Effective management of postoperative pain is a cornerstone of enhanced recovery after surgery, particularly in patients undergoing abdominal surgeries. A significant portion of the pain following abdominal procedures is attributed to the abdominal wall incision, which is a major source of nociceptive input [1]. Optimal postoperative pain management not only alleviates suffering but also plays a critical role in reducing perioperative morbidity, particularly in high-risk patients prone to acute coronary and thrombotic events. Opioids,

while commonly employed for perioperative analgesia, are associated with a range of side effects, including nausea, vomiting, respiratory sdepression, and the potential for dependency. Consequently, a multimodal analgesic approach has gained prominence, incorporating regional anesthesia techniques to enhance pain relief while minimizing opioid-related adverse effects [2]. Regional anesthesia and analgesia methods offer numerous advantages, extending their benefits beyond the perioperative period. Among these,

The transversus abdominis plane (TAP) block, initially described by Rafi, has emerged as an effective technique for blocking sensory afferents that supply the anterior abdominal wall [3]. The TAP block targets the nerves within the fascial plane between the internal oblique and transversus abdominis muscles, providing substantial pain relief. Two principal types of the TAP block have been described: the posterior and subcostal approaches. Posterior TAP blocks are particularly effective for analgesia following lower abdominal surgeries [4-8], while the subcostal TAP block, first introduced by Hebbard et al., has been shown to alleviate pain from incisions extending above the umbilicus [9, 10].

More recently, TAP catheter-based techniques have been integrated into multimodal analgesia regimens for various abdominal procedures, including gastrointestinal surgeries, cesarean sections, abdominal hysterectomies, and prostatectomies. These techniques involve the continuous infusion of local anesthetics, providing sustained analgesia to the skin and muscles of the anterior abdominal wall. Ultrasound for guiding the TAP block was first described by Hebbard et al. [9]. The advantage over neuraxial techniques is the absence of hemodynamic instability, early mobilization, and not requiring prolonged urinary catheterization. Compared to neuraxial techniques, TAP blocks offer several distinct advantages, including the absence of significant hemodynamic instability, early patient mobilization, and elimination of the need for prolonged urinary catheterization. Despite these benefits, TAP blocks remain underutilized in clinical practice [11]. On the other hand, thoracic epidural analgesia has long been regarded as the gold standard for managing postoperative pain after upper abdominal surgeries. It provides superior pain relief by blocking both sensory and motor pathways, facilitating improved respiratory function and early recovery [12, 13]. However, its use is often associated with potential complications such as hypotension, urinary retention, and risk of epidural hematoma, particularly in anticoagulated patients.

This study seeks to compare the analgesic efficacy of right-sided continuous transversus abdominis plane (TAP) block with continuous thoracic epidural anesthesia in patients undergoing right-sided upper gastrointestinal surgeries. By evaluating

postoperative pain relief over 72 hours, this research aims to determine whether TAP block, with its favorable safety profile and minimal invasiveness, can serve as an effective alternative to thoracic epidural anesthesia in this patient population. The study also aims to address gaps in the existing literature by providing a direct comparison of these techniques in a clinical setting, with a focus on pain scores, analgesic consumption, and clinical outcomes.

This was a prospective, randomized, single-center study. Approval was obtained from the Institutional Research Ethics Committee, Indira Gandhi Institute of Medical Sciences (IGIMS), Patna, Bihar (India). The trial was executed at the Indira Gandhi Institute of Medical Sciences (IGIMS) in accordance with the International Conference on Harmonisation (ICH) guidelines for Good Clinical Practice (GCP). Full written informed consent was obtained from each participant before the intervention.

Inclusion Criteria:

1. Age Range: Adults between the ages of 18 to 75 years at the time of the procedure.
2. Physical Status: Patients classified as American Society of Anaesthesiologists (ASA) Physical Status I or II, indicating they are either healthy or have mild systemic disease without substantive functional limitations.
3. Type of Surgery and Anesthesia: Patients scheduled for right-sided upper gastrointestinal surgeries performed under spinal anesthesia, ensuring a consistent surgical approach for the study.
4. Dermatomal Level of Surgical Incision and Drain Sites: Upper abdominal surgical incisions where the lower end is at or above the thoracic T10 dermatome. This includes:
   • Extended right subcostal incision for partial hepatectomy.
   • Rooftop (chevron) incision for radical nephrectomy.
   • Transverse incision for pancreatic surgery (e.g., Whipple’s procedure, total pancreatectomy, and distal pancreatectomy).

