Comparison of Ultrasound-Guided Transversus Abdominis Plane Block and Caudal Epidural Block for Pain Relief in Children Undergoing Infraumbilical Surgeries.

Background: Caudal epidural block combined with general anesthesia remains a popular choice of anesthesia for both supraumbilical and infraumbilical surgeries. More recently transversus abdominis plane block performed under ultrasound guidance is being described as an effective technique for postoperative analgesia for lower abdominal surgeries. The present study aims to compare the efficacy of ultrasound -guided TAP block and caudal epidural for paediatric infraumbilical surgeries. Aims and
Objectives: To compare the duration and efficacy of postoperative pain relief between TAP block and caudal epidural block in children undergoing lower abdominal surgeries.
Methods: Fifty children of age group 2-7 years undergoing lower abdominal surgeries were randomized to groups T and C. All patients were given general anesthesia as per standardized anesthesia protocol. Group T were given ultrasound guided TAP block with 0.5 ml.kg-1 of 0.2% Ropivacaine. Group C were given 1 ml.kg-1 of 0.2% ropivacaine as caudal block. All the children were assessed using FLACC scale. Their vitals, pain scores, duration of postoperative analgesia and requirement of supplemental analgesics were noted.
Results: Rescue analgesic requirement was significantly less in Group T compared to Group C. Mean postoperative analgesia time was significantly more in Group T (342 mins) as compared to Group C (198 mins).
Conclusion: Ultrasound guided TAP block provides better postoperative analgesia after loer abdominal surgeries in children. Copyright:

INTRODUCTION

Pain especially in pediatric population can result in both physical and emotional effects not only on children themselves but also on their caretakers. Treating perioperative pain is therefore a primary responsibility of an anesthetist.

General anesthesia remains to be the commonly used technique in children, and regional anesthesia is used as an adjuvant for intraoperative and postoperative pain relief.[1] Although caudal epidural block is considered a safe and popular technique for both supraumbilical and infraumbilical surgeries, one of the main drawbacks is the limited duration of action.[12] More recently, transversus abdominis plane (TAP) block performed under ultrasound guidance has been described as an effective technique for postoperative analgesia after lower abdominal surgery.[34] This block includes deposition of drugs into the neurofascial plane between internal oblique and transversus abdominis to achieve a myocutaneous sensory neural blockade. Under ultrasound guidance, this block is simply performed, effectively blocking anterior rami of thoracolumbar nerves (T6-L1).[4]

Efficacy and uses of TAP block and caudal epidural have been compared and demonstrated in individual surgeries such as hernia repair and pyeloplasty.[5] However, there is a paucity of literature regarding their comparison in a wide range of infraumbilical surgeries. The present study aims to compare the efficacy of ultrasound-guided TAP block and caudal epidural for pediatric infraumbilical surgeries.

Objectives of the study

Primary objective

To compare the duration of postoperative analgesia of TAP block and caudal epidural block after lower abdominal surgeries.

Secondary objective

To compare the quality of pain relief and requirement of rescue analgesia for the first 24 h postoperatively

To compare the incidence of side effects, if any.

MATERIALS AND METHODS

This randomized trial was conducted in 50 children undergoing infraumbilical surgeries at a tertiary care center in eastern India. Fifty children satisfying the inclusion criteria were included in the study. Written informed consent was obtained from the parents or guardians of these patients. After obtaining approval from ethics committee, the study was carried out over a period of 1 year. The participants were randomly allocated into two groups Group T and Group C, having 25 participants each, using computer allocated random numbers. Randomization was done in sealed envelopes [Figure 1].

Figure 1

Consort diagram

Inclusion criteria

Children of age group 2–7 years

Weight 5–20 kg

Belonging to the American Society of Anesthesiologists (ASA) physical status classes I and II.

Exclusion criteria

Children having known allergy to the drugs used

Local infection at the site of block

Children having known contraindications to caudal block

Parents refusal for consent.

All children were kept nil per oral 8 h for milk and solids and 2 h for clear fluids. A standardized anesthesia protocol was followed. A peripheral venous cannula was inserted in the preoperative room. For children with a venous access, general anesthesia was induced with intravenous propofol (3–5 mg.kg−1) and injection fentanyl (1–2 μg.kg−1) intravenous. In participants where venous access could not be achieved, they were induced with sevoflurane 1%–5% in 100% oxygen. Further venous access was achieved and injection fentanyl (1–2 μg.kg−1) was given intravenously. Patients were connected to standard monitors such as baseline heart rate, oxygen saturation, continuous electrocardiography, and end-tidal carbon dioxide. Subsequently, anesthesia was maintained with muscle relaxants and sevoflurane after insertion of endotracheal tube.

