Continuous Transversus Abdominis Plane Block After Laparoscopic Sleeve Gastrectomy in 50 Consecutive Cases

Abstract

Purpose

Enhanced recovery after bariatric surgery is important for decreasing morbidity, enhancing functional recovery and shortening the length of stay. Ultrasound-guided transversus abdominis plane (TAP) block has been known to decrease pain scores and opioid requirement after bariatric surgery. We aimed to investigate the efficacy of continuous TAP block in 50 consecutive cases of laparoscopic sleeve gastrectomy (LSG).

Materials and Methods

From February 2022 to April 2022, 50 cases of LSG were performed with ultrasound-guided TAP blocks. The data was compared to that of 157 cases of primary LSG that had been performed from January to December of 2021. Ultrasound guided TAP block was performed from the epigastric port site 3 to 5 mm in size that was placed for liver retraction during LSG. The lateral border of the rectus abdominis muscle was identified. A 17-gauge T-peel inducer and sheath (On-Q^® Pain Buster^®) were inserted in a medial to lateral direction towards the TAP. Fifteen to 20 mL of normal saline was injected for plane dissection and the catheter was inserted through the sheath after removal of the inducer. The same was performed for the other side in the same order. The elastomeric pump was injected with 100 mg of 0.5% bupivacaine and connected to the 2 catheters.

Results

There was no significant difference in mean age, initial body weight, preoperative body mass index (BMI), incidence of diabetes, hypertension, obstructive sleep apnea, and length of postoperative hospital stay between the TAP group and the non-TAP group. The TAP group had a higher incidence of dyslipidemia. There were statistically significant differences in the clinical outcomes regarding the numerical rating scale (NRS) score at postoperative 12, 24 and 48 hours, opioid injection within 24 hours (non-TAP group 36.82% vs. TAP group 20%, P value=0.037) and ramosetron injection within 24 hours (non-TAP group 9.45% vs. TAP group 0%, P value=0.017). There was no significant difference between the 2 groups in postoperative NRS scores at 1 and 6 hours, incidence of nausea or vomiting, injection of acetaminophen, non-steroidal anti-inflammatory drugs, or metoclopramide within 24 or 48 hours, injection of opioid or ramosetron within 48 hours. There were 2 cases of complications related to continuous TAP block where there was difficulty in removing the catheters and needed to be removed under local anesthesia.

Conclusion

Although continuous TAP block did not reduce cumulative opioid consumption, the need for additional opioid and antiemetic injection can be reduced within the postoperative 24 hours.

INTRODUCTION

The global incidence of severe obesity (defined as body mass index [BMI] ≥35 or ≥40 kg/m², depending on ethnicity) has continued to rise over the past 2 decades becoming a significant public health challenge [1]. This trend is driven by multifactorial causes including the increased consumption of highly processed foods, genetic predispositions, and environmental influences. As lifestyle and pharmacological interventions have been proven insufficient for sustained weight loss, the role of metabolic and bariatric surgery (MBS) has expanded considerably. MBS, including procedures such as sleeve gastrectomy and Roux-en-Y gastric bypass, has demonstrated substantial and sustained weight loss, improvement in obesity-related comorbidities (such as type 2 diabetes, hypertension, and obstructive sleep apnea), and reductions in all-cause mortality [2]. Furthermore, emerging data from large-scale registries and long-term follow-up studies continue to support the safety, efficacy, and cost-effectiveness of MBS in appropriate patient populations [3].