Exclusion Criteria:

1. Refusal for Procedure: Patients who do not consent to the placement of an epidural or transversus abdominis plane (TAP) catheter, which is integral to the study protocol.
2. High Body Mass Index (BMI): Patients with a BMI greater than 30, as obesity could affect the efficacy and safety of the intervention.
3. Coagulation Disorders: Patients with known coagulation disorders or thrombocytopenia, defined as a platelet count of less than 150,000, to minimize the risk of bleeding complications.
4. Infection: The presence of an active infection at the planned site of needle insertion, as increases the risk of complications such as abscess formation.
5. Use of Specific Medications: Patients receiving opioids or alpha-2 agonists for sedation, premedication, or postoperative analgesia (with the exception of tramadol), as these drugs could confound pain management outcomes.
6. History of Relevant Drug Allergy or Chronic Pain: Patients with a history of relevant drug allergy or chronic pain.
7. Incision Characteristics: Patients where the lower end of the surgical incision extends below the T10 dermatome or extends laterally beyond the anterior axillary line.

Study Design and Perioperative Management: The perioperative management was standardized across both study groups, with the exception of the insertion of subcostal transversus abdominis plane (TAP) catheters at the conclusion of surgery in the TAP group. All patients underwent preoperative epidural catheter placement. Patients were randomized into two groups assigned via a computer-generated sequence to receive either epidural analgesia (Group E) or bilateral subcostal TAP catheter analgesia (Group T) for postoperative pain management. Postoperative care was provided either on a surgical ward or in a high-dependency unit, as determined by the attending anaesthetist.

Epidural Group (Group E) Protocol:

1. Preoperative Preparation: An epidural catheter was placed in the thoracic T7–T9 region before surgery.
2. Induction of Anesthesia: General anaesthesia was induced using intravenous propofol (1.5–2 mg/kg) and fentanyl (1–2 µg/kg). Tracheal intubation was facilitated by a non-depolarizing neuromuscular blocking agent.
3. Maintenance of Anesthesia: Anaesthesia was maintained with desflurane in an oxygen-air mixture. Intraoperative analgesia was provided via the epidural catheter, with 20 mL of 0.25% bupivacaine administered during surgery. Prophylactic ondansetron (0.05 mg/kg) was also administered.
4. Postoperative Analgesia: Upon emergence from anaesthesia, patients were transferred to the recovery area, where patient-controlled epidural analgesia (PCEA) was initiated. The PCEA regimen included a background infusion of 0.125% bupivacaine with fentanyl (2 µg/mL), a bolus dose of 2 mL, and a lockout period of 30 minutes. The infusion rate started at 6 mL/h and was titrated upward in 2 mL/h increments, up to a maximum of 12 mL/h, based on the block height assessed using ethyl chloride spray. Block height was routinely evaluated every 6 hours.

TAP Catheter Group (Group T) Protocol:

1. Preoperative and Intraoperative Management:Similar to the epidural group, an epidural catheter was placed, and general anaesthesia was administered. Intraoperative analgesia was provided via the epidural catheter with 20 mL of 0.25% bupivacaine.
2. TAP Catheter Placement:At the end of surgery, while patients remained under general anaesthesia, bilateral subcostal TAP catheters were inserted. A total of 1 mg/kg of 0.375% bupivacaine was injected through each catheter.
   • Technique:The skin was prepared with 2% chlorhexidine, and a high-frequency (5–10 MHz) ultrasound probe was used to identify the transversus abdominis plane. A 16-G Tuohy needle was advanced into the plane, and 10 mL of saline was injected to confirm proper placement. An epidural catheter was then threaded 6–7 cm into the space and secured.
3. Postoperative Analgesia:Patients received 8-hourly bolus injections of 1 mg/kg of 0.375% bupivacaine through each TAP catheter for the first 72 hours postoperatively.

Rescue Protocols and Failure Management:

• Epidural Group (Group E):If the epidural was ineffective in recovery, it was re-sited, and intravenous morphine (up to 10 mg) was administered for pain relief. If pain persisted despite maximal epidural infusion (12 mL/h), a 7.5 mL bolus of 0.25% bupivacaine was administered. If two boluses failed to control pain, patient-controlled analgesia (PCA) with morphine was initiated, and the patient was excluded from the study.
• TAP Catheter Group (Group T):If a TAP catheter was ineffective, it was re-sited under local anesthesia. Persistent pain led to the removal of the catheters and the initiation of epidural analgesia. Catheter displacement necessitated re-siting under local anesthesia. Therapeutic failure was defined as inadequate pain control from the surgical wound and drains, while technical failure was defined as the inability to insert TAP catheters due to poor tissue planes.

