Comparison of Analgesic Efficacy of Ultrasound-Guided Transversus Abdominus Plane Block and Caudal Block for Inguinal Hernia Repair in Pediatric Population: A Single-Blinded, Randomized Controlled Study.

BACKGROUND: Caudal analgesia was a widely practiced regional anesthesia technique in pediatric population. Transversus abdominus plane block (TAP) block has recently emerged as a promising analgesic method in pediatric lower abdominal surgeries. AIM: This study aimed to compare the analgesic efficacy of ultrasound-guided TAP block and caudal block.
SETTING: This study was conducted in the department of anesthesiology of a tertiary care teaching hospital.
DESIGN: This was a prospective, single-blinded, randomized controlled study.
MATERIALS AND METHODS: Sixty-two children of American Society of Anesthesiologists Class I and II undergoing inguinal hernia repair received TAP block at a dose of 0.5 ml.kg- 1 of 0.25% bupivacaine (Group A) or caudal block at a dose of 1 ml.kg- 1 of 0.25% bupivacaine (Group B) after randomization. The children were analyzed by comparing the post operative pain scores and duration of analgesia. Statistical analysis was done with IBM SPSS software 23 version. Unpaired sample t-test and Mann-Whitney U-test were used to compare the means of continuous variables. Fisher's exact test/Chi-square test was used to find the association between categorical variables.
RESULTS: Both groups were comparable in terms of age, gender, weight, and surgery duration. Duration of analgesia was longer in TAP block group compared to that of caudal analgesia (12.93 ± 2.91 h vs. 6.52 ± 1.67 P < 0.001). The postoperative pain scores were comparable up to 6 h and at 24 h. Pain scores at 12 h and 18 h were significantly higher in caudal analgesia group compared to that of TAP block group.
CONCLUSION: Children who received TAP block had prolonged duration of analgesia and lower pain scores compared to those who received caudal analgesia. Copyright:

INTRODUCTION

Regional anesthetic techniques combined with general anesthesia decrease the requirement of inhalational anesthetics and opioids and attenuate the stress response to surgery. Regional anesthesia in combination with general anesthesia facilitates smooth recovery and provides good immediate postoperative analgesia with less systemic analgesic requirements.[1] Caudal analgesia is safe, reliable, and effective for intraoperative and postoperative analgesia in pediatric lower abdominal surgeries, especially when combined with general anesthesia.[2] Caudal analgesia can have a risk of 0.07% complications such as dural puncture, intraosseous injection, hematoma formation, local anesthetic systemic toxicity, subcutaneous swelling, and urinary retention.[3] Transversus abdominus plane (TAP) block provides effective intraoperative and postoperative analgesia for lower abdominal surgeries.[4] Ultrasound guidance (US guidance) allows real-time visualization of anatomical structures and spread of the injected local anesthetics in TAP block. TAP block was more useful than caudal analgesia in children with vertebral anomalies, older pediatric patients weighing >25 kg, and children with intracranial anomalies.[5] With TAP block, complications such as dural puncture and urinary retention can be avoided, but the incidence of other rare complications such as injury to bowel, peritoneum, and vascular aspirations can occur.[67] Although few studies were available on the comparison of caudal analgesia and TAP block in pediatric population with different combinations of local anesthetic concentrations, comparative studies between both groups were limited in our South Indian population.[48910] The primary aim of this study was to compare the analgesic efficacy of US-guided TAP block and conventional caudal block for inguinal hernia repair. The primary outcomes assessed were postoperative pain score and duration of analgesia. The secondary outcomes assessed were frequency and dose of rescue analgesia needed along with time to first rescue analgesia.

MATERIALS AND METHODS

Setting

This study was conducted in the department of anesthesiology of a tertiary care teaching hospital in South India. This study was approved by the institutional ethics committee (CSP/MED/17/JAN/33/25), and it was conducted from February 2017 to August 2019.

Design

A prospective, single-blinded, randomized controlled trial (RCT) was done to assess the analgesic efficacy of US-guided TAP block and caudal block for inguinal hernia repair in pediatric population.

