Ultrasound-Guided Erector Spinae versus Ilioinguinal/Iliohypogastric Block for Postoperative Analgesia in Children Undergoing Inguinal Surgeries.

CONTEXT: Erector spinae plane (ESP) block is a promising technique in the field of pediatric postoperative analgesia considering its safety and simplicity.
OBJECTIVE: The objective of the study is to compare the efficacy of ultrasound (US)-guided ilioinguinal/iliohypogastric nerve (IIN) block and ESP block for postoperative analgesia after pediatric unilateral inguinal hernia repair. PATIENTS AND METHODS: Sixty patients randomized into two equal groups. ESP group received US-guided ESP block, and IIN group received US-guided IIN block. Block in both groups was done with 0.5 mL/kg 0.125 bupivacaine + fentanyl 1 μg/mL injectate. Primary outcome is to compare both groups regarding time to first analgesic request. Secondary outcomes include evaluation of postoperative FLACC score, number of patients requiring rescue analgesic, number of rescue analgesic doses, parental satisfaction, incidence of postoperative vomiting, and motor weakness.
RESULTS: IIN group showed a significantly higher FLACC score at 4 and 6 h, significantly higher number of rescue medication doses and number of patients needed rescue analgesia. The ESP group carries a significantly higher parental satisfaction and a significantly longer time to first rescue analgesic compared to IIN group.
CONCLUSION: The findings suggest that US guided ESP block resulted in a more effective and longer duration of postoperative analgesia following a pediatric unilateral inguinal hernia repair compared to IIN block.

INTRODUCTION

Adequate postoperative analgesia is of great concern. It is vital to ensure early mobilization and discharge of the patients. Many side effects complicate the use of opioid in pediatrics such as somnolence, vomiting, and up to respiratory depression.[1] Nowadays, the use of ultrasound (US)-guided nerve block resulted in the revolutionary change in the field of regional anesthesia in pediatrics. Many truncal blocks are used for both upper and lower abdominal surgeries with a high success rate.[2] Ilioinguinal/iliohypogastric nerve (IIN) blockade is one of the most common techniques used in pediatric anesthesia for peripheral nerve block, and it has been shown to be as effective as caudal block for inguinal hernia repair.[3]

The novel erector spinae plane (ESP) block is an interfacial plane block carries promise as a simpler and safer alternative to thoracic epidural or paravertebral block. The efficacy of this technique for the management of acute and chronic pain in the thoracic region is reported.[45] In the lumbar region, it may have the same anatomical considerations to get good results.

The aim of this prospective, randomized, observer-blinded, controlled study is to compare the efficacy of US-guided IIN block versus US-guided ESP block for pediatric unilateral inguinal hernia repair with respect to postoperative analgesia.

The primary outcome is to compare both groups regarding time to first analgesic requirement. Secondary outcomes include evaluation of postoperative FLACC score, hemodynamic changes, number of patients requiring rescue analgesic, parental satisfaction, incidence of postoperative vomiting (POV), and motor weakness.

PATIENTS AND METHODS

Patients

This prospective randomized controlled trial was conducted after gaining approval from the institutional ethics committee (R.18.05.202) and registration in clinical trials.gov (NCT03640598). Written informed parental or legal guardian consent was obtained before randomization. Sixty patients of the American Society of Anesthesiologists physical Status I and II aged from 6 months to 3 years scheduled for elective unilateral inguinal hernia repair were enrolled in this study. Exclusion criteria included a history of clinically significant cardiac, hepatic, renal, or neurological conditions, coagulopathy, known allergy to amide local anesthetics, and local infection at injection sites.

Randomization

Before surgery, patients were allocated randomly to one of two equal groups (each group involved 30 patients) using a computer-generated program. IIN group received US-guided IIN block with (0.5 mL/kg 0.125 bupivacaine + fentanyl 1 μg/mL injectate). ESP group received US-guided ESP block with (0.5 mL/kg 0.125 bupivacaine + fentanyl 1 μg/mL injectate). All blocks were performed by the same anesthetist who is experienced in US-guided nerve blocks. The blocks were performed using a high-resolution portable US machine (M-turbo; Fujifilm SonoSite Inc., Bothell, Washington, USA), with a 5–13 MHz linear (not hockey) probe with a sterile cover and 22 G spinal needles. One surgical team performed all surgical procedures.