With the increased practice of various MBS procedures, there is increasing interest in enhanced recovery after surgery (ERAS) protocols to improve outcomes, reduce complications, and shorten hospital stays. A key component of ERAS in bariatric patients is optimized perioperative pain management, which is particularly important given evidence suggesting that individuals with obesity may have increased pain sensitivity and altered pain thresholds [4,5]. Patients undergoing MBS typically experience a combination of acute and potentially chronic pain, driven by multiple factors. Sources of pain include: incisional and visceral nociceptive pain from trocar sites, tissue dissection, and stretching during insufflation [6]; referred shoulder pain, mediated by phrenic nerve irritation from residual carbon dioxide in the abdomen and finally inflammatory pain arising from surgical trauma; systemic low-grade inflammation associated with obesity, which can heighten nociceptor sensitivity [6]. Acute postoperative pain is known to peak within the first 24–48 hours. A prospective cohort analysis of over 1,200 abdominal surgery patients found that a substantial proportion experienced clinically meaningful pain (visual analog scale [VAS] ≥4) during mobilization at 24 hours, markedly higher than at rest, though pain generally declined by 48–72 hours thereafter [7].

Utilizing opioids for rescue analgesic in this postoperative period has been known to reduce cardiopulmonary function in the obese population who already have a higher incidence of obstructive sleep apnea [8]. Additionally, pharmacokinetic alterations in obesity—such as reduced morphine volume of distribution and increased peak plasma levels—lead to higher central opioid concentrations, further exacerbating respiratory depression after standard dosing, as seen in obese children with severe obstructive sleep apnea [9]. Beyond the direct respiratory effects, opioids may also worsen cardiovascular function in obese patients by causing hypotension, vasodilation, and negative inotropic effects—raising concern in individuals with comorbid hypertension, arrhythmias, or heart failure [10]. Moreover, prolonged opioid exposure in high-risk patients increases the potential for dependence and long-term addiction, particularly when mental health comorbidities are present [11]. These aspects have prompted efforts to tailor multimodal, opioid-sparing analgesic strategies to this population [12] in order to enhance recovery, minimize opioid use, and support early mobilization in the metabolic bariatric surgical setting.

There has been a notable increase in the use of regional nerve blocks in MBS with transversus abdominis plane (TAP) blocks emerging as a particularly effective component of multimodal analgesia. The TAP block delivers local anesthetic between the internal oblique and transversus abdominis muscles, where sensory thoracolumbar nerves (T6–L1) run toward the abdominal wall—effectively blocking afferents responsible for somatic incision pain from both upper and lower abdominal regions [13]. This fascial plane access can be achieved via the subcostal, mid-axillary, or lumbar triangle of Petit (posterior) routes. Cadaveric and imaging studies (magnetic resonance imaging and sensory mapping) have shown that the subcostal approach provides broader cephalad spread—typically blocking between T7 and L1, with some reaching T6—while the mid-axillary approach tends to cover T10 to L1 dermatomes, usually blocking fewer cephalad levels [14]. In one comparative study of posterior vs. subcostal TAP blocks in 50 adult patients, the subcostal approach resulted in a median of 4 dermatomal segments blocked (most cephalad T8 [interquartile range {IQR} T7–T9]), whereas the posterior/lateral (mid-axillary) technique yielded a median of 3 segments, with most cephalad at T10 (IQR T9–T10), a statistically significant difference (P<0.001) [15]. Thus, for upper abdominal procedures like bariatric surgery, the subcostal TAP block may provide superior sensory coverage and analgesia compared to mid-axillary or posterior techniques. A network meta-analysis of 22 studies compared different regional anesthesia techniques in bariatric cases and found that TAP block consistently produced the greatest reduction in opioid use, pain scores, postoperative nausea and vomiting [PONV], and rescue analgesic requirements compared to other blocks [16]. In a recent 2025 single-center retrospective analysis involving 332 patients undergoing laparoscopic Roux-en-Y gastric bypass, TAP block significantly reduced pain at 1 hour postoperative (mean VAS 2.77 vs. 3.84; P<0.001), though no long-term opioid consumption differences were observed; importantly, no TAP-related complications occurred [17].

Although single-shot TAP blocks have been extensively studied, evidence for continuous TAP block via catheter infusion in MBS remains extremely limited. Most randomized trials and meta-analyses focus on single-shot techniques and demonstrate early postoperative benefits within 24 hours—but no high-quality studies have yet randomized patients to catheter-based continuous TAP infusion vs. single-shot or control groups in the bariatric setting [18]. Therefore, we aimed to investigate the efficacy of continuous TAP block in 50 consecutive cases of laparoscopic sleeve gastrectomy (LSG).

