Analgesic effect of ultrasound-guided erector spinae plane block versus ultrasound-guided caudal block in pediatric open renal surgeries: A randomized comparative study

Abstract

Background: 

We aimed to compare erector spinae plane block (ESPB) and caudal block (CB) with ultrasound guidance as regards time of first request of rescue analgesia, opioid consumption, degree of postoperative pain relief, and incidence of complications in pediatric patients undergoing open renal surgeries such as nephrectomy and pyeloplasty.

Materials and Methods: 

Fifty children were recruited to undergo unilateral open renal surgeries and divided into two-equal groups randomly. The age of both genders ranged from 2 to 6 years . After general anesthesia had been induced, blocks were given. After the surgical procedure and during the first 12 h of the postoperative period, the quality of analgesia was assessed immediately postoperative and then at 1, 2, 3, 4, 6, 8, and 12 h postoperatively using Children’s Hospital of Eastern Ontario Pain Scale (CHEOPS). Opioid was intravenously given as rescue analgesia (0.05 mg/kg) when needed in both groups if CHEOPS pain score exceeded 6. It could be given every 8 h if needed.

Results: 

As regards the time of the first request of rescue analgesia and total morphine consumption postoperatively, there was a marked difference between the two groups in favor of erector spinae plane block as no rescue analgesia was needed during the first 12 h in the postoperative period. It was proved that both blocks under ultrasound guidance were safe with no recorded complications were noted either intra or postoperatively.

Conclusion: 

ESPB provided effective prolonged analgesia postoperatively with lower pain scores as compared with the CB in children undergoing open renal surgeries.

Introduction

Proper postoperative pain management is highly recommended to allow early ambulation and short hospital stay. Many drugs can be used for pain control in the pediatric population such as acetaminophen, non-steroidal anti-inflammatory drugs, and opioids.^[1] Although opioids are potent analgesics, they have many disadvantages such as respiratory depression, nausea, vomiting, and decreased intestinal motility.^[2]

Currently, regional anesthesia is used as an adjuvant to general anesthesia for intraoperative and postoperative analgesia in pediatric patients. Caudal epidural analgesia is commonly used for this purpose. It has many advantages such as being easily performed, safe, and reliable. However, its main disadvantage is the short duration of action if given as a single injection.^[3]

The Erector Spinae Plane Block (ESPB) was first described for thoracic neuropathic pain management in adults^[4] followed by its application for postoperative analgesia in children.^[5] ESPB can provide good analgesia for pediatric patients undergoing open renal surgeries such as nephrectomy^[6] and pyeloplasty.^[7] Regarding literature, studies comparing caudal analgesia to ESPB in pediatric patients undergoing open renal surgeries are lacking. Therefore, in this study, we hypothesized that ESPB may have a superior analgesic effect than caudal block (CB) in children undergoing unilateral open renal surgeries.

Materials and Methods

This prospective, randomized controlled study was conducted in Cairo University Children’s Hospital from January 2021 to March 2022, after ethical committee approval (MD-323-2020). The trial was registered at clinicaltrials.gov (NCT05289401). Written informed consent was obtained from the parents before the enrollment. This study included children aged 2–6 years with the American Society of Anesthesiologist (ASA) physical status of I or II scheduled for unilateral open renal surgeries such as nephrectomy and pyeloplasty. Study exclusion criteria included refusal of the block by parents, bleeding disorders (platelet count < 100,000, INR > 1.5, prothrombin concentration < 60%), skin infection or lesion at the puncture site, history of allergy to any of the study’s drugs, and contraindications to neuraxial block.

Patients were randomized using online randomization software into two equal groups. Data regarding group assignment and drug preparation were put inside sequentially numbered closed envelops. A dedicated research assistant was assigned for opening the envelops, drug preparation, and informing the group assignment to the operator with no further involvement in the study. Surgeon, intraoperative attending anesthetist, and postoperative data collector were blinded to the block given.

