Is Ultrasound-Guided Transversus Abdominis Plane Block Superior to a Caudal Epidural or Wound Infiltration for Intraoperative and Postoperative Analgesia in Children Undergoing Unilateral Infraumbilical Surgery? A Double-blind Randomized Trial.

Background and Aim: Caudal block (CB) is the standard of care in pediatric surgeries. Ultrasound (USG) transversus abdominis plane (TAP) block has also been used as an effective regional anesthesia technique. We compared the duration of postoperative and intraoperative analgesia between TAP block, CB, and local wound infiltration (LI) in children undergoing unilateral infraumbilical abdominal surgery. Materials and
Methods: One hundred and twenty children, 3-10 years old and American Society of Anesthesiologists Grade I and II, undergoing elective unilateral infraumbilical abdominal surgery were allocated to three groups. Group TAP: USG-guided TAP block with 0.5 ml/kg of 0.25% bupivacaine; Group CB: CB with 0.75 ml/kg of 0.25% bupivacaine; and Group LI: Local wound infiltration along the incision with 0.5 ml/kg of 0.25% bupivacaine. The primary outcome was the efficacy of postoperative analgesia using modified objective pain score (MOPS), and the secondary outcome was to determine intraoperative analgesia with fentanyl requirement and minimum alveolar concentration (MAC) hour of isoflurane among the three groups.
Results: The MOPS was statistically better in Group TAP compared to group CB and group LI at 8 and 24 h postoperatively. The mean ± standard deviation duration of postoperative analgesia in groups CB, LI, and TAP was 6.84 ± 0.47, 2.3 ± 1.26, and 9.78 ± 1.02 h, respectively. The intraoperative requirement of fentanyl and MAC hour was least in Group CB.
Conclusion: We found that USG-guided TAP block is a good alternative, with longer and effective postoperative analgesia compared to CB. However, the quality of intraoperative analgesia was best in group CB. Local infiltration was a poor alternative. Copyright:

INTRODUCTION

In pediatric anesthesia, good and long-lasting analgesia is necessary during perioperative period for pain-free children and satisfied parents.[1] A central neuraxial block like the caudal epidural block (CB) is the gold standard for abdominal and lower limb surgery in children.[2] Epidural block may be contraindicated; for instance in sepsis, coagulation abnormalities, and spinal deformities. In such situations, the surgeon often infiltrates the wound with local anesthetic as a simple alternative.

In recent years, there has been a shift from neuraxial to peripheral nerve blocks due to their better safety profile, especially in children.[3] One such peripheral block, transversus abdominis plane (TAP) block, provides good analgesia to the parietal peritoneum, skin, and muscle of the anterior abdomen wall, which works well when postoperative pain is mainly somatic.[4] With the advent of ultrasound (USG)-guided technique, TAP block has increased in popularity, due to its improved success rate, as drug is delivered under direct visualization.

We planned to compare the efficacy and duration of postoperative analgesia between the three study groups, for example, CB, LI, TAP in children undergoing unilateral infraumbilical abdominal surgery, using the modified objective pain score (MOPS), time to first rescue analgesia and total analgesic requirement in 24 h. For intraoperative analgesia, we noted the total fentanyl requirement and minimum alveolar concentration (MAC) hour of isoflurane during surgery.

MATERIALS AND METHODS

This was a prospective, randomized, double-blind (observer-blinded) study conducted in a tertiary care hospital from 2013 to 2016 after approval from the Institutional Ethics Committee (IEC/VMMC/SJH/Thesis/Nov-13/11). The trial was registered with the Clinical Trials Registry India (CTRI/2014/09/005023). Written informed parental consent was taken for all patients. One hundred and twenty American Society of Anesthesiologists physical status I/II, children aged 3–10 years, weighing <20 kg scheduled for unilateral infraumbilical abdominal surgery were randomized using a computer-generated random number chart and allocated by sealed envelope technique to receive one of three blocks. Children whose parents did not consent, those who had blood coagulopathies, local infection, bilateral lower abdominal surgery were excluded from the study.

