Abstract
In this chapter, the authors discuss the issues related to post-operative neonatal apnea with an example of an infant hernia repair. Neonatal apnea, its etiology and associated risk factors is reviewed. The use of infant spinal anesthesia versus general anesthesia and its relationship to neonatal post-operative apnea is discussed.
A two-month-old, 6 kg male infant is scheduled for inguinal hernia repair. The patient was born at 32 weeks of gestation and is currently breast-fed.
What Is an Inguinal Hernia?
An inguinal hernia is a protrusion of a portion of fatty tissue or intestine through the inguinal canal, a tubular passage in the lower abdominal wall. It occurs in 1–5% of all newborns but its prevalence is higher in infants born prematurely and in boys. It is most common in boys because the spermatic cord and testicles descend through the inguinal canal during development.
An incarcerated inguinal hernia occurs when the protruding tissue cannot be massaged back into the abdomen. It can lead to strangulation, in which blood supply to the protruding tissue becomes jeopardized. Strangulated hernias require immediate surgical intervention.
Inguinal hernia repair is one of the most commonly performed surgical procedures in children. A unilateral hernia is usually diagnosed on routine physical exam in healthy school aged children. Bilateral hernias occur more commonly in premature infants and, because of the potential risk of incarceration, will usually be repaired before the child is discharged from the hospital. Therefore, these children will present with all of the usual medical problems associated with prematurity.
Which Anesthetic Method Will You Choose for This Procedure?
There are many ways to anesthetize children for hernia repairs. Different factors are taken into consideration when deciding on an anesthetic technique, including the health of the child, preference of the surgeon, and the skills of the anesthesiology provider. Older children with uncomplicated unilateral hernias can receive maintenance of general anesthesia by facemask or laryngeal mask with inhaled agents. When laparoscopic examination of the contralateral side is performed, endotracheal intubation and neuromuscular blockade may be indicated, depending on the surgeon’s preference for abdominal wall relaxation and desired degree of intra-abdominal insufflation.
The anesthetic technique for bilateral hernia repair for the small infant is different from that of the older child. The hernias can consist of large bulging sacs (in the male) and can present a surgical challenge. For these cases we prefer general anesthesia with neuromuscular blockade and endotracheal intubation. In some cases of extreme prematurity and small size (e.g., less than 3 kg), when the infant is scheduled to return to the intensive care unit, we may choose to maintain endotracheal intubation into the postoperative period while the infant fully recovers. Caudal analgesia is performed for postoperative pain relief.
Pain relief for inguinal hernia repair is accomplished using regional analgesia. Caudal analgesia with dilute local anesthesia is often used for bilateral repair, and a peripheral nerve block is used for unilateral repair. However, in ambulatory children in whom a caudal block may cause lower extremity weakness, bilateral peripheral nerve blocks are performed. Analgesia may be supplemented with a small dose of an IV opioid and ketorolac.
Premature infants often exhibit central apnea following the administration of general anesthesia (GA). There are several anesthetic strategies designed to prevent this complication and these include the use of regional anesthesia instead of GA, and administration of caffeine in the perioperative period to boost ventilatory drive. Most reported studies investigating the use of spinal or epidural anesthesia report a lower incidence (not a complete absence) of postoperative apnea, as long as additional systemic sedative agents are avoided. When adjuvant sedatives, such as ketamine, are administered intraoperatively, the risk of postoperative apnea increases to a level similar to that of GA.
Caffeine is a respiratory stimulant which can decrease the incidence of postoperative apnea, bradycardia, and hypoxemia in susceptible infants. For NICU patients undergoing surgery, communication between the anesthesiologist and neonatologist is essential. The patient may currently be receiving caffeine and may not require a perioperative dose. Other patients may be going home soon after surgery; thus, a perioperative dose of caffeine will complicate discharge planning.
Almost all studies on the risk of postoperative apnea following GA were performed prior to the advent of short-acting anesthetic agents, such as sevoflurane, desflurane, and remifentanil. Some studies have shown that these newer agents of limited duration result in a decreased incidence of postoperative apnea. However, definitive data on the association of postoperative apnea with use of these agents is lacking.
Both retrospective and prospective studies have been performed in an attempt to delineate the types of patients at risk for postoperative apnea. Characteristics of premature infants that are more likely to develop postoperative apnea include low gestational age, low postconceptional age (PCA), preoperative apnea of prematurity, and anemia (usually defined as a hemoglobin level <10 g/dL) (Figure 18.1). The PCA at which postoperative apnea will not occur is unknown; however, there are no reports of postoperative apnea in infants aged greater than 60 weeks PCA (Figure 18.2). (These statements are based on older studies that attempted to determine PCA-based risk, but the term “postconceptional age” has been abandoned in favor of the more reliable “postmenstrual age.”) The true risk for an individual patient is indeterminate and is likely a continuum based on the infant’s gestational and chronological age, and coexisting medical conditions.
Figure 18.1 Predicted probability of apnea in recovery room and postrecovery room by weeks postconceptual age as demonstrated by review of multiple studies.
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