Study protocol

The general anesthesia was induced with 8% sevoflurane in 100% oxygen. After an adequate depth of anesthesia is reached, a venous access was established, then, a disposable laryngeal mask airway was placed. Anesthesia was maintained with 1–1.5 minimal alveolar concentration of isoflurane under spontaneous ventilation. Standard intraoperative monitors were applied for the measurement of noninvasive blood pressure, electrocardiogram, heart rate, pulse oximetry, and end-tidal carbon dioxide concentration. Baseline readings (before block) were recorded. The skin incision was made 15 min after the block. The failed block was defined as an increase in heart rate to more than 20% of the baseline, movement at the time of skin incision or pain (FLACC ≥4) on admission to postanesthesia care unit (PACU).

Block technique

Group ilioinguinal/iliohypogastric nerve

Following aseptic preparation of the skin and probe, the probe was placed immediately medial and slightly cephalic to the upper aspect of the anterior superior iliac spine to get a short-axis view of the nerves situated between the internal oblique and transversus abdominis muscles (IO and TA), with the peritoneum immediately beneath the TA muscle. Using an in-plane technique, the needle (short beveled) was advanced, placing the needle tip ~1 cm caudal to the probe surface to allow for optimal needle tip visibility ~1 cm deep [Figure 1]. Advancement of the needle was continued until a characteristic “tenting” of the interface between external and IOs is seen. The needle was then further advanced till interface between the IO and TA muscle, under real-time visualization of the solution surrounding the two hypoechoic IIN.[6]

Figure 1

Short axis view at anterior superior iliac spine. IIN = Ilioinguinal-iliohypogastric nerves, EO = External oblique muscle, IO = Internal oblique muscle, TA = Transversus abdominis muscle, P = Periton, N = Needle

Group erector spinae plane

After hemodynamic stability, the patient was placed in the lateral position. Following aseptic preparation of skin and probe, a high-frequency linear US transducer was moved 2.5 cm laterally on the parasagittal plane to visualize the transverse process (TP) of first lumbar (L1) vertebra. The needle was directed in-plane between the TP of L1 and fascial sheath of erector spinae muscles [Figure 2] with real-time visualization of the spreading injectate.[7]

Figure 2

Long axis view at paraspinous region of (first lumbar). TP = Transverse process, ES = Erector spinae muscle, N = Needle, INJ = Injectate between erector spinae and transverse process

Intraoperative management

Following the block, heart rate and mean blood pressure were recorded every 5 min to ensure the blockade is adequate especially at surgical incision. The surgical procedure was allowed to start 15 min after the performance of the block. In case of patient movement at skin incision or increase in heart rate to more than 20% of the baseline, fentanyl at 0.5 μg/kg was administered and repeated as required every 3 min if the above parameters do not return to within 20% of the baseline values. More than 30% decrease in heart rate and systolic blood pressure, respectively, as compared with the baseline values were treated with atropine or ephedrine as appropriate, but the postoperative data of those patients were excluded from the statistical analysis.

Postoperative management

Children were transferred to the PACU for continuous vital signs monitoring and pain assessment. Patients were monitored every 15 min during the PACU stay for 1st h and every 30 min in the daycare unit until discharge from the hospital. The FLACC pain scale was used for pain assessment scale at 0, 1, 2, 4, and 6 h postoperatively. For rescue analgesia, paracetamol suppository 15 mg/kg was given for patients with FLACC score of 4–5. And for those with FLACC score >6, 15 mg/kg intravenous paracetamol was administered. Following rescue analgesic administration, pain scores were recorded every 5 min to assess pain relief or the need for further rescue analgesic medications. The number of patients who needed postoperative rescue analgesics and time to the first analgesic request was recorded. Significant muscle weakness was assessed by four P's (push, pull, pinch, and punt) method 3 h after the block.[8] About 6 h postoperatively, patients were discharged from the hospital if they were pain-free and there was no other indication to be admitted to the surgical ward. A simple pain scale was explained for parents to complete a postoperative chart (0 = no pain/child is calm; 1 = minimum pain/child is irritable; 2 = mild pain/child is consolable; and 3 = severe pain/child is inconsolable). Parents were directed to give 15 mg/kg paracetamol suppositories when pain score is 2 or 3, but not more than every 6 h. One hour after paracetamol administration, parents evaluated their child; if is still in pain, oral ibuprofen 10 mg/kg was given every 8 h as needed.

Collection of data

The time to the first analgesic request, FLACC pain scale at 0, 1, 2, 4, 6 h postoperative, and the amount of rescue analgesic was recorded at the PACU and the daycare unit by nurses blinded to the patient's group and the procedures. An anesthesiologist not involved in the study got contact with the parents and asked them about the number of doses of rescue analgesic given in on the day following hospital discharge. Parents were also asked about any complications as nausea or vomiting and if they were satisfied with the analgesia provided for their children. All data were collected blindly.

