|Year : 2015 | Volume
| Issue : 2 | Page : 50-56
Feasibility and perioperative pain-relieving efficacy of ultrasound-guided transversus abdominis plane block in morbidly obese patients undergoing laparoscopic bariatric surgery
Abeer A Sherif1, Hala M Koptan MD 1, Samer M Soliman2
1 Department of Anesthesia, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Anesthesia, Faculty of Medicine, Ain Shams University, Cairo, Egypt
|Date of Submission||01-May-2013|
|Date of Acceptance||01-Jun-2013|
|Date of Web Publication||30-Dec-2016|
Hala M Koptan
Departement of Anesthesia and Intensive Care, Menoufia
Source of Support: None, Conflict of Interest: None
The implementation of adequate postoperative analgesia is beneficial in morbidly obese patients. Transversus abdominis plane (TAP) block is a new regional anesthetic technique that has been implemented successfully for pain control after laparoscopic surgery in nonobese patients, and is challenging to perform on obese patients. The introduction of ultrasound guidance has enabled greater precision of needle placement in the desired tissue plane in such patients.
Patients and methods
Hundred patients were included in this study. Patients were assigned randomly to two equal groups: group 1 (TAP, n = 50) and group 2 (control, n = 50). The following parameters were recorded: total volume of morphine consumed, numeric rating scores at rest and on coughing, postoperative nausea and vomiting, time to mobilization, patient, and surgeon satisfaction scores.
Lower numeric rating scores was reported among patients who received TAP block; cumulative morphine consumption was consistently lower at 24 and 48 h, postoperatively. Patient satisfaction with pain relief was rated as good by 85% of the patients in the TAP block group and 45% of the patients in the control group.
Ultrasound-guided TAP block is a feasible technique for effective multimodal postoperative analgesia in morbidly obese patients undergoing laparoscopic sleeve gastrectomy.
Keywords: TAP block, ultrasound, morbid obese, bariatric surgery
|How to cite this article:|
Sherif AA, Koptan HM, Soliman SM. Feasibility and perioperative pain-relieving efficacy of ultrasound-guided transversus abdominis plane block in morbidly obese patients undergoing laparoscopic bariatric surgery. Res Opin Anesth Intensive Care 2015;2:50-6
|How to cite this URL:|
Sherif AA, Koptan HM, Soliman SM. Feasibility and perioperative pain-relieving efficacy of ultrasound-guided transversus abdominis plane block in morbidly obese patients undergoing laparoscopic bariatric surgery. Res Opin Anesth Intensive Care [serial online] 2015 [cited 2017 Aug 18];2:50-6. Available from: http://www.roaic.eg.net/text.asp?2015/2/2/50/161334
| Introduction|| |
Obesity is characterized by excess body fat; the complexity of the bariatric patient dictates the choice of safe anesthetic strategies that minimize the stress related to the operation . The implementation of adequate postoperative analgesia is beneficial in morbidly obese patients because of their higher risk for developing postoperative pulmonary complications . The main goal of the regional analgesia technique applied to patients in this procedure is to cover the nociceptive and adrenergic stimulation originating from the manipulation of the gastrointestinal tract and the abdominal wall . Optimum adherence to adequate postoperative analgesia without interference with bowel motility, enabling early alimentation as well as mobilization, reducing the risk of thrombosis and pulmonary complications, can promote early return to normal life, allowing early start of the postoperative weight loss program . Transversus abdominis plane (TAP) block is a new regional anesthetic technique that was first described by Rafi ,. TAP blocks have been implemented successfully for pain control after laparoscopic surgery in nonobese patients. It is important to realize that landmark guided TAP blocks are challenging to perform on obese patients ,. The introduction of ultrasound guidance has enabled greater precision of needle placement in the desired tissue plane ,. However, visualization of the abdominal wall muscles can be hindered by morbid obesity and could lead to failed regional anesthesia . This prospective, randomized, double-blinded, controlled study was carried out to evaluate the feasibility and efficacy of ultrasound-guided (USG) TAP block in patients with morbid obesity undergoing laparoscopic bariatric surgery. We hypothesized that USG-TAP block is feasible and effective in reducing pain score and attenuating morphine consumption during the first 48 h after surgery compared with standard treatment. The primary endpoints were the amount of morphine required in the first 48 h and the comparison of the total amount of morphine used. As a secondary outcome, numeric rating scores (NRS) for pain were assessed at rest and coughing 30 min after the end of the operation and regularly for the next 48 h. The secondary outcomes included the incidence of postoperative nausea and vomiting (PONV), cost-effectiveness, and quality of recovery after the anesthesia. Satisfaction with the analgesic regimen received was determined at the end of the assessment.
