Case 60 - congential diaphragamtic hernia

Question 1

Describe the pathophysiology of congenital diaphragamtic hernia

Answer 1

• occurs during fetal development
• posterolateral diaphragm defect on the Left side = most common site
• abdominal contents hernia into pleural cavity –> impair lung development –> pulmonary hypoplasia
• although ipsilateral side is primarily affected, contralateral lung also is abnormal:
  
  • decreae number of bronchi and alveoli
  • inappropriate muscularized pulm arteries

Physiologic changes

• increase in PVR and persistent pulm HTN
  
  • persistent pulm HTN –> patent foramen ovale and ductus arteriosus –> hypoxia and acidosis –> further leads to patent ductus arteriosus (closes only with increase PaO2)

Question 2

is congenital diaphramatic hernia an emergent surgery?

Answer 2

No

• may be associated with congenital anomalies (CVS, GI, GU, craniofacial)

Initial managment

• intubate
• improve ventilation and oxygenation
• once stabilized, perform surgery

Question 3

What are the clinical features of CHD?

Answer 3

pathophys review

• herniation of abdominal contents into thorax causing hypoplastic lungs.
• hypoplastic lungs –> increase PVR –> persistent pulm HTN of newborn –> patent ductus arteriosus and foramen ovale –> hypoxia and acidosis (becuase reduced blood flow to lungs)

Clinical features:

• tachypnea
• cyanosis
• scaphoid abdomen
• absence of breath sounds on affected sides
• heart sounds shifted to contralateral side

Question 4

how is CHD diagnosed?

Answer 4

In utero

• ultrasonography may show disease

Post-natally

• CXR –> definitive diagnosis –> abdominal contents in thoracic cavity

Question 5

What is the preop managment of a neonate with CHD?

Answer 5

1) AVOID bag mask ventilation
* can cause distension of abdominal organs in thorax –> compress the lungs further –> prevent futher oxygenation and ventilation

2) Tracheal intubation

3) maintain insp pressure < 40 cm H2O

• at risk for pneumothorax of contralateral lung
  
  • contralateral lung affected 2/2 gas flow to path of least resistance = contralateral lung

4) insert OG tube
* decompress stomach to avoid compression of lungs
5) transfer to NICU for sabilization

Question 6

What is the pulmonary goals for CHD patients?

Answer 6

AVOID INCREASES IN PVR

factors that increase PVR

• Hypoxia
• hypercarbia
• acidosis
• hypothermia
• sympathetic stimulation

Other ways to decrease PVR

• inhaled nitric oxide
• pulmonary vasodilators
• avoid volume overload and subsequent pulm edema
• ECMO

Question 7

What is permissive hypercapnia? How may this be beneficial to CHD patients?

Answer 7

Permissive hypercapnia

• Allow PaCo2 to increase, while maintaing adequate oxygneation and acid-base balance.
  
  • PaCO2 can lead to resp acidosis, but you can correct pH with other measures like bicarb or THAM solution

permissive hypercapnia and CDH pts

• goal is to avoid increase in PVR.
• in order to decrease PaCo2, higher inspiratory pressure required to maintain ventilation –> result is barotrauma / risk of pneumothorax
• in permissive hypercapnia, allow PaCo2 to increase, but maintain normal acid-base balance with bicarb and THAM.
• maintain pre-ductal SaO2 > 90%

Question 8

What are the anestheic considerations for neonates with CDH?

Answer 8

1) Avoid increases in PVR

• hypoxia, hypercarbia, acidosis, hypothermia, symp stimulation = all increase PVR
• adequate oxygenation
• hyperventilation
  
  • continue permissive hypercapnia if employed pre-operatively
  • keep an eye on peak insp press if hyperventilating
• Alkalosis
  
  • serial ABGs
• Normothermia

2) Avoid increases in peak inspiratory pressure

• may need higher peak inspiratory pressure to maintain adequate ventilation and oxygenatoin
  
  • places lungs at risk for barotrauma and pneumothorax (contralateral lung more affected)
• consider decrease TV and increase RR –> may decrease inspiratory pressures

3) continue pharmacologic infusions (NO, pulm vasodilat)
4) avoid N20
* can cause intestinal distension –> impede abd closure

Question 9

All of a sudden, the blood pressure starts to decrease, and neonate is progressively becoming unstable and deteroriating. What is the most likley cuaes, what do you do?

Answer 9

• avoid high peak inspiratory pressure > 40 cm h2o
• if neone suddenly beocmes unstable, think pneumothorax of contralateral lung
  
  • needle decompression
  • followed by chest tube insertion

Question 10

Would you extubate the neonate after surgery?

Answer 10

NO

• despite surgery fixing the defect, the PVR is not going to be normalied immedietly
• pulm HTN may persist, and neonates will require oxygen and ventilatory support
• the neonate still has pulmonary hypoplasia that will not change immedietly with surgery