MATERIALS AND METHODS

From February 2022 to April 2022, 50 cases of LSG were performed with ultrasound-guided continuous TAP block (TAP group). The data was compared to that of 157 cases of primary LSG that had been performed from January to December of 2021 (non-TAP group). Initially, a retrospective matched control analysis had been planned. However, the patient characteristics were proven to be statistically homogenous between the 2 groups and the decision to include all the primary LSG cases from 2021 was made.

1. Technique

After completing LSG, the operation sites were sutured. An ultrasound probe was placed in a transverse plane at the epigastrium to identify the linea alba and the rectus abdominis muscles. The probe was then positioned in an oblique subcostal plane below the lower costal margin for identification of the rectus abdominis and transversus abdominis and the peritoneal lining. The epigastric port site, which was 3 to 5 mm in size and had been used for liver retraction during LSG, was used for the insertion of the 17-gauge T-peel inducer and sheath (On-Q^® Pain Buster^®) (Fig. 1). With the probe parallel to the costal margin, the inducer is inserted in a medial to lateral direction toward the lateral border of the rectus abdominis until the tip is placed directly posterior to the rectus abdominis and above the transversus abdominis. Fifteen to 20 mL of normal saline was injected for TAP plane dissection and the catheter was inserted through the sheath after removal of the inducer. The sheath was peeled and discarded. The same procedure was performed for the other side in the same order. The elastomeric pump was injected with 100 mg of 0.5% bupivacaine and connected to the 2 catheters for continuous infusion over 48 hours at a rate of 2.08 mL/hr (Fig. 2). All procedures were performed by a single surgeon.

Fig. 1. Location of the epigastric post site after sleeve gastrectomy. The epigastric port site, which was 3 to 5 mm in size and had been used for liver retraction during laparoscopic sleeve gastrectomy, was used for the insertion of the 17-gauge T-peel inducer and sheath (On-Q^® Pain Buster^®).

Fig. 2. Procedure sequence of continuous TAP block. With the probe parallel to the costal margin, the inducer is inserted in a medial to lateral direction toward the lateral border of the rectus abdominis until the tip is placed directly posterior to the rectus abdominis and above the transversus abdominis (A). Fifteen to 20 mL of normal saline was injected for TAP plane dissection and the catheter was inserted through the sheath after removal of the inducer (B). The sheath was peeled and discarded. The same procedure was performed for the other side in the same order (C, D). The elastomeric pump was injected with 100 mg of 0.5% bupivacaine and connected to the 2 catheters for continuous infusion.

TAP = transversus abdominis plane.

2. Outcomes

The primary outcome was to assess the postoperative 24-hour cumulative amount of opioid consumption in morphine milligram equivalents. The secondary outcomes included postoperative additional pain management (including non-steroidal anti-inflammatory drugs, acetaminophen, and additional opioid injections) and medication for PONV in the postoperative 24 and 48 hours, length of postoperative and total hospital stay and change in numerical rating scale (NRS) scores.

3. Statistical analysis

Quantitative variables with normal and non-normal distribution were expressed as mean ± standard deviation and median (IQR), respectively. Frequency (%) was used to represent qualitative variables. Qualitative variables were analyzed using the χ² test, and quantitative variables with normal distribution were analyzed using Student’s t-test. Quantitative variables with abnormal distribution were also analyzed by the Mann-Whitney test. The normal distribution of variables was evaluated by the Shapiro-Wilk test. A P value <0.05 was significant in all analyses. All analyses were performed by SPSS 20 software (Statistical Package for Social Sciences; IBM Corp., Armonk, NY, USA).

RESULTS

1. Patient demographics

There was no significant difference in mean age, sex distribution, initial body weight (kg), initial BMI between the non-TAP group and TAP group. The incidence of dyslipidemia was higher in the TAP group (Table 1).

