Post-operative bilateral continuous ultrasound-guided transversus abdominis plane block versus continuous local anaesthetic wound infusion in patients undergoing abdominoplasty

Abstract

Background and Aims:

Transversus abdominis plane (TAP) block and continuous local anaesthetic wound infusion are used as part of multimodal analgesia to treat postoperative pain after lower abdominal surgeries. The aim of this randomised controlled study was to assess the efficacy of the two techniques and compare the two in patients undergoing abdominoplasty.

Methods:

Ninety female patients undergoing abdominoplasty were allocated to receive continuous wound infusion with saline (control group, GC, n = 30), continuous bilateral TAP block with 0.25% levobupivacaine (group GT, n = 30), or continuous wound infusion with 0.25% levobupivacaine (group GW, n = 30). The primary end-point was morphine requirement in the first 48 h. Numerical rating scale (NRS) at rest and during movement, time to first morphine dose and time to first ambulation were recorded.

Results:

Morphine requirement in the first 48 h was significantly higher in GC than GW and GT (61.9 ± 12.8, 21.5 ± 9.5, and 18.9 ± 8.1 mg, respectively; P = 0.001), but GW and GT were comparable (P = 0.259). NRS was significantly higher in GC during movement in the first 24 h. GW and GT showed significantly longer time to first morphine dose (6.5 ± 1.7 and 8.9 ± 1.4 h, respectively, vs. 1.2 ± 0.3 h in GC) and significantly shorter time to first ambulation (7.8 ± 3.1 and 6.9 ± 3.4 h, respectively, vs. 13.2 ± 4.9 h in GC) (P = 0.001).

Conclusion:

Continuous bilateral ultrasound-guided TAP block and continuous local anaesthetic wound infusion significantly decreased total morphine consumption in the first 48 h compared to placebo; however, both treatment techniques were comparable.

INTRODUCTION

Abdominoplasty is one of the most frequent aesthetic surgical procedures, especially in the current era of bariatric surgeries.[1,2] Patients scheduled for surgery usually suffer from preoperative emotional stress and anxiety due to expected postoperative pain. Hence, adequate pain management during postoperative period is of great importance for both the patient and surgeon and should be planned during the perioperative anaesthesia care. This helps in shortening the hospital stay and also achieves earlier mobilization, better overall patient satisfaction, and decreased hospital costs.[3,4] Opioids can effectively control postoperative pain, however, are associated with dose-related side effects including respiratory depression, sedation, pruritis, nausea, and vomiting.[5] Hence, alternatives such as local anaesthetic wound infiltration or regional nerve block have been incorporated to improve analgesia after abdominoplasty.[6] Transversus abdominis plane (TAP) block was first described in 2001 and was designed to anaesthetise the anterior rami of T6 through L1 while they traverse the space between the transversus abdominis muscle and internal oblique muscle.[7]

We hypothesised that both continuous TAP block and continuous local anaesthetic wound infusion would have many advantages which would translate directly into decreased opioid needs and its unwanted associated side effects, better analgesia, and earlier ambulation during the postoperative period.

Therefore, the aim of this study was to assess the efficacy of continuous ultrasound-guided TAP block and continuous local anaesthetic wound infusion and compare the two techniques in patients undergoing abdominoplasty.

METHODS

After approval of local ethical committee of the hospital institute and obtaining a written informed consent from all patients, 90 female patients with an American Society of Anesthesiologists (ASA) physical status I or II, age between 25 and 50 years, and posted for abdominoplasty were enrolled in this prospective randomised controlled study between November 2016 and December 2017.

Patients with known allergy to any of the study drugs, body mass index >35 kg/m², hepatic disease, chronic preoperative opioid consumption, and those who refused to participate in the study were excluded.

All patients received IV midazolam (2.5 mg) 30 min before surgery. General anaesthesia (GA) was standardised for all study subjects after applying the standard monitors including five lead electrocardiogram, noninvasive blood pressure, pulse oximeter, neuromuscular monitoring, and bispectral index (BIS) sensor (Aspect Medical System, Norwood, MA, USA). Induction was performed with propofol (2.5 mg/kg), cisatracurium (0.15 mg/kg), and fentanyl (1 μg/kg). After tracheal intubation, the lungs were mechanically ventilated with a mixture of 40% O₂ and 60% N₂O to keep the end-tidal CO₂ between 30 and 35 mm Hg. Intraoperatively, sevoflurane 1%–2% and fentanyl (1–2 μg/kg/h) were administered to maintain BIS between 40 and 60, and IV cisatracurium 0.02 mg/kg was given if one twitch appeared on the train of four (TOF). Abdominoplasty technique was consistent for all patients (rising of the abdominal flap and plication of the anterior rectus fascia from xiphoid process to symphysis pubis) and performed by the same experienced surgeon. All treating staff and outcome assessors were blinded to the study groups.

