Perioperative management of infant inguinal hernia surgery; a review of the recent literature

Abstract Inguinal hernia surgery is one of the most common electively performed surgeries in infants. The common nature of inguinal hernia combined with the high‐risk population involving a predominance of preterm infants makes this a particular area of interest for those concerned with their perioperative care. Despite a large volume of literature in the area of infant inguinal hernia surgery, there remains much debate amongst anesthetists, surgeons and neonatologists regarding the optimal perioperative management of these patients. The questions asked by clinicians include; when should the surgery occur, how should the surgery be performed (open or laparoscopic), how should the anesthesia be conducted, including regional versus general anesthesia and airway devices used, and what impact does anesthesia choice have on the developing brain? There is a paucity of evidence in the literature on the concerns, priorities or goals of the parents or caregivers but clearly their opinions do and should matter. In this article we review the current clinical surgical and anesthesia practice and evidence for infants undergoing inguinal hernia surgery to help clinicians answer these questions.


| INTRODUC TI ON
Inguinal hernia surgery is one of the most common electively performed surgeries in infants. 1 An indirect inguinal hernia, such as occurs in children, is defined as a protrusion of abdominal contents (e.g. intestines, ovary, omentum) through a patent processus vaginalis. It occurs in 3%-5% of babies born at term and up to 15% of babies born before 33 weeks gestational age. 2 The most common risk factors for development of an infant inguinal hernia include preterm birth (9%-20% risk), male sex (87% under the age of 1 year are male), very low birth weight, and mechanical ventilation. [3][4][5] Even in asymptomatic infants, the presence of an inguinal hernia necessitates surgical repair due to the high risk of incarceration; in children under 1 year of age this has been reported at around 8% 3 and the risk is highest in preterm children at around 20%. 5,6 Development of a hernia within 2 months of age significantly increases likelihood of developing a subsequent contralateral hernia following surgery, 7 therefore bilateral repair is most commonly performed in preterm infants.
Neonates and infants have higher perioperative risks than older children due to differences in developmental physiology, as well as the increased likelihood of comorbidities associated with congenital abnormalities and preterm birth. 8,9 A review of perioperative mortality in an Australian tertiary pediatric centre showed that neonates (aged <30 days) have the highest risk of pediatric perioperative mortality of 180.1 per 10 000 anesthetics, compared with 40 deaths per 10 000 anesthetics in infants (31 days to <1 year) and 16 deaths per 10 000 anesthetics in older children 10-17 years. 10 This was echoed in a similar, more recent study in another Australian centre showing perioperative mortality in neonates to be 227 per 10 000 anesthetics. 11 Neonates and infants have a high rate of severe respiratory and cardiovascular adverse events under anesthesia of 35%, which is higher than older children. 1,12 Children born preterm account for around 10% of births worldwide. They have a higher rate of associated comorbidities such as chronic lung disease, retinopathy of prematurity, necrotising enterocolitis and neurologic conditions such as intraventricular hemorrhage and periventricular leukomalacia. 13 Consequently, they have a greater likelihood of requiring surgery as well as having greater perioperative risks than infants born at term.

| TIMING
Whilst the need for repair of inguinal hernia appears to reach universal agreement amongst the surgical community due to the risk of incarceration and resultant morbidity, there remains much doubt as to the ideal timing of the operation in infants with non-incarcerated inguinal hernias. The decision regarding timing of repair is a balance of the surgical risk of incarceration favoring early repair against the perioperative anesthetic risk which favors delayed repair, as there is good evidence that the overall anesthetic and post operative respiratory risks are inversely related to post menstrual age. 1,14 A longitudinal population-based study showed an overall incarceration rate of around 8% in infants, which was double the overall rate for children 0-15 years of age at 4%. This study did not find any difference in incarceration rates in preterm infants compared to those infants born at term, however it was not designed specifically to explore timing of surgery. 3 In contrast to this, several studies, including a recent meta-analysis of early versus delayed repair in preterm infants, showed a significant reduction in risk of incarceration with early repair, but a higher risk of post operative respiratory complications. 5,15 A large multicentre randomized trial comparing outcomes in preterm infants undergoing inguinal hernia surgery either prior to discharge or at 55-60 weeks post menstrual age aims to address this important question definitively and is nearing completion. 16 The European Pediatric Surgeons' Association Evidence and Guideline Committee recently released a recommendation that postponing repair in infants until after discharge may be beneficial in preventing respiratory complications and hernia recurrence. 17 However, a consideration must also be made of the social factors of the infants' family; where loss to follow up, significant financial hardship and long distance from their treating hospital, such as families living in regional and remote Australia or Canada, may necessitate repair prior to discharge to balance the overall best interests of the infant and their family. Spinal failure is generally defined as failure to find the subarachnoid space, insert local anesthetic or establish an adequate block.

