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Ultrasound-Guided Lumbar Erector Spinae Plane Block versus Caudal Block for Postoperative Analgesia in Hip and Proximal Femur Surgery in Pediatric Patients: A Randomized controlled Study

Background: Several infants endure substantial pain after hip operations, which can have a negative impact on their health by causing restlessness, depression, and sleep disruption. According to recent research, 20% of infants experience prolonged postsurgical pain 6 to 12 months following major surgery, which is linked to functional impairment and a lower quality of life. Methods: 76 children, ranging from 1 year to 7 years old, scheduled for hip or proximal femur procedures were randomly assigned to receive either unilateral ultrasound guided erector spinae plane (ESPB) with 0.5 mL/Kg of bupivacaine 0.25% or caudal epidural anesthesia (CEA) with 0.5 mL/Kg of bupivacaine 0.25%. The primary outcome was the Face, Legs, Activity, Cry, and Consolability (FLACC) score 2 hours postoperatively. The secondary outcomes were pain scores every 15 minutes for the first hour and then at 6, 12, and 24 hours postoperatively, block failure rate, time taken to perform a successful block, , and the time for first rescue analgesia. Results: The FLACC score 2 hours postoperatively wasn’t superior in ESPB group compared to CEA group, in the contrary it was higher in the ESPB group compared to the CEA group at 15, and 30 minutes postoperative (p = 0.005, p = 0.004 respectively). The time to first rescue analgesia was prolonged in the CEA group (p value < 0.001), time to perform successful block was comparable between groups. Conclusions: ESPB hasn’t shown a superior analgesic effect to CEA in pediatrics undergoing hip and proximal femur operations.


Introduction
Several infants endure substantial pain after hip operations, which can have a negative influence on their health because it is linked to agitation, sadness, and sleep disruption [1]. According to the latest research, roughly 20% of children experience prolonged postsurgical discomfort 6 to 12 months following major surgery [2], [3], which is linked to functional impairment and a lower quality of life [3]. As a result, it is critical to properly address pain problems throughout acute hip fracture treatment.
Opioids are frequently recommended for postoperative pain relief. They also have several serious side effects, including nausea, vomiting, constipation, severe sedation, disorientation, and respiratory depression.
To avoid post-operative pain, regional anesthetic technologies have been extensively employed in pediatric surgery [4]. Caudal epidural anesthesia (CEA) is a well-established neuraxial technique that has been extensively utilized in pediatrics undergoing lower abdominal and lower extremity surgeries [5]. Although the effectiveness and safety of CEA are well established, it has various contraindications such as anatomical anomalies or infection at the site of injection that can hinder its usage.
In regional anesthesia, ultrasonography monitoring has made single dose and continual procedures safer. When paired with general anesthesia, the usage of intraoperative and postoperative analgesic medicines can be decreased, in addition to ensuring a quick and painless rehabilitation [6] , [7]. The Erector Spinae Plane Block (ESPB) is a relatively novel block that has shown promising results in a few research papers [8] , [9]. The ESPB has been used for postoperative analgesia of lower extremity procedures in adults [10]. By spreading to the paravertebral area, the local anesthetic mixture may produce multiple dermatomal analgesic effects that address both somatic and visceral pain. The dermatomal spread of the ESPB is affected by the injected area, local anesthetic volume, and concentration. Elkoundi et al. [11] described a successful ultrasound-guided ESPB at the level of the L2 transverse process in a 4-year-old girl prior to surgical repair for hip dysplasia. No research has compared the analgesic impact of erector spinae blocks versus caudal blocks in pediatric patients undergoing hip and proximal femur operations.
In this study, we aim to evaluate whether ESPB have a superior analgesic effect over CEA in pediatric patients undergoing hip or proximal femur surgeries. This article is protected by copyright of Korean Journal of Anesthesiology. All rights reserved.