Table 1. Baseline characteristics.

Characteristics	Non-TAP group (n=201)	TAP group (n=50)	P value
Age (years)	34 (28–41)	32.5 (28.25–38.5)	0.379
Sex (male/female)	53 (26.37)/148 (73.63)	16 (32)/34 (68)	0.149
Initial body weight (kg)	101.6 (93.3–117.5)	110.75 (95.32–123.95)	0.149
Preoperative BMI (kg/m2)	37.2 (34.87–40.28)	38.05 (34.79–41.71)	0.432
Hypertension	64 (31.84)	23 (46)	0.086
Dyslipidemia	89 (44.28)	40 (80)	<0.001
Type 2 diabetes mellitus	54 (26.87)	12 (24)	0.816
Osteoarthritis	9 (4.48)	3 (6)	0.710
Obstructive sleep apnea	43 (21.39)	13 (26)	0.610
History of psychiatric disorder	18 (8.96)	2 (4)	0.382
Polycystic ovarian syndrome	32 (15.92)	10 (20)	0.631

Values are presented as number (range) or number (%).

TAP = transversus abdominis plane, BMI = body mass index.

2. Perioperative outcomes

There was no significant difference in the perioperative outcomes including total and postoperative length of hospital stay, intraoperative complications, and postoperative episodes of nausea or vomiting (Table 2). The 24-hour cumulative opioid consumption was comparable between the 2 groups (Table 3). However, the TAP group had a significantly lower percentage (36.8% in the non-TAP group vs. 20% in the TAP group) of need for additional opioids within the initial 24 postoperative period. The request for additional control of nausea or vomiting with ramosetron within the initial 24 postoperative period was required in 9.45% of the non-TAP group while there were none in the TAP group (P=0.017). There were 2 cases of complications related to continuous TAP block where there was difficulty in removing the catheters and needed to be removed under local anesthesia. Firm fixation of the catheter to the fascia had occurred in both cases.

Table 2. Perioperative outcomes.

Characteristics	Non-TAP group (n=201)	TAP group (n=50)	P value
Length of postoperative hospital stay	3 (3–3)	3 (3–3)	0.909
Length of hospital stay	4 (4–5)	4 (4–4)	0.942
Intraoperative complications	1 (0.5)	0 (0)	>0.990
Nausea	85 (42.93)	18 (36)	0.539
Vomiting	7 (3.48)	3 (6)	0.538

Values are presented as number (range) or number (%).

TAP = transversus abdominis plane.

Table 3. Postoperative medication for pain and postoperative nausea and vomiting.

Characteristics		Non-TAP group (n=201)	TAP group (n=50)	P value
24-Hour cumulative opioid consumption		157.5 (147.5–200)	150 (150–167.5)	0.270
Opioid in
	24-Hour	74 (36.82)	10 (20)	0.037*
	48-Hour	18 (8.96)	4 (8)	>0.990
Acetaminophen in
	24-Hour	1 (0–1)	1 (0–1)	0.773
	48-Hour	0 (0–1)	0 (0–1)	0.371
NSAID in
	24-Hour	4 (1.99)	0 (0)	0.587
	48-Hour	12 (5.97)	4 (8)	0.532
Metoclopramide in
	24-Hour	65 (32.34)	18 (36)	0.746
	48-Hour	10 (4.98)	5 (10)	0.188
Ramosetron in
	24-Hour	19 (9.45)	0 (0)	0.017*
	48-Hour	2 (1)	1 (2)	0.488

Values are presented as number (range) or number (%).

TAP = transversus abdominis plane, NSAID = non-steroidal anti-inflammatory drug.

^*P<0.05.

3. Change in postoperative NRS scores

The NRS scores at postoperative 1 hour, 6 hours, 12 hours, 24 hours, and 48 hours were collected for statistical analysis (Table 4, Fig. 3). This figure shows the change in NRS score over time. The NRS scores in the TAP group were significantly higher than the non-TAP group at postoperative 12, 24 and 48 hours. The possible reasons are hypothesized in the discussion. There was no significant difference between the 2 groups at postoperative 1 hour and 6 hours.