| Patients and methods|| |
After obtaining approval from the ethics committee, 100 patients scheduled for laparoscopic sleeve gastrectomy were enrolled in this study. Inclusion criteria were as follows: BMI more than 35 kg/m 2 , ASA grades I to III, and age older than 18 years. Exclusion criteria were patient refusal, contraindication to regional anesthesia, ASA IV or V, peripheral neuropathy, acute intercurrent heart disease, chronic opiate use, and known allergic reaction to local anesthetics, paracetamol, or morphine. Patients were excluded if the procedure proceeded to laparotomy. After obtaining written informed consent from all patients included in the study, they were allocated by sealed envelopes to one of two groups: group 1 (n = 50), USG-TAP block, which received standard care in terms of regular postoperative analgesia according to the anesthesia department protocol, and group 2 (n = 50), the control group. The patients and the staff providing postoperative care were blinded to the group assignment. In the receiving area, all patients enrolled in the study received premedication that consisted of midazolam 2 mg, intravenous. Multiparametric monitoring including ECG, pulse oximetry, end-tidal carbon dioxide, and noninvasive blood pressure was started. Intravenous infusion was started and vital signs were recorded. For all patients enrolled in the study, general anesthesia was administered with fentanyl (1-2 μg/kg), propofol (2-3 mg/kg), and rocuronium (0.6 mg/kg). Anesthesia was maintained with nitrous oxide, oxygen, and sevoflurane. Local infiltration of the surgical site was not performed by the surgeon so as not to present a confounding variable. At the end of the procedure, when vital signs were stable, and before extubation, TAP block was performed under ultrasound guidance using a Sonosite M-Turbo ultrasound device and a linear transducer (Sonosite, USA); probe, transducer with a frequency of 5-12 MHz). The skin was prepared with a 2% chlorhexidine solution. After draping the needle insertion site, the probe was placed transversely on the anterolateral abdominal wall between the iliac crest and the subcostal margin on the right side (on the level of the right anterior axillary line between the 12th rib and the iliac crest). The three muscles (external oblique, internal oblique, and transversusabdominis) of the anterior abdominal wall were identified. A 22-G, spinal needle was inserted medial to the probe by the in-plane technique and advanced in a lateral direction. When the tip of the needle reached the TAP between the internal oblique and transversusabdominis muscles, and after identification of the neurofascial plane between the internal oblique and the transversusabdominis muscle, 1 ml of 0.5% bupivacaine was injected into the patients of the TAP block group after negative aspiration and the spread of the drugs was confirmed. Then, the remaining 19 ml was injected. Adequate spread of the drug was confirmed by an oval-shaped hypo echoic fluid pocket at TAP with ultrasound imaging. The same steps were repeated on the other side (bilateral USG-TAP block). After block implementation in group 1 patients, anesthetic gases were discontinued and extubation was performed in the two studied groups. When the patient showed adequate recovery from anesthesia, the patient was transferred to the recovery room, where close observation of hemodynamic parameters was carried out. On arrival to the postanesthesia care unit, all patients received a intravenous patient-controlled analgesia (PCA) system, which provided 1 mg of morphine on demand with a block-out interval of 20 min and a maximum 6 h dose of 10 mg. Nursing staff were instructed to use an NRS of 3 or more to define an end-point for administering morphine. The reports of pain on the NRS and requirement for opioids were assessed every 5 min for the first 30 min, then hourly for the next 12 h, and every 6 h thereafter until 48 h after surgery. All patients received regular postoperative analgesia comprising paracetamol 1 g, intravenous, four times daily. Ondansetron 4 mg was prescribed for nausea and vomiting prophylaxis. Subcutaneous enoxaparin 4000 IU daily was prescribed as deep venous thrombosis prophylaxis. Two hours after recovery, the patients left the postanesthesia care unit.
