Neonatal Apnea

Bodhankar Uday
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Evaluation of the Apneic Infant (6)
History:
- Perinatal complications and Apgar scores
- Gestational and postnatal age
- Drugs given to mother or infant
- Preceding infant and environmental temperatures
- Risk factors for infection


Potential cause Associated history or signs Evaluation
InfectionFeeding intolerance, lethargy, temperature instabilityComplete blood count, cultures if appropriate
Impaired oxygenationCyanosis, tachypnea, respiratory distressContinuous oxygen monitoring, arterial blood gas measurement, chest x-ray examination
Metabolic disordersJitteriness, poor feeding, lethargy, CNS depression, irritabilityGlucose, calcium, electrolytes
DrugsCNS depression, hypotonia, maternal historyMagnesium, screen for toxic substances in urine
Temperature instabilityLethargyMonitor temperature of patient and environment
Intracranial pathologyAbnormal neurological examination, seizuresCranial ultrasound examination
Gastroesophageal refluxDifficulty with feedsSpecific observation, barium swallow


Electroencephalography: An EEG may be necessary to complete the workup if there is any question about the neurologic status of the infant. PneumographyPneumography : A pneumogram is another essential tool in the diagnosis of apnea. Chest leads provide a tracing that gives a continuous recording of both heart rate and chest wall movement and can detect periods of central apnea and periodic breathing.

Abnormal pneumogram: An abnormal pneumogram is defined as one in which one of the following patterns is demonstrated.
- Periods of prolonged apnea (cession of respiratory movement of > 20 seconds).
- Short apnea (cessation of respiratory movement of < 20 seconds) if accompanied by bradycardia.
- Episodes of periodic breathing lasting more than 5% of the total quiet or sleep time.

Four-channel pneumogram: A more accurate instrument for the diagnosis of apnea is a 4-channel pneumogram, in which a nasal thermistor to detect airflow and a pulse oxymeter are added to the standard heart rate and chest wall channels. With the addition of thermistor, central apnea can easily be distinguished from obstructive apnea. The addition of the pulse oxymeter helps in determining if there are significant oxygen desaturations during periods of apnea or heart rate drops. This distinction carries more than academic interest, since treatment of the disorder should be directed specifically to the type of apnea that is detected.

Pneumograms have been widely used as screening tests to predict SIDS or life-threatening apnea in asymptomatic preterm and term infants. However, no prospective controlled study has confirmed that these 12- to 24- hour recordings of heart rate and thoracic impedance are predictive of SIDS or life-threatening apnea. No studies to date have proved that the pneumogram has predictive value that distinguishes who will survive from those who will die. However, pneumograms occasionally may be helpful in clinical management e.g. to distinguish false from true apnea monitor alarms. (7)

Polysomnography: In research-oriented centers, a polysomnogram (a study that monitors specific EEG leads and muscle movement) can be used for a more thorough workup of apnea. This study will not only determine the type of apnea that occurs but can also relate it to the sleep stage of the infant. While polysomnography is certainly not indicated in all infants with apnea, its use may be beneficial in determining the exact pathogenesis of this enigmatic condition. Only after a thorough diagnostic evaluation, can adequate therapy for apnea be instituted. (1)

All preterm infants should be closely monitored for the development of this often life-threatening condition. Close attention should be paid to the type of monitoring that is given to infants in intensive care units. Preterm infants are commonly on heart rate monitors only, and they will be identified as having apnea only if the heart rate drops below the monitor alarm limit (usually set at 80 beats/min). In this case, these infants may suffer profound hypoxia before bradycardia develops, or they may have apnea with significant hypoxemia but without a drop in heart rate. In order to detect apnea, these infants should have continuous monitoring of respiratory activity or monitoring of oxygenation, or both, using either transcutaneous oximetry or pulse oximetry. (1)


References
Neonatal Apnea Neonatal Apnea 12/19/2001
<< Apnea Pathophysiology Principles of Therapy >>
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