Postoperative Analgesic Regimen: Both groups received a standardized postoperative analgesic regimen, including regular paracetamol (1 g every 6 hours) and intravenous tramadol (50–100 mg every 6 hours as needed).

Outcome Measures:

1. Primary Outcome:Visual analogue scale (VAS) pain scores during coughing at 8, 24, 48, and 72 hours postoperatively.
2. Secondary Outcomes:VAS pain scores at rest, postoperative nausea scores, tramadol usage, patient satisfaction at 72 hours, success rates, therapeutic failure rates, catheter re-siting rates, and complications related to the techniques.

Pain Assessment: Patients were assessed for pain at 8, 16, 24, and 48 h postoperative. Assessment of the pain was done using the visual analog scale (VAS) and scores were noted for:

1. Pain at rest
2. Pain on coughing
3. Consumption of rescue analgesia.

Postoperative pain was graded into four categories depending on the VAS scores:

1. Nil = VAS score 0
2. Mild = VAS score 1–3
3. Moderate = VAS score 4–6
4. Severe = VAS score >6.

Sample Size: A power analysis was conducted using G*power software, version 3.0.1 (Franz Foul Universitat, Kiel, Germany). It was determined that a sample size of 30 patients per group would provide 80% power to detect significant differences, with an effect size of 0.50 and a significance level of 0.05.

Statistical Analysis: The collected data was organized into a table using Microsoft Excel 2019. Subsequently, the data was transferred to GraphPad version 8.4.3 for further statistical analysis. A difference was deemed significant if the p-value was less than 0.05.

We initially allocated 62 patients randomly to the study (Figure 1). However, we excluded one patient from the epidural group (Group E) and one from the TAP catheter group (Group T). The reasons for exclusion were lateral extension of the surgical incision in one patient and damage to the lumbar plexus during surgery in the other. From the remaining 60 patients, ultimately, we randomized thirty patients to the epidural group (Group E) and thirty patients to the TAP group (Group T) (Figure 1).

Figure 1: Consort flow diagram for patient enrollment, allocation, and analysis.

The demographic profiles of patients in both groups were comparable. The mean age was 47.56 ± 8.67 years in the Epidural Group (Group E) and 42.24 ± 9.76 years in the TAP Catheter Group (Group T), with no significant difference (p = 0.059). Gender distribution was similar: 18 males and 12 females in Group E, and 17 males and 13 females in Group T (p = 0.793). The mean BMI was 24.45 ± 1.86 kg/m² for Group E and 24.17 ± 1.99 kg/m² for Group T (p = 0.878). ASA physical status was also comparable, with no significant differences between the groups (p = 0.774). Overall, the demographic characteristics were largely similar between the two groups.

Table 1: Showing the different demographic profiles of the patients of both groups.

Pain scores at rest: The comparison of pain scores at rest between the two study groups at different time intervals is presented in Table 2. At 8 hours postoperatively, 80% of patients in the Epidural Group (Group E) reported no pain, compared to 70% in the TAP Catheter Group (Group T), with no significant difference between the groups (p = 0.524). Mild pain was reported by 16.67% of Group E and 20% of Group T, while moderate pain was reported by 3.33% of Group E and 10% of Group T. At 16 hours, 83.34% of Group E and 73.34% of Group T reported no pain, with no significant difference (p = 0.604). Mild pain was reported by 13.33% of Group E and 23.33% of Group T, and moderate pain was reported by 3.33% in both groups. At 24 hours, a significant difference was observed, with 90% of Group E reporting no pain compared to 50% of Group

T (p = 0.002). Mild pain was reported by 6.67% of Group E and 46.67% of Group T, while moderate pain was reported by 3.33% in both groups. Similarly, at 48 hours, 86.67% of Group E reported no pain compared to 53.34% of Group T, showing a significant difference (p = 0.013). Mild pain was reported by 10% of Group E and 43.33% of Group T, and moderate pain was reported by 3.33% in both groups. Overall, the Epidural Group demonstrated significantly better pain control at rest at 24 and 48 hours compared to the TAP Catheter Group, while no significant differences were observed at 8 and 16 hours.

