- The small and limited number of alveoli in
neonates and infants reduces 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) is
important because it limits oxygen reserves during periods of apnea
(eg, intubation) and readily predisposes them to atelectasis and
- Neonates and infants have a proportionately larger
head and tongue, narrow nasal passages, an anterior and cephalad
larynx, a long epiglottis, and a short trachea and neck. These anatomic
features make neonates and most young 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.
- Stroke volume is relatively fixed by a noncompliant
and poorly developed left ventricle in neonates and infants. The
cardiac output is therefore very dependent on heart rate.
- Thin skin, low fat content, and a higher surface
relative to weight allow greater heat loss to the environment in
neonates. This problem 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
higher alveolar ventilation and lower FRC compared with older children
and adults. This higher minute ventilation-to-FRC ratio with relatively
higher blood flow to vessel-rich organs contributes to a rapid rise
in alveolar anesthetic concentration and speeds inhalation induction.
- Minimum alveolar concentration (MAC) is higher
in infants than in neonates and adults for halogenated agents. 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 a preferred induction agent in pediatric anesthesia.
- Children are more susceptible than adults to
cardiac arrhythmias, hyperkalemia, rhabdomyolysis, myoglobinemia,
masseter spasm, and malignant hyperthermia (MH) after administration
of succinylcholine. If a child unexpectedly experiences cardiac
arrest following administration of succinylcholine, immediate treatment
for hyperkalemia should be instituted.
- Unlike in adult patients, profound bradycardia
and sinus node arrest can develop in pediatric patients following
the first dose of succinylcholine without atropine pretreatment.
- 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 higher risk for MH and the potential for
both iatrogenic hypothermia and hyperthermia.
- Meticulous fluid management is required in small
pediatric patients because of extremely limited margins of error.
A programmable infusion pump or a buret with a microdrip chamber
should be used for accurate measurements. Drugs are flushed through
low dead-space tubing to minimize unnecessary fluid administration.
- Laryngospasm can usually be avoided by ...
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