Patients were randomised using computer-generated numbers using random allocation software QuickCalcs (GraphPad Software Inc., La Jolla, CA, USA) and sealed opaque envelopes into three groups: continuous wound infusion with normal saline (control group, GC, n = 30), continuous bilateral TAP block (GT, n = 30), and continuous wound infusion with 0.25% of levobupivacaine (GW, n = 30).

In group GT, TAP block was performed under complete aseptic technique after skin closure and covering the wound while the patients were in supine position and still under GA using SonoScape ultrasonography machine. A linear multifrequency (6–13 MHz) ultrasound (US) probe was placed transversely between the costal margin and the iliac crest in the mid axillary line. An 18-G Tuohy needle (B. Braun, Perifix, Germany) was advanced in-plane from medial to lateral under real-time US visualization with intermittent aspiration to be positioned in the plane between transversus abdominis and internal oblique muscles. One milliliter of normal saline was injected to confirm the needle position, and then 20 mL of levobupivacaine 0.25% was administered through the needle in the form of two injections, each containing 10 mL in the superolateral and inferolateral directions to provide two boluses of medication in the TAP space, one above the umbilicus and the other below it. A multiorifice 20-G epidural catheter was threaded and advanced 7–8 cm into the TAP and then the needle was removed. The same technique was repeated on the other side. The bilateral catheters were taped to the skin and then connected through a Y-connector to a prefilled electronic infusion pump delivering 10 mL/h of 0.25% of levobupivacaine (5 mL per catheter) for 48 h (the study period).

In group GW, two multiorifice 20-G epidural catheters were inserted by the surgeon superficial to the abdominal fascia on each side of the anterior abdominal wall. The two catheters were fixed to the skin the same way as in GT using an introducer needle 1 inch. from the two lateral edges of the wound. 10 mL of 0.25% levobupivacaine was administered in each catheter after closure of the skin. The two catheters were taped to the skin and connected through a Y-connector to a prefilled electronic pump delivering 4 mL/h of 0.25% of levobupivacaine (2 mL per catheter) for 48 h.

In group GC, the surgeon inserted two multiorifice 20-G epidural catheters the same way as in group GW; however, normal saline was injected instead of levobupivacaine for postoperative infusion at the same rate.

Thirty minutes before extubation, IV ondansetron 4 mg as antiemetic prophylaxis, IV paracetamol 1 g and intramuscular 30 mg of ketorolac were administered to all patients. During the perioperative period, all patients received IV ringer lactate solution at a rate of 4 mL/kg/h. At the end of the procedure, residual neuromuscular blockade was reversed with a mixture of atropine (10 μg/kg) and neostigmine (40 μg/kg) and the trachea was extubated when the patient was adequately breathing with BIS ≥85 and TOF >90%.

Patients were transferred to postanaesthesia care unit (PACU) with the electronic infusion pumps where the infusion started while covering the name and rate of the infusate. In PACU, IV patient-controlled analgesia (PCA) morphine was initiated with a bolus of 1 mg, lockout period of 6 min, and 4-h maximum dose of 40 mg without background infusion. Pain was assessed at rest and during movement (or with knee flexion) by PACU and ward nurses during the first postoperative 48 h using the Numerical Rating Scale (NRS) ranging from 0 to10 (where 0 referred to no pain and 10 to severe intolerable pain), 1 h after arrival to PACU (H1), then at 3 h (H3), 6 h (H6),12 h (H12), 24 h (H24), 36 h (H36), and 48 h (H48) postoperatively.

Time to first ambulation of the patient, time to first morphine dose, and total PCA morphine consumption in the first postoperative 48 h were recorded. Postoperative sedation level was monitored using Pasero Opioid-induced Sedation Scale.[8] Moreover, patients were monitored for respiratory depression (respiratory rate ≤8), pruritis, and postoperative nausea and vomiting and recorded as absent or present.

