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 to pauses close together, followed by a series of short, shallow breaths With periodic