Group T

Children were positioned in the supine position and skin disinfection was done using povidone iodine. High-frequency linear probe was connected to the ultrasound machine and the anterior abdominal wall was scanned. Sterility was maintained by covering the edge of the probe with a sterile transducer sheath and applying a sterile gel over the area to be scanned. Placing the probe transversely at the level of the umbilicus images of the rectus abdominis muscle was obtained. Then, the probe was slid laterally, toward the posterolateral part of the abdominal wall to lie between the iliac crest and subcostal margin, across the midaxillary line. After a clear view of the abdominal wall muscles, from superficial to deep, namely external oblique, internal oblique, and transversus abdominis muscle and the peritoneal cavity deeper to it, a 5 cm 23 gauge block needle with side port was introduced anteriorly under aseptic precautions, in plane to the ultrasound probe, until the tip of the needle lay in the plane between the internal oblique and transversus abdominis muscles. One milliliter of 5% dextrose was injected in the plane, to confirm the correct placement of the needle. Following negative aspiration for blood, 0.5 ml.kg−1 of 0.2% ropivacaine was given in the TAP, seen as a dark hypoechoic shadow between the two muscles, pushing the internal oblique anteriorly and transversus abdominis muscle deeper. This was done bilaterally if required, dividing the total volume equally.

Group C: Caudal epidural block

Patients were placed in the left lateral position with knees drawn up to chest. After skin preparation with betadine solution, the sacral hiatus was identified by palpating the sacral cornu with the index finger of the nondominant hand. A 23 gauge needle was inserted at 45°–60° to the skin over the sacral hiatus. After piercing the sacrococcygeal membrane, felt as a distinct pop, the needle angle was dropped to 20°–40° from the skin, and the needle was advanced to about 2–4 mm into the caudal space. The position of the needle in the caudal space was confirmed by the “whoosh test.” After careful negative aspiration for blood or cerebrospinal fluid, 1 ml.kg−1 of 0.2% ropivacaine was given in the caudal space.

The surgical procedure was started 15 min after the administration of the block, caudal, or USG-guided TAP block, according to the group to which they belonged to heart rate (HR), NIBP and SpO2 were recorded every 5 min from the beginning of the surgical procedure until the removal of the laryngeal mask airway or endotracheal tube, by a blinded investigator, who was not aware of the block given. When there was more than 20% increase in HR or mean arterial pressure despite administration of 1 minimum alveolar concentration of sevoflurane intraoperatively, the patient to be supplemented with fentanyl at a dose of 1 mcg.kg−1. Sevoflurane and nitrous oxide gas mixture were stopped at the end of the procedure, and the children were given 100% oxygen and were extubated after they regained consciousness and shifted to the recovery room. Any side effects or adverse events which occurred during the block procedure, intraoperative period, and after extubation were recorded. All children were assessed for pain using faces, legs, activity, cry, and consolability (FLACC) behavioral pain assessment score, and their vitals and pain scores were monitored during the immediate postoperative period in the recovery room, then every hour for the first 6 h and every 2 h for the next 18 h, after surgery.

Supplemental analgesics in the form of injection paracetamol 20 mg.kg−1 were given whenever the FLACC score was more than 3. However, if pain persisted, then intravenous fentanyl 1 μg.kg−1 was supplemented.

Duration of postoperative analgesia was calculated from the time of extubation till the time of the first analgesic requirement. The total dose of rescue analgesic was also noted.

Adverse effects such as nausea, vomiting, retching were also recorded in the form of yes or no format.

Pain score

Out of the various composite observational pain measurement tools for pediatric population, FLACC score is one such score to assess pain in children belonging to age group 2 months to 7 years.[6] It includes five behaviorial criteria – facial expression, crying, legs, activity state, and consolability. Each criterion is scored from 0 to 2 based on severity. Summation of scores of all five criteria leads to a total score of 0–10.

In awake patients: Patients were observed for 1–5 min. Their legs and body uncovered. Patient was repositioned and activity observed. Consoling conversations were initiated if required.

In patients who were asleep: Patients were observed for 1–5 min. Their legs and body uncovered. Patients were repositioned if possible and body assessed for tenseness and tone.

Assessment of behaviorial score:

0 = relaxed and comfortable

1–3 = mild discomfort

4–6 = moderate pain

7–10 = severe discomfort/pain.

Statistical analysis

All the collected data were entered in Microsoft Excel sheet and then transferred to as statistics has been analysed by statistician, he used SPSS Software version 22 (FUJIFILM Sonosite, Inc. Bothell. WA98021 USA). Qualitative data were presented as frequency and percentages and analyzed using Chi-square test. Quantitative data were presented as mean and standard deviation and compared by t-test. P < 0.05 was taken as level of significance.