Patients were asked to evaluate and record their satisfaction about pain control during the study period using 7-point Likert-like verbal rating scale (1 = strongly dissatisfied, 2 = dissatisfied, 3 = partly dissatisfied, 4 = undecided, 5 = partly satisfied, 6 = satisfied, 7 = strongly satisfied).

The primary outcome of this study was the total PCA morphine consumption in the first 48 h postoperatively, and the secondary outcomes were NRS pain scores, time to first PCA morphine dose, time to first ambulation, and associated morphine adverse effects including nausea and vomiting, respiratory depression, drowsiness, and pruritis.

Sample size was calculated according to the pilot study from the first 15 patients at an alpha error of 0.05 and a beta error of 0.1. Assuming that 30% difference in the total morphine consumption between the groups would be clinically significant and the calculated effect size was 0.7, a minimum of 26 patients were required for each group. We enrolled 30 patients in each group to accommodate for any dropout. Data were analyzed using SPSS (Statistical Package for Social Science) software version 20 (SPSS Inc., Chicago, IL, USA). Chi-square (χ²) test was used for comparison of qualitative data (ASA grade) between the groups. Shapiro–Wilk test was used for testing normal distribution of all data. A one-way analysis of variance (ANOVA) test was used to compare continuous variables (time to first morphine dose, total PCA morphine in 48 h, time to first ambulation, etc.) between the groups; if ANOVA results were significant, Tukey post hoc test was used for multiple comparisons between every two groups. Kruskal–Wallis test ranked the data from all groups together. Continuous data were expressed as mean ± standard deviation and median (interquartile range). P1, P2, and P3 represent the comparison between GC and GW, GC and GT, and GW and GT, respectively. A value of P < 0.05 was considered statistically significant.

RESULTS

A total of 106 patients were eligible for the study; however, 6 patients refused to participate in the study and 10 patients met the exclusion criteria. Thus, 90 patients were included in the study and randomised into three groups: GC (n = 30), GW (n = 30), and GT (n = 30). No patient was excluded from the study due to deviation from the study protocol. The results of the pilot study were not included in this study. The three groups were similar with regard to demographic characteristics, ASA physical grade, duration of surgery, and duration of anaesthesia [Table 1]. Total PCA morphine consumption during the first 48 h postoperatively was significantly higher in control group compared with GT and GW (P = 0.001), while both GT and GW were comparable (P = 0.259). Time to first morphine dose was significantly longer in GT and GW than in GC (P = 0.001). Furthermore, it was significantly longer in GT than GW (P = 0.001) [Table 2]. Regarding NRS pain scores during rest, there were no significant differences between the three groups [Figure 1]; however, control group showed higher pain scores during movement than GW and GT in the first 24 h [Figure 2]. No significant differences were detected between the three groups with regard to incidence of morphine-related side effects [Table 3]. Patients in GT and GW were more satisfied with the achieved analgesia than patients in the control group [Table 4].

Table 1.

Demographic and operative data

Table 2.

Time to first morphine dose, total PCA morphine in first postoperative 48 h, and time to first ambulation

Figure 1.

Numerical Rating Scale pain scores at rest. NRS, Numerical Rating Scale; GC, control group; GW, continuous wound infusion group; GT, TAP block group; H1, 1 h after arrival to PACU; H3, 3 h postoperative; H6, 6 h postoperative; H12, 12 h postoperative; H24, 24 h postoperative; H36, 36 h postoperative; H48, 48 h postoperative

Figure 2.

Numerical Rating Scale pain scores on movement. *Means significant; NRS, Numerical Rating Scale; GC, control group; GW, continuous wound infusion group; GT, TAP block group; H1, 1 h after arrival to PACU; H3, 3 h postoperative; H6, 6 h postoperative; H12, 12 h postoperative; H24, 24 h postoperative; H36, 36 h postoperative; H48, 48 h postoperative

Table 3.

Incidence of morphine-related side effects

Table 4.