Sample size

G power program (version (3.1.9), faculty at the Institute for Experimental Psychology in Dusseldorf, Germany) was used to calculate sample size for this study, with priory analysis. The time to first rescue analgesia was used as the primary effect. One-tailed t-test for the difference between two independent means was the computed statistical test. The effect size was calculated as 0.8 (large effect size), α error was 0.05, and power (1-β error) of 0.90 was used. The resulted sample size was 28 patients for each group. To compensate for dropouts and deviation from normality, a total of 60 cases were enrolled in this study.

Statistical analysis

The analysis of data was done using Statistical Package for Social Sciences (SPSS), (IBM Crop. released 2013. IBM statistics for window. version 22. Armonk, NY, USA: IBM Crop). First, Shapiro–Wilk test was used to test data distribution. The presentation of the data was in the form of mean and standard deviation, median, and range or numbers and percentages. Unpaired t-test will be used to compare mean values (normally distributed data) of both groups. While, for categorical data (pain score), Mann–Whitney U-test was used. Fisher's exact test was used for the comparison of categorical data. Statistical significance was considered at P ≤ 0.05.

RESULTS

A total of 60 children were enrolled in this study [Figure 3]. The two groups of participants did not show statistically significant difference regarding patient characteristics, duration of surgery [Table 1]. No significant difference between both groups regarding hemodynamic variables (heart rate and mean blood pressure) but with a significant difference in comparison with basal values [Table 2].

Figure 3

Consort flow chart

Table 1

Demographic data of the studied groups and duration of surgery

Group	IIN (n=30)	ESP (n=30)	P
Age (months)	23.10±13.86	18.70±11.95	0.1
Gender (male/female)	17/13	19/11	0.6
Weight (kg)	13.40±3.94	12.80±4.34	0.5
Height (cm)	82.40±8.40	82.40±8.11	1.0
Duration of surgery (min)	39.00±5.01	37.00±8.53	0.2

Data presented as mean±SD, IIN=Ilioinguinal/iliohypogastric, ESP=Erector spinae plane, SD=Standard deviation

Table 2

Heart rate and mean blood pressure of the studied groups

Group	IIN (n=30)	ESP (n=30)	P
HR
Basal	117.90±4.40	120.30±6.91	0.1
15 min	114.90±6.87†	115.70±8.55†	0.6
30 min	113.60±6.51†	115.10±9.68†	0.4
45 min	113.90±5.50†	114.60±7.65†	0.6
60 min	113.50±6.36†	114.00±9.04†	0.8
MBP
Basal	90.40±6.73	90.90±3.98	0.6
15 min	86.40±6.97†	86.10±4.58†	0.8
30 min	86.90±6.50†	84.70±5.59†	0.1
45 min	85.80±5.76†	84.20±4.63†	0.2
60 min	84.90±4.97†	83.40±4.27†	0.2

Data presented as mean± SD, †P value ≤ 0.05 was considered as statistical significance on comparison to basal value. IIN=Ilioinguinal/iliohypogastric, ESP=Erector spinae plane, HR=Heart rate, MBP=Mean blood pressure, SD=Standard deviation

There was a statistically significant increase in IIN group regarding the FLACC score at 4 and 6 h [Figure 4] and a significant decrease regarding the time to first rescue analgesic [Figure 5] compared to ESP group. The ESP group carries a significantly higher parental satisfaction [Table 3].

Figure 4

FLACC Scale of the studied groups

Figure 5

Time to first rescue analgesic (minutes)

Table 3

Outcome data

Group	IIN (n=30)	ESP (n=30)	P
Patients receiving pain rescue medication in daycare unit and at home, n (%)	15 (50)	7 (23.3)	0.03*
Pain rescue medication number (n)	4 (2-6)	0.5 (0-2)	<0.0001*
Parental acceptance, n (%)	24 (80)	29 (96.6)	0.04*

Data presented as median (minimum-maximum)/n (%).*P≤0.05 was considered as statistical significance. IIN=Ilioinguinal/iliohypogastric nerve, ESP=Erector spinae plane

No patients of either group received rescue analgesic in PACU, while in daycare unit or at home, 15 patients of IIN group and 7 patients in ESP group received paracetamol suppository. IIN Group recorded a significantly higher number of rescue medication doses compared to ESP group [Table 3].

No statistically significant difference regarding the incidence of POV (9 [30%] and 12 [40%] for IIN and ESP groups, respectively P = 0.4). No motor weakness was reported in either group at 3 h.