All the patients received premedication (0.02 mg/kg atropine, 0.2 mg/kg midazolam, and 2 mg/kg ketamine) intramuscularly 15–20 min before operating room arrival. Patients were monitored using electrocardiogram, noninvasive blood pressure, pulse oximetry, end-tidal CO₂, and temperature monitoring. After intravenous access was secured, general anesthesia was induced in both groups using fentanyl (1 µg/kg) and propofol (2 mg/kg) over 20–30 s, and atracurium (0.5 mg/kg). Anesthesia was maintained using isoflurane (1%–1.5%) in a mixture of oxygen and air (50/50) and atracurium (0.1 mg/kg/25 min). Controlled mechanical ventilation was used to keep end-tidal carbon dioxide at 35–40 mmHg. Heart rate and mean arterial blood pressure were measured before and after induction of anesthesia, after block, and every 5 min throughout the surgical procedure, but they were recorded every 15 min for 1 h.

All blocks were performed by the same operator (with 5-year experience in pediatric anesthesia) using 6–13 Hz linear transducer connected to SonoSite M Turbo ultrasound machine, Fuji Film SonoSite, Inc., WA, USA. Patients in CB group (n = 25) received CB in the left lateral position with the upper hip flexed at right angle and the lower one at 45°. Under aseptic condition, the transducer was positioned in the transverse plane over the coccyx just cephalad to the point of injection, and the sacral hiatus was visualized between two hyperechoic lines: the upper line represented the sacrococcygeal ligament whereas the lower represented the dorsum of the pelvic surface of the sacrum. When the probe was placed in a longitudinal plane between the sacral cornu, the dorsal surface of the sacrum, dorsal aspect of the pelvic surface of the sacrum, and the sacrococcygeal ligament were viewed. The local anesthetic was injected as a bolus of 1.2 mL/kg bupivacaine 0.125% with the needle placed in plane in order to cover up to midthoracic level and not exceed bupivacaine’s toxic dose (2 mg/kg).^[8]

Patients in the ESPB group (n = 25) received unilateral block in the lateral decubitus under aseptic conditions. The intercostal nerves of T9-11 are responsible for the dermatomal supply of open nephrectomy/pyeloplasty; therefore, the ESPB was performed at the level of T9. The transducer was placed longitudinally 1–3 cm lateral to the spinous process of the 9^th thoracic vertebrae. The erector spinae muscle and transverse process were visualized, and a 22-gauge 50 mm needle was introduced craniocaudally using the in-plane technique toward the fascial plane deep to erector spinae muscle. The correct location of the needle was confirmed by injecting 0.5–1 mL saline. After negative aspiration, 0.5 mL/kg of 0.125% bupivacaine was injected. Inadequate analgesia (20% increase in the heart rate and/or mean arterial pressure in absence of other causes of hemodynamic changes) was treated by intravenous fentanyl (0.5 µg/kg).

After the surgical procedure had been completed, all the patients received neuromuscular blocking drug reversal using neostigmine (0.04 mg/kg) and atropine (0.02 mg/kg), and then they were extubated and transferred to the postanesthetic care unit (PACU). Postoperative pain was assessed by a blinded anesthesiologist in the PACU at 0, 1, 2, 3, 4, 6, 8, and, 12 h using Children’s Hospital Eastern Ontario Pain Scale (CHEOPS) pain score^.[9] Inadequate analgesia was considered if the CHEOPS was more than 6 and was managed by 0.05 mg/kg morphine. Failure of the block was defined as CHEOPS score > 6 at the time of transfer to post anesthetic care unit.

The primary outcome was the time to first rescue analgesia requirement in minutes (from the time of intervention to the first registration of CHEOPS pain score of more than 6) during the first 12 h of the postoperative period. The secondary outcomes were total morphine consumption in milligrams during the first 12 h postoperatively, CHEOPS pain score, intraoperative hemodynamic variables, and occurrence of complications in both groups such as bradycardia, hypotension, postoperative nausea or vomiting, hematoma, urine retention, lower limb weakness, pneumothorax, or local anesthetic toxicity.

Sample size

The primary outcome was duration of analgesia. A previous study for caudal block in pyeloplasty surgery in children had reported duration of analgesia to be 280±100 minutes (10). The sample size was calculated using MedCalc software to detect a mean difference of 25% between both groups. A minimum number of 46 patients was needed to have a study power of 80% and an alpha error of 0.05. The number was increased to 50 patients (25 patients per group) to compensate for possible dropouts.