Materials and Methods
The investigation was a clinical trial that was prospective, double-blinded, and randomized. The institutional research ethics committee of Cairo University El-Kasr Alainy Hospital gave its approval to this study under IRB number MD-340-2020. ClinicalTrials.gov preregistered the trial with the identifier NCT 05157516. In compliance with the 2013 Helsinki Declaration, the study was carried out between December 2021 and June 2022. All patients screened and meeting eligibility criteria were invited to participate in the trial, and those enrolled gave written informed consent by their parents or legal guardians. Patients were asked for their consent when they arrived at the operating room for their procedure or on the ward if they were hospitalized the night before.
Inclusion criteria included both sexes, ASA 1-2, ages 1-7 years old, scheduled for hip or proximal femur surgeries not having any contraindication to peripheral regional anesthesia blocks-refusal of participation by parents or caregivers, known local anesthetic (LA) drug sensitivity, bleeding disorders with INR > 1.5 and/or platelets < 100,000/mm3, pre-existing infection at block site were also excluded from the study.
Using a randomly generated number table produced by a computer, patients were allocated to one of the study groups. Patients whose numbers ended in evens were referred to as ESPB patients, and those whose numbers ended in odds as CEA patients. The patient study code number and group allocation were typed on separate pages, folded, and concealed in sequentially numbered sealed envelopes. Block randomization in groups of six individuals was applied to ensure an even number in each group as the study progressed. The groups were named "ESPB" (erector spinae plane block) and "CEA" (caudal epidural block). Independent third party possessed the randomization key. Both patients and the This article is protected by copyright of Korean Journal of Anesthesiology. All rights reserved.
anesthetists involved in postoperative data collection were blinded to the group to which the patient was allocated.
Before arrival to the OR, children were premedicated by intramuscular injection of atropine 0.02 mg/Kg, midazolam 0.1 mg/Kg, and ketamine 2 mg/ Kg before admission to operation theater (O.R).
Upon arrival to O.R; perioperative monitoring including continuous Electrocardiogram (GE-Datex Ohmeda 3 lead ECG cable), pulse oximetry (GE-Datex Ohmeda pediatric finger SpO2 sensor), noninvasive arterial blood pressure (GE-Datex Ohmeda NIBP cuff) were applied. Baseline vital signs were noted, including non-invasive measurements of the heart rate, oxygen saturation, and systolic, mean, and diastolic arterial pressures, and then general anesthesia was induced by sevoflurane. A peripheral venous cannula was inserted after the loss of consciousness, then atracurium at a dose of 0.5 mg/kg was given intravenously to facilitate endotracheal intubation, and fentanyl at a dose of 1 µg/kg was given to abolish the stress response of intubation. Pressure controlled ventilation was adjusted to maintain normocapnia (CO 2 : 35-40 mmHg). Anesthesia was maintained by using 1-1.5% isoflurane in a mixture of oxygen and air (50/50) and atracurium top-ups at a dose of 0.1 mg/kg every 30 minutes. The patients were randomly assigned into 1 of 2 groups according to the intervention used, whether: Both the blocks were performed by the primary investigator under the supervision of a consultant anesthesiologists with experience in regional anesthesia and who were familiar with the ESPB and CEA block. After the induction of general anesthesia, envelopes were opened to reveal the group allocation. Prior to the start of surgery, blocks were carried out under fully aseptic conditions.
Patients randomized to the ESPB group received it with ultrasound guidance using SonoSite M Turbo (USA). The scanning probe was the linear multi-frequency 6-13 MHz transducer (L25 x 6-13 MHz This article is protected by copyright of Korean Journal of Anesthesiology. All rights reserved. linear array), which was placed in a sterile cover, using a 22G/50-mm block needle (Pajunk Sonoplex, Geisingen, Germany) as follows: A unilateral block was performed in the lateral decubitus position, and each patient was turned on his/her side so that the blocked side was the uppermost one. Strict sterile techniques were implemented; skin sterilization with povidone-iodine at the site of needle entry was performed. The 2 nd lumbar vertebral level was determined using US by identifying the lumbosacral junction (LSJ), which is the point of lordotic transition from the relatively straight line of the dorsal side of the lumbar vertebrae.
