|Year : 2017 | Volume
| Issue : 2 | Page : 81-84
Ultrasound-guided transversus abdominis plane block: An evaluation of its efficacy in reducing post-operative opioid requirements in caesarean section
Shahid Adeel, Priti Narayan, Mahesh M Chandrashekaraiah, Khadija A Abuhassan, Rahma M Elsemeen, Sharon Skowronski
Department of Anaesthesia, King Hamad University Hospital, Muharraq, Bahrain
|Date of Web Publication||7-Nov-2017|
Mahesh M Chandrashekaraiah
Department of Anaesthesia, King Hamad University Hospital, Bldg 2345, Road 2835, Area 228, Muharraq
Source of Support: None, Conflict of Interest: None
Background: Different volumes of local anaesthetic are employed in transversus abdominis plane (TAP) block to provide analgesia for lower abdominal surgeries. Our aim was to compare the efficacy of high versus low volume of bupivacaine TAP block in providing postoperative analgesia for caesarean sections. Settings and Design: Prospective, single-blind, randomized comparative study was performed during post-operative period. Materials and Methods: Sixty patients who had received spinal anaesthesia for caesarean section were randomly allocated to one of three groups: Group A received 20 ml of 0.25% bupivacaine, Group B received 30 ml of 0.166% bupivacaine on each side TAP block under ultrasound guidance, respectively, and Group C did not receive TAP block. Multi-modal analgesia comprising paracetamol, diclofenac and patient-controlled analgesia (PCA) morphine was administered to all patients. The primary outcome measure in our study was 24-h post-operative morphine consumption through intravenous (IV) PCA. Other secondary outcome measures were pain scores, nausea, sedation and patient satisfaction scores. Statistical Analysis: Statistical analysis done using analysis of variance, Fisher's Exact test and Kruskal–Wallis test. Results: Our primary outcome measure of 24-h cumulative PCA morphine consumption was 18.2 ± 6.5, 17.9 ± 8.6 and 19.4 ± 8.4 mg in groups A, B and C, respectively (P = 0.819). In the secondary outcome measures, 100% of study population in group A & B and 95% of group C had pain score of 0-3 on Numerical Rating Scale (P = 1.000) at 24 hr. 19, 15 and17 patients in group A, B and C, respectively, agreed and 1, 5 and 3 patients in group A, B and C, respectively, very strongly agreed with patient satisfaction survey for pain management (P = 0.265). Conclusion: TAP block as a part of multi-modal analgesia is debatable in the context of reducing the need of post-operative opioids. The present study was unequivocal in that two different volumes of same dose of local anaesthetic failed to demonstrate any clinical or statistical significance in decreasing post-operative opioid consumption following caesarean section.
Keywords: Patient-controlled analgesia, transversus abdominis plane block, ultrasound-guided regional anaesthesia
|How to cite this article:|
Adeel S, Narayan P, Chandrashekaraiah MM, Abuhassan KA, Elsemeen RM, Skowronski S. Ultrasound-guided transversus abdominis plane block: An evaluation of its efficacy in reducing post-operative opioid requirements in caesarean section. J Obstet Anaesth Crit Care 2017;7:81-4
|How to cite this URL:|
Adeel S, Narayan P, Chandrashekaraiah MM, Abuhassan KA, Elsemeen RM, Skowronski S. Ultrasound-guided transversus abdominis plane block: An evaluation of its efficacy in reducing post-operative opioid requirements in caesarean section. J Obstet Anaesth Crit Care [serial online] 2017 [cited 2018 Sep 24];7:81-4. Available from: http://www.joacc.com/text.asp?2017/7/2/81/217776
| Introduction|| |
Transversus abdominis plane (TAP) block as an effective part of post-operative multi-modal analgesia for lower abdominal surgeries has been a subject of debate over the past few years. TAP provides analgesia to the parietal peritoneum and anterior abdominal wall by blocking the nerves traversing between the transversus abdominis and internal oblique muscle., The first abdominal plane block was used in 1980s with multiple injections into the abdomen, whereas a blind landmark approach via the lumbar triangle of Petit, with a targeted single shot was first described in 2001 by Rafi. The iliac crest, the latissimus dorsi, encloses the triangle inferiorly, posteriorly and external oblique that forms the medial border.The recent development is the use of ultrasound to guide injection of the local anaesthetic to achieve a more effective block., Till date, several different volumes and concentrations of local anaesthetic have been tested.,, Efficacy of TAP block not only depends on concentration but also depends on the volume of the injected local anaesthetic as higher volume is considered to spread more toward paravertebral spaces and block more nerves.,, Our study aims to compare the efficacy of 20 ml of 0.25% bupivacaine (100 mg) each side, and 30 ml of 0.166% bupivacaine (100 mg) each side along with a control group. Other instances where higher volume with low concentration local anaesthetic has been found to be efficacious are in the serratus anterior plane block, as demonstrated by Blanco et al., wound infiltration techniques as employed in breast surgeries and joint infiltration in knee arthroplasties.
