Caudal vs Dorsal Penile Nerve Block for Postoperative Analgesia in Children Undergoing Hypospadias Repair (CaD-DPNB)

BACKGROUND AND RATIONALE Hypospadias repair remains one of the most common pediatric urological procedures, with thousands of cases performed annually worldwide. Despite continuous refinement of surgical techniques, perioperative pain management in this population poses consistent clinical challenges. Children undergoing hypospadias repair typically experience significant postoperative discomfort due to tissue manipulation, dissection of delicate structures, and exposure of the highly innervated penile shaft. Poorly controlled postoperative pain may lead to increased stress responses, delayed discharge, impaired healing, and difficulties with early postoperative voiding. Because pain expression in young children is complex and often non-verbal, anesthesiologists rely on validated objective scoring systems-such as the FLACC scale-to assess discomfort and guide analgesic therapy.

Regional anesthesia is widely employed as an adjunct to general anesthesia to enhance perioperative analgesia while reducing the need for systemic opioids. Among the most widely used techniques are the caudal epidural block and the dorsal penile nerve block. Each technique has distinct advantages, limitations, and implications for recovery, ambulation, and analgesic duration. Caudal block is traditionally considered the gold standard for infra-umbilical surgeries in pediatrics due to its ease of application, high success rate, and ability to provide profound postoperative analgesia. However, concerns persist regarding delayed motor recovery, urinary retention, and potential adverse hemodynamic effects.

In contrast, the dorsal penile nerve block provides targeted sensory blockade limited to the penile region, minimizing motor involvement and typically allowing earlier mobilization. It is frequently favored in ambulatory settings or when rapid recovery is required. However, its duration of action may be shorter, and there is ongoing debate about whether it can provide analgesic efficacy equivalent to caudal anesthesia following more extensive penile reconstruction, such as hypospadias repair. Given the variation in practice patterns and the lack of high-quality comparative studies in the local setting, this trial was designed to provide a head-to-head comparison of the two regional techniques under standardized anesthetic conditions. The objective was to characterize their intraoperative stability, postoperative pain control, recovery profile, need for rescue analgesia, and safety, enabling clinicians to make informed decisions tailored to patient characteristics, surgical technique, and postoperative care priorities.

STUDY DESIGN OVERVIEW This trial was designed as a prospective, randomized, and comparative clinical study conducted at the Pediatric Surgery Unit of Ain Shams University Hospitals. The study was carried out over a six-month period, following institutional ethical approval, and adhered strictly to the principles of good clinical practice and the Declaration of Helsinki. All participants were recruited consecutively from eligible children scheduled for primary hypospadias repair. A computer-generated randomization sequence was utilized to allocate patients into two equal groups receiving one of two regional anesthesia techniques. All procedures were performed by anesthesiologists with extensive experience in pediatric regional anesthesia, ensuring consistency and proficiency across techniques. A standardized perioperative protocol was applied to all cases to avoid confounding variables. General anesthesia was induced and maintained using identical agents, ventilation strategies, and monitoring parameters. The regional blocks were administered after induction but before surgical incision. Hemodynamic stability, adequacy of analgesia, and possible complications were monitored meticulously throughout the intraoperative and postoperative periods. Data collection continued for the first 24 hours after surgery, with measurements obtained at fixed postoperative intervals. Pain scores, hemodynamic variables, time to ambulation, and need for rescue analgesia were recorded using objective and validated tools. All study staff responsible for postoperative evaluation were blinded to group allocation to minimize assessment bias.

ANESTHETIC MANAGEMENT PROTOCOL A unified anesthetic protocol was implemented for all participants to ensure consistency. Upon arrival in the operating room, each child underwent inhalational induction using 8% sevoflurane in 100% oxygen. Intravenous access was then secured with an appropriately sized cannula (22-24G). Routine monitoring included electrocardiography, non-invasive blood pressure, oxygen saturation, and end-tidal CO₂. Once anesthetized, participants were intubated without the use of neuromuscular blocking agents to prevent interference with motor-based postoperative assessments.