Recruitment of subjects

All consecutive children aged between 6 months and 8 years with American Society of Anesthesiologists (ASA) category I and II and underwent inguinal hernia repair were included in the study after obtaining written informed consent from their parents/guardians. Children with ASA III, IV, and V; infection at the site of caudal injection, any anatomical abnormalities precluding safe placement of TAP block and caudal block, bleeding diathesis, allergy to local anesthetics, emergency surgeries, prior neurological or spinal disorders, and failed regional blocks were excluded from the study. The study children were adequately fasted and premedicated with oral midazolam 0.5 mg.kg−1 20 min before the procedure. All children were monitored with a pulse oximeter in the preoperative holding area.[11] Randomization was done by computer-generated block randomization into two groups: Group A (US-guided TAP block) and Group B (conventional caudal block) [Figure 1]. Parents/guardians of the children were blinded to the mode of block received. The study participants were monitored with routine preinduction monitors (noninvasive blood pressure, electrocardiography, oxygen saturation, and end-tidal carbon dioxide). Baseline values were recorded and documented. The children were anesthetized by inhalational induction with 6%–8% sevoflurane. An intravenous line was secured, and sevoflurane concentration was reduced to 1%–2%. Intravenous fentanyl 2 μg.kg−1 and atracurium 0.5 mg.kg−1 were given. All children were intubated with appropriate endotracheal tube. Anesthesia was maintained with 33% oxygen, 67% air, and sevoflurane 1%–2% mixture with closed circle system. Based on randomization, the patients received either US-guided TAP block or conventional caudal block. Both caudal block and TAP blocks were given by two senior anesthesiologists who had experience of >10 years in both conventional and US-guided blocks in pediatric population. Under strict aseptic precautions, Group A children's abdominal wall was painted and draped. US-guided TAP block was given using a high-frequency linear transducer probe 13-6 MHz (SonoSite, Inc., Bothell, WA 98021, USA) which was covered with a sterile drape sheet and the transducer area was covered with 3M Tegaderm adhesive used for dressing. An US probe was placed in a transverse plane to the lateral abdominal wall in the mid-axillary line between the lower costal margin and the iliac crest. The 20 g jelco needle (smith medical) was introduced in the plane along the US probe and 0.5 ml.kg−1 of 0.25% bupivacaine was injected between the internal oblique and transversus abdominus muscles. Under strict aseptic precautions, Group B patients received a conventional caudal block. Sacral cornua and sacral hiatus were palpated over the skin. 20–22G jelco needle was inserted at 60°–80° angle with the skin surface and was advanced until the sacrococcygeal ligament was passed with a “pop” by the “standard loss of resistance” technique for identification of the caudal space. Then, the angle was reduced by 20°–30°, the needle was advanced further by 2–3 mm in the sacral canal and after negative aspiration of blood or cerebrospinal fluid, 1 ml.kg−1 of 0.25% bupivacaine was injected in the sacral canal. Surgical incision was started 15 min after the placement of blocks. During surgical incision, regional blocks were considered to be failed if there is an increase in heart rate or mean arterial pressure or both >15% of baseline after induction. Patients with failed blocks were excluded from the study. Intraoperative monitoring included heart rate, systolic blood pressure, diastolic blood pressure, oxygen saturation, and capnography. All patients were monitored before induction and every 15 min during the procedure till the end of the procedure. Duration of the surgery was noted in both groups. In all children, the neuromuscular blockade was reversed with intravenous neostigmine 0.05 mg.kg − 1 and glycopyrrolate 0.01 mg.kg − 1 at the end of procedure. All children were shifted to the postanesthesia care unit (PACU). Pain scores were assessed as a primary outcome. The pain scores were assessed at 30 min and 1 h after shifting to the PACU. The pain scores were also assessed at 6 h, 12 h, 18 h, and 24 h in the postoperative ward. All pain scores were assessed by the assigned anesthesiologists in the PACU and by the ward staff in the concerned ward using Face, leg, activity, cry, consolability scale scale. If the pain score was >4, intravenous paracetamol was given at a dose of 7.5 mg.kg−1 for children weighing <10 kg and 15 mg.kg−1 for children weighing >10 kg. Duration of analgesia was also assessed as a primary outcome. Duration of analgesia was defined as time from the administration of caudal block or TAP block to pain score >4. The total number of times rescue analgesic used and time to 1st rescue analgesic dose and total paracetamol consumption were measured as the secondary outcome. Any complications secondary to block were noted in both groups.

Figure 1

Consort diagram

The sample size calculated was 62.31 in each group which was based on the primary outcome of pain scores in a previous study[8] with effect size of 0.16, α error of 5%, and power of 90%.

Statistical analysis was done with International Business Machines Corporation statistical package for social sciences 23 version, New York, USA. To describe about the data, descriptive statistics, frequency analysis, and percentage analysis were used for categorical variables and mean and standard deviation were used for continuous bivariate samples in independent groups. To find significance in categorical data, Fisher's exact test/Chi-square test was used. For continuous variables, the unpaired sample t-test was used and Mann–Whitney U-test was used to compare nonnormally distributed parameters. Shapiro–Wilk test was used for measuring normality. Hemodynamic variables such as heart rate, systolic blood pressure, and diastolic blood pressure were analyzed by repeated-measures analysis of variance. In the above statistical tools, the probability value (P value) < 0.05 was considered statistically significant.

