Analgesic efficacy of the external oblique intercostal fascial plane block on postoperative acute pain in laparoscopic sleeve gastrectomy: a randomized controlled trial
Article information
Abstract
Background
Laparoscopic sleeve gastrectomy (LSG) causes significant postoperative pain, necessitating effective multimodal analgesia strategies. This study evaluated the efficacy of the external oblique intercostal block (EOIB) in this context.
Methods
This prospective, randomized, controlled, single-blind study conducted between April and December 2023 included 60 patients who underwent LSG. Patients were divided into the EOIB (30 ml 0.25% bupivacaine/side) and control (no block) groups. The primary outcome was the cumulative intravenous morphine milligram equivalent (MME) consumption in the first 24 h postoperatively. Secondary outcomes included 12-h MME consumption, pain scores, intraoperative remifentanil use, rescue analgesia requirements, time to first analgesic request, nausea/vomiting scores, antiemetic use, and American Pain Society Patient Outcome Questionnaire-Revised Turkish Version (APS-POQ-R-TR) scores.
Results
The control group had significantly higher median opioid consumption than the EOIB group at 12 (14.4 vs. 5.8 mg; P < 0.001) and 24 h (25.9 vs. 10.6 mg; P < 0.001) postoperatively. The need for rescue analgesics did not differ significantly (43.3 vs. 23.3%; P = 0.1). The EOIB group exhibited significantly higher patient satisfaction (APS-POQ-R-TR score 2.91 vs. 4.42; P < 0.001) and consistently lower pain scores across all time points (P < 0.001). The EOIB group had lower nausea/vomiting scores (P < 0.001), fewer patients requiring antiemetics (16.7% vs. 40%; P = 0.045), longer time to first morphine request (57.5 vs. 25 min; P < 0.001), and lower remifentanil use (850 vs. 1050 μg; P < 0.001).
Conclusions
The preoperative EOIB, as a part of multimodal analgesia, provides effective analgesia for acute pain in patients undergoing LSG.
Introduction
Obesity is a global health concern that is currently treated with diet, medication, and bariatric surgery [1]. Laparoscopic sleeve gastrectomy (LSG) is a common bariatric procedure that often causes moderate-to-severe postoperative pain [2]. This includes parietal pain from trocar incisions (50%–70%), visceral pain from organ manipulation (10%–20%), and referred pain from diaphragmatic irritation (20%–30%), typically experienced in the left shoulder [3]. Parietal pain involves the T7–T10 dermatomes; visceral pain is transmitted via the celiac, aortic, and renal ganglia and splanchnic nerves linked to the T5–T12 spinal segments with the vagus nerve also contributing; and referred pain is transmitted by the phrenic nerve to the cervical plexus (Supplementary Fig. 1) [4,5].
Adequate pain control after LSG is crucial for early mobilization and prevention of complications. Multimodal analgesia with nonsteroidal anti-inflammatory drugs (NSAIDs), local anesthetics (LA), lidocaine, ketamine, and dexmedetomidine is typically recommended [6]. However, these drugs have significant side effects: NSAIDs can cause ulcers, gabapentinoids increase the risk of respiratory depression, dexmedetomidine can lead to hypotension and bradycardia, ketamine may cause hallucinations and dizziness, and lidocaine infusions can cause neurological changes and arrhythmias [7,8]. Neuraxial techniques have limitations, including neurological complications, risk of infections, placement difficulties, and a higher rate of catheter migration, particularly in patients with obesity, which may lead to higher initial failure rates and the need for early catheter placement [9]. Intrathecal morphine can cause delayed respiratory depression, nausea, vomiting, itching, and urinary retention [10].
