|Year : 2017 | Volume
| Issue : 4 | Page : 934-939
A comparative study of postoperative analgesia provided by ultrasound-guided transversus abdominis plane block using two concentrations of bupivacaine in patients undergoing inguinal hernia repair
Rajesh Prabhu1, Dewan Roshan Singh2, N Krishnaveni3
1 Department of Critical Care Medicine, Mahatma Gandhi Medical College and Research Institute, Sri Balaji Vidyapeeth University, Puducherry, India
2 Department of Anaesthesiology, Mahatma Gandhi Medical College and Research Institute, Sri Balaji Vidyapeeth University, Puducherry, India
3 Department of Anaesthesiology, Sri Venkateshwaraa Medical College and Research Institute, Puducherry, India
|Date of Web Publication||28-Nov-2017|
Dewan Roshan Singh
Department of Anaesthesiology, Mahatma Gandhi Medical College and Research Institute, Sri Balaji Vidyapeeth University, Pillaiyarkuppam, Puducherry - 607 402
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Pain after open inguinal hernia surgery can be moderate to severe and is known to prolong hospital stay and delay return to normal daily activities. Settings: A randomized controlled trial conducted in the Department of Anesthesiology in a tertiary care hospital. Aims and Objectives: To compare the efficacy of postoperative analgesia provided by equal volumes of 0.125% and 0.25% bupivacaine administered in an ultrasound (US)-guided transversus abdominis plane (TAP) block in patients undergoing unilateral inguinal hernia repair. Materials and Methods: After obtaining Institutional Ethics Committee approval and informed consent, sixty patients posted for inguinal hernia repair were recruited. Randomization was done using a sealed envelope technique. Patients were divided into two groups; Group 0.125 received 20 ml of 0.125% bupivacaine and Group 0.25 received 20 ml of 0.25% bupivacaine through US-guided TAP block at the end of surgery. Visual analog scale (VAS) scores and duration of analgesia were recorded. Results: There was no significant difference in the VAS scores among both groups. The duration of analgesia provided by 0.25% bupivacaine was significantly longer than that provided by 0.125% (Group 0.125 - 355.67 ± 118.88 min and Group 0.25 - 635.73 ± 195.58 min; P < 0.05). No complications were noted in both groups. Conclusion: The duration of analgesia provided by 0.25% bupivacaine was significantly longer than that provided by 0.125% bupivacaine through US-guided TAP block in inguinal hernia repair.
Keywords: Bupivacaine, postoperative analgesia, ultrasound-guided transversus abdominus plane block
|How to cite this article:|
Prabhu R, Singh DR, Krishnaveni N. A comparative study of postoperative analgesia provided by ultrasound-guided transversus abdominis plane block using two concentrations of bupivacaine in patients undergoing inguinal hernia repair. Anesth Essays Res 2017;11:934-9
|How to cite this URL:|
Prabhu R, Singh DR, Krishnaveni N. A comparative study of postoperative analgesia provided by ultrasound-guided transversus abdominis plane block using two concentrations of bupivacaine in patients undergoing inguinal hernia repair. Anesth Essays Res [serial online] 2017 [cited 2019 Jul 22];11:934-9. Available from: http://www.aeronline.org/text.asp?2017/11/4/934/207810
| Introduction|| |
Inguinal hernia surgery is one of the most common surgeries. Although the management of pain after an inguinal hernia surgery has improved, it still continues to be a matter of debate. Despite the use of multimodal analgesia, pain after a hernia surgery continues to remain a major concern. Pain after open hernia surgery can be moderate to severe and is known to be associated with prolonged hospital stay and delayed return to normal daily activities. In addition, inadequately treated postoperative pain may be a risk factor for persistent pain after hernia surgery.
Multiple approaches, including but not exclusive to pharmacological interventions, have been used to manage pain after hernia surgery, but optimal evidence-based pain therapy remains unknown. In 2009, the European Hernia Society published guidelines on the treatment of inguinal hernia in adult patients, but except for the suggestion that local anesthetic (LA) techniques should be preferred, not much in regard to posthernioplasty pain management was discussed.
Abdominal field blocks and costo-iliac block have been used in anesthesia for surgery involving the anterior abdominal wall for several decades. A technique involving multiple injections of LA in the abdominal wall was used in the 1980s. This technique was improved with a blind landmark technique, through the “lumbar triangle of Petit.” They have been extensively used as they are mostly technically unchallenging; however, they provide limited analgesic fields; hence multiple injections are usually required. Mostly, these blocks have blind end points (pops) making their success unpredictable.