RESULTS

There was no statistically significant difference in age, gender, weight, ASA status, and intraoperative fentanyl usage and surgery duration between the two groups [Table 1]. The mean duration of analgesia in TAP block was 12.93 ± 2.91 h, which was significantly longer when compared to caudal analgesia (6.52 ± 1.67 h) with a P < 0.001 [Figure 2]. The mean number of rescue analgesic doses in TAP block group (0.77) was statistically significantly lesser when compared to that of caudal analgesia group of 1.55 with a P < 0.001 [Table 2]. Seven children in the TAP block group did not require rescue analgesic dose. Twenty-four children in the TAP block group and 14 children in the caudal group received single-dose rescue analgesic during the study period. Seventeen children in the caudal group received two doses of rescue analgesic drug during the study period [Figure 3].

Table 1

Demographic characteristics

	Group A	Group B	df	95% confidence interval of difference		P
				Lower	Upper
Age (in years)
Mean±SD	3.74±2.04	3.94±2.22	60	−1.27	0.89	0.77
Median	4	4
IQR (25, 75)	2, 5	2, 6
Gender (male:female), n (%)	28:3 (90.3:9.7)	29:2 (93.5:6.5)				1.00
Surgery duration in minutes (mean±SD)	33.20±4.95	32.90±6.94	60	−2.76	3.36	0.84
Weight in kilogram (mean±SD)	13.45±4.19	14.16±4.10	60	−2.81	1.39	0.52
ASA status (ASA1:ASA2)	21:10	20:11				0.78
Total intraoperative fentanyl consumption (µg), (mean±SD)	29.29±8.29	29.52±9.51	60	−4.76	4.30	0.92

P<0.05 significant. SD=Standard deviation, df=degree of freedom, IQR=Interquartile range from 25th to 75th percentiles, ASA=American Society of Anesthesiologists

Figure 2

Duration of analgesia comparison between both groups

Table 2

Duration of analgesia and number of rescue analgesic doses and paracetamol consumption comparison between both groups

	Group A	Group B	df	95% confidence interval of difference		P
				Lower	Upper
Duration of analgesia in hours (mean±SD)	12.93±2.91	6.52±1.67	60	5.20	7.61	<0.001**
Mean number of rescue analgesic requirement	0.77±0.42	1.55±0.50	58	−1.01	−0.53	<0.001**
Time to first rescue analgesia	10.52±1.57	5.85±1.82	60	3.80	5.53	<0.001**
Postoperative paracetamol consumption
Mean±SD	142.58±105.57	307.74±143.72	60	−229.22	−101.09	<0.001**
Median	150	300
IQR (25, 75)	(50,230)x	(190,400)

Values are in mean±SD. **Signifies P<0.001. SD=Standard deviation, df=degree of freedom, IQR=Interquartile range

Figure 3

Number of rescue analgesic dose comparison between both groups

Pain scores at 30 min, 1 h in PACU, and 6 h and 24 h after shifting to the ward were comparable, but pain scores at 12 h and 18 h were significantly higher in caudal analgesia group compared to that of TAP block group [Table 3]. Time to 1st rescue analgesic dose was also statistically significantly longer in the TAP block group (10.52 vs. 5.83 h, P < 0.001). Total amount of paracetamol consumption in the postoperative period was also statistically significantly lower in the TAP block group when compared to that of the caudal analgesia group (142.58 mg ± 105.57 vs. 307.74 mg ± 143.72, P < 0.001). We observed statistically significant difference in heart rates (P < 0.001), systolic blood pressures (P < 0.001), and diastolic blood pressures (P < 0.001) within the groups and between the groups from baseline to 24 h in the ward [Tables 4-6].

Table 3

Mean pain score comparison in the postanesthesia care unit every 30-min interval and in ward every 6 h interval up to 24 h

Pain score comparison	Group A	Group B	P
At 30 min in the PACU
Mean±SD	1.45±0.88	1.68±0.79	0.28
Median	1	2
IQR (25, 75) percentile	(1,2)	(1,2)
At 1 h in the PACU
Mean±SD	1.54±0.52	1.35±0.76	0.29
Median	2	1
IQR (25, 75) percentile	(1,2)	(1,2)
At 6 h after shifting to the ward
Mean±SD	1.48±1.02	2.06±1.28	0.22
Median	2	2
IQR (25, 75) percentile	(0,2)	(1,2)
At 12 h after shifting to the ward
Mean±SD	1.65±1.51	3.10±1.81	0.002*
Median	2	3
IQR (25, 75) percentile	(0,3)	(2,5)
At 18 h after shifting to the ward
Mean±SD	3.03±1.76	4.29±1.34	0.003*
Median	4	5
IQR (25, 75) percentile	(1,5)	(4,5)
At 24 h after shifting to the ward
Mean±SD	1.35±1.42	1.10±1.30	0.50
Median	1	1
IQR (25, 75) percentile	(0,2)	(0,2)