Comparison of patient's satisfaction between the three groups

DISCUSSION

Pain management after major abdominal surgeries remains challenging. Previous studies on postoperative pain management after abdominoplasty have failed to achieve effective analgesia beyond the recovery room.[9,10] So many investigators have been searching for a safe and reliable analgesic technique for pain control after abdominoplasty.[6,11]

The analgesic effect of TAP block has been compared with placebo or local anaesthetic wound infiltration in various surgeries such as cesarean deliveries, open gynecologic procedures, nephrectomy, and inguinal hernia repair.[12,13,14,15,16] Analgesia achieved through local anaesthetic infiltration of the subcutaneous or subfascial planes of the wound has different mechanisms of action including simple local anaesthesia, anti-inflammatory effect, and systemic absorption of the local anaesthetic.[17,18]

TAP block is a multifaceted block, working through local field effects in addition to distal effects because of a far spread of the local anaesthetic. Introduction of ultrasound in daily clinical anaesthesia practice increased the accuracy and success of TAP block through instillation of the local anaesthetic in the correct plane between the transversus abdominis and internal oblique muscles.[19,20] Open and blind TAP block techniques were studied for pain control after abdominoplasty.[1,11] However, to the best of our knowledge, no other study has investigated the effect of ultrasound-guided continuous bilateral TAP block versus continuous wound infusion with levobupivacaine 0.25% for pain control in patients undergoing abdominoplasty.

In this study, the main finding was that both continuous TAP block (GT) and continuous wound infusion (GW) with levobupivacaine 0.25% decreased postoperative PCA morphine consumption by more than 65% compared with placebo in patients undergoing abdominoplasty. However, no significant difference was detected between both treatment techniques regarding opioid-sparing effect. Time to first morphine dose was significantly prolonged in GT and GW than GC. Furthermore, it was prolonged in group GT than GW. Although NRS at rest was found to be comparable in the three groups, patients in GT and GW had better analgesia than in the control group during movement in the first 24 h with no significant difference between the treatment groups. All patients were ambulated on the first day of surgery; however, patients in group GT and GW could move at significantly earlier time than patients in group GC. The decreased total postoperative morphine consumption in the treatment groups resulted in lower incidence of morphine-related side effects; however, it did not reach a statistical significance. Patients in GT and GW were significantly more satisfied with the achieved analgesia than patients in the control group; however, GT and GW were comparable.

Our results are in concurrence with previous studies.[12,14] Both TAP block and local anaesthetic wound infusion were proved to have comparable total postoperative morphine consumption in patients undergoing open gynecologic procedures.[13,14] Furthermore, no differences were found between the two techniques in terms of postoperative analgesia in postcaesarean section patients.[12] However, TAP block was found to induce lower visual analog pain scores during movement than continuous wound infiltration which may be due to different types of surgery than in our study.[13]

The results of this study confirmed the hypothesis that ultrasound-guided continuous TAP block and continuous wound infiltration are effective and reliable techniques for pain control in patients undergoing abdominoplasty. Hence, patients can ambulate and discharge from the hospital earlier with less postoperative complications and less overall costs. In a systematic review and meta-analysis, TAP block and local anaesthetic wound infusion were found comparable with regard to postoperative analgesia.[21] Moreover, in another meta-analysis, continuous local anaesthetic wound infusion was equivalent to epidural analgesia regarding pain scores at rest and during movement after abdominal surgery.[22]

In contrast, some other studies found differences between TAP block and local anaesthetic wound infusion in postoperative analgesia and opioid consumption.[15,16]

In a previous study, local anaesthetic wound infiltration was found superior to TAP block with regard to postoperative analgesia after laparoscopic nephrectomy. Furthermore, TAP block did not reduce the total opioid consumption. These results may be due to the timing of TAP block administration as it was performed preoperatively; the half-life of ropivacaine is about 2 h and the mean surgical time was 162 min which means wearing off of the local anaesthetic effect. Therefore, postoperative TAP block is recommended rather than preoperative administration.[15]

In another study, patients with TAP block had lower pain scores and less total postoperative morphine requirements compared with local anaesthetic wound infiltration after open inguinal hernia repair.[16]

A potential confounding issue regarding blinding of the study is likely to come up. In spite of the efforts done to make the patients and assessors blind to the study groups, there was some probable awareness to group allocation because different rates of the infusate (levobupivacaine or saline) among the groups and remaining fluids in the infusion pumps at constant times might have been noticed as covering the infusion pumps was not enough to make them completely blind. However, setting the total postoperative PCA morphine consumption in the first 48 h as the primary outcome of the study rather than the NRS pain scores may partially compensate for the inappropriate blinding of the study.

CONCLUSION

Continuous bilateral ultrasound-guided TAP block or continuous local anaesthetic wound infusion significantly decreased total 48 h postoperative PCA morphine consumption than the control group. Even though both the treatment techniques were comparable with each other overall, early postoperative analgesia was better in the TAP block group than the wound infusion group.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.