A neonate with respiratory failure

Prepared by...................Sataporn Muangin, M.D.
CC : Newborn baby girl with respiratory failure
PI : 24 hours of age, baby girl was referred from Lampang Regional Hospital (LRH). She was born at 38 weeks gestation to 30 year-old mother, G2P1. The pregnancy was uneventful. Prenatal blood screening (VDRL,Anti HIV, HBsAg) were all negative. The delivery was normal at a community hospital. Apgar score were 6 and 7 at 1 and 5 min, respectively. Her birth weight was 2950 g. At 1.5 hr of age, she became dusky with respiratory distress. She was transferred to LRH where she was intubated and put on a ventilator. Chest x-ray (Figure 1) was done, showed bowel-gas pattern on the right side of chest, compatible to Congenital Diaphragmatic Hernia (CDH). She was administered 100 % oxygen with O2Sat around 90-95% during on conventional ventilation. After initial stabilization, she was later on referred to Chiangmai University Hospital.
Significant PE

On arrival ,vital sign T 37c PR 130/min BP 57/32. She was on endotracheal tube with manual bagging, O2Sat 92 %(left leg). She was alert and active with occasional agitation. Her chest was bulging with decreasing breath sound on the right side. Heart sounds were normally heard on the left side. The abdomen was scaphoid with no detected bowel sounds. The rest of her physical exam were in normal.
Figure 1. Chest film shows a bowel-gas pattern on the right side of chest.
Provisional diagnosis: Congenital Diaphragmatic Hernia with respiratory failure
Any differential diagnosis on Chest x-ray?
Figure 2. Chest film shows cystic lesions in the left lung field. A patient is diagnosed as congenital cystic adenomatoid malformation
Clinical course of this patient
A baby was placed on a mechanical ventilator in considerably high settings and 100 % oxygen. Her preductal oxygen saturation occasionally fell to around 80% and gradually returned to around 92-95% after the stimuli. Since she had the lability in oxygenation, PPHN was diagnosed and the treatments during 24-48 hrs of age were based on the principle treatment of PPHN. She was sedated with fentanyl and paralyzed with pavulon. Inotropes were commenced to keep systolic blood pressure higher than normal limit. She was given NaHCO3 several times to correct acidosis as shown in her blood gas .
At 48 hrs of age , she had a rapid increase in preductal oxygen saturation to 99% and the settings as well as oxygen requirement were gradually weaned to minimal assisting . She had been stable and went on surgery for hernia repaired at 96 hrs of age.
How to approach CDH: Excerpt from NeoReviews

The Neonatologist's, Perinatologist's and Surgeon's perspectives October 1999
Incidence: 1: 2,000 to 1:5,000 live births
Approximately 90% of all CDHs occur on the left hemithorax. (Figure 3)

Prenatal diagnosis

This condition is often missed on routine ultrasonography. Visualization of the fluid-filled bowel with peristalsis at the level of the four chamber view of the heart is diagnosis. Associated findings include absence of intra-abdominal stomach bubble and shift of the heart and mediastinum away from the side of herniation. Polyhydramnios is frequently seen.
Differential diagnosis

Congenital cystic adenomatoid malformation
mediastinal cystic teratoma
bronchogenic cysts
neurogenic tumors
Obstetric management

Prenatal counseling

1. multidisciplinary teams (Obstetrician, Perinatologist, Neonatologist, Surgeon and Geneticist)
2. the option of pregnancy termination should be offered before the fetus becomes viable (before 22 weeks)

