APNEA OF PREMATURITY.ppt
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1、GARRETT S. LEVIN, M.D. DEPARTMENT OF PEDIATRICS DIVISION OF NEONATOLOGY,APNEA OF PREMATURITY,Definition of Apnea,Apnea is the most common problem of ventilatory control in the premature infant frequently prolonging hospitalization and the need for cardiopulmonary monitoring. The standard definition
2、of apnea is cessation of inspiratory gas flow for 20 seconds, or for a shorter period of time if accompanied by bradycardia (heart rate less than 100 beats per minute), cyanosis, or pallor.,Incidence of Apnea versus Gestational Age Although there is considerable variation in incidence and severity o
3、f apnea in premature infants, both are inversely related to gestational age. Approximately 50% of infants less than 1500 grams birth weight require either pharmacologic intervention or ventilatory support for recurrent prolonged apneic episodes. The peak incidence occurs between 5 and 7 days postnat
4、al age. Apnea of Prematurity is a specific diagnosis and usually resolves between 34 to 36 weeks postconceptual age.,ONSET USUALLY BY THIRD DAY OF LIFE!,The more hypoxic, the flatter the response to carbon dioxide.,Proposed Pathogenic Mechanisms of Apnea,Primary central respiratory center depression
5、,Decreased or inhibitory upper afferent input to the central respiratory center,Abnormal or hyperactive reflexes,Decreased or inhibitory lower afferent input to the central respiratory center,Hypoxemia,Primary central respiratory center depression - likely to result in central apnea Fewer neuronal s
6、ynapses Decreased carbon dioxide (CO2) sensitivity Decreased neurotransmitter levels Metabolic disorders Sepsis Suppression by drugs Decreased or inhibitory upper afferent input to the central respiratory center - likely to result in obstructive, central, or mixed apnea Less cortical traffic Sleep s
7、tate, especially REM sleep Seizures Metabolic disorders Sepsis Suppression by drugs,Abnormal or hyperactive reflexes - likely to result in central apnea Heads paradoxical reflex (gasp and apnea following lung inflation) Laryngeal receptors (taste buds) acting through superior laryngeal nerves Poster
8、ior pharyngeal reflex (apnea induced by deep repeated suctioning) Vascular receptors (apnea induced by large vessel distension) Decreased or inhibitory lower afferent input to the central respiratory center - likely to result in central apnea Sensory receptors (temperature receptors on face) Chemore
9、ceptor immaturity Hypoxemia - likely to result in central or mixed apnea Immature ventilatory response to hypoxemia Presence of lung disease Decreased lung volume Patent ductus arteriosus Anemia Hypotension with decreased oxygen delivery to the brain,Physiologic Effects of Apnea Decrease in arterial
10、 oxygen tension Decrease in heart rate Decrease in peripheral blood flow EEG changes suggesting CNS depression if apnea is severe Increase in venous pressure Decrease in muscle tone,Diseases Associated with Apnea Apnea is only a symptom and frequently occurs secondary to other disease processes. How
11、ever, Apnea of Prematurity is a specific diagnosis and also one of exclusion. Other causes of apneic spells should be pursued if the apnea progresses in severity, fails to respond to appropriate therapy, severe episodes occur on the first day of life, or it appears at a gestational age where it shou
12、ld not occur. Apnea should be treated with simultaneous attention focused on the primary disease. Treatment of these associated problems may result in a decrease in the frequency and severity of apneic spells. These causes include: Respiratory Distress Syndrome Pulmonary mechanical problems such as
13、Airleak, or Atelectasis Infectious causes such as Sepsis, Meningitis, or Pneumonia Intracranial Hemorrhage Seizures Anemia Gastroesophageal Reflux Necrotizing Enterocolitis Patent Ductus Arteriosus Hemorrhagic Shock Metabolic disturbances such as Hypoglycemia, Acidosis, Hyponatremia, Hypocalcemia Ma
14、ternal Drugs Inappropriate Thermal Environment - Hyperthermia,Types of Apnea Apnea has been classified into three types depending on whether inspiratory muscle activity is present. If inspiratory muscle activity fails following an exhalation, it is termed Central Apnea. If inspiratory muscle activit
15、y is present without airflow, this is termed Obstructive Apnea.If both central and obstructive apnea occur during the same episode, this is termed Mixed Apnea. It is important to characterize a patients apnea episodes into one or more types for treatment consideration.,Principles of Therapy for Apne
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