Ketamine as Adjunctive Analgesic With Bupivacaine in Paravertebral Analgesia for Breast Cancer Surgery

Breast cancer is perhaps the most common cancer in women that requires frequent surgical intervention. Nearly 40% of post-operative breast surgery patients experience significant acute post-operative pain, with a pain score above five reflecting inadequacy of conventional pain management. Most of the responses of the human body to post-surgical pain have been proven to be detrimental to the patient's homeostasis and recovery. Moreover, the incidence of chronic postoperative pain in breast surgery patients is as high as 50% and inadequate analgesia is considered as an independent risk factor. Hence, a number of therapeutic measures have been accepted as a part of the "multi-modal" approach to post-operative pain control. Thoracic Paravertebral Block (PVB) is used for pain relief after thoracotomy , and mastectomy. PVB can provide profound, long lasting sensory differentiation. The resulting greater attenuation of surgical stress response may translate into reduced inotropic stimulation of the heart. Additionally, unlike general anesthesia, PVB can provide superior postoperative analgesia, less nausea and vomiting, shorter recovery time; require fewer analgesic, earlier mobilization, and earlier home readiness for discharge. The use of PVB in patients undergoing ambulatory breast surgery has cost-saving potential. There is little systematic research on the efficacy and tolerability of the addition of adjunctive analgesic agent in paravertebral analgesia. The addition of adjunctive analgesics, such as fentanyl and clonidine to local anesthetics has been shown to enhance the quality and duration of sensory neural blockade, and decrease the dose of local anesthetic and supplemental analgesia .

Ketamine is an anaesthetic agent with potent analgesic properties. Its mode of action includes noncompetitive antagonism at N-methyl d-aspartate (NMDA) receptors and a local anaesthetic effect. ketamine has been extensively used through epidural and caudal routes with variable results.It possesses some definite advantages over the conventional local anaesthetic agents as it stimulates cardiovascular system and respiratory system.The advantages of ketamine include a good analgesic effect, cardio vascular stability in a hypotensive state, bronchodilatation in asthmatics, and the absence of awareness. Disadvantages include increased heart rate and blood pressure, emergence phenomenon, laryngospasm and apnea, increases in intracranial and intraocular pressure, and the lack of visceral anesthesia.