Assessment and data collection
For determination of feasibility, time to perform the procedure, number of attempts, and complications were measured and recorded on the basis of a subjective four-point scale rating (1, easy; 2, average; 3, difficult; 4, very difficult). The average time to achieve an adequate block was collected. To determine the effectiveness of pain control, NRS was assessed every 5 min for the first 30 min, and then hourly for the next 12 h and every 6 h thereafter until 48 h after surgery. The two groups studied were compared for opioid consumption, pain scores, and any complications such as hematoma at the site of injection and local anesthetic toxicity.
Outcome measures for this clinical trial
The primary endpoints of the study were the amount of morphine required in the first 48 h, and comparison of the total amount of morphine used in the two groups studied. The secondary endpoints were NRS in the two groups studied during rest (NRSr) and at coughing (NRSc). Nausea/vomiting and dizziness events were also recorded. After transfer to the ward, the patient was managed with a standard protocol, intravenous PCA+paracetamol 1 g, intravenous, every 6 h. All analgesics administered in the recovery room and ward were recorded as doses and time given. Incidences of side effects (nausea, vomiting, and respiratory depression), antiemetic requirements, surgeon satisfaction, anesthesia resident satisfaction, and patient satisfaction were all recorded. On the basis of this, the following parameters were recorded: total volume of morphine consumed, NRS from 0 (no pain) to 10 (worst pain imaginable) both at rest and on coughing, nausea (on a four-point scale: 0, no nausea or vomiting;1, nausea no vomiting; 2, vomiting; 3, persistent vomiting), level of sedation (1, fully alert; 2, drowsy when undisturbed; 3, consistently drowsy; 4, arousal only with stimulation; 5, unaroused); and nausea or pruritus requiring treatment. The PCA was discontinued after 48 h. Patients' progress was recorded by the nurses and medical staff, and was assessed for suitability for discharge from day 5. Time to mobilization and discharge was documented. After the operation, the surgeon was asked to qualify the operative conditions according to the following numeric scale: 0, unsuccessful; 1, poor; 2, acceptable; and 3, perfect. Before discharge, the patient was also asked to rate the operative conditions according to the following numeric scale: 4 (excellent), no pain; 3 (good), minor pain with no need for supplemental analgesics; 2 (moderate), pain that required supplemental analgesic; and 1 (unsuccessful), patient did not tolerate the regional analgesic technique.
For the purpose of sample size calculation, we considered that a clinically important difference in 48 h morphine consumption would be a 25% absolute reduction in the TAP group compared with the control group. A power analysis was carried out based on 95% power with a type I error of 0.05 and a four-point difference in NRS (SD = 3). On the basis of this assumption, 35 patients were required for the intravenous PCA+TAP block group and 40 patients were assigned to the control group. To minimize any effect of data loss, we decided to recruit 50 patients in each group into our study, assuming a 10% dropout rate. All analyses were carried out using SPSS software (version 16; SPSS Inc., Chicago, Illinois, USA). Descriptive statistics for quantitative continuous variables were the mean and SD for parametric variables, and median and range (minimum and maximum) for nonparametric variables. Normality assumptions were assessed with histograms.
Normality assumptions were demonstrated with histograms, Skewness, Kurtosis and Kolmogorov/Smirnov testing's. Descriptive statistics for qualitative categorical variables were calculated as frequencies. Comparisons of means were performed using Student's t-test for parametric variables and the Mann-Whitney test for nonparametric variables. Comparison of frequencies with the χ2 or Fisher's exact test was carried out when the counts in cells were inferior to five. Comparison of nonparametric variables for more than two groups was carried out using the Kruskal-Wallis test. The amount of morphine required at 48 h and the duration of surgery were compared between the two groups using Student's t-test. The NRS, the PONV scores, and the duration of the postoperative stay were compared between the two groups using the Mann-Whitney U-test. Categorical variables were compared using Fisher's exact test. The a levels for all analyses were set as P value less than 0.05. The results were described as mean (SD) or median (interquartile range). Data with P value less than 0.05 were considered statistically significant.