The interventions were divided into three groups:

Group CB: Received caudal block with 0.25% bupivacaine in a dose of 0.75 ml/kg body weight

Group LI: Received local wound infiltration with 0.25% bupivacaine in the line of incision by the surgeon to a maximum of 0.5 ml/kg body weight

Group TAP: Received USG TAP block with 0.25% bupivacaine in a dose of 0.5 ml/kg body weight.

All patients underwent a preanesthetic check-up. A local anesthetic cream was applied to the area 30 min prior to surgery. Oral midazolam 0.5 mg/kg body weight was given as premedication. Vitals and oxygen saturation were monitored preoperatively. An intravenous line was secured.

In the operation theatre, the electrocardiogram, pulse oximetry (sPO2), and noninvasive blood pressure (NIBP) were monitored, and the baseline values were recorded. The patients were induced intravenously with injection fentanyl (2 ug/kg body weight) followed by injection propofol (2–3 mg/kg body weight). The airway was secured with an appropriate size Proseal laryngeal mask airway. Correct placement was confirmed, and anesthesia was maintained on isoflurane in N2O/O2 in 3:2 ratio on spontaneous respiration. Intraoperatively, a balanced salt solution (Ringer Lactate) was given at 15 ml/kg body weight/hour. Group TAP patients were placed, supine, and abdominal skin preparation was done. A 5–10 MHz USG linear probe, covered with a sterile plastic cover, was placed in the horizontal plane just below the umbilicus to identify the posterior rectus sheath and the rectus abdominis muscle. As the probe was moved laterally, a distinct plane between external oblique, internal oblique, and transversus abdominis muscle was seen. A 50 mm, 22G blunt needle was inserted in an in-plane approach close to the anterior axillary line and positioned in the fascial plane between the internal oblique and transversus abdominis. After negative aspiration, the predetermined dose of local anesthetic was injected. An oval spread in the fascial plane between internal oblique and transversus abdominis confirmed correct placement [Figure 1].[5] In Group CB, patients were placed in the lateral position with one or both hips flexed, and the sacral hiatus was palpated. After sterile preparation, a needle (22G) was advanced at 60° angle cephalad until a pop was felt as the needle pierced the sacrococcygeal ligament and then advanced 2 mm. The needle position was confirmed by the whoosh test. Aspiration for blood and cerebrospinal fluid was done to rule out intravascular or intrathecal placement and if negative the calculated amount of the local anesthetic drug was injected slowly in small aliquots with repeated negative aspiration.[6]

Figure 1

Image of the abdominal wall showing the plane of infiltration of the local anesthetic external oblique, internal oblique, transversus abdominis with local anesthetic deposition in the transversus abdominis plane

In Group LI, at the start of surgery, the surgeon infiltrated the line of incision in layers with bupivacaine 0.25% up to a maximum of 0.5 ml/kg body weight. Before handing over the patient to the surgeon, a rectal suppository of acetaminophen 20–25 mg/kg body weight was administered in all three groups. The surgical incision commenced 5 min after the block.

Intraoperatively, heart rate, NIBP, SPO2, and end-tidal CO2 were recorded throughout the surgery at fixed intervals. If there was an increase in heart rate or blood pressure by 25% at the time of skin incision, additional fentanyl 1 ug/kg was given. At the end of the surgery, MAC hour and the total amount of fentanyl per kg body weight were calculated. The patient was transferred to the postanesthesia care unit (recovery room) for further monitoring.

During the postoperative period, the vital signs were monitored (heart rate, blood pressure, and saturation), and assessment of pain was done using MOPS (crying, movement, agitation, posture, verbal and each criterion had a score of 0, 1, 2 at 0 h, 1 h, 2 h, 4 h, 8 h, 12 h, and 24 h, respectively). Rescue analgesia (syrup paracetamol 15 mg/kg body weight or injection paracetamol 10 mg/kg body weight) was given at a score of 4. Time to first rescue analgesia and the total dose of paracetamol used in the first 24 h postoperatively was noted.