Table 4. Postoperative NRS scores.

NRS	Non-TAP group (n=201)	TAP group (n=50)	P value
1-Hour	3 (3–3)	3 (3–3)	0.441
6-Hour	3 (3–3)	3 (3–3)	0.155
12-Hour	3 (3–3)	3 (3–3)	0.033*
24-Hour	3 (3–3)	3 (3–3)	0.015*
48-Hour	3 (3–3)	3 (3–3)	0.001*

Values are presented as number (range).

NRS = numerical rating scale, TAP = transversus abdominis plane.

^*P<0.05.

Fig. 3. NRS score. This figure shows the change in NRS score over time in the TAP group and non-TAP group.

NRS = numerical rating scale, TAP = transversus abdominis plane.

DISCUSSION

In the context of metabolic bariatric surgery, the significance of ERAS lies in its potential to positively impact patient outcomes and overall healthcare efficiency. Minimized opioid use is important in reducing respiratory depression and PONV which are symptoms that are already common in patients who receive sleeve gastrectomy [19]. ERAS emphasizes multimodal pain management techniques, including regional anesthesia, non-opioid analgesics, and local anesthetic infiltration, which can reduce the reliance on opioids and their associated risks [20].

Despite visceral pain being more dominant after MBS, TAP block can provide targeted and effective pain relief to the anterior abdominal wall, reducing somatic pain arising from surgical incisions. This effect can lead to improved patient comfort in the immediate postoperative phase and early ambulation, which is particularly important in bariatric surgery patients to prevent complications like deep vein thrombosis and pneumonia [21]. TAP has been known to mainly reduce somatic pain than visceral pain due to its limited spread of analgesics [22] but as most of the medication spreads under the costal margin effectively interrupting the transmission of pain signals from the surgical site to the central nervous system thus resulting in significant coverage of postoperative pain. Historically, obesity was considered a contraindication for TAP block. However, ultrasonography allows identification of anatomical landmarks especially at the epigastrium abdominal wall which is surprisingly accessible due to its relatively decreased thickness [23].

Although there have been many attempts to further establish the benefits of TAP block in laparoscopic MBS, the results have been inconclusive. A 2019 meta-analysis of randomized trials (n=525) demonstrated that ultrasound-guided TAP significantly reduced postoperative pain scores at multiple time points, decreased opioid requirements and accelerated ambulation by approximately 2.2 hours without significant complications [18]. Another systematic review and trial-sequential meta-analysis including 1,025 patients across 13 trials confirmed that TAP block lowered pain at rest at 2, 12, and 24 hours postoperative and decreased morphine-equivalent opioid consumption through 24-hour post-surgery, with no major safety concerns [24]. However, not all studies have demonstrated consistent benefit. In a recent study, TAP block did not have an effect on perceived pain. These findings highlight the fact that the effectiveness of TAP blocks depend on factors such as the type of surgical procedure, patient characteristics, and the specific technique used [25,26].

Continuous TAP blocks can be hypothesized to provide more sustained pain relief compared to single-shot TAP blocks having the potential to reduce the need for additional systemic opioids. They have been known to be particularly effective for managing postoperative pain during the first few days after laparoscopic surgery [27,28,29]. The disadvantages of the procedure are that it is more technically complex because of the placement of the catheters and the risk of complications related to the catheter placement [30,31].