| Results|| |
A total of 95 patients were studied; 48 patients received intravenous PCA+TAP block and 47 patients received standard care (intravenous PCA). All participants underwent the same surgical technique and the same general anesthetic procedure, all of which were carried out by the same surgeon between August 2012 and January 2014. There were a higher number of women among the control group patients (group 2) than among TAP block patients (group 1), but this difference was not statistically significant. The two groups studied were comparable in age, weight, ASA status, BMI, and duration of surgery. [Table 1] shows no statistically significant differences between the two groups studied in demographic data. No intraoperative or early postoperative complications related to the anesthetic technique, the surgical technique, or the TAP block were recorded. The neurofascial plane between external oblique and transversusabdominis muscles was clearly visualized. Three patients in the TAP block group had a failed block as their 24 h morphine consumption and NRS were significantly higher than the other patients in the same group (group 1) and compared with the control group (group 2). The NRS was categorized into four categories to better describe the intensity of pain as follows: no pain, 0; mild, 1-3; moderate, 4-7; and severe, 8-10. Lower NRS were reported among patients who received the TAP block; the median NRS of TAP block patients (group 1) were consistently lower at 30 min, hourly till 6, 12, 24, and 48 h at rest, and on coughing. This reduction in the pain scores reported in the group 1 patients was statistically significant in comparison with the control group (group 2) [Table 2] and [Figure 1] and [Figure 2]. Lower morphine consumption was reported in TAP block patients; TAP block reduced morphine consumption (mg) at all time intervals during the course of the study. During the first hour postoperatively, the median requirement of morphine was 9.31 ± 3.14 mg in TAP block patients, whereas it was 19.6 ± 2.45 mg in the control group, and there was a statistically significant difference between the two groups studied (P < 0.001). The cumulative morphine consumption was consistently lower at 24 h (group 1, 16.18 ± 1.6; group 2, 44.9 ± 1.23; P < 0.001) and 48 h (group 1, 8.73 ± 0.13; group 2, 12.75 ± 0.17; P < 0.001) postoperatively; this lower cumulative morphine consumption in TAP block patients showed a statistically significant difference in comparison with the control group. [Table 3] shows that the cumulative morphine consumption was significantly reduced at 24 h and 48 h in patients who received a TAP block, the group 1 patients, and this reduction showed a statistically significant difference in comparison with the control group. The prolonged sedative effect of the intravenous morphine affected the time to ambulation. Time to ambulation was 6.85 ± 1.8 h in TAP block patients (group 1) and 11.79 ± 2.6 h in the control group (group 2); thus, shorter time to ambulation was found in TAP block patients than in the control group, and there was a statistically significant difference between the two groups studied (P < 0.001). Patients in the control group remained more sedated due to larger amount of morphine consumption (score 2-3). Four patients in the control group required biphasic intermittent positive pressure ventillation (BIPAP) support postoperatively. Patient satisfaction scores were significantly higher in the TAP block patients (group 1); this difference was statistically significant in comparison with the control group (group 2) [Figure 3] and [Table 4]. Patient satisfaction with pain relief was rated as good by 85% of patients in the TAP block group and 45% of the patients in the control group (P < 0.05). There was a statistically significant difference in the incidence and severity of PONV in the two groups studied; group 2 patients (control group) reported higher incidence of PONV [Table 3]. The control group required more rescue antiemetic than the TAP block patients (group 2). There was no statistically significant difference between the two groups studied in postoperative stay in the hospital, and time to discharge was comparable between the two groups studied.