After induction and stabilization, regional anesthesia was performed according to the group assignment. All techniques were executed under sterile conditions using using isoflurane (1-2%) in a mixture of oxygen and air. Ventilation parameters were adjusted to maintain normocapnia. Throughout surgery, continuous monitoring allowed detection of inadequate analgesia. A >20% rise from baseline in mean arterial pressure or heart rate was considered indicative of insufficient block. In such cases, fentanyl 1 µg/kg was administered, and the participant was subsequently excluded from per-protocol analysis to ensure the study accurately reflected the analgesic performance of each regional technique. At the end of surgery, inhalational agents were discontinued, and extubation was performed once all criteria were met, including adequate spontaneous breathing, protective reflexes, and hemodynamic stability. Patients were then transferred to the post-anesthesia care unit (PACU) for initial recovery and postoperative monitoring. DPB is designed to target the primary sensory nerves of the penis at the most proximal location accessible extracorporeally, maximizing analgesic coverage of the penile shaft and glans. It minimizes motor involvement, preserves lower-limb function, and is well suited for early mobilization. Caudal block provides sensory and motor blockade to the lumbosacral dermatomes, ensuring extensive analgesia for penile and perineal surgeries. Its principal advantage is its prolonged analgesic duration, although transient motor impairment may delay ambulation.

PERIOPERATIVE MONITORING AND SAFETY OVERSIGHT

Intraoperative monitoring continued throughout the procedure, with recordings of heart rate, mean arterial pressure, oxygen saturation, and end-tidal CO₂ at predetermined intervals. Any adverse events, such as hypotension, bradycardia, local anesthetic systemic toxicity, arrhythmias, or signs of block-related complications, were documented. Postoperative monitoring focused on detecting pain, hemodynamic alterations, sedation levels, nausea, vomiting, urinary retention, motor impairment, and block-related complications. All assessments were performed in the PACU and continued in the ward at 3, 6, 9, and 12-hour intervals, with additional observations made as clinically necessary. Pain assessment utilized the FLACC scale because of its reliability and effectiveness in non-verbal and preverbal pediatric populations. All nurses and assessors were trained in FLACC scoring to avoid inter-observer variability.

DATA COLLECTION AND MANAGEMENT All collected data, including demographic variables, perioperative measurements, and postoperative findings, were entered into standardized data sheets and subsequently transferred to a secure electronic database. Data accuracy was verified by dual-entry validation. Confidentiality of participant information was strictly maintained, with de-identified codes used for all analyses.

STATISTICAL HANDLING AND ANALYTIC FRAMEWORK Quantitative variables were initially assessed for normality using the Shapiro-Wilk test. Parametric data were analyzed using the independent-samples t-test to compare means between the two groups. Non-parametric variables, including FLACC scores, were analyzed using the Mann-Whitney U test. Categorical variables, such as ASA status, were analyzed using the chi-square test. A 95% confidence interval and significance threshold of p \< 0.05 were applied.

STUDY FLOW AND CLINICAL OBSERVATIONS The flow of participants from recruitment through follow-up was documented in accordance with CONSORT guidelines. No block-related complications, such as hematoma, infection, or systemic toxicity, were observed. Both regional techniques demonstrated favorable safety profiles. Clear differences emerged between the two groups in postoperative hemodynamics, pain trajectories, timing of rescue analgesia, and recovery parameters. These findings provided robust comparative insights into the performance of each regional anesthesia modality under consistent surgical and anesthetic conditions.

INTERPRETATION AND CLINICAL SIGNIFICANCE The trial revealed distinct advantages and limitations of each regional technique. Caudal block offered superior early postoperative analgesia and significantly prolonged the time to first analgesic requirement. It also resulted in reduced total consumption of rescue analgesics within 24 hours. These outcomes highlight its value in situations where extended postoperative pain control is a clinical priority. However, the caudal block was associated with delayed ambulation, likely resulting from transient motor involvement in the lower limbs. This consideration is crucial in fast-track surgical settings or when early mobilization is required. The dorsal penile nerve block provided effective analgesia with shorter recovery time and earlier ambulation, making it an appropriate choice for ambulatory care or settings aiming for rapid discharge.

The findings underscore the importance of individualized analgesic planning based on the surgical context, patient characteristics, and recovery goals. Both blocks are safe and effective when performed by skilled practitioners.

CONCLUSION This detailed clinical investigation provides comprehensive comparative data on two widely used regional anesthesia techniques for hypospadias repair. By standardizing anesthetic management, surgical technique, and postoperative assessment, the study establishes strong evidence to guide pediatric pain management and optimize perioperative outcomes.