The fascial plane block is a promising alternative. Various fascial plane blocks such as the erector spinae plane block (ESPB), oblique subcostal transversus abdominis plane block (OSTAP), quadratus lumborum block (QLB), transversus abdominis plane block (TAPB), and modified thoracoabdominal nerve block through the pericostal approach (M-TAPA) are used in upper abdominal surgeries [11–15]. However, the OSTAP and M-TAPA blocks might not effectively block the lateral cutaneous branches [16,17]. The TAPB, ESPB, and QLB can be challenging to perform in patients with obesity because of visualization difficulties [18]. The relatively new external oblique intercostal block (EOIB) provides analgesia for anterolateral upper abdominal surgeries by blocking both the lateral and anterior cutaneous branches of the intercostal nerves between T6–7/T10–11. This technique is easier to perform because of the superficial location of the target fascial plane [19].
The effectiveness of EOIB in reducing morphine consumption in patients undergoing LSG has been demonstrated in the literature [20]. However, our study introduces several novel contributions to this field. Beyond evaluating the analgesic efficacy of EOIB, we confirmed block success through dermatomal analysis, providing objective and quantifiable evidence of its sensory coverage. Moreover, recognizing the volume-dependent nature of EOIB, our study uniquely assessed its efficacy with high-volume LA administration, an area that has been insufficiently explored in previous research. The primary aim of this study was to evaluate the effect of preoperative EOIB on cumulative opioid consumption within the first 24 hours postoperatively in patients undergoing LSG. We hypothesized that patients receiving preoperative EOIB would demonstrate significantly reduced cumulative opioid consumption within the first 24 postoperative hours compared to the control group.
Materials and Methods
Study design
This prospective, randomized, single-blind study was approved by the Medical Ethics Committee of Ondokuz Mayis University in February, 2023 (Approval No. 2022/324). This study was registered at ClinicalTrials.gov (Registration No. NCT05822479) before patient enrollment and was conducted in accordance with the principles of the Declaration of Helsinki (64th WMA General Assembly, Fortaleza, Brazil, October 2013). The Consolidated Standards of Reporting Trials (CONSORT) 2010 Statement was also considered when preparing this manuscript [21].
Participants
This study included patients scheduled for elective LSG at a tertiary university hospital between April, 2023 and December, 2023. Written informed consent was obtained from all participants before the study. The inclusion criteria were as follows: patients aged 18–65 years with a body mass index > 35 kg/m2 and an American Society of Anesthesiologists physical status score of II-III. Exclusion criteria were as follows: patients with drug allergies (opioids, NSAIDs, LA); neuropsychiatric disorders; cognitive impairment; inability to communicate; history of drug addiction; injection site or systemic infection; use of anticoagulants or bleeding disorders (coagulopathy, abnormal international normalized ratio, thrombocytopenia); significant cardiovascular, hepatic, renal, or endocrine disorders; history of chronic pain syndrome or long-term opioid use (> 4 weeks); obstructive sleep apnea syndrome (OSAS; apnea-hypopnea index > 5/h); chronic obstructive pulmonary disease; and requiring postoperative intensive care follow-up.
Randomization, blinding, and allocation concealment
Study randomization was performed by an anesthesia assistant who was not involved in patient follow-up. The patients were randomly assigned to the control or EOIB group (n = 30 each). Randomization was performed using a web-based program called Research Randomizer with a 1:1 ratio and a block randomization list (block size = 4) [22]. Sequentially numbered opaque sealed envelopes containing participation numbers were stored in a locked cabinet in the operating room until the day of surgery. One hour before surgery, an anesthesia nurse who was not involved in the randomization process asked the patients to choose one of the envelopes and determine the patient group. The block procedure was performed by an anesthesiologist who was not part of the study in the regional anesthesia room 30 min before the patients underwent surgery. To ensure block quality and standardization, the procedure was conducted by an experienced anesthesiologist who had successfully performed an EOIB at least 30 times. An anesthesia assistant who was not involved in the study performed postoperative pain assessments and data collection. The surgeons, nurses, anesthesiologists, and individuals involved in the analysis of the results were all blinded to patient randomization.