| Materials and Methods|| |
This single-blinded, randomized comparative study was conducted after Institutional Ethics Committee approval, with written and informed consent from the patients. Sixty patients recruited were randomly assigned to one of three groups, namely group A – low-volume group (20 ml of 0.25% bupivacaine each side; dose 100 mg), group B – high-volume group (30 ml of 0.166% bupivacaine each side; dose 100 mg) and group C – received multi-modal analgesia without TAP block. Participants were randomized to three groups using http://www.graphpad.com/quickcalcs/randomize2/. Our hypothesis was high-volume group (Group B) will have less intravenous patient-controlled analgesia (IV-PCA) morphine requirement in post-operative period among the entire study group. The group A in contrast to group B received less volume but high concentration, although dose of bupivacaine was similar to group B. The study subjects included all pregnant women belonging to American Society of Anaesthesiologists (ASA) classes 1 and 2 scheduled to undergo elective caesarean sections (C-section) and had consented for to receive spinal anaesthesia for the surgery. Exclusion criteria were emergency C-section, drug allergy and body mass index (BMI) more than 35 kg/m 2. All our patients received spinal anaesthesia with a combination of 2.2 ml of 0.5% hyperbaric bupivacaine (11 mg) along with 20 mg (0.4 ml) of fentanyl. Intra-operatively, all patients received 1 g IV paracetamol (max 20 mg/kg) at the time of rectus sheath closure and rectal diclofenac 100 mg fixed dose at the end of the procedure. Patients in group A received ultrasound-guided TAP block using 0.25% bupivacaine 20 ml on each side (total dose 100 mg) along with multi-modal analgesia that comprised paracetamol 1 g IV Q 6 h, diclofenac 50 mg per oral Q 8 h ( first dose 16 h after rectal diclofenac) and IV-PCA morphine. The PCA pump settings were concentration 2 mg/ml, bolus dose 1 mg, lockout interval 5 min, 4-h maximum limit 30 mg. Group B received lower concentration 0.166% bupivacaine but higher volume, 30 ml on each side (total dose 100 mg) along with multi-modal analgesia. Control arm group C received only multi-modal analgesia as described above.
The ultrasound-guided TAP block was performed at the end of surgery using the following technique: Keeping the patient in supine position, a high frequency (13-6 MHz) linear ultrasound transducer in transverse plane placed in mid-axillary line on the lateral abdominal wall between the iliac crest and lower costal margin. After obtaining the image of abdominal wall viewing external oblique, internal oblique and transversus abdominis in line, a 22-guage 50–80 mm needle (Insulated Stimuplex A) inserted with an in-plane approach until it reached the fascial plane between the internal oblique and transversus abdominis muscles. On reaching the plane, needle position verified by injecting 2 ml saline, followed by the local anaesthetic. The end-points of successful block was the expansion of the TAP with the local anaesthetic. That is seen as a hypo-echoic space. An investigator blinded to the group allocation assessed the severity of pain, nausea, sedation and patient satisfaction at 0, 6, 12 and 24 h post-op. Numerical rating scale (NRS) (0–10) was used for assessing pain control in which 0 score for no pain and 10 scores for worst imaginable pain. Measurement of nausea was done by using hospital categorical scoring system for nausea that scored 0 as no nausea, mild nausea was scored as 1, moderate as 2 and severe nausea was scored as 3. Sedation scores were measured by the investigator using a sedation scale, which scored 0 for awake and alert, 1 for drowsy but easy to arouse, 2 for normal sleep asleep but easily roused, score of 3 was awarded to patients who were very drowsy and difficult to rouse. Patient satisfaction scores measured on a five-point Likert scale at the end of first 24 h. The patients were asked whether they were satisfied with the analgesia provided in the first 24 h and they were asked to choose between one of five variables: strongly disagree, disagree, neither agree nor disagree, agree and strongly agree. Primary outcome measure in our study was 24 h post-operative morphine consumption through IV-PCA. Secondary outcome measures were pain scores, nausea, sedation and patient satisfaction scores.
