified pectoral nerve block can provide good analgesia for surgery as well as post operatively. Objective: This study aimed to compare the efficacy of the modified pecs block for acute pain management following modified radical mastectomy for breast cancer. Methodology: This was single blinded randomized clinical trial of patients scheduled to undergo modified radical mastectomy for breast cancer in Kenyatta National Hospital. They were randomized into two groups using random generated numbers, sealed in envelopes. The control group received standard analgesia while the intervention group received the Pecs II block. Post operatively they were followed up at 4, 12, 18 and 24 post-operative hours. Pain intensity was scored using the visual analogue scale, carried out by a blinded research assistant. Patients need for rescue analgesia, time to rescue analgesia, post-operative complications and patient pain satisfaction scores were also collected. Morphine injection was used for rescue analgesia. Data was entered into SPSS and analyzed for mean, median and proportion. Comparisons were done using Man Whitney U-test, Chi square and Fischer‘s exact test as appropriate. Logistic regression was done for multivariate analysis. Statistically significant was taken at p-value <0.05. Results: We recruited 40 patients that randomized into intervention group (18) and into control group (22). There was no significant difference in all baseline characteristic s except for weight that was found in logistic regression to be independently associated with higher risk for poor pain control post operatively. There were significantly lower visual analogue scale scores in the Pecs II group, at the 4th post-operative hour as compared to those who received standard analgesia, with median scores of 0 (0-1) versus 4 (2-5) p<0.001.We also found a longer time to rescue analgesia in the block group, with a median of 13 hours, as compared to 7.5 hours in the control group. The incidence of side effects in the block group was 27.8% and 68.2% in the control group. The most common side effect was nausea, with 5.6 % and 36.4 % in the block and standard analgesia groups, respectively. Conclusion: The Pecs block provides for a safe mode of post-operative analgesia that provides excellent acute post-operative pain, within the first 24 hours, and is associated with few administrations associated complications. Its efficacy is also comparable to standard analgesia, with fewer side effects.