Innervation of the anterior abdominal wall arises from the spinal nerves T7–L1. All these nerves, during some point before reaching the target destination, traverse the plane between the internal oblique and the transversus abdominis muscles. The aim of a transversus abdominis plane (TAP) block is to deposit LA in the plane between the internal oblique and transversus abdominis muscles targeting the spinal nerves in this plane. By blocking these nerves, the innervation to abdominal skin, muscles, and parietal peritoneum can be interrupted. The block can be performed blind or using ultrasound (US) guidance.
The landmark technique initially described was fairly successful and the advent of US guidance for needle tip visualization and LA spread in regional anesthesia techniques has resulted in a greater accuracy of the TAP block.
Following the advent of US guidance for TAP block, few studies have been undertaken using this block for postoperative analgesia in various surgeries including appendicectomy, cesarean sections, and laparoscopic procedures. The efficacy of postoperative analgesia provided by 0.25% and 0.5% bupivacaine in ultrasonography (USG)-guided TAP block has been compared, and it has been concluded that 0.25% is as effective as 0.5% bupivacaine.
The purpose of our study was to try and bring down the LA concentration to 0.125% from the already established concentration of 0.25%. We were aiming to establish that if analgesia provided by the lower concentration was found to be as effective as the higher concentration, then we can bring down the concentration of drug used in the block. This would also help us in bringing down the plasma levels and the incidence of adverse effects related to the concentration of the LA used.
Aims and objectives
To compare the efficacy of postoperative analgesia provided by equal volumes of 0.125% and 0.25% bupivacaine administered in an US-guided TAP block in patients undergoing unilateral inguinal hernia repair.
| Materials and Methods|| |
After obtaining Institutional Ethical Committee approval and informed consent, sixty adult patients of American Society of Anesthesiologists physical status Classes 1 and 2, who were posted for an elective unilateral hernia surgery with a mesh, were enrolled for the study. Patients who were posted for emergency surgeries, with a previous history of LA sensitivity and patients who refused to be part of the study were excluded from the study. Assuming a prolongation in duration of postoperative analgesia by 120 min, the calculated sample was 30 in each group with power of 0.8 and α error of 0.05. At the end of surgery, using a sealed envelope method, patients were randomly assigned to two groups. Thirty patients received 0.125% bupivacaine (Group 0.125) and thirty patients received 0.25% bupivacaine (Group 0.25) [Figure 1].
The patients were visited on the evening before the surgery and were familiarized with a 100 mm visual analog scale (VAS) for pain, 0 mm being “no pain” and 100 mm being “most severe pain.” Patients were premedicated with tablet ranitidine 150 mg and tablet alprazolam 0.5 mg previous night and morning of the surgery. Patients were shifted to the operation theater complex, and in the preoperative holding area, intravenous (IV) access was established, preloading was done with normal saline at 10 ml/kg, and patients were premedicated with injection midazolam 0.3 μg/kg IV. Patients were shifted into the operation theater. A single dose subarachnoid block with 3 ml of 0.5% hyperbaric bupivacaine was administered using a 25–26 G Quincke spinal needle for intraoperative anesthesia. At the end of the surgery, the patients were randomized into two groups, namely Group 0.125 and Group 0.25.
Patients were positioned in the supine position. After skin disinfection with 5% alcoholic povidone-Iodine solution, the abdominal wall was scanned using a linear array transducer probe (6–13 MHz) connected to a portable US unit (MicroMaxx, SonoSite ™, Bothell, WA, USA). The edge of the probe was covered by a sterile plastic transducer sheath, and a sterile gel was applied on the skin. The US probe was initially positioned on the anterior wall with the medial head of the probe at the level of umbilicus. Adjustments were made to obtain optimal images until rectus abdominis muscle was observed. Then, the probe was replaced laterally toward the anterolateral part of the abdominal wall between the iliac crest and the subcostal margin in the anterior axillary line. The orientation of the probe was perpendicular to a line joining the anterior superior iliac spine and the inferior rib to obtain a transverse view of the abdominal layers. The probe was tilted, rotated, or both to improve visualization of the three layers of the lateral abdominal wall, respectively, from superficial to the depth, external oblique, internal oblique, transversus abdominis, and most deeply, peritoneal cavity [Figure 2]. 23-G Quincke spinal needle was advanced from an anteromedial to a lateral direction using the in-plane insertion with US real-time assessment. The entry point was distant of the medial side of the probe to obtain a needle-beam angle of more than 45° ensuring visibility of the entire needle during the procedure. The progression of the needle, visible as a bright hyperechoic line, was assessed under direct USG. The injection site was defined between aponeurosis of internal oblique and transversus abdominis muscles. During insertion, the transducer was moved with careful manipulation to continuously visualize the shaft and the tip of the needle and the aforementioned structures. When the tip was correctly located in the targeted plane, patients in Group 0.125 were injected with 20 ml of 0.125% bupivacaine and patients in Group 0.25 were injected with 20 ml 0.25% bupivacaine. The drug was injected with intermittent aspiration, and the correct placement of the needle was confirmed by expansion of the LA solution as a dark shadow between aponeurosis of the internal oblique (which moved anteriorly) and the transversus abdominis muscles pushing the muscle deeper. The time of completion of injection was noted as the block time in the test pro forma. The test solutions were prepared by an anesthetist who was blinded to the postoperative assessment of the patient.