Block procedure
Preoperatively, in the regional anesthesia room, patients scheduled for the EOIB were monitored using electrocardiography, noninvasive arterial blood pressure, and peripheral oxygen saturation. Oxygen was administered at a flow rate of 3 L/min via a nasal cannula. After initiating the intravenous (IV) lactated Ringer’s infusion through a 20–22 gauge IV cannula, intravenous midazolam was administered at a dose of 0.03 mg/kg (ideal body weight [IBW]) to achieve a Ramsey Sedation Score of 2 (awake, calm, and observing their surroundings).
Ultrasound-guided EOIB
The EOIB was performed as described by Elsharkawy et al. [19]. Briefly, the patients were placed in the supine position, and the area between the midclavicular and anterior axillary lines at the sixth to tenth rib levels was prepared following the asepsis/antisepsis rules. After covering the linear ultrasonography probe (8–13 MHz GE LOGIQ V1 Ultrasound System®) with a protective sterile plastic sheath, the probe orientation marker was directed cranially and positioned sagittally between the midclavicular and anterior axillary lines at the level of the sixth rib. The sixth rib was identified by counting upward from the subcostal margin (tenth rib). After positioning the probe, the cranial end was slightly internally rotated to obtain a paramedian sagittal oblique view. The following structures were identified from superficial to deep: skin-subcutaneous tissue, external oblique intercostal muscle, intercostal muscles, pleura, and lungs. The needle entry site was determined to be cranial to the sixth rib and medial to the anterior axillary line. Subsequently, 2 ml of 2% lidocaine (Aritmal®, Vem İlaç) was infiltrated into the skin and subcutaneous tissues. A block needle (21-G, 100-mm short bevel; Stimuplex® Ultra 360®, B. Braun) was then advanced in a superomedial-inferolateral direction for 2–3 cm into the external oblique intercostal muscle, reaching the plane between the sixth and seventh ribs. Thereafter, 1–2 ml of 0.9% normal saline was injected to confirm correct placement. After hydrodissection, 30 ml of LA mixture consisting of 0.25% bupivacaine (Marcaine®, AstraZeneca) + 1:400000 adrenaline was injected into the plane in 5-ml increments with negative aspiration after each increment. LA spread over the sixth rib between the sixth and seventh ribs was observed. The needle was directed toward the eighth rib to enhance the spread of the LA (Fig. 1 and Supplementary Video 1). The same procedure was repeated on the opposite side. The resulting sensory block was checked every 5 min using the pinprick test, covering the T6–T10 dermatomes at the posterior axillary line of the lateral cutaneous nerves and the T6–T9 dermatomes at the midline of the anterior cutaneous nerves (Fig. 2). An anesthesia assistant who was not involved in the EOIB application or patient follow-up performed the dermatome examination. The EOIB was considered successful for patients with a sensory block score ≥ 1 (0 = no sensory block; 1 = touch sensation present, no pain; 2 = no touch sensation or pain) in all dermatomes, and the remaining patients were excluded from the study.
Anatomical and ultrasound-guided approach for external oblique intercostal block. (A) Anatomical landmarks and needle insertion points: reference points, including the anterior axillary and midclavicular lines, needle insertion sites between the sixth and tenth ribs, relevant muscles, and the rectus sheath, are illustrated. (B) Cross-sectional anatomy: needle trajectory through the external oblique intercostal muscle showing the sixth and seventh ribs, intercostal muscle, and pleura. The blue-shaded area illustrates the spread of local anesthetic. (C) Ultrasound imaging: ultrasound image shows the needle trajectory for the EOIB, highlighting the external oblique intercostal muscle, intercostal muscle, pleura, and lungs. The blue area represents the spread of the local anesthetic and the green dashed line indicates the pleura. EOIM: external oblique intercostal muscle, ICM: intercostal muscle, EOIB: external oblique intercostal block.
Approximate dermatomal coverage following a successful external oblique intercostal block. The orange area indicates sensory blockade of the lateral branches of the intercostal nerves (T6–T10), while the yellow area indicates blockade of the anterior branches (T6–T9/10).