Data were analyzed using the Statistical Package for the Social Science (SPSS) version 22.0, Armonk, NY: IBM Corp. Continuous data were reported as mean ± standard deviation (SD), or median (quartiles) and were analyzed using the Students t test or Mann–Whitney U test as appropriate according to data distribution. Categorical data were reported as frequency (%) and were compared using the Chi-square or the Fisher’s Exact test as appropriate. Probability values (P-values) less than 0.05 were considered statistically significant.

Results

50 pediatric patients were included in this study [Figure 1]. No one was excluded as there was no failure of block (failure of the block was defined at the time of transfer to post anesthetic care unit if CHEOPS score is more than 6). The demographic data of the patients regarding age, weight, ASA physical status, surgery duration, and type of surgery were comparable between both groups [Table 1]. There was no need for extra analgesia intra-operative in the form of fentanyl (0.5 µg/kg) among all patients in the two groups.

Figure 1:: CONSORT’s flowchart

Table 1:: Age, weight, and surgery duration of both groups

As regards the first request of rescue analgesia during first postoperative 12 h period, 20 patients out of 25 (80%) in caudal group needed rescue analgesia with median (1^st, 3^rd quartiles) time to analgesia of 300 (240, 420) min and total opioid consumption of 1.05 (0.90, 1.20) mg; while none in the ESPB group required rescue analgesia during the same period, P-value < 0.001 for both outcomes [Table 2].

Table 2:: The post-operative rescue analgesia requirements (presented as median and IQR)

The hemodynamic (heart rate and mean arterial blood pressure) preoperatively at baseline and intraoperatively showed no statistically significant differences between both groups except for mean arterial blood pressure at 15 min after block with P-value = 0.005 [Tables 3 and 4].

Table 3:: Heart rate of both groups intraoperatively (presented in mean ± SD)

Table 4:: Mean arterial blood pressure of both groups intraoperatively (presented in mean ± SD)

Comparing CHEOPS between the two groups immediately postoperatively and then at 1, 2, 3, 4, 6, 8, and 12 h revealed that there was a statistically significant difference during the postoperative 12 h (P-value < 0.001) with lower scores recorded in ESPB group [Table 5].

Table 5:: CHEOPS score of both groups postoperatively (presented as median and IQR)

No complications such as bradycardia, hypotension, postoperative nausea or vomiting, hematoma, urine retention, lower limb weakness, pneumothorax, or local anesthetic toxicity were reported in both groups.

Discussion

This prospective randomized study was designed to compare ESPB with CB regarding duration and quality of analgesia in 50 pediatric patients undergoing unilateral open renal surgeries.

Although there was no need for extra analgesia intra-operatively among all patients in both groups, there was a significant difference between both groups after 12 h postoperatively with lower CHEOPS scores recorded in ESPB Group. As regards the first request for rescue analgesia, there was a statistically significant difference between the two groups in favor of ESPB group, as well as total morphine consumption, showed statistically lower values in favor of ESPB group.

Regarding intraoperative hemodynamic, both blocks could stabilize hemodynamic parameters during operations. No complications such as bradycardia, hypotension, postoperative nausea or vomiting, hematoma, urine retention, lower limb weakness, and/or local anesthetic toxicity were reported in both groups.

Regional nerve blocks are a part of the multimodal analgesia required to provide good postoperative pain control. The introduction of ultrasound imaging allowed targeting neural structures easily even if they are close to sensitive structures and therefore, decreasing the volume of administered local anesthetic.^[11]

One of these regional analgesia techniques is the ESPB, which is considered a good alternative to neuraxial blockade for many surgical procedures with potent analgesic effect. The block has advantages as there is no risk of epidural hematoma, or direct spinal cord trauma.^[12,13] The ESPB has an analgesic effect by blocking of the dorsal and ventral rami of the spinal nerves and sympathetic nerve fibers.^[14,15] Local anesthetic injected into at the ESPB was discovered to spread both superiorly and inferiorly as this plane is continuous along the vertebral column as proved radiographically.^[16] Many studies reported effective analgesia of ESPB at different levels from cervical to lumbar regions, for procedures as pyeloplasty, lipoma excision, tracheoesophageal fistula, inguinal herniorrhaphy, and hip reconstructions.^[7,17-23]

Regarding pediatric population, a retrospective review^[24] demonstrated that ESPB was effective for several surgeries, involving incisions from T1 to L4. This was similar to the meta-analysis performed by Luo and Tong, which found that ESPB lowered the pain scores and subsequently reduced the need for rescue analgesics postoperatively.