RESULTS

As seen in Table 1, patient's age, weight, gender, and ASA ratio were considered as demographic parameters. Age and weight were analyzed by using t-test, and Chi-square test was used to analyze the gender and ASA ratio. All the study groups were comparable in terms of age, weight, gender, and ASA grade.

Table 1

Demographic profile

	Group C	Group T	P
Age (years)	5.50±1.4	5.37±1.3	0.496
Weight (kg)	16.17±6.05	15.43±5.4	0.599
Gender (male/female)	15/10	16/09	0.791
ASA (I/II)	17/8	19/6	0.584

As seen in the above table, Patient’s age, weight, gender, and ASA ratio were considered as demographic parameters. Age and weight were analyzed by using t-test and Chi-square test was used to analyze gender and ASA ratio. All the study groups were comparable in terms of age, weight, gender, and ASA grade. ASA: American Society of Anesthesiologists

As seen in Table 2, there was no significant difference between duration of surgery in both study groups.

Table 2

Duration of surgery

	Group C	Group T	P
Duration of surgery	47.15±3.4	45.98±4.7	0.781

As seen in the above table, there was no significant difference between duration of surgery in both study groups

As seen in Table 3, there was no significant difference in FLACC score in both study groups at various time intervals.

Table 3

Face, legs, activity, cry, and consolability score

FLACC score	Mean±SD		Group T
	Group C	Group T
15 min	4.2±1.0	4.3±0.9	0.895
2 h	4.4±0.4	4.5±0.7	0.720
4 h	4.7±0.2	4.8±0.5	1.000
6 h	4.4±0.6	4.5±0.6	0.810
8 h	4.3±0.7	4.4±0.5	0.699
10 h	4.4±0.5	4.6±0.6	0.785
12 h	4.3±0.5	4.5±0.4	0.782

As seen in the above table, there was no significant difference in FLACC score in both study groups at various time intervals. FLACC: Face, legs, activity, cry, and consolability SD: Standard deviation

As seen in Table 4, 76% of the patients belonging to Group T and 56% of patients belonging to Group C did not require rescue analgesia, and the difference was found to be statistically significant.

Table 4

Requirement of rescue analgesia

Requirement of rescue analgesia	Group C (%)	Group T (%)	Total (%)
Yes	11 (44)	6 (24)	17 (34)
No	14 (56)	19 (76)	37 (74)
Total	25 (100)	25 (100)	50 (100)

Chi-square test, P - 0.001, as seen in the above table, 76% of the patients belonging to Group T and 56% of patients belonging to Group C did not require rescue analgesia and the difference was found to be statistically significant

As seen in Table 5, rescue analgesia requirements were significantly higher in Group C (2.21 ± 0.2) as compared to group T (1.56 ± 0.5).

Table 5

Mean rescue analgesia requirements

	Group C	Group T	P
Mean rescue analgesia requirements	2.21±0.2	1.56±0.5	0.011

As seen in the above table, rescue analgesia requirements were significantly higher in Group C (2.21±0.2) as compared to Group T (1.56±0.5)

As seen in Table 6, mean postoperative analgesia was significantly higher in Group T (342 min) as compared to group C (198 min).

Table 6

Duration of postoperative analgesia

	Group T	Group C	P
Duration of postoperative analgesia	342 min	198 min	0.001

As seen in the above table, mean postoperative analgesia was significantly higher in Group T (342 min) as compared to Group C (198 min)

There was no significant difference in the incidence of vomiting in both study groups as seen in Table 7.

Table 7

Side effects

Side effects	Group C	Group T	P
Vomiting	3	9	0.451

As seen in the above table, there was no significant difference in the incidence of vomiting in both study group

DISCUSSION

Since the first description of caudal epidural block by Meredith Campbell in 1933, this block has emerged as a safe and reliable technique for subumbilical surgeries in pediatric surgical patients.[7] The advent of ultrasonography into anesthesia practice has influenced not only the success but also its use can decrease the complications associated with blind blocks. Ultrasonographic guidance enables precise deposition of LA drug around the targeted peripheral nerves.[8] Hence, ultrasonography-guided TAP block has emerged as the commonly used peripheral nerve block in children undergoing infraumblical surgeries.[910] Studies document a number of local anesthetics being used for both the type of blocks; ropivacaine is used in the present study due to its higher safety profile and less cardiac toxicity.[7] Dose of ropivacaine 0.2% remains in a range of 0.5–1 ml.kg−1, a lower dose has been selected as TAP block has been found to be efficacious even at these doses.[11] The present randomized controlled study was undertaken to compare the analgesic efficacy of ultrasonography-guided TAP block in children undergoing lower abdominal surgery with standard-of-care compressed earth block technique.