In the control group, no regional block was performed. Patients received standard analgesia consisting of intraoperative and postoperative multimodal analgesic medications as detailed in the 'Analgesia Management' section.
Anesthesia management
After administration of the block, the patients were taken to the operating room. Anesthesia was administered as follows: induction was performed with propofol (1.5–2.5 mg/kg lean body weight [LBW]), and remifentanil (1 μg/kg LBW IV bolus over 30–60 s, followed by an infusion of 0.25 μg/kg/min). Endotracheal intubation was performed using rocuronium bromide (0.6–1.2 mg/kg LBW IV) to achieve a zero train-of-four (TOF) count. During the operation, neuromuscular blockade was maintained with repeated bolus doses of 0.1–0.2 mg/kg LBW IV rocuronium to keep the TOF count at 1–2 [23]. Maintenance of anesthesia was achieved with O2/air (inspired oxygen fraction 40%), age-adjusted 0.8–1.2 minimum alveolar concentration sevoflurane, and 0.1–0.25 µg/kg/min IV remifentanil infusion. The heart rate and blood pressure were allowed to vary by no more than 20% from the preoperative values by adjusting the remifentanil infusion rate. At the end of the procedure, extubation was performed after reversing rocuronium with a combination of 0.02 mg/kg IV atropine and 0.04 mg/kg IV neostigmine to achieve a TOF ratio > 0.9.
Analgesia management
During the pre-anesthesia visit, patients were informed about the numerical rating scale (NRS), an 11-point scale ranging from 0–10 (where 0 indicates “no pain” and 10 indicates “the worst pain imaginable”). The patients were instructed to select the most appropriate value corresponding to their pain intensity during the postoperative period. Patients were also educated on how to use the patient-controlled analgesia (PCA) device and were informed that they could request opioids using the PCA device if their NRS score at rest was ≥ 4.
Following induction, all patients were administered 20 mg IV tenoxicam and 100 mg tramadol during the intraoperative period. At the time of surgical incision, 0.05 mg/kg IBW IV morphine was administered. Thirty minutes before the end of the procedure, 1 g of IV paracetamol was administered, followed by subsequent doses every 8 h postoperatively. Additionally, postoperative PCA (BodyGuard 575 Pain Manager, Caesarea Medical Electronics GmbH) was initiated in the recovery unit for all groups (requested dose: 20 μg/kg IV morphine, lockout interval: 10 min, 4-h limit: 80% of the total calculated dose, basal infusion: none). For rescue analgesia (patients with an NRS score ≥ 4 at rest despite PCA requests), 25 mg IV meperidine was administered in the recovery unit, and 50 mg intramuscular (IM) meperidine was administered in the ward. The doses of IM and IV meperidine for rescue analgesia were calculated as IV morphine milligram equivalents (MME) using an opioid equivalent analgesic dose calculator (http://www.globalrph.com/narcotic). NRS scores were evaluated at 0 (upon communication with the patient), 3, 6, 12, 18, and 24 h postoperatively, both at rest and during coughing or deep breathing. The calculated MME amounts of IM and IV meperidine were added to the morphine requested from the PCA to record the cumulative opioid consumption at 12 and 24 h.
Postoperative nausea and vomiting
For postoperative nausea and vomiting (PONV) prophylaxis, patients were routinely administered 8 mg IV dexamethasone before induction and 0.15 mg/kg IBW IV ondansetron 20 min before the end of the procedure. PONV was evaluated using a verbal descriptive scale (0 = none; 1 = mild nausea; 2 = moderate nausea; 3 = vomiting once; 4 = vomiting more than once). Patients with a score ≥ 3 were administered an additional 4 mg IV ondansetron. If the score remained ≥ 3 despite the administration of ondansetron, 10 mg IV metoclopramide was administered.