This is in line with an earlier case report^[6] in 2018, which used the ultrasound-guided ESPB for postoperative pain management in two pediatric cases who underwent nephrectomy for Wilms tumor and proved the efficacy of the ESPB with no complications recorded and with less opioid consumption postoperatively. The block was done by dosage of 0.5 mL/kg 0.25% bupivacaine. Although the dose of local anesthetic administered in the current study was much lower (0.5 mL/kg of bupivacaine 0.125%), the ESPB provided good analgesia. So, we recommend this reduced dose to avoid complications that may occur if the injected LA exceeds the maximum allowable dose (2 mg/kg) of bupivacaine. This was consistent with a case report^[7] who performed continuous ESPB for an open pyeloplasty in an infant using ropivacaine and showed effective analgesia.

Another retrospective study^[25] included 141 pediatric patients, who received ESPB for 13 different indications, of which six patients underwent nephrectomy and two patients underwent pyeloplasty. They concluded that the ESPB is effective for postoperative pain control in broad-spectrum surgeries in pediatric population. They performed the block using 0.5 mL/kg 0.25% bupivacaine with a maximum volume of 20 mL.

Also, a retrospective review^[26] performed to evaluate the effectiveness of ESPB with 0.5% ropivacaine using catheter technique in 22 children undergoing thoracic, abdominal, and hip surgery and concluded that ESPB provided effective analgesia intra and postoperatively.

To the best of our knowledge, no study had compared ESPB with CB to provide perioperative analgesia in unilateral open renal surgeries in children. CB has been the most popular pediatric regional intervention used for intra and postoperative pain control since its description in 1933. Its advantages are being easily performed and reliable, but it offers analgesia for a short duration.^[27]

Similar to our results, a study^[27] showed that CB reduced pain score postoperatively. 40 patients aged from 2 months to 14 years undergoing renal surgery were enrolled in their study. The dose of bupivacaine used in study was 1.2 mL/kg bupivacaine 0.2% whereas the dose used in our study was 1.2 mL/kg bupivacaine 0.125%. They compared fentanyl 2 μg/kg versus morphine 15–20 μg/kg as additive to LA and found that the need for opioid and non-opioid rescue analgesic during first 24 h of the postoperative period was much lower in morphine group than fentanyl group.

Another randomized study compared CB with the paravertebral block in pediatric patients undergoing renal surgeries and found that paravertebral block produced superior analgesia than CB. Fifty children were included in this study. Both blocks were performed with 0.2% ropivacaine with 1:200,000 adrenaline.^[28]

Also, another study^[29] evaluated the CB effects on 96 children, aged 6 months to 7 years, in laparoscopic upper urinary tract surgery and concluded that CB with 1.3 mL/kg of 0.15% ropivacaine decreased intraoperative fentanyl usage and produced good postoperative analgesia.

This study has some limitations. It was conducted in a single center and pain was assessed postoperatively for only 12 h. Future studies are recommended to assess the analgesic effect for longer duration and different age groups with larger sample size.

Conclusion

ESPB produced a longer duration of postoperative analgesia and reduced the postoperative analgesic requirements as compared with CB in pediatric patients undergoing open renal surgeries such as nephrectomy and pyeloplasty.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Author contribution

Omnia A. Mandour—study design and manuscript preparation.

Iman Riad Abdel-Aal—literature search, statistical analysis, and manuscript review.

Chahenda Tarek Salem—study interventions, data analysis, and manuscript editing.

Amr Raafat Refaat—Concepts, definition of intellectual content, experimental studies, and data analysis.