|Figure 2: Relationship of ultrasound probe to the needle and the layers of the anterior abdominal wall|
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Postoperatively, the intensity of the pain was recorded using VAS scores on a 100 mm scale hourly. On the first complaint of pain by the patient or a VAS score of more than 50 mm, a rescue analgesic of tramadol 75 mg IV was administered. The time of rescue analgesic time was noted. The time duration in minutes between drug injection in the block and the time of first rescue analgesic dose was noted as the duration of analgesia provided by the US-guided TAP block.
Any complications associated with the TAP block, namely injection site hematoma and signs of peritoneal injections were watched for and documented.
| Results|| |
The distribution of patients included in the study did not differ significantly with respect to age. The mean age of patients in Group 0.125 was 38.70 ± 16.62 years and the mean age of patients in Group 0.25 was 43.07 ± 13.89 years and was statistically not significant (P = 0.274).
In Group 0.125 (n = 30), a total of 16 patients (53.3%) underwent surgery on the right side and 14 patients (46.7%) to the left. In Group 0.25 (n = 30), 16 patients (53.3%) underwent surgery on the right side and 14 patients (46.7%) on the left side. The distribution of the patients included in the study in both groups did not differ significantly (P = 1.00) with respect to the side of the surgery performed.
After executing the block, the intensity of pain was closely monitored in the postoperative period using a 100 mm VAS for pain 0 being no pain and 100 being the most painful. This assessment was done every second hourly and the results were recorded. On VAS score being more than 50 mm, a rescue analgesic tramadol 75 mg IV was administered and the time of the first analgesic was noted.
The VAS scores at the end of 2 h (V2 h) after the block in Group 0.125 (30.3 ± 8.50) and Group 0.25 (26.3 ± 6.69) did not differ significantly (P = 0.048). All sixty patients in both groups were still in the study.
The V4 h after the block in Group 0.125 (37.9 ± 6.75) and Group 0.25 (31.7 ± 6.99) did not differ significantly (P = 0.059). One patient from Group 0.125 had already received a rescue analgesic at this point of time.
The V6 h after the block in Group 0.125 (37.8 ± 8.33) and Group 0.25 (36.0 ± 6.75) did not differ significantly (P = 0.515). Twenty-one patients from Group 0.125 had already received a rescue analgesic at this point.
The V8 h after the block in Group 0.125 (30.0 ± 14.14) and Group 0.25 (37.8 ± 5.77) did not differ significantly (P = 0.103). All but two patients from Group 0.125 had already received a rescue analgesic at this point. In Group 0.25, three patients had received a rescue analgesic at this point of time.
The V10 h after the block in Group 0.125 were 40 ± 0 and Group 0.25 were 36.4 ± 0.674. The VAS scores did not differ significantly (P = 0.617). Twenty-nine patients from Group 0.125 and 19 patients from Group 0.25 had already received a rescue analgesic at 10 h postblock.
The V12 h after the block in Group 0.125 (40 ± 0) and Group 0.25 (32.5 ± 8.37) did not differ significantly (P = 0.432). At the end of 12 h, one patient from Group 0.125 and five from Group 0.25 were yet to receive a rescue analgesic.
The V14 h after the block in Group 0.125 (40 ± 0) and Group 0.25 (32.5 ± 5.00) did not differ significantly (P = 0.272). At the end of 14 h, one patient from Group 0.125 and four patients from Group 0.25 were yet to receive a rescue analgesic.
At the 16 h mark, all the thirty patients in Group 0.125 had already received a rescue analgesic and were excluded from the study. Four patients from Group 0.25 had a mean VAS score of 35.0 ± 5.77.
At the 18 h mark, all the thirty patients in Group 0.125 had already received a rescue analgesic and were excluded from the study. Two patients from Group 0.25 had a mean VAS score of 46.7 ± 5.77.
The statistical analysis of the second hourly VAS scores is depicted in [Table 1].