Quality of postoperative pain management and patient satisfaction
Patient satisfaction and the quality of pain management in all patients from both groups were assessed using the Turkish version of the American Pain Society Patient Outcome Questionnaire (APS-POQ-R-TR). The questionnaire consists of 18 primary and 3 secondary questions. These questions aim to evaluate pain intensity, frequency of severe pain, impact of pain on daily activities and emotional well-being, side effects of treatment, patients’ perceived analgesic benefit, level of engagement in treatment, non-pharmacological methods used to alleviate pain, and overall patient satisfaction [24].
Surgical approach
After the induction of anesthesia, the patients were placed in the supine position. The first trocar (12 mm) was inserted approximately 20 cm below the xiphoid process, and CO2 gas at a pressure of 13–15 mmHg was used to expand the abdominal cavity. Subsequently, four additional trocars, ranging in size from 5 to 15 mm, were placed, and the surgical procedure was performed transperitoneally with the patient in the reverse Trendelenburg position. Following surgery, a drain was inserted through a 5 mm port in the left anterior axillary line (Supplementary Fig. 2).
Outcomes
The primary outcome was the cumulative IV MME consumption in the first 24 h postoperatively. The secondary outcomes included cumulative IV MME consumption in the first 12 h postoperatively; NRS scores for rest/activity at 0, 3, 6, 12, 18, and 24 h; intraoperative remifentanil consumption; number of patients requiring rescue analgesia; time to first analgesic request from the PCA; nausea and vomiting scores; number of patients requiring antiemetics; and revised APS-POQ-R-TR scores at 24 h postoperatively. Hemodynamic data, block-related complications (hematoma, infection, pneumothorax, and LA toxicity), and opioid-related side effects (itching, fatigue, sedation, and respiratory depression) were also recorded.
Sample size calculation
The sample size was determined by considering the cumulative opioid consumption (in MME) within the first 24 h postoperatively in a preliminary pilot study that included 10 patients per group. The sample size was calculated using G*Power software, version 3.1.9.7. The minimum number of patients to be included in each group was 25 with a 95% CI, 80% test power (1-β), and 0.8253421 effect size. The mean ± SD were 20.58 ± 4.75 mg in the control group and 15.72 ± 6.84 mg in the EOIB group. Considering the possibility of missing data, the sample size was increased by 20%. Thirty patients were thus included in each group, resulting in a total of 60 patients.
Statistical analysis
Statistical analyses were performed using SPSS software, version 26 (IBM Inc.). Descriptive statistics for categorical variables were presented as frequencies (n) and percentages (%). Comparisons between categorical variables were performed using Pearson’s chi-square or Fisher’s exact tests, as appropriate. The Shapiro–Wilk test was used to assess the normality of the distribution of the numerical variables. Descriptive statistics for numerical variables were presented as the mean ± SD and 95% CIs for normally distributed data and median values with interquartile ranges (Q1, Q3) for non-normally distributed data. An independent sample t-test was used to compare two independent groups of normally distributed data.
The Mann–Whitney U test was used to compare two independent groups with non-normally distributed data. For pain scores at rest and with activity, two-way repeated-measures analyses of variance were performed, which accounted for each group, the measurement times (0, 3, 6, 12, 18, 24 h), and the interaction term between the group and measurement time. For pairwise comparisons with further testing, a Bonferroni correction was applied, and the significance level was accepted as P < 0.0083. Statistical significance was defined as P < 0.05 with two-tailed.
Results
Between April and December 2023, 70 patients were assessed for eligibility. Five were excluded, three who used noninvasive continuous positive airway pressure devices due to OSAS and two who declined study participation. During follow-up, two patients in the control group and one in the EOIB group were excluded due to the need for postoperative intensive care. In addition, one patient from Group EOIB was excluded due to a change in the surgical method, and another from Group EOIB due to a failed block in the dermatomal examination. In conclusion, the data of 60 patients (EOIB group [n = 30 patients] and control group [n = 30 patients]) were analyzed according to our protocol (Fig. 3).
Consolidated Standards of Reporting Trials (CONSORT) flow diagram of participants. EOIB: external oblique intercostal block.