The vertebra proximal to the LSJ was labelled the third lumbar vertebra (L3). The ultrasound transducer was placed at the mid-vertebral line in the sagittal plane. The transducer was shifted from the midline, 3.5-4 cm laterally to the side of the surgery to visualize the erector spinae muscle and transverse process. Using the out-of-plane technique, we advanced the needle until it reached the transverse process. The correct location of the needle tip in the fascial plane deep to the erector spinae muscle was confirmed by injecting 0.5-1 ml saline and seeing the fluid lifting the erector spinae muscle off the transverse process while not distending the muscle (hydro dissection). Once the needle was in the correct location, a negative aspiration test was confirmed. Then 0.5 mL/kg of bupivacaine 0.25% was injected, taking care not to exceed the maximum recommended dose (2 mg/kg of bupivacaine).
The spread of the injectate was observed to be distributed within this plane. Then we turned the patient Then, after palpating the landmarks (the upper posterior iliac spine and the sacral hiatus form the edges of an equilateral triangle), an epidural puncture was achieved in the most proximal region of the sacral hiatus with the needle inclined 45-60° to the skin. The palpating index finger of the left-hand lay on the spinous process S4. The needle was inserted just below the spinous process S4. After perforation of the membrane, which occludes the sacral hiatus, the needle was advanced, not more than 1-3 mm, to avoid a bloody puncture or an intrathecal injection. A volume of 0.5 mL/kg of bupivacaine 0.25% was injected, taking care not to exceed the maximum recommended dose (2 mg/kg of bupivacaine) and the volume was usually restricted to 25ml. [11] The surgical incision was performed fifteen minutes after the blocks, Intraoperatively, the increase in hemodynamics in response to skin incision by more than 20% of baseline values (5 min after intubation) or thereafter throughout the whole operation was managed by intravenous administration of fentanyl 0.5 µg/Kg with a maximum dose of 2 µg/Kg.
At the end of surgery, inhalational anesthesia was discontinued, and reversal of muscle relaxation with atropine (0.02 mg/Kg) and neostigmine (0.05 mg/Kg) was administered intravenously after the return of spontaneous breathing. Patients were transferred to the post-anesthesia care unit (PACU) for 60 minutes to complete recovery and monitoring.
In the PACU and post-operative period, the pain score (face, legs, activity, and cry consolability scale After discharge from the PACU, the analgesic plan was to alternate doses of intravenous paracetamol 15 mg/kg for patients weighing kg or 7.5 mg/kg for patients weighing ≤ 10 kg, and ketorolac 0.5 mg\kg every 6 hours if the pain score is ≥ 4\10.
The primary outcome was the FLACC score at 2 hrs. postoperative.
The secondary outcomes were the FLACC score that was collected in the post-anesthesia care unit (PACU) every 15 minutes postoperative for the first hour and then at 6, 12, and 24 hours for the first 24 hours postoperatively; block failure rate; the block was considered a failed block if the patient required more than two doses of rescue analgesia in the first hour postoperatively; time taken to perform a successful block (block time); the incidence of adverse effects; and duration of the block. time starting immediately after giving the block till the first postoperative analgesic rescue, which was given if the pain score ≥ 4\10, degree of contralateral motor blockage, and lower limb weakness by modified Bromage scale.

