Neonates and infants have fewer and smaller alveoli, reducing lung compliance; in contrast, their cartilaginous rib cage makes their chest wall very compliant. The combination of these two characteristics promotes chest wall collapse during inspiration and relatively low residual lung volumes at expiration. The resulting decrease in functional residual capacity (FRC) limits
oxygen reserves during periods of apnea (eg, intubation attempts) and readily predisposes them to atelectasis and hypoxemia.
Compared with older children and adults, neonates and infants have a proportionately larger head and tongue, narrower nasal passages, an anterior and cephalad larynx, a longer epiglottis, and a shorter trachea and neck. These anatomic features make neonates and infants obligate nasal breathers until about 5 months of age. The cricoid cartilage is the narrowest point of the airway in children younger than 5 years of age.
Cardiac stroke volume is relatively fixed by a noncompliant and immature left ventricle in neonates and infants. The cardiac output is therefore very sensitive to changes in heart rate.
Thin skin, low fat content, and a greater surface area relative to weight promote greater heat loss to the environment in neonates. Heat loss is compounded by cold operating rooms, wound exposure, intravenous fluid administration, dry anesthetic gases, and the direct effect of anesthetic agents on temperature regulation. Hypothermia has been associated with delayed awakening from anesthesia, cardiac irritability, respiratory depression, increased pulmonary vascular resistance, and altered drug responses.
Neonates, infants, and young children have relatively greater alveolar ventilation and reduced FRC compared with older children and adults even after adjustment for weight. This greater minute ventilation-to-FRC ratio with relatively greater blood flow to vessel-rich organs contributes to a rapid increase in alveolar anesthetic concentration and speeds inhalation induction.
Minimum alveolar concentration (MAC) for halogenated agents is greater in infants than in neonates and adults. Unlike other agents,
sevoflurane has the same MAC in neonates and infants. Sevoflurane appears to have a greater therapeutic index than
halothane and has become the preferred agent for inhaled induction in pediatric anesthesia.
Children are more susceptible than adults to cardiac arrhythmias, hyperkalemia, rhabdomyolysis, myoglobinemia, masseter spasm, and malignant hyperthermia associated with
succinylcholine. When a child experiences cardiac arrest following administration of succinylcholine, immediate treatment for hyperkalemia should be instituted.
Unlike adults, children may have profound bradycardia and sinus node arrest following the first dose of succinylcholine without
A viral infection within 2-4 weeks before general anesthesia and endotracheal intubation appears to place the child at an increased risk for perioperative pulmonary complications, such as wheezing, laryngospasm, hypoxemia, and atelectasis.
Temperature must be closely monitored in pediatric patients because of their greater risk for malignant hyperthermia and the potential for both iatrogenic hypothermia and hyperthermia.
Meticulous attention to fluid intake and loss is required in younger pediatric patients because these patients have limited margins of error. A programmable infusion pump or ...
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