The demographic data, surgical characteristics, and hemodynamic values were similar between the two groups (Table 1 and Supplementary Fig. 3). However, the cumulative opioid consumption in MME for the first 12 and 24 h postoperatively was significantly higher in the control group than in the EOIB group. At 12 h, the control group had a median MME consumption of 14.4 mg (10.8, 20.5), while the EOIB group consumed 5.8 mg (4.5, 7.2), resulting in a significant mean difference of −9.11 mg (95% CI [−11.69 to −6.53], P < 0.001). At 24 h, the control group consumed 25.9 mg (22.1, 29.7) compared to 10.6 mg (8.7, 13.8) in the EOIB group, with a mean difference of −13.86 mg (95% CI [−16.94 to −10.79, P < 0.001) (Fig. 4 and Table 1). In our study, no significant difference was found between the groups in terms of the number of patients who required rescue analgesics (control group: 13 patients [43.3%]; EOIB group: 7 patients [23.3%]; P = 0.1) (Table 1). Kaplan–Meier analysis demonstrated a significant difference in the probability of not requiring rescue analgesia over the first 24-h postoperative period between the EOIB and control groups (Breslow, P = 0.024). During the initial period (0–2 h), the EOIB group exhibited a higher probability of not requiring rescue analgesia (approximately 95%) than the control group (approximately 80%). This advantage was maintained throughout the follow-up period (2–24 h), with the EOIB group stabilizing at approximately 80%–85%. In comparison, the control group gradually decreased to approximately 60% by 24 h (Supplementary Fig. 4).
Demographic, Intraoperative, and Postoperative Outcomes
Comparison of cumulative IV MME consumption at 12 and 24 h postoperatively. This boxplot compares the cumulative IV MME consumption between the control and EOIB groups at 12 and 24 h postoperatively. At both time points, the EOIB group demonstrated significantly lower IV MME consumption compared to the control group (P < 0.001 for both comparisons). IV MME: intravenous morphine milligram equivalent, EOIB: external oblique intercostal block.
A comparison of pain scores at rest and with activity between the study groups indicated that the control group consistently had significantly higher scores at all time points compared to the EOIB group (P < 0.001 for all comparisons). A statistically significant difference was found in the NRS scores over time (P < 0.001), with the group variable significantly influencing this time variation (P = 0.001 for NRS at rest; P < 0.001 for NRS during activity). Additionally, a significant difference was observed between the groups (P < 0.001) (Table 2 and Supplementary Fig. 5). Patient satisfaction and pain management quality, assessed using the APS-POQ-R-TR, were significantly higher for all subfactors, and the total score for the control group was higher than that for the EOIB group. The total APS-POQ-R-TR scores were 4.42 ± 0.81 (95% CI [4.13–4.71]) for the control group and 2.91 ± 0.52 (95% CI [2.72–3.10]) for the EOIB group (P < 0.001) (Table 3).
NRS Pain Scores at Rest and during Activity at Different Time Points according to Group
APS-POQ-R-TR Questionnaire Results at 24 h Postoperatively
A comparison of PONV scores showed significantly higher scores in the control group than in the EOIB group at all time points (P < 0.001) (Supplementary Table 1). Significantly more patients in the control group (12 patients, 40%) required postoperative antiemetic treatment compared to the EOIB group (5 patients, 16.7%) (P = 0.045). Additionally, the time to the first morphine request via PCA was significantly longer in the EOIB group (median 57.5 min [40, 97.5]) compared to the control group (median 25 min [17, 31.3]) (P < 0.001). Intraoperative remifentanil consumption was also significantly higher in the control group (median 1050 µg [913.8, 1262.5]) compared to the EOIB group (median 850 µg [690.8, 975]) (P < 0.001) (Table 1). We observed no complications related to the block, medication, or surgery.
Discussion
Our study on patients who underwent LSG found that the preoperative EOIB with ultrasound significantly reduced opioid use in the first 24 h compared to the control group. Improvements were also observed in remifentanil use, pain scores, time to first morphine request, nausea and vomiting scores, antiemetic requirement, and APS-POQ-R-TR scores. No significant differences were found in intraoperative hemodynamics or complications between the groups.