DISCUSSION

The current study was aiming to compare the analgesic efficacy of US-guided IIN block versus US-guided ESP block for pediatric unilateral inguinal hernia repair. The study documented a more potent and prolonged analgesia achieved by US-guided ESP block compared with IIN block with no detected complications.

Inguinal hernia repair is one of the most common day surgeries in pediatrics. Adequate postoperative analgesia is essential for rapid mobilization and early discharge of the patient.[9]

Performing the landmark-based regional anesthetic techniques in pediatrics carry many risks of mechanical complications due to proximity to important structures, local anesthetic overdose plus masking of warning signs by the applied sedation or general anesthesia in this age group.[9] The introduction of US into the practice of pediatric regional anesthesia resulted in a breakthrough in this field especially in small children due to the superficiality of most nerves.[10]

The anterior abdominal wall incision is responsible for most of the pain experienced after abdominal surgery.[9] Many truncal blocks for upper and lower abdominal procedures are used with comparable analgesia and more safety compared to central neuraxial techniques.[11]

IIN nerve blockade is one of the most common techniques used in pediatrics. Abdellatif reported that for unilateral inguinal surgery in pediatrics, especially hernia repair, the efficacy of US-guided (IIN) block for postoperative analgesia is comparable to that of caudal block with a lower volume (0.1 mL/kg of 0.25% bupivacaine) of the local anesthetic.[12]

The usual volume of local anesthetic used for (IIN) block is 0.3–0.5 mL/kg. However, Willschke et al. reported in their prospective randomized study a considerable reduction in the local anesthetic volume (down to 0.075 mL/kg) when using the US-guided technique for (IIN) block.[10] In our study, we used a volume of 0.5 mL/kg of 0.125% bupivacaine to be standardized with that used for ESP block.

ESP block is recently defined in September 2016.[13] The ease of application and relative safety of the technique may be the cause of widespread interest among clinicians.[7] The block used successfully in adult for perioperative analgesia and chronic pain as well, but there is limited experience with children.[13]

ESP block involves the injection of local anesthetic in the fascial plane superficial to the tip of the TP and deep to the erector spinae muscle. This block was reported to be similarly effective as epidural analgesia.[14] The block has many clinical indications, but its mechanism of action is still not fully understood. Muñoz et al. performed the block in pediatric patients undergoing oncological thoracic surgery. They noticed an extensive multi-dermatomal sensory block of the anterior, posterior, and lateral thoracic wall. The authors explained the analgesic effect by the spread of the local anesthetic to the paravertebral space blocking both rami of thoracic spinal nerves (dorsal and ventral) plus rami communicantes which supply the sympathetic chain.[15] The same explanation was provided by Ueshima and Hiroshi who studied the spread of local anesthetic solution during the ESP block and documented a paravertebral spread. Moreover, the fascial plane underlying the erector spinae muscle allows for marked craniocaudal spread resulting in multidermatomal coverage-following a single injection.[16]

Thomas and Tulgar reported in their study on children undergoing laparoscopic cholecystectomy that ESP block involves both somatic and visceral nerve fibers. They also noted that distant application of local anesthetics to any vital organs or nerves resulted in rare mechanical complications.[17]

Aksu and Gürkan reported an opioid-sparing effect of ESP in pediatric undergoing bilateral inguinal hernia repair.[18] In another study by Aksu and Gürkan underwent ESP block in two pediatric cases undergoing nephrectomy for Wilms tumor and they describe the block as a promising technique in the field of pediatric postoperative analgesia considering its safety and simplicity.[7]

The current study showed significantly decreased pain score in patients received ESP block compared to those received IIN block. Accordingly, the time to the first request of analgesia was significantly longer in ESP group. Children belonging to ESP group received their first rescue analgesia after hospital discharge. Moreover, patients belonging to ESP group received a significantly less doses of postoperative rescue analgesic medications. This prolonged and more potent analgesia achieved with ESP block may be explained by the paravertebral spread of local anesthetic. Law et al. reported in their meta-analysis that paravertebral block is more potent than other forms of nerve block for inguinal herniorrhaphy.[19] There was no difference between both groups regarding hemodynamic parameters or side effects. However, parental satisfaction was significantly higher in ESP group compared to IIN group.

Limitations

The follow-up was limited to the first 6 h postoperatively as inguinal hernia repair is a day-case surgery and the early discharge is recommended by our hospital policy.

CONCLUSION

The findings suggest that US-guided ESP block resulted in a more effective and longer duration of postoperative analgesia following a pediatric unilateral inguinal hernia repair compared to IIN block.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.