The sample size was calculated to detect a mean difference in efficacy and duration of analgesia among the three groups. To detect the difference with 95% confidence level and 80% power, we enrolled 40 patients in each group.

The data were recorded in a predesigned pro forma and managed using a Microsoft Excel spreadsheet. For quantitative variables, the data were presented in terms of range (minimum, maximum), mean and standard deviation or median (Q1, Q2). Qualitative variables were summarized as frequency (%). The statistical significance of quantitative variables in the three groups was done using ANOVA for normally distributed data and the Kruskal–Wallis test for data that were not normally distributed. The Chi-square/Fisher's exact test was used to compare the frequency of qualitative variables among the groups. A P ≤ 0.05 was considered statistically significant. SPSS 21.0 statistical software version (IBM, Chicago, Illinois, USA) was used for data analysis.

RESULTS

One hundred and twenty patients (40 per group), undergoing elective unilateral infraumbilical surgery were included in the study [Figure 2]. Age, weight, gender and type of surgery were comparable across the three groups with no significant difference [Table 1].

Figure 2

Consort flow chart

Table 1

Demographic parameters

Parameter	Group CB	Group LI	Group TAP	P
Age (years)*	6.18±2.17	6.28±2.42	6.19±2.03	0.98
Weight (kg)*	14.54±3.25	15.4±3.12	16.05±2.35	0.07
Sex: Male/female	37/3	38/2	38/2	0.86
Procedure: Herniotomy/orchidopexy	27/3	31/9	28/12	0.58

*Values are mean±SD. SD: Standard deviation, CB: Caudal block

The total amount of fentanyl/kg body weight used intraoperatively was different in all groups and was found to be statistically significant between CB and LI, CB and TAP [Table 2].

Table 2

Intraoperative use of total fentanyl/kg body weight

Group	Intraoperative total fentanyl/kg body weight (mean±SD)	P
CB	2.05±0.22	0.02 (Group CB vs. TAP)
LI	2.28±0.45	0.0067 (Group CB vs. LI)
TAP	2.22±0.42	0.6 (Group TAP vs. LI)

SD: Standard deviation, CB: Caudal block, LI: Local wound infiltration, TAP: Transversus abdominis plane

Variations were observed intraoperatively in MAC hour and duration of anesthesia (minutes) in all three groups. Mean values of MAC hour were noted, which was statistically significant between groups CB and TAP and groups CB and LI. The difference in the mean duration of anesthesia was statistically significant among all three groups [Table 3].

Table 3

Intraoperative variation of minimum alveolar concentration and duration of anesthesia (min)

Group	Duration of anaesthesia (min)*	MAC hours	P
CB	50.95±5.67	0.8±0.07	Group CB versus TAP <0.001
LI	50.55±3.77	1.03±0.14	Group CB versus LI 0.001
TAP	59.18±7.88	1.07±0.7	Group LI versus TAP 0.16

*Comparison of duration of anesthesia among the 3 groups showed that the difference was statistically significant with P<0.001. MAC: Minimum alveolar concentration, CB: Caudal block, LI: Local wound infiltration, TAP: Transversus abdominis plane

Postoperative MOP score was observed for 24 h. The values were significantly different between groups CB and TAP at 8 h, between groups LI and TAP at 0, 1, 2, and 4 h and between groups CB and LI at 0, 1, 2, and 4 h, respectively [Table 4 and Figure 3].

