Pulmonary Problems of the Neonate. Jon Palmer, VMD, DACVIM Chief, Neonatal Intensive Care Service New Bolton Center, University of Pennsylvania, USA

Transcription

1 Pulmonary Problems of the Neonate Jon Palmer, VMD, DACVIM Chief, Neonatal Intensive Care Service New Bolton Center, University of Pennsylvania, USA

2 Lower Respiratory Diseases Ventilation/Perfusion Abnormalities Pneumonia Secondary pulmonary disease

3 Ventilation/Perfusion Abnormalities Mismatching Shunting Retention/ reversion to fetal physiology Hypoventilation Progressive atelectasis

4 Ventilation/Perfusion Abnormalities Mismatching o Uneven perfusion Poor cardiac output Poor vascular reactivity to oxygen? o Uneven ventilation Body position Weakness Fatigue Hypoventilation o Fatigue o Central weakness o Upper airway disease

5 V/Q Mismatching Arterial Arterial ph Pco Po HCO BE O 2 SAT 75% 100% O 2 content Fio 2 RA INO 2

6 Ventilation/Perfusion Abnormalities Fetal to neonatal cardiopulmonary physiology o Delayed transition Many not occur at birth May not occur for 12 hr Few signs noted (ABG) o Tachypnea - normal o Failure transition Persistent Pulmonary Hypertension o Idiopathic Congenital interstitial pneumonia Congenital heart defect

7 Ventilation/Perfusion Abnormalities o Reversion to fetal circulation Induced pulmonary hypertension o Severe sepsis Pulmonary vasoconstriction o Significant acidosis o Significant hypoxemia Marked systemic hypotension o Severe sepsis Systemic vasodilation Both may play a role o After normal birth systemic and pulmonary BP similar

8 Ventilation/Perfusion Abnormalities o Reversion after birth caused by Hypoxemia Inflammatory mediators Systemic hypotension o Reversion as a safety net o Neonatal period dangerous Full decrease in pulmonary resistance o May take 2-3 weeks Ductus arteriosus/ foramen ovale remain patent Increases pulmonary resistance/ decreases systemic pressure o Increase right to left shunt fraction o Significant hypoxemia

9 Right to Left Shunt Arterial Arterial ph Pco Po HCO BE O 2 SAT O 2 cont Lac Fio 2 RA INO 2

10 Arabian Colt 48 hr old foal Weak, needed assistance rising o But able to ambulate Tachycardic and tachypneic Dysphagic (milk out nose) At 48 hr noticed blue mucus membranes

11 Right to Left Shunt Arterial Arterial Venous ph Pco Po HCO BE O 2 SAT < O 2 cont Fio 2 RA INO 2 INO 2

12

13 Hypoventilation Hypoventilation = increased Paco 2 o Casually misused decreased respiratory rate Decreased alveolar ventilation o Depressed respiratory center Neonatal Encephalopathy Phenobarbital therapy Head trauma Sepsis o Neuromuscular disease Spinal cord injury Botulism o Respiratory muscle fatigue Weak foal Stiff lungs

14 Hypoventilation Decreased alveolar ventilation o Limitation movement thorax or lungs Fractured ribs Pneumothorax/ hemothorax Diaphragmatic hernia o Pulmonary Disease - decreased compliance Atelectasis Pneumonia Surfactant? Obstructive lesions - increased rz o Pharyngeal collapse

15 Progressive Atelectasis Unable to maintain FRC (Functional Residual Capacity) o Weakness/compliant chest wall o Stiff lungs Some alveoli collapse on exhalation o Repetitive collapse eject surfactant o Some alveoli don t reopen o Closed alveoli pull on others More alveoli close Decreased compliance o As more atelectasis o Causes more fatigue Self-perpetuating

