Comparison of efficacy of different concentration of bupivacaine in ultrasound-guided transversus abdominis plane (TAP) block for postoperative pain relief in lower segment cesarean section

Abstract

INTRODUCTION: Women undergoing cesarean delivery present distinctive set of challenges to the anaesthesiologist in the immediate postoperative period. These women want to be active in the postoperative period to care their child. The American college of obstetrics & gynecology states that the objective of postoperative analgesia in cesarean section patients is to hasten early ambulation, postoperative recovery and promote maternal infant bonding. Various modalities of treatment are available for controlling postoperative pain effectively like usage of opioids/NSAIDS, regional techniques and field blocks. As a part of postoperative analgesic regimen, initially opioids are required for effectual analgesia. But opioids can cause side-effects like emesis, nausea, itching, sedation, and respiratory depression. Hence alternative regimen that reduces opioid requirements will be beneficial in this population. Post-cesarean section pain and discomfort may be anticipated due to skin incision, uterine incision and uterine contraction. A significant amount of pain the patients feel is due the surgical incision. Hence blocking sensory nerve supply of the anterior abdominal wall will provide effective postoperative analgesia. TAP block is one of the regional anaesthetic techniques that block the innervation of abdominal wall. McDonnell and his colleagues demonstrated the effectiveness of transversus abdominis plane (TAP) block for postoperative analgesia in cesarean section patients. He performed TAP block with 1.5 mg/kg ropivacaine and demonstrated reduced postoperative visual analog scale pain scores. It has been very well proved by various studies that TAP block is a promising approach in providing good postoperative analgesia. Mcmorrow and his collegues in their study used 1mg/kg of 0.375% bupivacaine in landmark based approach of TAP and showed its effectiveness. Especially use of ultrasound for TAP block, provides real time images that can be seen during the procedure and drugs can be given more exactly into the desired location than performing a blind technique to block the nerves. This technique increases the safety of the procedure. In a study done by Hyun jung shin and his colleagues, in patients undergoing gynecological surgeries, they used 0.375% ropivacaine in TAP block under ultrasound guidance and concluded that US-TAP block has decreases narcotic use and improves the patient satisfaction. Costello and colleagues used 20 ml of 0.375% ropivacaine bilaterally in TAP under ultrasound guidance and demonstrated its opioid sparing effects in postoperative analgesic regimen. Baaj and his colleagues used 40 ml of 0.25% bupivacaine in ultrasound guided TAP block and proved its effectiveness. Though there are many clinical trials using various local anaesthetics in different concentrations in TAP block, there is no standard guidelines regarding the choice of local anaesthetics, its dose and concentration to be used. Since there have been no published dose-response studies investigating the effective analgesic dose of bupivacaine for use in a TAP block for postoperative analgesia, we proposed a study primarily examining the effect on requirement of first dose of rescue analgesia when 0.25% bupivacaine, and 0.375% bupivacaine are used for TAP blocks. Hence the goal of our study is to compare the effectiveness of 0.25% Bupivacaine and 0.375% Bupivacaine in ultrasound-guided TAP (Transversus Abdominis Plane) and the intensity of blockade provided by them as a part of postoperative analgesic regimen in patients undergoing lower segment cesarean section via pfannensteil incision. AIM OF THE STUDY: The aim of our study is to compare the efficacy of 0.25% Bupivacaine and 0.375% Bupivacaine in ultrasound-guided TAP (Transversus Abdominis Plane) block for postoperative analgesia in lower segment cesarean section under standardized general anaesthesia. MATERIALS AND METHODS: This study was conducted in Government Kilpauk Medical College after obtaining ethical committee approval of our institute. 40 Parturients belonging to ASA physical status I & II undergoing elective Lower segment cesarean section were enrolled in our study. All the patients were explained about the purpose and details of the study. Informed written consent was obtained from each patient. This study was conducted between the period of July 2012-October 2012. Study Design: Our study was a prospective double blinded randomized control study. Patient Selection Criteria: All these 40 patients were examined, evaluated clinically and biochemically and made familiar with study plan were assessed for Elective LSCS after considering the inclusion and exclusion criteria under General Anaesthesia with physical status ASA I & II and were Grouped into two Groups with 20 patients in each Group. Inclusion Criteria: 1. ASA Class I & II, 2. Patients undergoing elective LSCS under pfannensteil incision. Exclusion Criteria: 1. Age 35 years, 2. BMI >30, 3. ASA Class III & IV (Severe PIH, Stenotic Valvular Heart disease), 4. Emergency Surgery (Includes Fetal distress, threatened rupture, hemodynamic compromise) , 5. History of allergy to local anaesthetics, 6. Patients not willing for TAP block/General Anaesthesia, 7. patients with a history of diabetes mellitus, 8. patients undergoing a vertical midline skin incision, 9. Psychiatric patients, 10. Bleeding diathesis, 11. Difficult Airway. Study Group Selections: The 40 selected and assessed patients planned for Elective LSCS under General Anaesthesia with physical status ASA I & II were randomly divided into two Groups of 20 patients each, as GROUP A : 20 patients received bilateral TAP Block with 15ml of 0.25% Bupivacaine on each side labeled as Standard Drug solution A. GROUP B : 20 patients received bilateral TAP Block with 15ml of 0.375% Bupivacaine on each side labeled as Study Drug solution B. The analyzer then allotted them into 2 Groups. 20 patients who had received 30ml of 0.25% bupivacaine were assigned to Group A or study Group. Remaining 20 patients who had received 30ml of 0.375% bupivacaine were allocated to Group B. All the patients were given test dose of Bupivacaine pre-operatively. Study Period: The study period was from the time of initiation of block upto the requirement of first rescue analgesic dose. Observation Period: Patients in both the Groups were monitored and observed in the PACU for 24 hours for any side effects and complications. Materials Used in our Study: 1. Ultrasound machine with a transducer (7-13 MHz), 2. Sterile gloves, 3. Ultrasound probe cover, 4. Antiseptic solution for skin disinfection, 5. ultrasound gel, 6. 23 gauge spinal needle, 7. 20ml syringe with injection tubing. SUMMARY: A prospective randomized double blinded study was designed to compare the efficacy of 0.375% and 0.25% bupivacaine in ultrasound guided transversus abdominis plane block in patients undergoing elective lower segment ceaserean section under general anesthesia. Based on the analysis of the results and discussion in our study, the conclusions arrived at are summarized as below. • There was no statistically significant difference in demographic profiles between the two studied Groups. • There was no statistically significant difference in Onset of analgesia between the two studied Groups. • The duration of analgesia was significantly prolonged with 0.375% Bupivacaine than 0.25%.[mean duration of analgesia –average of 365min with Group A vs 544min with Group B]. • Both the Group of patients very well maintained their vital parameters throughout the study period. • There was no failure of TAP block in either of the Group and all patients had post operative pain relief for 6-10 hours. • Patient satisfaction in all the patients in both the Groups are good. • There was no adverse reactions or side effects in either of the Groups. • There was no complications like local anaesthetic toxicity noted in both the Groups. CONCLUSION: Hence, we conclude that usage of 0.375% of Bupivacaine in USG guided TAP block significantly provide more prolonged duration of post operative pain relief after Elective LSCS compared to equivolume dose of 0.25% bupivacaine We also conclude that 15 ML of 0.375% of Bupivacaine can be safely used in each side of TAP block for providing post operative pain relief after Elective LSCS without producing any adverse or toxic effects.