| SURG IC AL TECHNIQUE S L APAROSCOPIC VER SUS OPEN
Failure rate is reported at 9-20%. 31,33 This failure rate may likely be higher in some settings such as clinicians or centres with a lower volume of practice. Surgery that continues for longer than the duration of the block can be managed in many ways, such as sedation or analgesic adjuncts, but can require conversion to GA. Conversion to GA during the surgery can provide increased stress to the treating team, and potential for increased risk to the patient.
The GA Compared to Spinal Anesthesia Study-Comparing Apnea and Neurodevelopmental Outcomes, a Randomized Controlled Trial (the GAS study) compared outcomes in infants undergoing either awake regional or GA and showed no significant difference in overall apnea rates, with only a small difference in favor of awake regional for early (less than 30 mins post op) apneas within the postanesthesia care unit. 34 Importantly, this study was designed to look at neurodevelopment and consequently infants born less than 26 weeks gestational age and those with risk of adverse neurodevelopmental outcome were excluded from the study, which may have influenced this result.

| C AU DA L B LO CK
Caudal block, injection of local anesthetic into the caudal epidural space, is one of the most commonly performed regional blocks in children for surgery 35 either as a sole anesthetic technique or more often as an adjunct to sedation or GA. Successful block with a caudal in children has been reported as high as 94%. 36 Caudal block has been shown to provide surgical anesthesia for

| G ENER AL ANE S THE S IA
GA is the most common anesthetic technique performed on infants undergoing surgery in Europe. 1 The benefits are optimal surgical conditions (an immobile patient, no time pressure) and a technique that is familiar to clinicians routinely involved in caring for infants.
However, the downside is the common need for airway instrumentation, administration of opioids for analgesia and the potential concern of the effect of agents administered on the developing brain.

| NEURO DE V ELO PMENT
The effect of anesthesia on the developing brain is a topic of much debate, brought to light following findings of neuronal apoptosis and functional deficits in rodents exposed to general anesthetic medications in 2003. 54  The only large randomized controlled trial aiming to assess neurodevelopmental effects of anesthesia published to date, the GA or Awake-regional Anesthesia in infancy (GAS) study showed equivalence in full scale intelligence quotient between infants undergoing GA or regional anesthesia for inguinal hernia surgery. 56 However, the results of the GAS study were included in two recent meta-analyses; one which showed that childhood exposure to GA has a statistically significant increased risk of behavior problems and neurodevelopmental disorder diagnoses, 57 and the other, that a brief or single early anesthetic exposure is not associated with objective measures of intelligence but is associated with a significant increase in parental reports of behavior problems. 58 Evidence to date suggests the neurodevelopmental impact of anesthesia remains questionable and should encourage practitioners to continue avoiding or limiting general anesthetic exposure in infants where practicable.

| CONSUMER ENG AG EMENT-PRIORITIE S OF PARENTS
Consumer engagement is an emerging priority in the area of medicine and research. This has come about from the recognition that the question the clinical and research teams are asking, or the answers they are seeking, may not clearly align with the priorities of the con-

SUMMARY
As the most common operation performed in infants, inguinal hernia repair has been the topic of much debate and research over the past four decades. Despite this, there are still many questions that have not been definitively answered. To develop the ideal multidisciplinary perioperative care plan, the anesthetist must take into consideration the infant's specific comorbidities and risk, the surgical timing, technique and skill set, their own specific skills and preferences as well as the institutional setting. It may be helpful for clinicians to develop their own decision tree to select the optimal anesthetic technique for each infant. More work is needed to explore the parent/caregiver concerns and priorities regarding their infant's perioperative journey.

CO N FLI C T O F I NTE R E S T S TATE M E NT
Britta S von Ungern-Sternberg is a section editor for Pediatric Anesthesia.

DATA AVA I L A B I L I T Y S TAT E M E N T
Data sharing is not applicable to this article as no new data were created or analyzed in this study.