Pediatric emergency medicine trisk 2460 2460
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Heart Rate
Normal resting heart rate for a neonate can range between 80 and 180 beats/min.
Over the first few weeks of life heart rate will decrease to 80 to 140 beats/min.
During rest and deep sleep, the heart rate will typically be in the lower range, and
in the higher range with activity or agitation. A healthy infant will show
variability in heart rate with subtle changes during inspiration and exhalation and
when alternating between sleep and alert states. Loss of heart rate variability has
been associated with systemic illnesses, such as shock and infection.
Bradycardia can be defined as either a 20 to 30 beat decrease below the
infant’s baseline or below 80 beats/min at rest. Neonates respond to poor cardiac
output by increasing their heart rate because stroke volume cannot increase
acutely. Therefore, bradycardia is often a late sign of cardiac failure after the
normal compensatory mechanisms have collapsed. Sinus bradycardia may also
occur with hypothermia, hypothyroidism, malnutrition, or electrolyte
disturbances. Premature infants may also present with recurrent bradycardic
events, particularly during episodes of increased vagal tone due to gastrointestinal
reflux, emesis, or in association with hypoxemia due to apnea. A 12-lead
electrocardiogram can help distinguish sinus bradycardia from conduction
abnormalities and heart disease. Some full-term infants have a low resting heart
rate that may reach 80 to 90 beats/min. Any infant with bradycardia who shows
other signs of cardiovascular instability, such as hypotension and poor capillary
refill, or systemic signs of lethargy or poor feeding, should be treated and
stabilized immediately.
Neonatal tachycardia can be defined as a heart rate >190 beat/min. Sinus
tachycardia may occur in the setting of shock, dehydration, or hypovolemia, as a
mechanism to increase cardiac output. Neonatal tachycardia can also occur with
fever, hyperthyroidism, severe anemia, hypoglycemia, or electrolyte disturbances,
such as hypocalcemia. The most common conduction abnormality that results in
tachycardia in the neonate is supraventricular tachycardia (SVT), which can lead
to cardiac failure and shock if sustained.
For more details on clinical considerations and management of heart rate
anomalies in the neonate, see Section: Neonatal Cardiac Emergencies.
Respiratory Rate
The normal respiratory rate of a newborn is between 30 and 60 breaths/min.
Periodic breathing is a normal finding that presents with pauses between breaths
that can last up to 10 seconds. Most commonly, the infant will have 2 to 3 pauses
close together, followed by a series of short, shallow breaths. With periodic