In the present study, demographic parameters such as patient's age, weight, gender, and ASA status were analyzed by using t-test and Chi-square test. All the study groups were comparable in terms of age, weight, gender, and ASA grade. Furthermore, no significant difference was found between duration of surgery in both study groups. Further intraoperative hemodynamic variables were similar in both the groups. This is in accordance with the study of Kumar et al. where TAP block and caudal epidural were compared to investigate postoperative analgesia in children undergoing hernia surgery.[11] No significant difference in FLACC score in both study groups at various time interval was observed. This finding is in agreement with the study of Alsadek et al. who compared pain scores in 60 pediatric patients receiving TAP block and caudal epidural analgesia using 0.25% bupivacaine.[12]

In the present study, 76% of the patients belonging to Group T and 56% of patients belonging to Group C did not require rescue analgesia in the late postoperative period (190 min). This finding coincides with the study conducted by Sethi et al., where 80 patients were enrolled to receive caudal epidural or TAP block using 0.25% bupivacaine and it was analyzed that the number of patients who did not receive any supplemental postoperative analgesia in postoperative period (362.5 min) were significantly more in the TAP group (n = 8) versus the caudal group (n = 2).[13] The study results showed that, in children, the clarity on pain profile perception following TAP block is not very clear. They also concluded that in children, it would be relevant that to access the success of TAP block under GA, the duration of postoperative analgesia needed to be observed.

In the present study, rescue analgesia requirement was significantly higher in Group C (2.21 ± 0.2) as compared to Group T (1.56 ± 0.5). Kodali et al. compared analgesic efficacy of ultrasound-guided TAP block and caudal epidural in 62 children and recorded postoperative analgesia to be better in children receiving TAP block (12.93 ± 2.91 h vs. 6.52 ± 1.67 h).[14] Robert B Bryskin et al.[15] assessed transversus plane block versus caudal block for lower abdominal surgeries in children along with multimodal analgesia for pain management and noted less total morphine requirement in patients receiving TAPB. Kumar et al. showed that postoperative analgesia was better in TAP block as compared to caudal epidural using 0.2% ropivacaine for unilateral hernia surgeries.[11] Ahmed et al. showed that patients who received TAB block required less postoperative rescue analgesia with a better impact on pain scores than caudal block.[5]

In the present study, mean postoperative analgesic time was significantly higher in Group T (342 min) as compared to Group C (198 min). Kodali et al. have explained this difference in duration of postoperative analgesia attributable to increased vascularity of caudal space leading to faster clearance of the drug compared to TAP block where the drug spreads along a neurofascial plane.[14] Elbahrawy and El-Deeb reported a duration of 306 ± 18 min in children receiving tap block versus 259 ± 22.4 min in children receiving caudal analgesia for unilateral lower abdominal surgeries.[16] In children, the studies on the duration of postoperative analgesia with TAP block have shown to vary from 50 min in laparoscopic appendicectomy to 17 h in inguinal hernia repair.[910] The inconsistency in duration of analgesia can be due to the lack of agreement in the pain assessment scales in different studies and also to the variability in the systemic opioid/nonopioid analgesia used during the intraoperative and postoperative period.[910]

Regarding side effects, there was no any history of urinary retention, infection at the site of injection, or itching. Only side effect in our study is nausea and vomiting. There is no significant difference in the incidence of vomiting in both study group (Group C: n = 3, Group T, n = 9). This finding was in agreement with the study conducted by Sethi et al. in which there was no difference in the incidence of postoperative nausea-vomiting between the groups (Group C: n = 4, 11.1% vs. Group T: n = 7, 20.6%; P = 0.276).[13] Overall, ultrasound-guided TAP block was superior to caudal epidural which was also assessed by Elbahrawy and El-Deeb who noted that the patients given TAP block 0.1 ml.kg−1 of 0.25% ropivacaine were more satisfied than patients given caudal epidural block.[16] Singh et al. also noted higher satisfaction scores in patients receiving TAP block compared to caudal epidural in their study of 60 children undergoing lower abdominal surgeries. They also concluded that ultrasound guidance leads to better performance of block leading to higher overall success.[17]

Limitations of the study

A larger study sample size would have reflected authenticity of the study result. Furthermore, as a wide variety of surgeries were covered hence tissue handling also varied thus influencing pain scores.

CONCLUSION

We conclude that ultrasound-guided TAP block provides better postoperative analgesia after lower abdominal surgeries in children. There is reduced requirement of systemic analgesics including opioids in the postoperative period leading to enhanced recovery. Hence, ultrasound-guided TAP block should be considered as an effective and better alternative to the more frequently administered caudal epidural block for postoperative analgesia.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.