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Plain and simple… Children are not small adults! Anatomic, physiologic and pharmacologic differences are quite prominent in children and these factors influence the approach used to manage children requiring anesthesia.
For years, sub-specialization in pediatric anesthesia has required fellowship training in a certified pediatric anesthesia program. However, it wasn’t until just recently that the Board of Anesthesia has recognized pediatric anesthesia as a unique specialty requiring a sub-board certification examination.
In the United States, it is estimated that approximately 6 million children will receive anesthesia in a given year. Infants, defined as children under 1 year of age, account for 1.5 million of the anesthetics performed. The goal of anesthesia is to provide amnesia, analgesia, immobility and maintain stable hemodynamic and respiratory parameters during a surgical procedure, interventional or diagnostic procedure or imaging study, then allow the child to emerge from anesthesia in a pain-free state.
There are many unique areas relevant to the provision of anesthesia for children.
The areas will include:
Anesthesia for the newborn: Newborns rarely undergo elective surgical procedures. Most procedures in the newborn are related to significant disease processes requiring surgical or procedural intervention. Examples include:
- Brain malformations
- Congenital cardiac disease
- Intestinal obstructions
- Tracheal esophageal fistulas
- Diaphragmatic hernia
- Lung malformations
- Airway abnormalities
Other indications related to complications of extreme prematurity, include retinopathy of prematurity, necrotizing enterocolitis, and patent ductus arteriosus, among others. The final category where anesthesia is required in the newborn period includes procedures necessary to assist in the hospital management of sick infants. These include line placements (IV’s, central lines, arterial lines) , radiological imaging, cardiac catheterization and interventional procedures.
Pharmacology: Anesthetic drugs are some of the most potent agents used in modern medicine and have to be selected based on the illness and/or underlying medical condition of the child as well as the type of monitoring needed for the procedure.
Airway management and ventilation.
In contrast to adults, children’s airways are, anatomically, more anterior; the tongue and head are larger. This makes the airway of small children more challenging, particularly with bag mask ventilation. Many strategies designed for adult airways are less reliable in children and therefore require an in-depth understanding of management strategies and are aided by prior experience. Ventilation also requires a different approach in children. The effects of positive pressure on hemodynamics is much more prominent, as the lungs and chest wall mechanics differ significantly from adults.
Anesthetic considerations in unusual pediatric diseases.
There are a large number of unusual and rare diseases in pediatrics that require a unique approach to anesthetic management. These include myopathies, neuropathies, inborn errors of metabolism, and developmental abnormalities of the heart, lung, brain, liver and kidneys. Additionally, some underlying conditions may not be identified prior to anesthetic induction. Examples include:
- Neuromuscular diseases
- Malignant hyperthermia
- Undiagnosed valvular heart disease
- Unilateral vocal cord paralysis
- Subglottic stenosis
- Late onset inborn errors of metabolism
Although we would prefer to have the diagnosis prior to induction of anesthesia, it is not uncommon to identify prior, undiagnosed maladies with the patient’s first anesthetic.
Psychosocial considerations in anesthetizing young children
Children are unique. They require significant preparation before receiving anesthesia. Preoperative evaluation today includes a thorough review of the child’s medical history and an exam. Psychological preparation is usually facilitated by the involvement of members of the child’s family. Many centers allow a parent to accompany their child to the OR to minimize the fear of surgery.
Let’s start in the newborn arena. Perhaps one of the most interesting developments in the past 10 years has been the concern for neurotoxicity from the exposure to anesthetic agents in early infancy. It has been recognized for decades that the brain overdevelops neuronal connections (synaptogenesis) in late gestation and early infancy and many of these connections are carefully removed through the process of apoptosis or programmed cell death. Programmed cell death is mediated by binding blocking agents to the NMDA receptors in the brain or by agonists binding to the GABA receptor. Unfortunately, many of the anesthetic agents in use today manifest at least part of their anesthetic effect by binding to the same group of receptors. Animal studies, primarily in newborn rodents, and a few in primates have demonstrated apoptosis and neurotoxic effects with high doses, repeated doses, prolonged exposure to single anesthetic drugs or exposure to a combination of drugs that affect both the GABA and NMDA receptor systems.
Apoptosis has been demonstrated in animal studies with exposure to inhalational anesthetics, ketamine, midazolam and propofol. Animal studies have also demonstrated a critical period of vulnerability when the maximal number of synapsis is created and the brain is primed for programmed cell death. This period occurs at different gestational ages in different animal species.
The finding of neurotoxicity and developmental abnormalities in theses animal studies raised enough concern that the FDA convened an advisory committee in 2007 to address changes to anesthetic practices in newborns and infants. The committee was reluctant to make recommendations because there was no human clinical data to validate the need for change and the majority of procedures performed in newborns and young infants were necessary and could not be delayed. A few retrospective studies evaluating hernia repair in children less than 6 months of age and urologic procedures in children less than 2 years of age suggested that early exposure to anesthesia might be associated with neurocognitive dysfunction.
These studies however, had an inherent bias and poor controls. A study from the Netherlands evaluating 1,143 identical twins exposed to anesthesia before age 3 did not demonstrate a relationship between early anesthetic exposure and cognitive performance by age 12. More recently, two prospective studies, the PANDA (Pediatric Anesthesia Neurodevelopment Assessment) and the GAS studies have been initiated. The PANDA study has published a feasibility study in the Journal of Neurosurgical Anesthesia in 2012. They performed a small pilot study comparing 28 sibling pairs. One sibling was exposed to anesthesia for repair of an inguinal hernia before 36 months of age. The other did not require a surgical intervention. The siblings underwent formalized neuropsychological testing between the ages of 6-11 years of age. The neuropsychologic testing did not reveal any difference between the two groups. A larger study is currently underway. No preliminary data is available from the GAS study, which compares regional anesthesia and inhalational anesthesia for infants undergoing hernia repair.
The concerns of general anesthesia in infancy remain unanswered. Preliminary data from the PANDA study and the twins study from the Netherlands suggests that if there is an effect from early anesthesia exposure, the effect of a brief exposure in infancy does not appear to be easily detected. On the other hand, the effect of more prolonged exposure to anesthetic agents in the OR, the ICU, or with repeated procedures remains completely unknown.