Previous studies have investigated the effects of the EOIB on pain associated with LSG. Specifically, in a study conducted by Kavakli et al. [20], a comparison between the patient group that received bilateral EOIBs and the control group revealed an average difference of −8 mg in postoperative morphine consumption (95% CI [−11 to −6]). In our study, the difference in opioid consumption was −13.86 mg (95% CI [−16.94 to −10.79], P < 0.001). In the literature, the median minimal clinically important difference (MCID) for 24-h opioid consumption is equivalent to 10 mg of intravenous morphine; this difference is considered significant for both absolute reductions and a 40% relative reduction [25]. The results of our study support the potential efficacy of the EOIB in postoperative pain management, with a statistically and clinically significant reduction. However, MCID values may vary for different surgical types and patient populations, such as bariatric surgery, and a specific MCID value for this field has not yet been established [26]. Although Kavakli et al. observed reduced NRS pain scores in the first 12 h, our study found consistently lower pain scores in the EOIB group at all intervals. This difference may be due to our focus on patients with successful blocks and the use of a higher volume of LA (60 vs. 40 ml). Kavakli et al. did not confirm block success with a dermatomal examination.
A study conducted by Doymus et al. [27] compared the efficacy of the EOIB (0.25% bupivacaine, 60 ml) with port-site LA injection. In that study, a 42.57% reduction in opioid consumption was observed, whereas our study found a 59.07% reduction in opioid consumption. Both studies showed clinically and statistically significant results. However, the need for rescue analgesia in the EOIB group in the study by Doymus et al. was twice as high as that in our study. Additionally, our Kaplan–Meier analysis showed that the EOIB group required less rescue analgesia during the 24-h postoperative period, particularly during the initial hours. This difference could be attributed to the fact that Doymus et al. did not test block success. Confirming the presence of dermatomal spread is critical for the reliability and consistency of results. Insufficient testing of block success can lead to underestimation of block efficacy and misinterpretation of postoperative opioid consumption data.
The literature indicates that various fascial plane blocks can be used in bariatric surgery. One such block is the M-TAPA block, known for its wide dermatomal spread (T3/4–T12/L1) [14]. However, the tight attachment of the transversus abdominis muscle to the inner surface of the last six costal cartilages and the presence of the linea semilunaris may limit the craniolateral spread of the LA injected between the costal cartilage and transversus abdominis muscle. In this scenario, the injection may block the anterior branches of the intercostal nerves (particularly T9–T11) but may not always effectively block the lateral cutaneous branches [16]. Therefore, the M-TAPA block can be considered an alternative to the OSTAP block. Although the OSTAP block involves the injection of LA into the same plane, technical differences, such as the position of the probe and the trajectory of the needle, are notable. Both techniques have been reported to provide significant dermatomal spread (T6–L1) but may be more suitable for supraumbilical and midline surgeries [17]. The EOIB, performed both in cadaveric studies (T7–T10) and in patients (T6–T9/10), provide consistent blockade of the supra-umbilical anterolateral abdominal wall [19]. These findings suggest that the EOIB is a more suitable option for dermatomal spread than the M-TAPA and OSTAP blocks.
Regarding the TAPB, systematic reviews and meta-analyses in bariatric surgery reveal inconsistent effects on postoperative opioid consumption compared to controls [28–31]. The TAPB can be challenging for obese patients due to subcutaneous fat and increased TAP depth, which affects the success of the block. In this context, emphasizing the differences in fat distribution in the relevant access area and the implications of depth is essential. Additionally, the TAPB does not reliably block the lateral and anterior cutaneous branches of the intercostal nerves. Similarly, Cosarcan et al. [31] found that the EOIB reduces opioid consumption as effectively as the combined TAPB and rectus sheath block.
