This prospective, single-center, parallel-group, randomized controlled trial with quintuple-blinded (patients, parents, cardiologists, intensive care unit [ICU] staff, and evaluators), parallel-group randomized controlled trial was conducted in a cardiac catheterization laboratory at Aboelriesh pediatric hospital.

This study received approval from the ethical committee board of Kasr Alainy school of medicine (approval number: MS-316-2020) on April 8, 2021. Prior to participant enrollment, the trial was registered at ClinicalTrials.gov on June 17, 2021 (registration number: NCT04931693). The protocol was written according to the Consolidated Standards of Reporting Trials (CONSORT) 2010 statement guidelines, adhered to the Standard Protocol Items: Statement of Recommendations for Interventional Trials (SPIRIT), and was carried out according to the current version of the Helsinki Declaration-2013 and Egyptian law on the protection of personal information. The patients’ legal guardians provided written informed consent before participation in the study.

We enrolled 40 children of both sexes, aged 1 to 9 years, who underwent transvenous subpectoral pacemaker insertion with either congenital or postoperative complete heart block, as described in the flow diagram (Fig. 1).

Patients with known coagulopathy, a rash or signs of infection at the injection site, known allergy to local anesthesia, previous subpectoral pacemaker insertion, or emergency procedure were excluded from the study.

Patients who met all the inclusion criteria were randomly allocated to either the control (Group C) or pectoral (Group P) group. In Group C, analgesics were administered intravenously to control perioperative pain, while in Group P, participants received 0.25% bupivacaine between the pectoralis major and minor muscles (PECS block type I) and below the pectoralis minor and above the serratus anterior muscles (PECS block type II) at a volume of 0.5 ml/kg divided equally between the two sites (0.25 ml/kg at each site).

An online randomization program (http://www.randomizer.org) was used to generate a random list, and patients were randomly allocated at a ratio of 1 : 1 into either Group P (n = 20) or Group C (n = 20). The random allocation numbers were concealed in closed opaque envelopes.

Complete histories, comprehensive clinical examinations, complete blood counts, coagulation profiles, and CRP levels as well as preoperative electrocardiography (ECG), echocardiography, and chest radiography were all conducted as part of the preoperative anesthetic evaluations. Children were given intramuscular both atropine 0.01 mg/kg and midazolam 0.02 mg/kg 20 min before being admitted to the operating room.

Upon arrival at the operating room, ECG, pulse oximetry (SpO2), non-invasive arterial blood pressure, temperature, end-tidal CO₂, and transcutaneous pacemaker pads were applied, and baseline readings were obtained before general anesthesia was induced with 8 vol% sevoflurane and a 50% oxygen in air. Following loss of consciousness, a peripheral venous cannula was inserted. For patients with an intravenous cannula already in place, 1.5 mg/kg propofol was used for induction. In both cases, 0.5 mg/kg intravenous atracurium was administered to facilitate endotracheal intubation and 2 µg/kg fentanyl was administered to eliminate the stress response associated with intubation. The patients’ lungs were ventilated with 50% oxygen in air at tidal volumes of 6–8 ml/kg, and the respiratory rate was adjusted to maintain the end-tidal carbon dioxide concentration at 30–35 mmHg. Anesthesia with 1% isoflurane, 0.1 mg/kg atracurium, and 0.50 µg/kg fentanyl were administered to maintain blood pressure and heart rate [HR] below 120% of baseline values.

A consultant regional anesthetist performed the ultrasound-guided PECS block for the children allocated to Group P. The chest was first prepared in a sterile fashion, and a linear ultrasound probe (S-Nerve^TM; SonoSite Inc., USA) was placed on the surgical side for pacemaker placement at the level of the third rib. The pectoralis major, pectoralis minor, and serratus anterior muscles were identified. A 22 gauge needle was advanced from the anteromedial to posterolateral direction using an in-plane technique until the fascial plane was reached, and 0.25 ml/kg of 0.25% bupivacaine was administered between the pectoralis major and minor muscles (PECS block I). The probe was moved laterally to identify the fourth rib. The needle was then advanced to administer another 0.25 ml/kg 0.25% bupivacaine between the pectoralis minor and serratus anterior muscles (PECS block II) (Fig. 2) [8].