Delivery management

1. The baby should be delivered in a center that has experienced personnel and available therapies.
2. Prompt intubation is needed and bag-mask ventilation should be avoided.
3. Placement of a nasogastric tube to provide intestinal decompression is recommended.
4. UVC access and paralysis are advised.
Preoperative stabilization
Since 1990, CDH was considered as a physiologic emergency, not a surgical emergency
Physiologic changes in CDH are lung hypoplasia and abnormal arteriolar muscularization, resulting in pulmonary hypertension (PPHN)
Therefore, delayed surgical repair was introduced.
" The mean age at the time of surgery is 72 hours"
What is persistent pulmonary hypertension of newborn
Previously, this condition was named "Persistent Fetal Circulation" (PFC).
PPHN is a potentially life threatening disorder that complicates the transition from fetal to postnatal life.
Figure 4. A diagram shows normal circulation in a newborn and persistent fetal circulation.
Any illnesses, resulting in hypoxemia or acidosis (respiratory and metabolic) may precipitate pulmonary vasospasm, decrease pulmonary blood flow. As a result, a right to left shunting through foramen ovale with/without ductus arteriosus can occur.

This shunting of relatively poor oxygenated blood into the systemic circulation results in relatively low systemic oxygenation if uncompensated by increased cardiac output , may reduce oxygen delivery.
Diagnosis

1. Lability of oxygen ("flip flop" phenomenon).
2. Different between Preductal and Postductal oxygenation (Figure 5)
3. Demonstration of shunt by two dimensional echocardiogram
4. Evidence of Supra-systemic Pulmonary Pressure by echocardiogram
5. Direct measurement of pulmonary pressure by cardiac catheterization
Principle treatment

Improve alveolar oxygenation

by keeping preductal O2Sat >90% and PaO2 level up to 60 mmHg

Minimize "inappropriate" pulmonary vasoconstriction

Ventilatory support and alkalosis

1. Gentle ventilation
2. Keep normal PaCO2 but some infants may benefit in low PaCO2 or higher than normal pH (recommend 7.45-7.55/never>7.55)

Maintenance of systemic arterial blood pressure

1. to decrease Rt-to-Lt shunt and increase pulmonary blood flow
2. Inotropes are frequently used to improve systemic blood pressure

Vasodilator

1. Only inhaled nitric oxide is a proven therapy (selective pulmonary vasodilator)
2. Others are Tolazoline, Magnesium sulphate, Nitroprusside but usually cause systemic hypotension

Figure 6. Nitric oxide administration
Therapeutic option for PPHN (Figure 7)


What is the outcome of CDH?
- Overall survival rate is difficult to ascertain because of the heterogenicity of geographic and institutional practices.
- Pre-ECMO era survival rate 40%
- ECMO era survival rate 63%
- CDH survivors have a number of significant medical issues after hospital discharge, including chronic lung disease, gastroesophageal reflux, growth failure , reherniation, volvulus, scoliosis, sensorineural hearing loss and developmental delay.
What is ECMO ? (Extracorporeal membrane oxygenation)
It is prolonged cardiopulmonary bypass for neonates with respiratory of cardiac failure complicated by pulmonary hypertension or ventricular failure who are unlikely to survive despite maximal medical management.
Figure 8-9. Shows a diagram and ECMO machine.

Criteria for ECMO is Oxygenation Index(OI) >40
OI = (MAP x FiO2 x100) / PaO2
MAP= Mean Airway Pressure
What have we learned form this patient?
- CDH is always in the differential diagnosis of neonatal respiratory distress
- Prenatal diagnosis improves outcome
- It is a physiologic emergency not a surgical emergency (Delayed surgical repair concept)
- Stabilization the patient (correct PPHN) before surgery is the most important
- Although the ECMO era the survival rate remains not great (63%)
Suggested readings:
1. LP Halamik. Congenital Diaphragmatic hernia. The Perinatologist's perspective.Neoreview. October 1999: e67-70
2. ED Skarsgard. Congenital Diaphragmatic hernia. The Surgeon's perspective.Neoreview. October 1999: e71-78
3. KV Meirs. Congenital Diaphragmatic hernia. The Neonatologist's perspective.Neoreview. October 1999: e79-87
Diagnosis : Congenital Diaphragmatic Hernia

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