Efficacy of Glucose in Serratus Anterior Plane Block to Reduce the Occurrence of Chronic Post-mastectomy Pain

Breast cancer is the most commonly diagnosed malignancy and the leading cause of cancer-related death in women. Although early detection and treatment have increased survival rates, chronic postsurgical pain (CPSP) is one of the most common complications of breast cancer surgery. Nearly 50% of patients suffer from chronic pain following breast cancer surgery which is known as Post Mastectomy Pain Syndrome (PMPS). There are several risk factors for PMPS, including younger age, invasive surgical interventions, adjuvant radiation therapy following surgery, and high pain score in the early postoperative period. Several regional anesthesia (RA) techniques, including paravertebral block (PVB), pectoral nerves (PECS) block, and the erector spinae plane block (ESPB), have been applied for acute pain control and prevention of chronic pain after breast cancer surgery (BCS). Recently, the serratus anterior plane block (SAPB) has become a newer interfacial plane block that appears to be safe and easily performed under ultrasound (de la Torre et al., 2014). A study concluded that preoperative SAPB with ropivacaine reduced the prevalence of CPSP at 3 months postoperativelyfrom 51.7% to 25.6%. Various adjuvants like fentanyl, clonidine, magnesium sulphate, nalbuphine, and dexamethasone have been used with bupivacaine in different blocks for prolonging the duration of analgesia and prevention of chronic pain. Using glucose 5% has been progressively applied to treat many peripheral entrapment neuropathies and has been proven to have outstanding effects in a few high-quality studies. Glucose 5% could decrease neurogenic inflammation by impeding the discharge of substance P and calcitonin gene-related peptides, which are pro-nociceptive substances that contribute to neurogenic inflammation and neuropathic pain. Exploiting the beneficial effect of glucose in regulating neuroinflammation and neuropathic pain, we hypothesize that the addition of glucose, as an adjuvant, to bupivacaine in the regional anesthesia technique for breast surgery could improve the quality of postoperative analgesia and prevent chronic pain after mastectomy. We hypothesize that the addition of glucose to bupivacaine could be superior to bupivacaine in ultrasound-guided SAPB in improving the quality of postoperative analgesia and preventing chronic pain after mastectomy. This randomized, double-blind study was designed to compare the efficacy and safety of co-administration of glucose and bupivacaine (study group), and bupivacaine alone (control group) in ultrasound-guided SAPB in patients undergoing modified radical mastectomy using the occurence of postmastectomy pain, 3 months after surgery, as the primary outcome.