In the present study, although there was no significant difference of cumulative opioid consumption during the hospital stay, continuous TAP block significantly reduced the need for additional opioid and antiemetic injection within the postoperative 24 hours. These results suggest the effectiveness of continuous TAP block in reducing immediate postoperative opioid consumption and PONV. Possible explanations in this discrepancy may be the variability in the individual pain thresholds and opioid sensitivity. Even when cumulative opioid use is similar, patient-to-patient variability in perception and response to pain can obscure group differences. Some patients in the non-TAP group may have used fewer opioids despite higher pain scores (undermedicated), while others in the TAP group might have used similar amounts despite lower pain (overmedicated). The TAP block may have reduced the need for breakthrough analgesia among a subset of patients who otherwise would have required rescue opioids—hence, the lower proportion needing additional opioids. The timing and pharmacokinetics of continuous TAP block may have contributed to these findings as well. The continuous infusion (2.08 mL/hr) delivers low-dose local anesthetic slowly. It may not have reached peak analgesic effect in the immediate postoperative period (when 24-hour opioid use was measured). The benefit may been more evident in the reduced rescue analgesic usage proportion and nausea rather than in the total opioid consumption. The block primarily covers the somatic component (abdominal wall pain) and not the visceral pain from gastric manipulation which could limit its effect on total opioid needs.

Although continuous TAP block was generally well tolerated, catheter-related complications occurred in 4% of cases, consisting of difficulty in catheter removal requiring minor intervention under local anesthesia. Firm fixation of the catheter to the fascia was observed in both instances. While these events did not result in long-term morbidity, they highlight a potential safety concern associated with prolonged indwelling catheters in the subcostal plane. The benefits of continuous TAP block—namely, reduced rescue opioid and antiemetic use—must therefore be weighed against the risk of mechanical complications and the additional procedural steps required. To minimize such risks, careful attention to catheter placement depth, avoidance of excessive fascial fixation, and use of ultrasound guidance throughout insertion and removal are recommended. Further studies should evaluate the incidence, risk factors, and prevention strategies for catheter-related issues to optimize the safety profile of continuous TAP analgesia in metabolic bariatric surgery.

The limitations of our study were the retrospective design, the small sample size, and the failure to discriminate somatic and visceral postoperative pain. The retrospective design with a historical control group carries the potential of selection and confounding biases. The relatively small sample size limited the power of the study to detect small differences in the primary outcome. Post hoc power analysis based on the observed effect size (Cohen’s d=0.21) indicated a statistical power of 26.8% at α=0.05. This suggests that the non-significant finding for 24-hour cumulative opioid consumption may be attributable, at least in part, to insufficient power rather than true equivalence between groups. Future studies with larger samples powered to detect small-to-moderate effects are warranted. The TAP group, surprisingly, seemed to have a higher NRS score compared to that of the non-TAP group. This may be due to the inconsistent method and documenter of the intensity of pain and also the possibility of the TAP group relatively experiencing more intense visceral pain. However, we were unfortunately not able to find a way to distinguish somatic and visceral pain based on the NRS scale. Another possibility for the higher NRS scores in the TAP group at 12 to 48 hours may be that the patients with the TAP block were able to tolerate mild-to-moderate pain better or perceived it as “acceptable pain” in the earlier period while experiencing any subsequent additional pain more intensely or discomfort related to the catheter or limited dermatome coverage of the regional block.

Although there was no significant difference in the cumulative opioid consumption between the 2 groups, we believe our findings are relevant to enhancing the postoperative care of patients undergoing metabolic bariatric surgery with the possibility of reducing rescue analgesics and PONV related to opioids with regional nerve blocks. Despite the shortcomings in refining the method of application and documenting of patient experience, our study highlights the importance of differentiating somatic and visceral pain for adequate control of postoperative pain. Additionally, as the study was performed at a single institution by a single surgeon, the possibility of generalized application requires further research with multicenter studies or randomized controlled trials.

Since conducting the study, our institute has modified our routine perioperative pain management strategy to a pre-incision single-shot TAP block to maximize the analgesic effect of bupivacaine for the patient postoperatively and to reduce extra costs that occurred due to the usage of the catheters [32]. Also, we have incorporated paragastric neural blockade routinely after sleeve gastrectomy to minimize the visceral pain with favorable outcomes [33].

CONCLUSION

Although continuous TAP block did not reduce cumulative opioid consumption, it significantly reduced the need for additional opioid and antiemetic injections within the first 24 postoperative hours.