Statistical Analysis
Evaluation of pain is usually subjective with high inter-personal variability. We conducted a pilot study to explore the actual data in our patients, with surgeons, the same surgical skills, and the same drugs that will be used in our study. According to Abdulatif et al., conducting a pilot study is considered the best method for sample size estimation. [13] In a pilot study on 10 pediatric patients not included in the final data analysis, pain scores (face, legs, to have a study power of 80% and an alpha error of 0.05. The number was increased to 76 patients (38 patients per group) to compensate for possible dropouts. Data were coded and entered using the statistical package for the Social Sciences (SPSS) version 26 (IBM Corp., Armonk, NY, USA). Data was summarized using mean and standard deviation for normally distributed quantitative variables or median and interquartile range for non-normally distributed quantitative variables, and frequencies (number of cases) and relative frequencies (percentages) for categorical variables. Comparisons between groups were done using an unpaired t test for normally distributed quantitative variables, while a non-parametric Mann-Whitney test was used for non-normally distributed quantitative variables. A Chi-square (c2) test was performed for comparing categorical data. Exact test was used instead when the expected frequency is less than 5. P-values less than 0.05 were considered statistically significant. This article is protected by copyright of Korean Journal of Anesthesiology. All rights reserved.

Results
The COSOLIDATED Standards of Reporting Trials (CONSORT) flow diagram for this trial is shown in figure 1. Eighty-seven individuals were first examined for appropriateness, with 76 fulfilling the eligibility requirements and being selected at random to obtain either an ESPB or a CEA block at Cairo University Children's Hospital (Abu El-Reesh). All the participants that were recruited were effectively followed up on, and no patients were abandoned to follow-up. Between the 2 categories, participants' demographic data and operational data (surgical duration, general anesthetic period) were equivalent.
Baseline participant information were comparable according to both groups, apart from the duration of general anesthesia and duration of surgery, which were prolonged in CEA compared to ESPB (p = 0.018, p = 0.002 respectively) ( Table 1). Tables 2 and 3. Hemodynamics were comparable except for mean arterial blood pressure (MAP) at 10, 20, 30, 50, and 60 minutes, and the mean of the MAP reading in the first 60 minutes intraoperative which was higher in the ESPB group compared to the CEA group. Table 4 shows the pain scores in both study groups in the first 24 hours after surgery. Scores were generally lower in CEA group but was significantly lower at 15-& 30-minutes post-operative with p value of 0.005 & 0.004 respectively, but the difference in mean FLACC score in the first 24 hours postoperative wasn't statistically significant between both groups with a p value of 0.19.

Patient hemodynamics for each group are presented in
The time to first rescue analgesia was prolonged in CEA than ESPB group with p value of <0.001, and the number of doses of rescue analgesia was lower in caudal than ESPB with p value of 0.035. Number of required rescue analgesic doses were higher in ESPB than CEA group. There were no adverse events related to the use of the regional anesthesia techniques in both groups, time needed to perform a Discussion This is the first randomized controlled study comparing ESPB block versus CEA in pediatrics undergoing hip or proximal femur surgeries. The main finding in our study was that ESPB was not superior to CEA considering analgesic effect in pediatric patients undergoing hip, or proximal femur surgery. In the contrary CEA showed a better analgesic effect that was demonstrated by the time to first rescue analgesia and lower pain scores in the early postoperative period. Perioperative hemodynamics were generally comparable between the two groups, both blocks could stabilize hemodynamic parameters after skin incision to the early post-operative period in PACU.
Agreeing with our finding, CEA had been previously reported as an excellent route for analgesia in pelvic and lower extremity procedures in children and was superior to general anesthesia alone in a study done by Wiegele et al. [14], and in comparison with Ultrasound-Guided Quadratus Lumborum Block in a prospective randomized study done by Salim et al. [15], and to lumbar plexus block in a study done by Villalobos et al. [16], and their results were in favor of CEA.
Tulgar et al. [17] performed ultrasound-guided ESP block performed at L4 level in adults undergoing hip and proximal femur surgeries. Computed tomographic imaging after the ESP block showed the spread of the contrast along the lumbar plexus from the T12 to S1 vertebrae, relying on the hypothesis that the local anesthetic would spread in ESPB at lumbar region similar to that performed at the thoracic levels [18]. We anticipated that lumbar ESPB performed at the L3 level would provide a higher dermatomal spread, hence, a better analgesic coverage in hip and proximal femur surgery.