Table 2: Showing the comparison of pain scores at rest in both study groups

The comparison of pain scores during coughing between the Epidural Group (Group E) and the TAP Catheter Group (Group T) at different time intervals is presented in Table 3. At 8 hours postoperatively, 66.67% of patients in Group E reported no pain during coughing, compared to 36.67% in Group T, with a statistically significant difference (p = 0.006). Mild pain was reported by 26.67% of Group E and 30% of Group T, while moderate pain was reported by 3.33% of Group E and 30% of Group T. Severe pain was reported by 3.33% of patients in both groups. At 16 hours, 56.67% of Group E and 23.33% of Group T reported no pain during coughing, showing a significant difference (p = 0.012). Mild pain was reported by 36.67% of Group E and 70% of Group T, while moderate and severe pain were each reported by 3.33% of patients in both groups. At 24 hours, a highly significant difference was observed, with 50% of Group E reporting no pain during coughing compared to only 10% of Group T (p = 0.0002). Mild pain was reported by 46.67% of Group E and 66.67% of Group T, while moderate pain was reported by 23.33% of Group T and none in Group E. Severe pain was reported by 3.33% of Group E and none in Group T. At 48 hours, 73.33% of Group E and 30% of Group T reported no pain during coughing, demonstrating a highly significant difference (p = 0.001). Mild pain was reported by 23.33% of Group E and 56.67% of Group T, while moderate pain was reported by 3.33% of Group E and 13.33% of Group T. No patients in either group reported severe pain at this time point. The Epidural Group (Group E) demonstrated significantly better pain control during coughing at all time points compared to the TAP Catheter Group (Group T), as evidenced by the higher proportion of patients reporting no pain and the statistically significant p-values (p = 0.006 at 8 hours, p = 0.012 at 16 hours, p = 0.0002 at 24 hours, and p = 0.001 at 48 hours). These findings suggest that epidural analgesia provides superior pain relief during coughing in the postoperative period compared to TAP catheter analgesia.

Table 3: Showing the comparison of pain scores at coughing in both study groups

The comparison of paracetamol (PCM) consumption between the Epidural Group (Group E) and the TAP Catheter Group (Group T) is presented in Table 4. In Group E, 13.33% of patients consumed 0 grams of PCM, while no patients in Group T consumed 0 grams, showing a

statistically significant difference (p = 0.049). For 1

gram of PCM consumption, 36.67% of Group E and 40% of Group T reported usage, with no significant difference between the groups. Both groups had an equal proportion of patients (36.67%) consuming 2 grams of PCM. For 3 grams of PCM, 13.33% of Group E and 20% of Group T reported usage, while 4 grams of PCM was consumed by 3.33% of Group

T and none in Group E. Overall, the total PCM consumption was significantly lower in the Epidural Group compared to the TAP Catheter Group, as evidenced by the higher proportion of patients in Group E requiring no PCM and the statistically significant p-value (p = 0.049). This suggests that epidural analgesia may reduce the need for additional analgesic medication compared to TAP catheter analgesia.

Table 4: Showing the comparison of paracetamol consumption in both study groups

The comparison of tramadol consumption between the Epidural Group (Group E) and the TAP Catheter Group (Group T) is presented in Table 5. In Group E, 93.33% of patients consumed 0 mg of tramadol, compared to 60% in Group T, showing a statistically significant difference (p = 0.002). For 50 mg of tramadol consumption, 6.67% of Group E and 36.67% of Group T reported usage, while 100 mg of tramadol was consumed by 3.33% of Group T and none in Group E. Overall, the total tramadol consumption was significantly lower in the Epidural Group compared to the TAP Catheter Group, as evidenced by the higher proportion of patients in Group E requiring no tramadol and the statistically significant p-value (p = 0.002). This suggests that epidural analgesia may reduce the need for additional opioid medication compared to TAP catheter analgesia

Table 5: Showing the comparison of tramadol consumption in both study groups

The management of postoperative pain is a critical component of patient care, particularly following major abdominal surgeries, where inadequate analgesia can lead to significant respiratory and cardiovascular complications. As our understanding of pain pathophysiology has advanced, regional

anesthesia techniques have gained prominence for their ability to provide effective pain relief while minimizing systemic side effects. This study compared two such techniques—thoracic epidural anesthesia (TEA) and continuous transversus abdominis plane (TAP) block—in patients

undergoing right-sided gastrointestinal surgery, with a focus on pain

scores, analgesic consumption, and clinical outcomes. Epidural analgesia has long been regarded as the "gold standard" for postoperative pain management due to its ability to provide superior analgesia and attenuate neurogenic inflammation [14,15,16]. However, it is not without limitations, including hemodynamic instability, technical challenges in catheter placement, and concerns in patients on anticoagulant therapy. In contrast, TAP blocks offer a simpler alternative with fewer systemic side effects, though their efficacy in providing comprehensive pain relief, particularly for visceral pain, has been questioned [17,18]. Our study aimed to address this gap by directly comparing these two techniques in a clinical setting.