*Signifies P<0.05. Values are in mean pain score±SD, median, IQR. IQR=Interquartile range, SD=Standard deviation

Table 4

Heart rate comparison at various time intervals

Heart rate (mean±SD)	Group A	Group B	df	F	P within the groups	P between the groups
Baseline after induction	100.00±11.30	101.29±12.34	4.04	17.54	<0.001**	<0.001**
5 min after block	97.42±10.05	100.23±11.03
15 min after block	91.68±7.88	92.94±7.83
30 min after block	87.06±6.63	88.81±7.04
45 min after block	84.29±5.99	87.43±3.54
At 30 min after shifting to the PACU	99.94±8.63	100.06±9.23
1 h after shifting to the PACU	89.35±4.77	90.23±6.47
6 h after shifting to the ward	91.55±7.67	93.68±7.64
12 h after shifting to the ward	86.68±5.17	92.81±9.68
18 h after shifting to the ward	88.29±6.52	98.52±11.09
24 h after shifting to the ward	98.97±14.27	103.68±11.19

**Signifies P<0.001. Repeated-measures ANOVA was used. df=degree of freedom, PACU=Postanesthesia care unit, SD=Standard deviation

Table 6

Diastolic blood pressure comparison at various time intervals

DBP	Group A	Group B	df	F	P within the groups	P between the groups
DBP baseline after induction	48.19±6.45	50.71±5.70	5.16	12.60	<0.001**	<0.001**
DBP 5 min after block	46.39±6.17	46.35±7.03
DBP 15 min after block	41.55±5.39	41.74±4.98
DBP 30 min after block	39.90±5.14	40.48±3.94
DBP 45 min after block	39.86±5.48	41.50±5.01
DBP in PACU at 30 min	49.13±3.47	48.87±3.93
DBP in PACU at 1 h	45.03±3.36	46.00±3.20
DBP 6 h after shifting to the ward	44.19±3.57	45.16±4.27
DBP 12 h after shifting to the ward	42.97±2.98	46.61±4.36
DBP 18 h after shifting to the ward	46.03±4.14	48.16±3.89
DBP 24 h after shifting to the ward	43.55±3.81	44.10±3.31

*Signifies P<0.05, **Signifies P<0.001. Repeated-measures ANOVA was used. df=degree of freedom, DBP=Diastolic blood pressure, PACU=Postanesthesia care unit

DISCUSSION

In the present study, both groups were comparable in terms of age, gender, weight, surgery duration, ASA status, and intraoperative fentanyl consumption. In this study, the mean pain scores were comparable at 30 min and 1 h in the PACU. The mean pain scores at 12 h and 18 h were significantly higher in the conventional caudal analgesia group compared to that of the TAP block group [Figure 4]. The mean pain scores at 12 h and 18 h were significantly higher in the conventional caudal analgesia group compared to that of the TAP block group. Duration of analgesia was longer in the TAP block group compared to that of the caudal group. The total number and dose of rescue analgesic doses were also lower in the TAP block group compared to those of the caudal group. Time to rescue analgesic dose was significantly longer in the TAP block group compared to that of the caudal group. We did not observe any complications in both groups. These results were comparable to those of a study done by Dalia M. El Fawy et al., in which TAP block pain scores were comparatively lower than that of caudal analgesia at 2, 4, 6, 8, 10, 12, 16, 18, 20, and 24 h postoperatively.[12] A study done by Aveline et al. also showed that the median visual analog scale (VAS) pain scores were significantly lower in US-guided TAP block at 4, 12, and 24 h compared to that of ilioinguinal/iliohypogastric nerve blocks.[13] Kendigelen et al. also showed that the postoperative VAS pain scores at 5 min, 1 h, 2 h, 6 h, 12 h, and 24 h were significantly lower compared to those of the infiltration group.[14] Alsadek et al. also showed significant difference in the postoperative pain score after 6 h between TAP block group and caudal group, and the number of rescue analgesic doses was also significantly lower in the TAP block group compared to that of the caudal group.[10] Another RCT by Petersen et al. showed that US-guided TAP block did not reduce postoperative pain scores compared to that of infiltration group in adult population aged from 18 to 75 years; this was explained by the use of combination of ilioinguinal/iliohypogastric nerve blocks with local infiltration.[15] Hamill et al. in their systematic review mentioned about reduction in pain scores and opiate consumption in abdominal wall blocks.[16] In a study by Kanojia and Ahuja, the postoperative pain scores after 4 h in the caudal group were more higher than that of TAP block group and duration of analgesia was significantly longer in the TAP block group (7.41 ± 0.78) compared to that of caudal group (5.07 ± 0.69).[17]