The paucity of data regarding ESPB in infants undergoing hip or proximal femur surgeries leads us to imitate the studies on adults concerning the ESPB technique, level of injection injectant type, and concentration. Moreover, we depended on the few studies or case reports on infants undergoing hip or This article is protected by copyright of Korean Journal of Anesthesiology. All rights reserved. proximal femur surgery for the injectant volume, and possible side effects. However, depending on the results of the only study [11] that have studied ESPB in a case report in a pediatric undergoing hip surgery raised our expectations on the superior analgesic effect of ESPB over CEA, causing us to anticipate a maximum FLACC scale of 3 in the first 24 hours postoperative as reported in their results, on that base we assumed that ESPB would have a superior analgesic effect over CEA by at least 20% lesser FLACC scale depending on the results of the pilot study performed on pediatric patients receiving CEA undergoing hip surgery.
Aliena et al. [19] noted that for painful sub-umbilical operations, caudal blocks are an effective technique to provide postoperative analgesia, agreeing with the findings of our study. However, in contrast to our study, they used the dose of 0.75 mL/kg of 0.25% bupivacaine while we used 0.5 ml/kg of the same concentration according to the local guidelines in our institute. We believe that lower bupivacaine dose not only facilitates earlier ambulation, but also helps in maintaining periprocedural cardiovascular stabilization and spontaneous respiration in patients at high risk of difficulty airway.
Although the time for the first rescue analgesia was 7 hours in their study compared to 3.2 hours in our study. Yet, a previous study comparing different dose of bupivacaine found that increasing bupivaicaine dose from 0.5ml/kg to 0.75 ml/kg results only on a modest higher level of spread. [20] A few previous studies have evaluated ESPB in hip surgeries in adults, as a case report done by Ahiskalioglu et al. [21] and a randomized controlled pilot study done by Abdelnasser et al. [22].
However, in the pediatric population, only one case report [18] is available for the use of this block in hip surgery. They studied the analgesic effect of ESPB in pediatric hip surgeries, and they concluded that ESPB performed at L2 level as an adjunct to general anesthesia provided reliable analgesia in pediatric hip surgeries. However, in contrast to our study, a dose of 0.3 ml/kg of 0.25 % bupivacaine This article is protected by copyright of Korean Journal of Anesthesiology. All rights reserved. was used while we used 0.5 ml/kg of the same concentration. They also did not calculate the block duration. Ahiskalioglu [23] used Lumbar Erector Spinae Plane Block as a main anesthetic method for hip surgery in high-risk elderly patients and concluded that ESPB when combined with mild sedation provides adequate and safe anesthesia in high risk elderly patients. However, the block duration in this study was about eight hours, which is longer than that in our study (2.35 hours); this could be explained by the different dosage and the different age groups of the two studies.
The limitations of our study were that the results of intraoperative hemodynamics and postoperative pain evaluation may be influenced by other factors such as surgery time, type of surgery, and age; nonetheless, the outcomes were applied equally to both randomized groups. Also, there were heterogenicity in the type of surgeries between both groups: however, we don't think this had an impact on the outcomes because the difference wasn't statistically significant. Furthermore, another limitation was that FLACC score interpretation can be misleading as it may affected by other non-pain-related distress; however, the FLACC score combined with other outcomes as hemodynamics, analgesic requirements can provide a reliable, and useful tool in assessing the pain intensity in such a challenging population. [24] Finally, we concluded that although ESPB hadn't shown a superior analgesic effect compared to CEA, on the contrary CEA resulted in a better analgesic effect especially in early postoperative period. Yet      shown as mean ± SD or as n (%).
This article is protected by copyright of Korean Journal of Anesthesiology. All rights reserved.