Comparison of Post Operative Analgesia following Epidural Bupivacaine and Epidural Bupivacaine with Verapamil in Orthopaedic Lower Limb Surgeries

Abstract

INTRODUCTION: \nRecent advances in neurosciences have demonstrated that peripheral tissue injury may lead to long alterations in central processing with reduction in threshold, amplification of response, expanded receptive fields and after discharges of dorsal horn neurons. Experimental studies have revealed that the input which are innocuous may also begin to pain. Comparable alterations may also occur in humans following surgical trauma, resulting in amplification and prolongation of postoperative pain. Nociceptive stimulation causes neurotransmitter release which is coupled with activation of voltage-dependent calcium conductance in synaptic terminal membranes of neurons. A disruption of calcium influx into cells interferes with normal sensory processing and contributes to antinociception. \nPeripheral tissue injury provokes both peripheral and central sensitization. Peripheral sensitization is a reduction in the threshold of nociceptor - afferent peripheral terminals, and central sensitization is an activity - dependent increase in the excitability of spinal neurons. There is considerable evidence that excitatory amino acids and neuropeptides are involved in nociceptive transmission in the dorsal horn of the spinal cord. The actions of excitatory amino acids are mediated by the N-methyl Daspartate (NMDA) receptor and non-NMDA receptors. Activation of NMDA receptors leads to Ca 2+ entry into the cell and initiates a series of central sensitization such as windup and long term potentiation in the spinal cord in the responses of cells to prolonged stimuli. This activation of NMDA receptors is responsible for the induction and the maintenance of enhanced responses for prolonged periods of time. This central sensitization may be prevented not only with NMDA antagonists such as ketamine and dextrometorphan, but also with calcium channel blockers that block Ca2+ entry into cells. This study was therefore designed to evaluate the analgesic efficacy of bupivacaine and verapamil mixture given through lumbar epidural route in patients undergoing elective orthopaedic lower limb surgeries and comparing the quality of analgesia with epidural plain bupivacaine. \nAIMS AND OBJECTIVES: \n1. To evaluate the analgesic efficacy of bupivacaine and verapamil mixture given through lumbar epidural route for postoperative analgesia in patients undergoing elective orthopaedic lower limb surgeries. \n2. To compare the quality of analgesia of epidural bupivacaine – verapamil mixture with epidural plain bupivacaine. \n3. To evaluate the hemodynamic response of epidural verapamil. \nMATERIALS AND METHODS: \nThe study population consisted of 40 ASA I & II patients in the age group of 18 years to 65 years admitted to undergo elective orthopaedic lower limb surgeries at Govt. Stanley Hospital, Chennai. After getting approval by the institutional ethics committee and after obtaining written informed consent from each patient the study was conducted. \nExclusion Criteria: \n1. Age more than 65 yrs, \n2. Systemic Hypertension, \n3. Ischemic heart disease / Rheumatic heart diseases, \n4. Sinus bradycardia / heart blocks/ conduction defects, \n5. Patients on Digitalis, calcium channel blockers and β- blockers, \n6. Preoperative hypotension, \n7. Local infection at lumbar area, \n8. Pre-existing neurological disorders, \n9. Coagulation defects & patients on anticoagulants, \n10. Patient refusal. \nPreoperative Assessment: \nAll the patients were examined prior to surgery. Routine clinical examination, Biochemical investigations, Electrocardiogram (12 leads) and chest X-ray were examined thoroughly for the conduct of anaesthesia. \nConduct of Anaesthesia: \nPatients were allocated randomly in a double binded fashion into two equal groups (20 in each group). Group P (placebo) received 2 ml of Normal Saline along with the first dose of epidural 0.5% bupivacaine. Group V (Verapamil) received 5 mg (2ml) of injection Verapamil epidurally along with the first dose of 0.5% bupivacaine. \nNo premedication was given. On arrival in the operating room, baseline cardiorespiratory parameters viz., Heart rate (HR), Systolic blood pressure (SBP), Diastolic Blood Pressure (DBP), Mean Arterial Pressure (MAP) and Respiratory rate (RR) were recorded. \nA good intravenous access was established at the non-operative side forearm of the patient using 18 G IV cannula. Preloading was done with crystalloids (10 ml/kg). \nWith the patient in sitting posture, after informing the procedure to the patient & under strict aseptic precautions, epidural space was identified at L3-L4 or L2 - L3 interspace using 17G Tuohy needle by Loss of Resistance technique. 19G epidural catheter was threaded in a cephalad direction & 3-4 cm catheter length was kept inside the epidural space. A test dose of 3 cc of \n1.5% lignocaine with adrenaline (5μg/ml) was given. Epidural catheter was fixed and secured with tapes. Patient turned into decubitus position. \nSTATISTICS AND ANALYSIS: \nForty patients posted for orthopaedic lower limb surgeries of ASA I & II were taken up for the study. They were allocated randomly in a double - blinded fashion into two groups in equal number of 20 each. Group P received 2 ml of placebo along with the first dose of epidural 0.5% bupivacaine and group V received 2 ml (5mg) of injection verapamil along with the first dose of \nepidural 0.5% bupivacaine. A standard anaesthetic technique was followed in all patients. The patients were assessed by the same observer in the postoperative period who was blinded for the group assignment. \nAll the datas were expressed as mean + standard deviation (SD). \nQualitative variables were compared with chisquare test . Quantitative variables were compared with the student t test . \nSUMMARY: \nThis randomised double blind study was designed to evaluate the analgesic efficacy of bupivacaine with verapamil mixture given through lumbar epidural route for postoperative analgesia in patients undergoing elective orthopaedic lower limb surgeries and the quality of analgesia was compared with epidural plain bupivacaine. \nForty ASA I & II patients undergoing elective orthopaedic lower limb surgical procedure under epidural anaesthesia were randomly allocated in a double blinded fashion to one of the two groups. Group P received 2 ml of normal saline along with first dose of 14 ml 0.5% bupivacaine. Group V received 2 ml (5 mg) of injection verapamil along with the first dose of 14 ml 0.5 % bupivacaine. \nPain in the postoperative period was assessed using a verbal rating scale (VRS). Pain score were significantly less in group V at 2, 6, 12, 48 hours (P < 0.05) than in group P. Overall pain score over 48 hours period also revealed better pain relief in group V (P<0.05) as compared to Group P. Time of first rescue analgesic (TFA) and the supplementary analgesic doses required for 48 hours were noted for the two groups. \nTime of first rescue analgesic (TFA) in group V (6. 42 ±0.63 hours) was significantly prolonged compared with group P (3.84 ± 0.46 hours). The postoperative analgesic consumption was also significantly less in Group V (4.25 doses for 48 hours) than in Group P (6.35 doses for 48 hours). The incidence of hypotension did not differ significantly between the two groups & there was no bradycardia in both the groups. \nSo this study demonstrates that addition of verapamil to bupivacaine definitely improves the quality of analgesia by reducing the over all pain score, prolonging the duration of the time of first rescue analgesia (TFA) and causing reduction of total analgesic consumption in the post operative period without any hemodynamic instability. \nCONCLUSION: \n1. Single dose administration of verapamil and bupivacaine mixture given through lumbar epidural route provides effective postoperative analgesia in patients undergoing elective orthopaedic lower limb surgeries, without any hemodynamic instability. \n2. Epidural verapamil significantly reduces the postoperative analgesic consumption.