The sample size was estimated using data from our pilot study, in which 24-h mean morphine consumption in control group was 20.6 mg with standard deviation of 6.1 mg using software G*power 3.1.92. The requisite sample size is computed in order to detect a difference in means of 30%. The power of study kept at 80% and 5% type I error. The sample size came out to be 20 in each group. The following statistical tests are employed to compute the results: analysis of variance, Kruskal–Wallis test and Fisher's Exact test using statistical software SAS 9.2, Statistical Package for the Social Sciences, version 15.0.
| Results|| |
[Table 1] depicts demographic and physical characters. There was no statistical difference among the three groups. Our primary endpoint of this study was 24-h cumulative use of IV-PCA morphine consumption as described in [Table 2]. It was observed that mean morphine consumption was 18.2 ± 6.5, 17.9 ± 8.6 and 19.4 ± 8.4 mg in groups A, B and C, respectively, demonstrating no clinical or statistical difference from the control arm (P = 0.819). [Table 3] illustrates post-operative pain score measured using NRS showed no difference among the three study groups for the first 24 h. The pain score was 0–3 NRS in 100% in both group A and B and 95% group C at 24 h (P = 1.000). [Table 4] depicts secondary end-point such as patient satisfaction with no statistical significance (P = 0.265). In our study, none of our patients required rescue anti-emetic during the first 24 h. Sedation score was also insignificant in our study population. None of our patients came under sedation score 3.
|Table 2: Cumulative 24 h IV-PCA morphine consumption in mgs (ANOVA test)|
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|Table 3: Numerical Rating Scale Pain Score for 24 h (Kruskal Wallis Test)|
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| Discussion|| |
TAP block is advocated over the last few years as a part of multi-modal post-operative analgesia for lower abdominal surgeries with variable success.,,, We examined equal dose; but two different concentrations of bupivacaine 0.25% versus 0.166% with two different volumes 20 and 30 ml each side, respectively, for the TAP block. Our primary goal was to find whether high-volume TAP block would decrease the IV-PCA morphine consumption and thereby fewer opioid-induced side effects. Our study assessed morphine requirements in the first 24 h post-surgery only as our hospital policy was to discontinue PCA in most cases after 24 h.
Our study was not able to demonstrate either clinical or statistically significant difference in any of the primary and secondary outcomes amongst all three groups. This is in contrast to recent studies that generally showed reduction in post-operative opioid requirements and low pain scores with TAP blockade.,, Our study also failed to demonstrate that higher volume of local anaesthetic could make any difference in the efficacy of block in terms of post-operative opioid requirements and pain scores. In addition, there was no demonstrable difference in the three groups concerning sedation scores and incidence of post-operative nausea and vomiting.
Our study, however, had similar results to McMorrow et al. In that particular study, patients in four groups received spinal anaesthetic (heavy bupivacaine 11–12.5 mg and fentanyl 10 μg) and either of the following: spinal morphine plus TAP with local anaesthetic, spinal morphine plus TAP with saline, spinal saline plus TAP with local anaesthetic or spinal saline plus TAP with saline. They concluded spinal morphine reduces post-operative pain, and adding TAP block to multi-modal analgesia did not offer added benefits. Of particular interest and relevance to our study was the IV morphine consumption in the groups with no spinal morphine, as spinal morphine unlike spinal fentanyl could outlast the effects of TAP local anaesthetic. The groups without spinal morphine either with or without TAP block did not demonstrate a significant difference in IV morphine consumption between them, thus questioning the efficacy of TAP block. In this particular study, ultrasound was not used. Whereas we did TAP block under ultrasound guidance.
Griffiths et al. also concluded that TAP block offered no additional benefit when used with multi-modal analgesia as compared to multi-modal analgesia alone in gynaecological cancer surgeries.
Freir et al. compared TAP block with multi-modal analgesia versus only multi-modal analgesia for patients undergoing cadaveric renal transplantation and concluded that there was no significant difference in post-op pain scores and morphine consumption in both groups in the first 24 h post-op. Recent meta-analysis done by Champaneria et al. concluded that TAP block is beneficial after caesarean section, but with intrathecal morphine use additional benefit is uncertain. However, we did not find any significant difference in IV-PCA morphine consumption among our three groups.
There could be few reasons why our study did not demonstrate a reduction in post-operative morphine consumption. Although our patients were age-matched and we did not include patients with BMI > 35 kg/m 2, our doses were not calculated on mg/kg body weight. In other words, patients with different heights and weights received the same total dose as long as they were BMI < 35 kg/m 2.
The second reason could be perhaps the dose of bupivacaine used in our study. McDonnell et al. used 1.5 mg/kg ropivacaine (maximal dose of 150 mg) or saline on each side. Belavy et al. used 0.5% ropivacaine 20 ml on either side. We used low concentration and dose.
Our choice of dose and concentration was mainly to conform whether low dose with high volume with good safety margin can provide clinical effect. Parturient was subjected more to the systemic effects of local anaesthesia toxicity. Several reasons were listed for this effect. Decreased plasma protein binding and, therefore, increased free drug fraction increased cardiac output that increases the uptake of local anaesthetic and increased neuronal susceptibility to anaesthetics, which may occur in pregnancy. To conclude, our study was unequivocal in that there was no added benefit with TAP block in reducing post-operative caesarean sections opioids requirements.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]