Advances in pediatric anesthesiology have greatly contributed to improved outcomes and survival in newborns and infants requiring surgical intervention. Newborn physiology is primarily characterized by a high metabolic rate, limited cardiopulmonary reserve, and decreased renal function. Multisystem organ immaturity underlies the differences in physiological response to anesthetics in the neonate, as compared to the older child or adult (1). Thus, providing anesthesia for the newborn requires many considerations beyond what is needed for the older child or adult.
Physiological differences between children and adults are important determinants when planning management of anesthesia in pediatric patients. The single most important difference that physiologically distinguishes pediatric patients from adults is oxygen consumption. Neonatal oxygen requirements are 2–3 times the adult requirement, ranging from 6 to 9 mL/kg/min. Increased oxygen demand is met by increased respiratory rate, as there is a minimal inspiratory reserve to increase tidal volume (2). As a result, infants have an increased risk of respiratory fatigue. Administration of high oxygen concentrations may depress respiratory drive in the newborn (1). Anatomic closure of the foramen ovale typically occurs within the first year of life, and anatomical closure of the ductus arteriosus begins at 10 hours of life, but is usually completed by 2 months of age. Neonatal circulation may revert to fetal circulation if the physiological parameters responsible for cardiac shunt closure are not maintained. As such, it is important to avoid factors that increase pulmonary vascular resistance (physiologic stress, hypoxia, hypercarbia, acidosis, and hypothermia) in newborns (1). Furthermore, maintenance of heart rate is essential in the neonatal period. Cardiac output is dependent on heart rate, as stroke volume is fixed due to decreased compliance of the immature ventricle. Thus, while maintaining preload is important during anesthetic management, increasing preload provides minimal benefit for improving cardiac output. The sympathetic nervous system is also immature in newborns. Bradycardia (slow heart rate) may occur after stimulating procedures such as laryngoscopy, oropharyngeal suctioning, or gastric tube placement rather than the expected tachycardia (fast heart rate) seen in patients with mature sympathetic nervous systems. Treatment with anticholinergic agents may be required (1).
Prior to surgery, a thorough pre-anesthetic history and physical examination must be performed with the goal of identifying potential anesthetic complications due to coexisting disease (1). A review of all organ systems, including identification of genetic syndromes and associated anomalies, should be conducted. Any previous anesthetic and surgical records should also be reviewed to reveal any potential difficulties with airway management or anesthetic emergence (1). Prior to the induction of anesthesia, infant patients should be given glucose-containing intravenous maintenance fluids to prevent hypovolemia or hypoglycemia caused by fasting. During preparation for anesthetic induction, the anesthesiologist must assess the risk of potential pediatric aspiration events (1). Risk factors for aspiration in the perioperative period include neurologic abnormality, emergency surgery, intestinal obstruction or increased abdominal pressure, light anesthesia, and the skill of the anesthesia provider. Infants and young children are particularly prone to regurgitation and aspiration for a variety of reasons including air swallowing while crying and decreased lower esophageal sphincter tone. In one study, almost all cases of pulmonary aspiration occurred in children who gagged or coughed during airway management, either because neuromuscular blockade was not administered or airway manipulation occurred before the child was completely paralyzed (1).
The American Academy of Pediatrics Committee on Drugs (COD) notes that children tend to be particularly susceptible to oversedation with anesthesia. Thus, provision for safe sedation in children (infants, in particular) requires skill and organization of resources to prevent severe negative patient outcomes (3). Pulse oximetry, particularly the type that provides an audible change in tone as the saturation changes, should be required for every patient sedated for a procedure, as it provides an early warning of developing oxygen desaturation (3). In addition, both clinicians administering anesthesia and those in the postoperative arena should always have the appropriate reversal agents (e.g., naloxone, flumazenil) at their disposal.
References
- Vadi, M., Nour, C., Leiter, P., Carter, H.(2017). Anesthetic Management of the Newborn Surgical Patient, Pediatric and Neonatal Surgery, Joanne Baerg, IntechOpen, DOI: 10.5772/66932. Available from: https://www.intechopen.com/books/pediatric-and-neonatal-surgery/anesthetic-management-of-the-newborn-surgical-patient
- Bansal, T., Hooda, S. (2013). Anesthetic Considerations In Paediatric Patients. Journal International Medical Sciences Academy 26(2):127-131.
- Guthrie, E. (2006, August 25). General Anesthesia in Pediatric Patients. Retrieved from http://stage.uspharmacist.com/article/general-anesthesia-in-pediatric-patients.