All procedures were performed by a pediatric electrophysiologist. Following the PECS block, the chest was reprepared and draped in a sterile manner, and 10 ml of contrast was injected under fluoroscopy through peripheral lines in the right and left arms to delineate the right and left subclavian veins. A 5-cm incision was made just below the clavicle in the left upper chest, and electrocautery was used to dissect the prepectoral fascia. A pocket was created under the pectoral muscle using blunt dissection. A micropuncture needle was used to gain access to the subclavian vein, which was then dilated to a larger introducer-sheath size. The pacemaker lead was then advanced through the sheath to a suitable location on the heart. After correct positioning was confirmed, the lead was connected to the generator and attached to the pectoral muscle. The device was placed in the pocket after sufficient irrigation with gentamicin-infused saline. Three distinct layers were formed by closing the fascial, subcutaneous, and superficial skin layers.

Since the implanted pacemakers were all rate-responsive, meaning the HR can increase in response to increased physical needs, vital signs (HR and non-invasive blood pressure) were recorded at the start of the block, every 15 min intraoperatively, and every 6 h postoperatively for 24 h.

After skin closure, inhalational anesthesia was discontinued and muscle relaxation was reversed after the return of spontaneous breathing. The patients were extubated and transferred to the pediatric intensive care unit (PICU) for recovery and monitoring.

After admission to the PICU, patients in both groups were managed according to the PICU protocol, which includes standard monitoring and intravenous analgesic paracetamol 7.5 mg/kg every 6 h. The Face, Legs, Activity, Cry, Consolability scale (FLACC) was assessed immediately post-operation in the PICU and every 6 h for 24 h (Table 1) [9]. When the FLACC scale score was ≥ 4 at rest, rescue analgesia, which comprised incremental intravenous morphine at a dose of 0.1 mg/kg (with a maximum single dose of 0.1 to 0.2 mg/kg/dose repeated every 60 min according to the patients’ response), was administered to maintain a resting FLACC scale score < 4. Cumulative 24-h analgesic consumption was recorded [10].

Data were collected independently by a researcher who was not aware of the treatment assignment and was not involved in clinical care decision-making. The baseline characteristics included age, sex, weight, and cause of complete heart block. Intraoperative data included the duration of surgery, duration of the block, hemodynamic parameters (HR, mean arterial pressure), and cumulative fentanyl and atracurium doses. Postoperative data included the postoperative pain score, time to first rescue analgesia, postoperative morphine consumption, and postoperative complications (postoperative nausea and vomiting, pneumothorax, and infection).

The primary outcome of this study was the mean pain score based on the FLACC scale in the first 24 h. Secondary outcomes were as follows: time to first postoperative rescue analgesia, total opioid consumption, total dose of muscle relaxants, perioperative hemodynamic parameters, and incidence of postoperative complications.

Forty children (20 in each group) met the inclusion criteria and were enrolled in this study. Group C (control) received conventional analgesics without any block, while Group P (pectoral) received PECS blocks. None of the patients were excluded from the study (Fig. 1). There were no statistically significant differences in baseline characteristics between the two groups (Table 2).

The mean pain score was significantly lower in the pectoral group compared to the control group (mean values [95% CI] for Group P and Group C were 0.54 [0.40, 0.73] and 3.52 [3.16, 3.72], respectively) (P < 0.001) (Table 3 and Fig. 3).

For the intraoperative variables, the mean duration of surgery was significantly longer in Group P than in Group C (P = 0.032). However, the mean cumulative doses of fentanyl and atracurium were also significantly lower in Group P than in Group C (P = 0.040 and P < 0.001, respectively) (Table 2).

Hemodynamic parameters (mean arterial pressure and HR) were measured at the following time points: baseline (T0), skin incision (T1), every 15 min until extubation, every 6 h following extubation. Our study showed no significant differences between the two studied groups at T0 (P = 1.00). However, a statistically significant difference was seen at each time point from T1 to T24 (P < 0.036), with higher values in the control group than the pectoral group (Fig. 4).

For postoperative variables, the postoperative FLACC pain scale score, compared to the control group, the pectoral group experienced significantly less pain at all time points (Table 3). The postoperative mean cumulative morphine dose was significantly lower in Group P than in Group C (P = 0.022) (Table 2).

The first request for rescue analgesia occurred later in the pectoral group than in the control group, with a median time of 2 h and 7 h in the control and pectoral groups, respectively (Table 2).

There were no statistically significant differences in the incidence of complications, such as PONV, pneumothorax, or infection, between the two groups (Table 2).