Figure 4

Pain score comparison between both groups

In contrast to our study, Elbahrawy and El-Deeb showed that both caudal and TAP block groups had comparable pain scores, but TAP block group had earlier discharge compared to that of caudal analgesia group.[4] In this study, duration of analgesia was significantly longer in the TAP block group compared to that of the conventional caudal analgesia group. The total number of times rescue analgesic required was significantly lower in the TAP block group compared to that of the conventional caudal analgesia group [Table 2]. In contrast to our results, a study done by Sethi et al. showed that duration of analgesia was longer in caudal epidural blockade than that of TAP block, and there was no difference in rescue analgesic requirement in both groups.[9] A study done by Sahin et al. showed that US-guided TAP block with high volume of (0.5–1 mL kg− 1) 0.25% levobupivacaine provided prolonged postoperative analgesia and reduced analgesic use without any clinical side effects after unilateral hernia repair in children.[18] Tobias evaluated the efficacy of TAP block in pediatric patients undergoing lower abdominal surgeries and reported that 80% had prolonged duration of analgesia lasting for 7–11 h, which was consistent with our study.[19] Sophia et al. also reported that TAP block was more efficacious than systemic analgesia and the time required for 1st dose rescue analgesic was 8.5–9 h in the postoperative period.[20] The prolonged duration of action in the TAP block when compared to that of the caudal block may be due to less vascularity of the transverse abdominus plane and local anesthetic deposited in the TAP block which spreads on the narrow fascial planes between the internal oblique and transverse abdominus planes. Caudal epidural space is relatively more vascular than the site of TAP block, which could have resulted in higher systemic absorption, faster clearance and lesser duration of analgesia in caudal anesthesia compared to TAP block. In a study by Bryskin et al., TAP block required lesser morphine than the caudal group (0.05 mg kg−1 ± 0.06 vs. 0.09 mg kg−1 ± 0.07, P = 0.03).[8] Similarly, in our study, postoperative rescue analgesic paracetamol consumption was significantly lower in the TAP block group. In contrast to the study by Alsadek et al., we observed significant hemodynamic changes during the study period.

Surgeon not being standardized was the limitation of the study. Moreover, the amount of tissue handling and experience varied between the surgeons. Anesthesiologists giving block were not blinded during the procedure.

In future, more studies should come on the comparison of TAP block with quadratus lumborum blocks or other truncal blocks.

CONCLUSION

In children undergoing inguinal hernia repair, TAP block provides superior analgesia compared to caudal analgesia as evidenced by lower postoperative pain scores. Duration of analgesia was longer in the TAP block, and number of required doses of rescue analgesics was lower in the TAP block group when compared to that of caudal group.

Financial support and sponsorship

This study was financially supported by the Department of Anaesthesiology, SRIHER, Porur, Chennai.

Conflicts of interest

There are no conflicts of interest.

Table 5

Systolic blood pressure comparison at various time intervals

SBP	Group A	Group B	df	F	P within the groups	P between the groups
SBP at baseline after induction	90.65±5.39	90.68±5.41	4.07	14.31	<0.001**	<0.001**
SBP 5 min after block	88.00±4.85	88.71±5.24
SBP 15 min after block	84.65±4.22	84.90±4.49
SBP 30 min after block	84.19±4.10	83.48±4.44
SBP 45 min after block	80.79±3.53	84.33±5.35
SBP in PACU at 30 min	90.52±3.46	90.10±3.93
SBP in PACU after 1 h	85.58±3.41	85.16±3.12
SBP 6 h after shifting to the ward	83.65±3.53	85.52±4.20
SBP 12 h after shifting to the ward	83.26±3.86	88.23±5.56
SBP 18 h after shifting to the ward	86.45±4.89	88.58±4.14
SBP 24 h after shifting to the ward	85.16±4.13	86.39±4.05

*Signifies P<0.05, **Signifies P<0.001. Repeated-measures ANOVA was used. df=degree of freedom, PACU=Postanesthesia care unit, SBP=Systolic blood pressure