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      Analgesic Effect of Morphine Added to Bupivacaine in Serratus Anterior Plane Block Following Modified Radical Mastectomy. Only a Local Effect? Randomized Clinical Trial

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          Serratus anterior plane (SAP) block, a novel regional anesthetic procedure, involves the anterolateral chest wall. Opioid receptors have been found on peripheral nerve terminals, so morphine may have a local action.


          This work aimed at exploring the analgesic efficacy of morphine added to bupivacaine in SAPB in patients for whom modified radical mastectomy was conducted and whether it is a mere local effect.


          Forty female patients were planned to have modified radical mastectomy participated in the study. Patients were randomly divided into two groups; Control group (C): received ultrasound-guided serratus anterior plane block with 20 mL of bupivacaine hydrochloride 0.25%; Morphine group (M): received the same in addition to 10 mg morphine sulfate. Intra- and post-operative blood samples were taken for the assessment of morphine serum levels. All patients were assessed for VAS scores during rest and movement (VAS-R and VAS-M). Time to the first request and the total amount of the rescue analgesia were recorded.


          In group M, Morphine was not detected in the plasma of all patients. Both VAS-R and VAS-M were significantly higher in group C than in group M ( P<0.001) and ( P≤0.003), respectively. Time to the first request of rescue analgesia was 8.5 h in group C compared to 20 h in group M ( P=0.005) with a median dose of acetaminophen consumption of 2 g in group C compared to 1 g in group M ( P=0.006).


          Ten mg of morphine, when added to bupivacaine in SAPB, improved postoperative analgesia in patients to whom modified radical mastectomy was conducted. This effect seems to be attributed merely to local mechanisms.


          The registration number of this study is NCT02962024 at www.clinicaltrial.gov .

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          Most cited references 29

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              Peripherally acting opioids and clinical implications for pain control.

              Opioid receptors are widely expressed in the central and peripheral nervous system and in the non-neuronal tissues. Data from animal and human clinical studies support the involvement of peripheral opioid receptors in analgesia, especially in the presence of inflammation. Inflammation has been shown to increase the synthesis of opioid receptors in the dorsal root ganglion neurons and enhance transport and accumulation of opioid receptors in the peripheral terminals of sensory neurons. Under the influence of chemokines and adhesion molecules, opioid peptide-containing immune cells extravasate and accumulate in the injured tissues. Stress, chemokines, cytokines, and other releasing factors in inflamed tissues stimulate these granulocytes to release opioid peptides. Once secreted, opioid peptides bind to and activate peripheral opioid receptors on sensory nerve fibers and produce analgesia by decreasing the excitability of sensory nerves and/or inhibiting release of pro-inflammatory neuropeptides. Research has revealed that local application of exogenous opioid agonists produces a potent analgesic effect by activating peripheral opioid receptors in inflamed tissues. The analgesic activity occurs without activation of opioid receptors in the central nervous system (CNS), and therefore centrally mediated side effects, such as respiratory depression, mental clouding, altered consciousness, or addiction, are not associated with peripheral opioid activity. This discovery has stimulated research on developing peripherally restricted opioid agonists that lack CNS effects. In addition, it has been recognized that opioid receptors modulate inflammation, and that opioids have anti-inflammatory effects. The anti-inflammatory actions of opioids are not well known or understood. Conflicting reports on mu-opioids suggest both anti-inflammatory and pro-inflammatory effects. This article will present the basis for peripheral opioid analgesia and describe current research directed at developing novel treatments for pain with improved side effect profiles.

                Author and article information

                J Pain Res
                J Pain Res
                Journal of Pain Research
                31 March 2020
                : 13
                : 661-668
                [1 ]Anesthesia, ICU, and Pain Relief, South Egypt Cancer Institute, Assiut University , Assiut, Egypt
                [2 ]Cancer Biology, National Cancer Institute, Cairo University , Cairo, Egypt
                [3 ]Cancer Biology (Pharmacology and Experimental Oncology), National Cancer Institute, Cairo University , Cairo, Egypt
                [4 ]Cancer Biology (Pharmacology and Experimental Oncology), South Egypt Cancer Institute, Assuit University , Assiut, Egypt
                [5 ]Clinical Pharmacy, Faculty of Pharmacy, Assuit University , Assiut, Egypt
                [6 ]Surgical Oncology, South Egypt Cancer Institute, Assiut University , Assiut, Egypt
                Author notes
                Correspondence: Ahmed H Othman Tel +20 1005098394Fax +20 88 2086609 Email ahmadhothman@gmail.com
                © 2020 El Sherif et al.

                This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms ( https://www.dovepress.com/terms.php).

                Page count
                Figures: 3, Tables: 3, References: 33, Pages: 8
                No funding was taken to accomplish this work.
                Original Research


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