Efficacy of Dexamethasone-Enhanced Transversus Abdominis Plane Block for PostoperativePain Management in Pediatric Laparoscopic Surgeries: A Prospective Randomized Trial

Introduction

Laparoscopic appendicectomy is a major surgery in which substantial postoperative pain is anticipated. The provision of adequate analgesia results in early ambulation and reduces postoperative morbidity. A multimodal approach to postoperative analgesia after laparoscopic abdominal surgeries is often recommended.¹ The various modes of pain management include parenteral administration of opioids and non-steroidal anti-inflammatory drugs (NSAIDs), wound infiltration with local anesthetics, and regional anesthesia techniques.^2,3 However, opioid use is associated with side effects such as nausea, vomiting, and pruritus, and NSAIDs cause nausea, vomiting, and gastric irritation.⁴ Regional anesthesia techniques such as TAP blocks have emerged as an effective alternative for intraoperative and postoperative analgesia.⁵

In the transversus abdominis plane (TAP) block, a local anesthetic is deposited between the transversus abdominis and internal oblique muscle to block the anterior division of T7-L1 nerves.⁶ Ultrasound-guided imaging allows direct visualization of the muscle layers, the advancing needle, and the injected fluid. The advantages include technical simplicity, high analgesic effectiveness, opioid-sparing, long duration, and minimal side effects^.7,8

Dexamethasone is a highly selective glucocorticoid and a potent anti-inflammatory drug used as an adjuvant to local anesthetics in various nerve blocks to extend analgesic duration and reduce side effects such as postoperative nausea and vomiting.⁹ The aim is to determine the efficacy of dexamethasone as an adjuvant in an ultrasonography-guided transversus abdominis plane (TAP) block for postoperative analgesic duration in children undergoing laparoscopic abdominal surgeries.

Materials & Methods

This prospective, randomized comparative study was performed after obtaining institutional ethics clearance [CTRI/2018/03/012434] and informed consent from the parents and assent consent from the child. The study was conducted on pediatric patients undergoing laparoscopic abdominal surgeries in hospitals attached to Bangalore Medical College and Research Institute from February 2021 to August 2022. Children were divided into two groups:

• Group A: Received a TAP block with 0.5 mL/kg of 0.2% Ropivacaine under ultrasound guidance.

• Group B: Received a TAP block with 0.5 mL/kg of 0.2% Ropivacaine combined with dexamethasone (0.3 mg/kg) under ultrasound guidance.

The inclusion criteria were children aged 2 to 8 years, both genders undergoing laparoscopic abdominal surge-ries with ASA grades 1 and 2. Exclusion criteria were parents refusing to give consent, children posted for emergency procedures, children with a history of allergy to local anesthetic, children with bleeding disorders, localized infection over the injection point, and evidence of peritonitis or septicemia. The primary outcomes included the duration of postoperative pain relief and the frequency and dosage of rescue analgesia (Tramadol 1 mg/kg).

Children followed standard nil per oral instructions, received premedication with 0.5 mg/kg of midazolam syrup, and were induced with sevoflurane (6-8%) in oxygen. After securing intravenous access, general anesthesia was maintained using fentanyl (2 mcg/ kg), propofol (1.5 mg/kg) or thiopentone sodium (3-4 mg/kg), and atracurium (0.5 mg/kg) for endotracheal intubation. Mechanical ventilation was pressure-controlled, targeting an end-tidal CO₂ (ETCO₂) of 32-34 mmHg. Vital parameters such as electrocardiogram (ECG) and peripheral capillary oxygen saturation (SpO₂), ETCO₂, anesthetic gas concentration, non-invasive blood pressure (NIBP), and temperature were continuously monitored.

The ultrasound-guided TAP block was performed with the patient in the supine position. The transducer was placed over the rectus abdominis and moved laterally above the iliac crest to the lumbar triangle of Petit. A 22G short-beveled block needle was inserted in-plane using a pediatric linear array transducer probe (5-13 MHz). Before administering the local anesthetic mixture, a hypoechoic fluid pocket between the internal oblique and transversus abdominis muscle confirmed correct needle placement. After the TAP block, inhalational agents and air were discontinued. Complete recovery was assessed through clinical observation and neuromuscular monitoring, and the patient was subsequently extubated. Reversal of the neuromuscular blocking agent was done with Inj. Neostigmine 0.05 mg/ kg and Inj. Glycopyrrolate 0.008 mg/kg. After extubation on the table and the immediate postoperative period, hemodynamic parameters like heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure, and SpO₂ were recorded at 30 minutes, 60 minutes, 2 hours, 4 hours, 8 hours, 12 hours, and 24 hours. After extubation, nausea and vomiting were assessed, and pain was evaluated using the CHEOPS pain scale. Patients receive Inj. Tramadol 1mg/kg IV as rescue analgesic once the CHEOPS was more than 6.

Patients were assessed, and data was recorded as a time to first rescue analgesia as an interval between the end of block performance and the first demand by the patient for rescue analgesia. The total amount of rescue analgesia was described as the total dose of Tramadol (1mg/kg) required in 24 hours since the end of block performance. Side effects, including nausea and vomiting, were recorded. Analgesic efficacy parameters like duration of analgesia, postoperative (CHEOPS) pain score for 24 hours, the time and amount of rescue analgesia, and postoperative nausea and vomiting were used in the postoperative period, every 30 minutes for the first hour, then every hour for 4 hours, then every 2nd hour for the next 4 hours and then every 4th hour for the next 16 hours.

