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Preterm infants with inguinal hernia did better with a late repair strategy after leaving the neonatal intensive care unit (NICU) and reaching 55 weeks' postmenstrual age compared with planning the surgery upfront, the HIP randomized controlled trial showed.

The proportion of infants with at least one serious adverse event during 10 months of follow-up was 28% with early repair versus 18% with late repair (risk difference −7.9%, 95% credible interval −16.9% to 0%), Martin L. Blakely, MD, MS, of the University of Texas Health Science Center in Houston, and colleagues reported in .

Bayesian analysis suggested a 97% probability that the late repair strategy was safer than operating during the initial stay in the NICU, and that likelihood appeared to particularly benefit babies born before 28 weeks' gestation and those with bronchopulmonary dysplasia (99% probability of benefit for both groups).

"These findings support delaying inguinal hernia repair until after initial discharge from the neonatal intensive care unit," study authors wrote. That decision "likely does not influence the overall duration of the neonatal intensive care unit stay, but may hasten the discharge by several days if later repair is chosen, which is likely important to parents and neonatologists."

Late repair was associated with shorter NICU stays after randomization (median 16.0 vs 19.0 days, 82% posterior probability of benefit) and fewer postoperative days in the hospital (6.0 vs 0.5 days).

"Serious adverse events among infants in the early repair group were usually related to anesthesia (apnea, prolonged intubation, bradycardia), which is consistent with prior reports," the researchers noted.

Neither group had any spermatic cord structure injuries, although two early repair group patients had intraoperative intestinal injuries (one full thickness and one serosal tear).

Eight infants had inguinal hernia incarceration, with one bowel injury requiring resection in the early repair group. None of the study participants required emergency hernia surgery.

Clinical resolution of the hernia before surgery occurred in seven of the early repair group patients (4%) and 17 (11%) of those in the late repair group, which the researchers said "supports later inguinal hernia repair and deserves further study."

Inguinal hernia occurs more often the lower the gestational age at birth, with rates up to 40% of males born at 24 weeks' gestation, the researchers noted. However, there are no guidelines or consensus on when to treat it to prevent inguinal hernia incarceration.

Serious comorbidities like acute respiratory distress syndrome and bronchopulmonary dysplasia are also common in this group, so early repair raises "concerns for surgical and anesthetic complications, possible prolonged mechanical ventilation, fragility of the tissues involved with the repair, and possible delayed discharge," they noted. Delayed repair might lower those risks but raise the likelihood of hernia-related complications.

Now with evidence from a randomized controlled trial, serious adverse event risk is an important consideration, Blakely's group argued.

The trial included 338 infants born with inguinal hernia before 37 weeks' gestation who were seen at 39 participating U.S. medical centers. Most were male (86%), many had comorbidities (50% bronchopulmonary dysplasia), and median birth weight was just 820 g. Exclusion criteria included factors affecting the timing of hernia repair, a planned operative procedure in which the inguinal hernia repair would be a secondary procedure, known major congenital or chromosomal abnormalities expected to impact neurodevelopmental outcomes, and inability to return for follow-up and late inguinal hernia repair.

Infants were randomized about 2 weeks prior to anticipated NICU discharge to a strategy of early or late inguinal hernia surgery. The latter group were planned to have it after NICU discharge and once they had reached at least 55 weeks' postmenstrual age, "a threshold selected based on current pediatric anesthesia guidelines that allows preterm infants to have elective outpatient operations when they are older than 55 weeks' postmenstrual age, given the decreased risk of anesthesia-related apnea or bradycardia," the researchers noted. In this group, the pediatric surgery team also counseled the family about signs of inguinal hernia incarceration and scheduled an in-person follow-up visit for 1 month after NICU discharge.

However, operation timing was impacted by change in medical condition or other factors in both groups, and didn't occur in the randomized timeframe for 7% of early and 18% of late repair groups.

Serious adverse events that were counted towards the primary outcome in 308 infants with data available at 10 months included:

• Pulmonary events (apnea requiring intervention, prolonged intubation, unplanned reintubation, stridor, or pneumonia)
• Cardiac events (bradycardia requiring intervention, cardiopulmonary resuscitation, or cardiac arrest)
• Surgical events (intraoperative injury, wound disruption, or surgical site infection)
• Hernia incarceration, recurrence, or reoperation
• Death

Limitations of the trial included the modest sample size accrued before the trial was stopped early for effectiveness and impacts of the COVID-19 pandemic on patient follow-up.

Nevertheless, the researchers concluded: "We believe the trial results are generalizable to most preterm infants with an inguinal hernia diagnosed during the initial neonatal intensive care unit stay, given the inclusive eligibility criteria and the large number of medical centers and diversity within the centers."

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