16 Wave Chest Fatigue No longer be able to hold the chest open Inspiration o Diaphragm contracts o Chest wall pulled towards the lungs o Abdomen expands Expiration o Diaphragm relaxes o Chest wall moves out o Abdomen moves in Significant fatigue o Respiratory failure o Respiratory/cardiac arrest Sleeping neonate

17 Progressive Hypercapnia Paco 2 > 60 mmhg (acidotic) o Release catecholamines Increased in CO Increase BP Catecholamine o Maximum catecholamine response With Paco 2 = 80 o Marked tachypnea

18 Progressive Hypercapnia Paco 2 > o CNS depression o Myocardial depression o Slow RR They look better Severe hypercapnia o Respiratory arrest o Cardiac arrest o Death Treatment o Mechanical ventilation o Methylxanthines (caffeine) o Doxapram

19 Positive Pressure Ventilation

20 Infectious Pneumonia Septicemia o Primary pulmonary infection Usually GI invasion Localize diffusely in lungs o Systemic infection Bacteremia Secondary localize in lungs Bacterial o Hematogenous colonization Usually opportunists variety of pathogens Nosocomial multiply resistant

21 Infectious Pneumonia Bacterial o Fungal o o Aspiration Often mixed infections Usually opportunists variety of pathogens Nosocomial multiply resistant Candida Usually multifocal o Pneumonia common o Hyperkeratotic tongue surface o Esophageal, intestinal lesions o Joint infections Can be primary or secondary Aspergillus Viral pathogens o o o Herpes Virus Equine Viral Arteritis virus Equine Influenza virus

22 Aspiration Pneumonia May or may not be symptomatic Lung changes caudal heart base o Except foals in lateral recumbency when they aspirate Signs o Respiratory effort and rate are increased o Pneumonic sounds Referred upper airway sounds o Apneustic breathing pattern o Radiographs or ultrasound examination o Hematology and blood fibrinogen Mixed bacterial flora expected Prognosis o Most important factor - stopping aspiration

23

24 Meconium aspiration Rare o Before birth Associated with asphyxia Fetal gasping o During delivery Liquid meconium - upper airways Diagnosis o Stained nasal discharge o Radiographic changes Signs o Persistent tachypnea o Inflammatory hemogram o No bacterial infection Persist up to a week or longer Tachypnea and hyperfibrinogenemia May be no radiographic/us changes o Secondary bacterial infections

25 Birth Trauma

26 Secondary Pulmonary Disease Traumatic Pulmonary Disease Fractured ribs o Pulmonary contusions o Pulmonary/Plural hemorrhage o Lacerations of major arteries o Pneumothorax o Traumatic diaphragmatic hernia Pleuritis and pleural effusion

27 Rib Fractures Physical Examination 2-4 cm above costochondral junction Involving 4 to 12 ribs in a straight line Any rib or set of ribs may fracture o Most frequently anterior chest (ribs 2-8) Over the heart Palpation - feeling click Auscultation - click associate with heartbeat Easily confirmed on radiographs o Ultrasound?? needs to be done casefully

28 Rib Fractures Hemorrhage Primarily bleeding from intercostal arteries Most often diffuse chest wall o Can be subpleural o Can develop hemothorax May be extensive - not evident externally Lung contusions - hemothorax Lacerations of the myocardium o No pericardial damage - Cardiac tamponade o Arrhythmias Trauma to other structures

29 Rib Fractures Clinical Signs Signs are variable From pain, anemia, cardiac arrhythmias o o Tachycardia Tachypnea Positional o o o Exacerbated during examination Exacerbated when down Weak, minimally responsive foal Distressed when on one side - relief when turned Exacerbated of hypotension when turned

30

31

32

33

34

35

36

37

38

39

40 Secondary Pulmonary Disease Abdominal Hypertension Abdominal hypertension o Ruptured bladder o Intestinal distension Acute enteritis Ileus Decreased pulmonary blood flow Increased atelectasis Decreased compliance Increased mismatching/shunt fraction

41