Sample size calculated according to the study conducted by Abdelwahab et al., the mean±SD for the time to first rescue analgesia was 13.75±3.85 and 16.6±6.02 for the group who was given dexamethasone as adjuvant and the TAP group, respectively, and the sample size was calculated as follows

Where σ = standard deviation

Zα = 1.96 for 95% confidence interval

So, the total sample size is 45 in each group.¹⁰

For statistical analysis, the data collected was entered into an Excel sheet and analyzed using SPSS version 21.0. Sociodemographic data is presented using descriptive statistics: mean, median, standard deviation, interquartile range (IOR), and percentage wherever applicable. The clinical, biochemical, and sonological parameters were evaluated using appropriate parametric and non-parametric tests. The findings were presented in tables, graphs, and figures using significant differences between variables.

Results

The demographic parameters, such as age, weight, and gender, were comparable between both groups, and there were no significant differences (Table 1). The mean CHEOPS score was comparable between Group A and Group B at baseline, 30 min, 1 hr, 2 hr, 12 hr, and 24 hr (P >0.05). The mean CHEOPS score was statistically significantly different in Group B at 4 hr, 6 hr, and 8 hr (P value 0.001). Overall, the mean CHEOPS score was high in Group A (Figure 1). The duration of analgesia was longer in Group B than in Group A, and the difference was statistically significant (P value <0.001) (Table 2). The total amount of rescue analgesia consumption was reduced in Group B than in Group A, and the difference is statistically significant (P value < 0.001) (Table 3).

There was no significant difference in heart rate between the two groups (Figure 2). There were no significant differences in systolic blood pressure, diastolic blood pressure, or mean arterial pressure (Figure 3) between the two groups. None of the patients experienced any post-operative complications such as nausea, vomiting, tingling, numbness, or throughout palpable pulses.

Discussion

Adding dexamethasone to Ropivacaine significantly prolonged postoperative analgesia and reduced the need for rescue analgesia in pediatric patients undergoing laparoscopic abdominal surgeries. This aligns with findings from Abdelwahab et al., which demonstrated that the efficacy of dexamethasone to bupivacaine in TAP blocks significantly reduced postoperative pain and analgesic requirements in children undergoing major abdominal surgery.^10,11 Our study extends these findings by showing similar benefits when using ropivacaine, a local anesthetic known for its favourable safety profile and longer duration of action than bupivacaine. Additionally, various studies have also demonstrated the efficacy of dexamethasone in enhancing postoperative pain relief when used with local anesthetics in peripheral nerve blocks and TAP blocks, respectively.^12,13,14

Dexamethasone's prolonged analgesic effect is likely due to its anti-inflammatory properties. Dexamethasone is a glucocorticoid that inhibits phospholipase A2, resulting in decreased production of inflammatory mediators such as prostaglandins and leukotrienes. This reduction in inflammation likely contributes to the prolonged analgesia observed in the dexamethasone group. Additionally, dexamethasone may directly affect peripheral nerves, enhancing the blockade of sodium channels by local anesthetics. This synergistic effect can explain the prolonged duration of sensory blockade and the delayed need for rescue analgesia.

Clinically, using dexamethasone as an adjuvant in TAP blocks has significant clinical implications. Effective pain management in pediatric patients is crucial for several reasons:

1. Enhanced recovery: Improved analgesia facilitates early ambulation, reduces the risk of postoperative complications such as atelectasis and deep vein thrombosis, and shortens hospital stays.^15,16

2. Reduced opioid consumption: By decreasing the need for rescue analgesia, dexamethasone helps minimize opioid consumption and its associated side effects, such as nausea, vomiting, and respiratory depression.

3. Patient Comfort: Lower pain scores and reduced analgesic requirements contribute to overall patient comfort and satisfaction, essential to postoperative care.¹⁷

One of our study's notable findings is the absence of significant side effects in the dexamethasone group. This is consistent with the safety profile of dexamethasone when used in adequate doses. No participants reported postoperative nausea, vomiting, or other adverse effects, underscoring the safety of this approach.

While our study provides valuable insights, it has certain limitations:

• Fixed dexamethasone dosage: We used a fixed dosage of dexamethasone, which may not be optimal for all patients. Future studies should explore dose-response relationships to identify the most effective and safe dosage.

• Single-centre study: As a single-center study, our findings may not be generalizable to all settings. Multi-center studies with large pattern sizes are needed to validate our results.

• Short follow-up period: Our follow-up period was limited to 24 hours postoperatively. More extended follow-up periods could provide more comprehensive data on the long-term effects of dexamethasone in TAP blocks.

Future researchers should be aware of the subsequent areas:

1. Optimal dosage: Determining the optimal dose of dexamethasone for different age groups and surgical procedures will help refine its use in clinical practice.

2. Combination with other adjuvants: Exploring the combined effects of dexamethasone with other adjuvants, such as clonidine or dexmedetomidine, could further enhance analgesic outcomes.

3. Long-term outcomes: It is crucial to evaluate the long-term effects of dexamethasone on postoperative recovery, including its impact on chronic pain development.

4. Mechanistic studies: Future studies are needed to elucidate the precise mechanisms by which dexamethasone enhances the efficacy of local anesthetics in TAP blocks.

Conclusion

The addition of dexamethasone to Ropivacaine in ultrasound-guided TAP blocks significantly prolongs postoperative analgesia and reduces the need for rescue analgesia in pediatric patients undergoing laparoscopic abdominal surgeries. This approach offers an effective method for improving pain management in this vulnerable population. By addressing the limitations and exploring future research directions, we can continue to optimize pain management strategies and improve outcomes for pediatric patients.

Conflicts of Interest

Nil