Table 4

Postoperative variation of modified objective pain score

MOPS value (mean±SD)	Group CB	Group LI	Group TAP	TAP versus CB*	TAP versus LI*	CB versus LI*
0 h	0±0	0.8±1.07	0±0	1.0	0.001	0.001
1 h	0±0	3.88±3.97	0.02±0.16	0.32	0.001	0.001
2 h	0.02±0.16	4.32±2.39	0.05±0.22	0.56	0.001	0.001
4 h	1.52±1.28	8.47±1.6	1.12±1.16	0.15	0.001	0.001
8 h	6.9±1.58	0±0	3.62±2.26	0.001	-	-
12 h	0±0	0±0	7.91±1.15	-	-	-

*P. CB: Caudal block, LI: Local wound infiltration, TAP: Transversus abdominis plane, SD: Standard deviation

Figure 3

Postoperative variation of modified objective pain (MOP) score between three groups, over a period of time

The time to first rescue analgesia (hours) defining the duration of analgesia is shown in Table 5 and was significantly different between all the groups.

Table 5

Time of rescue analgesia

Group	Time of rescue analgesia (h)	P
CB	6.84±0.47	Group CB versus TAP 0.001
LI	2.3±1.26	Group CB versus LI 0.001
TAP	9.78±1.02	Group LI versus TAP 0.001

CB: Caudal block, LI: Local wound infiltration, TAP: Transversus abdominis plane

The total dose of analgesic administered over 24 h (syrup paracetamol 15 mg/kg body weight) was also significantly different between all the groups [Table 6].

Table 6

Total requirement of paracetamol in 24 h/kg body weight

Group	Total analgesia in 24 h/kg body weight	P
CB	6.84±0.47	Group CB versus TAP 0.001
LI	2.3±1.26	Group CB versus LI 0.0037
TAP	9.78±1.02	Group LI versus TAP 0.001

CB: Caudal block, LI: Local wound infiltration, TAP: Transversus abdominis plane

The variations in intraoperative hemodynamic parameters such as heart rate, systolic blood pressure, and diastolic blood pressure were comparable among patients across the three groups. There were no side effects such as nausea, vomiting, urinary retention, and prolonged motor block which could have delayed discharge.

DISCUSSION

Our results showed that USG-guided TAP block provided longer and superior postoperative analgesia compared to caudal block and local infiltration. The mean duration of postoperative analgesia in the TAP group was nearly 10 h [Table 5], and the MOP scores show that the effect of caudal block waned after 4 h while that of TAP block persisted for longer (8 h). However, intraoperatively, caudal block had a lower requirement of fentanyl and isoflurane (MAC hour) indicating that intraoperatively caudal analgesia was better than with TAP block. Local infiltration provided the least analgesia among the three methods.

In a study by Kumar et al., 112 children (age group 2–8 years) who were undergoing elective inguinal hernia repair received either received USG-guided TAP block (n = 56) with 0.5 ml/kg of 0.2% ropivacaine and a similar number received caudal block with 1 ml/kg of 0.2% ropivacaine. USG-guided TAP block provided prolonged analgesia as compared with the caudal block at 6–24 h after the block, as shown by a statistically significant fewer number of rescue analgesic doses and lesser total rescue analgesic consumption in 24 h.[7] We too found that the total rescue consumption of analgesic doses of paracetamol was lower in the TAP group compared to the other two groups.

Al Sadek et al. compared 3 groups in lower abdominal operations – ultrasound-guided TAP block (received 0.5 ml/kg bupivacaine 0.25%) to ultrasound-guided caudal block (received 1 ml/kg bupivacaine 0.25%) and conventional analgesia (n = 20, control group). They used Children's Hospital Eastern Ontario Pain Scale, objective pain scale (OPS), postoperative complications, patient and parent satisfaction, and postoperative analgesia to assess pain. They found similar pain scores in the TAP and caudal group though the analgesic requirements were higher in the caudal group. The control group needed the maximum analgesia. Patient and parent satisfaction was the most in the TAP group and least in the control group.[8] Our results were similar to their study, however, our third group received local anesthetic in the wound.