|Figure 1: Comparison between both groups in the numeric rating scores (NRS)|
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|Figure 2: Comparison between both groups in the numeric rating scores (NRS)|
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|Table 2 Comparison between both groups in the numeric|
rating score at rest
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|Table 3 Comparison between the groups studied in morphine consumption (mg), time to ambulation (h), and postoperative side|
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| Discussion|| |
The results of our study showed that USG-TAP block in morbidly obese patients undergoing laparoscopic sleeve gastrectomy resulted in a consistent sensory block and lower NRS within 30 min of injection. Patients with TAP block had lower NRS at 6, 12, 24, and, 48 h after surgery. Pain scores at rest and on coughing were significantly lower in the TAP block group. The patients who received TAP block had significantly reduced cumulative morphine consumption at 24 and 48 h after surgery. The data documented by our investigator have been supported by the studies reported so far, which showed the utilization of a bilateral TAP block for midline lower abdominal surgery and for cesarean section using a landmark technique ,. The same data were reported later by Hebbard and colleagues, who described an USG technique for the TAP block, which they named the posterior TAP block. This block provides analgesia for lower abdominal surgery ,. The success rate of TAP block in our study was 94%. The three TAP blocks that did not work were probably because of inappropriate localization of the neurofascial plane as it is vital that the local anesthetic agent is deposited into the correct plane. Although ultrasound guidance improves accurate needle placement into the neurofascial plane, visibility can be impaired in the obese patient. The findings of our study correlated with the reports of all investigators who used TAP block in their studies in patients undergoing open and laparoscopic surgical procedures such as cesarean delivery, hysterectomy, inguinal and ventral abdominal hernia repair, cholecystectomy, appendectomy, bowel resection, and retro pubic prostatectomy ,. Most studies have shown that the TAP block decreases perioperative pain and reduces the use of opioids ,. Recent studies supported our findings; they have shown similar benefits in obese patients undergoing laparoscopic colorectal surgery and cesarean delivery . Attenuation of pain in the immediate postoperative period is very important for the perioperative management of morbidly obese patients as it decrease the need for opioids at the critical times of emergence from general anesthesia, extubation, and immediate management in the post anesthesia care unit (PACU) . Although epidural analgesia is a feasible analgesic technique, the technical challenge of placing an epidural catheter in morbidly obese patients often precludes its use in everyday clinical practice . Through the course of our study, we did not record any complications. When TAP block was first described, obesity was considered to be one of the contraindications because it is difficult to identify the triangle of Petit in obese patients . However, the introduction of ultrasound guidance allowed identification of the layers of the abdominal wall even in obese patients where landmarks are often obscured . However, some investigators reported different results. Ortiz et al.  compared TAP block and local anesthetic infiltration into trocar insertion sites in laparoscopic cholecystectomy and found no differences in pain scores and analgesic requirements. The same findings were reported by Sandeman et al. , who showed in his study no differences in postoperative analgesics between the TAP block group and the control group for laparoscopic appendectomy in children. In this study, the pain scores were lower in the TAP block group at all time intervals during the study. Carney et al. , supported our findings in their work, in which they studied the effect of TAP block with 0.75% ropivacaine and reported that the pain intensity decreased in the first 36 h after surgery and morphine requirements were reduced during the first 48 h. Similar findings were reported by Niraj et al. , who used 0.5% bupivacaine with a TAP block in an open appendectomy, and the morphine requirements and pain scores decreased in the first 24 h. The cost of USG-TAP block might vary widely from hospital to hospital. The price of local anesthetics, the ultrasound cost, and the procedure fee constitute the main cost of the USG-TAP block. In our institute, it is cheaper than intravenous PCA but more expensive than routine injections of opioids or NSAIDs. In terms of patient satisfaction with the analgesic regimen, our investigators reported higher patient satisfaction in the TAP block group, which was statistically significant in comparison with the control group. The success rate of TAP block in our study was 94%. The three TAP blocks that did not work were probably because of inappropriate localization of the neurofascial plane. The use of USG sensory block of the anterior abdominal wall with local anesthesia for postoperative pain relief is an attractive method because of its simplicity and safety. Effective analgesia has been shown to reduce postoperative stress response and accelerate recovery from surgery. TAP block is a promising technique with a potential for wide application in providing analgesia after surgery involving the anterior abdominal wall.
| Conclusion|| |
USG-TAP block is a feasible technique for effective multimodal postoperative analgesia in morbidly obese patients undergoing laparoscopic sleeve gastrectomy.
| Acknowledgements|| |
Conflicts of interest
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]