Postoperative analgesic effectiveness of the addition of morphine plus dexamethasone to the local anesthetic in ultrasound-guided brachial plexus block

Abstract

Objective: To describe and evaluate the postoperative analgesic effectiveness of the combination of morphine, dexamethasone and local anesthetic in ultrasound-guided brachial plexus block. materials and methods: A prospective, observational and analytical cohort study was conducted. The cohort was composed of 106 patients divided into three groups: 1. Local anesthetic (AL), 2. Local anesthetic plus dexamethasone (ALD) and 3. Local anesthetic plus dexamethasone and morphine (ALDM). The outcome variable was acute postoperative pain (DAP) and the need for analgesic rescue. The DAP was evaluated at 3, 6, 9, 12, 18 and 24 postoperative hours using an analogous verbal scale (VAS) and was additionally recorded if it required analgesic rescue. Additionally, latency time, duration of sensory and motor block were recorded. Analysis was done with stata14 software. Results: The overall incidence of postoperative pain was higher in the AL group (89%) than in the ALD group (58.3%) and ALDM (60%). At 3,6 and 9 hours postoperatively, no differences were found between the three groups. At 12 and 18 hours postoperatively, the incidence of pain in the ALD and ALDM groups was lower and significant (p < 0.05) with respect to the AL group. There were no statistically significant differences between the ALD and ALDM groups. At 24 post-operative time no statistically, significant differences were found between the three groups, however at that time the incidence of pain in the AL group was 38% vs 25% of the ALDM group vs 23% of the ALD group. At the end of the study, the intervention in the ALDM group and the ALD group presented Relative Risks (RR) of 0.68 and 0.65 respectively to the LA group. Conclusions: The addition of morphine and dexamethasone or morphine alone to the local anesthetic reduces the postoperative acute pain between 12 and 18 hours and prolongs the time of peripheral ultrasound-guided brachial plexus block. To evaluate differences between these coadjutant’s, a study with more power and controlled clinical trial type is required.