The time taken from the time of completion of the block to the administration of first dose of rescue analgesic was recorded as the duration of postblock analgesia provided by the drug. In our study, the duration of analgesia (mean ± standard deviation) in Group 0.125 (n = 30) was found to be 355.67 ± 118.88 min, and in Group 0.25 (n = 30), it was found to be 635.73 ± 195.58 min. The difference in the duration of analgesia provided by the two concentrations was found to be statistically significant (P < 0.001) [Table 2] and [Figure 3].
|Table 2: Duration of postoperative analgesia in minutes in the two groups|
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|Figure 3: Duration in minutes of postoperative analgesia achieved in both groups: 1 - Group 0.125%; 2 - Group 0.25%. The thick line indicated median values. The box represents 25%–75% values. The whiskers represent 5%–95% values. The asterisks (*) indicate high values outside the confidence interval and the circles indicate low values|
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| Discussion|| |
Historically, several techniques of regional analgesia have been proven to be effective in providing postoperative analgesia in patients undergoing open inguinal hernia repair. They include wound infiltration with LA, ilioinguinal/iliohypogastric nerve block, and TAP block. TAP block is anatomically advantageous because it provides a method to block the sensory supply to the whole anterior lower abdominal wall as confirmed by cadaveric studies as well as in volunteers.
The main complication of the blind TAP block is peritoneal injection of the LA agent. The introduction of US guidance allows the anesthesiologist to avoid this complication. Using the US, the three layers of the abdominal wall are identified with ease, and the needle can be followed throughout its course through the layers. The needle can then be placed accurately in the TAP and the spread of LA agent in the plane directly visualized.
Although the newer LA agents have a wider therapeutic index, they still have a high incidence of dose-related adverse effects, the most common being cardiotoxicity and neurotoxicity. Cardiotoxicity is commonly encountered if the LA is injected intravenously, particularly bupivacaine. Transient neurological damage is more directly related to the concentration of the LA injected in the vicinity of the nerve.
Several dose-ranging studies have been done before, and the investigators before us have reduced the concentration of bupivacaine required for effective analgesia with a USG-guided TAP block to up to 0.25%., No further reductions in the concentrations required were done at the time of starting our study.
The understanding that the TAP block is an effective analgesic option for posthernia repair pain, the US guidance reduces the incidence of complications and improves the accuracy of the block, and that the neurotoxicity of LA s is concentration dependent is what prompted us to undertake this study. In our study, we aimed to reduce the concentration of bupivacaine further lower to 0.125% and compare the efficacy of analgesia provided by this reduced concentration with that provided by the already established concentration of 0.25%.
In our study, we followed the approach mentioned and used successfully by El-Dawlatly et al. and Karim., All blocks were given using the SonoSite MicroMaxx US machine and a high-frequency linear probe.
In the postoperative period, the intensity of postoperative pain was assessed with second hourly VAS scoring for pain. On the first complaint of pain by the patient or a VAS score of more than 5, a rescue analgesic was administered and the time was noted. The time elapsed between the administration of the block and the first rescue analgesic is recorded as the duration of postblock analgesia.
The VAS scores were recorded every second hour from the time of drug administration. The VAS scores in the 0.25% bupivacaine group (V6 h = 3.60 ± 0.68) were comparable with the VAS scores noted with the studies done by Ra et al. (V6 h = 3.1 ± 1.55) and Aveline et al. who employed the same concentration in their studies.,
In our study, the second hourly VAS scores in patients who received 0.125% bupivacaine were consistently higher than the ones those received 0.25% bupivacaine, till the point of time when they received their dose of rescue analgesic. However, on statistical analysis of the available data, it was found that the values were not statistically significant across all time intervals.
The P values on comparison of the VAS scores across the two groups were V2 h = 0.048, V4 h = 0.059, V6 h = 0.515, V8 h = 0.103, V10 h = 0.617, and V12 h = 0.432. The intensity of pain as experienced by the patient in the postoperative period was lesser in the 0.25% group than in the 0.125% group, but it was not a statistically significant difference.
The duration of postblock analgesia was defined as the time from the injection of the LA to the first complaint of pain by the patient, at which point he received injection tramadol 75 mg. In the 0.125% group, this duration was found to be 355.67 ± 118.88 min, and in 0.25% group, it was found to be 635.73 ± 195.58 min. The difference in the duration of analgesia provided by the two concentrations was found to be statistically significant (P < 0.05).
We did not use a control or a placebo group in our study. Since 0.25% bupivacaine has already been established as the lower concentration by previous studies, we compared it against 0.125% bupivacaine directly, obviating the need for a placebo group. We used the duration for first rescue as the primary study parameter; it would have been ideal to assess the total rescue analgesic consumption as well as in the postoperative period.
| Conclusion|| |
There was no significant difference in the VAS scores among both groups. The duration of analgesia provided by 0.25% bupivacaine was significantly longer than that provided by 0.125% (Group 0.125: 355.67 ± 118.88 min and Group 0.25: 635.73 ± 195.58 min; P = 0.000). No complications were noted in both groups.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]