The ESPB is also a viable alternative for postoperative analgesia in bariatric surgery, significantly reducing opioid consumption compared to controls [11]. Although the increased adipose tissue in patients with obesity extends the distance that ultrasound waves must travel, reducing their penetration and the success of the block, recent literature suggests that performing the ESPB is not particularly difficult in obese patients [32]. Furthermore, since the ESPB is mainly performed in the lateral or prone positions, the EOIB offers a noteworthy positional advantage. Our study found that the EOIB was easy to administer in the supine position using a linear probe, suggesting that it may be a better alternative to the ESPB.
Another alternative method used in LSG is the QLB. Studies have shown that the QLB2 and QLB3 reduce opioid consumption and postoperative analgesia needs compared with control groups [13,33]. However, given that the QLB is technically challenging, time-consuming, and is associated with significant side effects, the EOIB may be a more viable option.
Ultimately, the EOIB may be preferable over other fascial plane blocks in bariatric surgery because of its ease of application and effective analgesia, especially in obese patients. Additionally, it offers significant advantages such as positioning (supine) and needle/catheter insertion site placement (away from the surgical field and vascular beds). We acknowledge that catheter-based techniques, which allow for repeated injections, are often compared to single-shot blocks for their potential to prolong analgesia. However, studies have demonstrated the effectiveness of single-shot techniques, particularly in obese patients [34]. Additionally, block efficacy has been observed to gradually decrease over time, with higher pain intensity noted during the first 8 h postoperatively [17,35]. Our study provides further support for the argument that effective analgesia within the first 24 h can be achieved with a single injection of the EOIB, as evidenced by significant reductions in opioid consumption and pain scores in the EOIB group compared to the control group. Nonetheless, future research comparing these approaches in bariatric surgery could offer valuable insights.
This study had several limitations. First, as this was a single-center study that lacked a sham group, the generalizability of the results may be limited. Second, given that this was a single-blind study, eliminating the placebo effect was not possible. Third, the sample size was determined based on the cumulative opioid consumption within the first 24 h, which may not be sufficient to evaluate secondary outcomes. Finally, routine administration of dexamethasone and ondansetron for postoperative nausea and vomiting prophylaxis may complicate the independent assessment of the effects of these drugs on pain and other side effects.
In conclusion, this study demonstrated that the preoperative EOIB significantly reduced opioid consumption in the first 24 h after LSG, effectively decreased pain scores, delayed the need for morphine, reduced nausea and vomiting, and enhanced patient satisfaction. No block- or medication-related complications were observed, confirming the safety of the EOIB as an analgesic.
Notes
Funding
This study was supported by the Commission Presidency of Scientific Research Projects of Ondokuz Mayis University, Samsun, Turkey, under project number PYO.TIP.1904.23.019.
Conflicts of Interest
No potential conflict of interest relevant to this article was reported.
Data Availability
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
Author Contributions
Elif Sarikaya Ozel (Conceptualization; Funding acquisition; Investigation; Methodology; Software; Writing – original draft)
Cengiz Kaya (Conceptualization; Funding acquisition; Investigation; Methodology; Software; Writing – original draft)
Esra Turunc (Investigation; Methodology; Software; Validation; Visualization; Writing – review & editing)
Yasemin B. Ustun (Investigation; Visualization; Writing – review & editing)
Halil Cebeci (Investigation; Methodology; Software; Validation; Visualization; Writing – review & editing)
Burhan Dost (Investigation; Visualization; Writing – review & editing)
Supplementary Materials
Sources of pain during laparoscopic sleeve gastrectomy.
Trocar and drain placement for laparoscopic sleeve gastrectomy.
Comparison of heart rate and mean arterial pressure between the control and EOIB groups. EOIB: external oblique intercostal block.
Kaplan–Meier curve for the percentage of patients not requiring rescue analgesics over 24 h.
Changes in NRS scores at rest (A) and during activity (B) over time according to group. NRS: numerical rating scale.
Comparison of postoperative nausea and vomiting scores by study groups.
Steps for performing an external oblique intercostal block.