The results demonstrated that epidural analgesia provided significantly better pain control at rest and during coughing at 24 and 48 hours postoperatively compared to TAP catheter analgesia. This is consistent with previous studies highlighting the superior analgesic efficacy of epidural techniques, particularly for dynamic pain associated with movement or coughing [14,15,16]. For instance, a similar study by Mishriky et al. [19] comparing epidural analgesia with TAP blocks in patients undergoing colorectal surgery found that epidural analgesia provided better pain relief during coughing and movement, with significantly lower opioid consumption. Similarly, our findings align with those of Johns et al., who reported that epidural analgesia was associated with lower pain scores and reduced supplemental analgesic use compared to TAP blocks in patients undergoing major abdominal surgery [20]. In terms of analgesic consumption, the epidural group required significantly less paracetamol (p = 0.049) and tramadol (p = 0.002) compared to the TAP group. This reduction in supplemental analgesic use aligns with the known ability of epidural analgesia to provide more comprehensive pain relief, including visceral pain, which is often inadequately addressed by TAP blocks [17]. The higher tramadol consumption in the TAP group may reflect the limitations of this technique in managing visceral pain, as previously reported [17,18]. A study by Baeriswyl et al. also highlighted the limitations of TAP blocks in providing visceral analgesia, noting that patients receiving TAP blocks required

significantly more rescue opioids compared to those receiving epidural analgesia [21]. Despite these advantages, the TAP catheter technique demonstrated certain practical benefits, including minimal hemodynamic effects, preservation of lower limb motor and sensory function, and enhanced patient mobility due to the absence of pump attachments [18]. These characteristics make TAP blocks an attractive option for patients in whom epidural analgesia is contraindicated or technically challenging. However, the need to re-site nearly half of the TAP catheters highlights a significant limitation, potentially reducing its overall efficacy and increasing the burden on healthcare providers. This finding is consistent with a study by Niraj et al., which reported a high failure rate of TAP catheters due to inadequate coverage of lateral incisions, necessitating re-siting or supplemental analgesia [22]. The study design was influenced by ethical considerations, as many patients had significant comorbidities or cancer diagnoses, making it imperative to provide optimal analgesia. The open-label nature of the study and the lack of blinding in outcome assessments may have introduced bias, though the use of standardized pain scales and objective measures of analgesic consumption helped mitigate this limitation. Additionally, the exclusion of patients with upper midline incisions, which are not routinely performed at our center, may limit the generalizability of our findings, as the efficacy of TAP blocks is reportedly greatest for such incisions [9]. While epidural analgesia provided superior pain relief and reduced the need for supplemental analgesics, the TAP catheter technique offered a viable alternative with fewer systemic side effects and enhanced patient mobility. The re-siting of TAP catheters in nearly half of the cases underscores the need for further refinement of this technique to improve its reliability and efficacy. For patients undergoing upper abdominal surgery with incisions limited to the T10 dermatome, subcostal TAP catheters may serve as an effective alternative to epidural analgesia, particularly in settings where epidural techniques are contraindicated or unavailable [10, 23]. Future studies should explore the use of adjuncts or modifications to TAP blocks to enhance their efficacy in managing visceral pain and reduce the need for catheter re-siting.

Our study showed that epidural analgesia provided superior pain relief, particularly at 24 and 48 hours postoperatively. The epidural group demonstrated better pain control both at rest and during coughing, with lower consumption of supplemental analgesics such as paracetamol and tramadol. Despite the need to re-site nearly half of the TAP catheters, they offered prolonged analgesia comparable to epidural infusion when used effectively with oral analgesia. TAP blocks may serve as a viable alternative for postoperative analgesia in upper abdominal surgery, especially when epidural analgesia is contraindicated or unavailable or those undergoing surgeries with incisions limited to the T10 dermatome.

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