On the other hand, Elbahrawy and El-Deeb, compared CB and TAP block in children undergoing daycare unilateral lower abdominal surgeries and found that postoperative pain score, time to first administration of rescue analgesia was statistically similar between the two groups. The parent satisfaction score was however better with the TAP group.[9]

Faried et al. compared ultrasound-guided TAP block to ilioinguinal/iliohypogastric nerve blocks in unilateral lower abdominal surgery. Similar to our results, the mean duration of analgesia as well as the time to first rescue analgesia was longer in the TAP block group than in the nerve blocks group.[10]

Similarly, Shaaban compared ultrasound-guided TAP block to local wound infiltration in children operated for appendectomy and inguinal hernia and found TAP block increased the time for the first analgesic dose by almost double when compared with the local infiltration group. In our study too, the findings were similar.[1112]

In our study, the total analgesic requirement in the first 24 h was the least in the TAP group. In fact, it was almost half the requirement in the other two groups. These observations too are consistent with the study by Tobias,[13] where children between 10 months and 8 years of age who had umbilical and lower abdominal surgery were included. Ultrasound-guided TAP block was given on both sides with 0.3 ml/kg of 0.25% bupivacaine with epinephrine 1:200,000 after completion of the surgical procedure. Adequate postoperative analgesia was seen in 8 of the 10 patients with the first request for postoperative analgesia varying from 7 h to 11 h.

In our study, intraoperative analgesia was assessed by comparing total fentanyl requirement and MAC hour values. The CB group required the least amount of fentanyl intraoperatively as compared to the other two groups. Furthermore, we observed that the intraoperative variation of MAC hour was least in the CB group. Both these findings suggest that TAP block and local infiltration did not block visceral pain during surgery.

Similar to our results, Ahmed and Rayan observed an increased requirement of intraoperative fentanyl in TAP block as compared to CB in unilateral groin surgery.[5] In contrast, Elbahrawy and El-Deeb, found no statistically significant differences between TAP and CB in terms of total intraoperative fentanyl use, postoperative tramadol requirement, time to first administration of rescue analgesia, and time in the post-anesthesia care unit in children undergoing day-care unilateral lower abdominal surgeries.[9]

On comparing the duration of anesthesia, TAP had the longest duration as the preparation and completion time was longer compared to the other two groups. This difference was statistically significant. Faried et al. showed that the time required for ilioinguinal/iliohypogastric nerve blocks was significantly more, by an average of 58 seconds, as compared to TAP block.[10]

As in previous studies,[14] we too did not find any difference in the hemodynamic parameters intraoperatively between the three groups, nor were there any side-effects that could have delayed discharge.[715]

Thus, TAP block provided superior postoperative analgesia with longer duration and was more efficacious as compared to caudal block and local infiltration of the wound. However, intraoperatively better analgesia was obtained with caudal block. The foremost disadvantage of TAP block is that it requires an anesthetist with expertise in ultrasound scanning and the availability of an ultrasound machine.

An USG TAP block is a relatively easy one; however, USG is time-consuming, needs added manpower to get the machine ready and the probe covered. This may be possible only in a tertiary center with added facilities. However, where a caudal block is contraindicated for some reason, a USG guided TAP block maybe a better alternative than wound infiltration.

Limitations

We did not assess patient or parent satisfaction with the block administered. This would have allowed for a more comprehensive assessment of the quality of analgesia. We also did not assess motor effects of the block as these could have affected discharge of the patient.

Another aspect we feel is that of the surgeon satisfaction. Some minor surgeries maybe better off with wound infiltration and postoperative paracetamol. As an USG TAP block is time-consuming and may require an induction room to save on OT time.

CONCLUSION

We suggest that ultrasound-guided TAP block is a good alternative, with longer and effective postoperative analgesia, as compared to caudal block, especially in situations where a caudal block may be contraindicated. However, it requires an ultrasound machine for correct placement of the drug. The caudal block provides good intraoperative analgesia, has moderate postoperative analgesia, and does not necessarily need an ultrasound machine. Local wound infiltration is a poor substitute, both in the intraoperative and postoperative period, as higher amounts of anesthetic drug are required.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.