NEONATAL EMERGENCIES-*INTRODUCTION*CONGENITAL DIAPHRAGMATIC HERNIA

Speaker: Dr Bhagirath.S.N

Moderator: Dr Sarika

Introduction

Changing trends

• Neonatal emergencies no longer imply a haste to operate

• On the contrary, emphasis is laid on preoperative approaches to

reduce the intraoperative morbidities.

• Probable exceptions to the rule are

Gastroschisis (usually attended to before 12-18 hours)

Airway webs causing airway obstruction

Acute subdural/ epidural hematomas (traumatic delivery)

• This delayed approach requires multi modal specialties to be available:

Specialised nursing units

Pediatric radiologists

Pediatric intensive care physicians

Specialised laboratory facilities

Introduction…..(contd)

Surgical Procedures• Can be broadly classified as those done in first week and between 1st & 4th week of life.

• before the first week of life:

Congenital Diaphragmatic Hernia

Omphalocele

Gastroschisis

Tracheo-esophageal fistula

Intestinal Obstruction

Meningomyelocele

• between 1st & 4th week of life:

Necrotising Enterocolitis

Pyloric stenosis (controversial)

•The associated burden of coexistent congenital anomalies and prematurity add to the problem.

•Mortality most often results not from the neonatal emergency listed here but from the morbidity associated with the coexistent congenital anomaly.

• This is especially seen in congenital anomalies of the heart which constitute a large chunk of the coexisting anomalies.

Congenital Diaphragmatic Hernia

Introduction

•First described in 1679 by Lazarus in post-mortem examination of a 24

year old man

• First successful repair was done in a 3 month old girl in 1929

• Gross, in 1946 achieved the first successful repair of neonatal hernia

within 24 hours of birth

• The present trend is to stabilise the patient with Nitric oxide

administration (for pulmonary hypertension), high frequency

ventilation, pulmonary vasodilators and procedures like Extra corporeal

membrane oxygenation (ECMO)

• 25% - 30% come with associated congenital anomalies like Ventricular

Septal defect, vascular rings, coarctation of aorta, trisomy 13 and

trisomy 18, meningomyelocele and anencephaly.

Congenital Diaphragmatic Hernia

• Incidence: 1 in 3000-5000 live births• Mortality rate: 40% - 50% (previously), < 75% (at present)

• Embryology

6th week 7th week 16th week

Congenital Diaphragmatic Hernia..(contd)

Why does it always ascend upto the left side. (90%).?• delayed closure of the left half of the diaphragm compared to the right

• happens through one of the three defects

left or right posterolateral foramen of Bochdalek

Anterior foramen of Morgagni

“Eventration” of the diaphragm

incomplete muscularization of the diaphragm results in a hernial sac.

Sac is pushed up into the thorax secondary to raised intra-abdominal

pressure

This is “eventration” of the diaphragm. Eventration is additionally explained by incomplete innervation of the diaphragm by the phrenic nerve leaving behind atonic areas.

Congenital Diaphragmatic Hernia..(contd)

Antenatal Diagnosis

• Mainstay is Ultrasonography

USG reveals reduction in alveoli and bronchioli (pulmonary hypoplasia) Malrotation of intestines

• Foetal MRI

• Chest X-ray

Assessment of course and severity of condition

• Early gestational diagnosis• Severe mediastinal shift• Polyhydramnios• small lung to thorax transverse area ratio• Herniation of liver or stomach

Clinical presentation

Depends on • Time during foetal life when the gut pushes up into the thoracic cavity

early in foetal life-results in pulmonary hypoplasia (bilateral hypoplastic lungs) and abnormal pulmonary vasculature

later in foetal life-results in persistent pulmonary hypertension due to mechanical compression

Classical findings:

Scaphoid abdomen

Reduced or absent breath sounds on affected side

Hypoxia

Evidence of bowel in thorax by auscultation or radiography

Preoperative care

Understanding the pathophysiology of CDH

• The associated morbidity stems not directly from the mechanical compression per se, but instead from effects that the long standing compression has, namely- pulmonary hypoplasia and hyper reactive pulmonary vasculature

• Therefore, hastening to operate in order to relieve this compression does precious little in reversing these long standing effects.So what then is the solution..?

-Preoperative stabilisation using a multi modal approach:

1. Conventional ventilation with permissive hypercapnia

Maintain a saturation of 85%

Allow PCO2 to rise to 45-55 mm of Hg

Preoperative care…..(contd)

2. High frequency Oscillatory Ventilation

3. Surfactant administration

4. Extra Corporeal Membrane Oxygenation (ECMO)

Venoarterial ECMO: pumping blood from right atrium through membrane oxygenator and counter current heat exchanger before returning to aorta.

Venovenous ECMO: Instead of returning it to aorta, blood is returned to femoral vein

Perioperative care

1. Obtain I.V. access if not already cannulated.

2. Minimise gastric distension by using nasogastric tube and avoiding

high levels of positive pressure ventilation (bag and mask ventilation

contra indicated)

3. Preoxygenate well.

4. Awake intubation is preferred (without muscle relaxant)

5. Maintain anaesthesia with low concentration of volatile agents, opoids,

muscle relaxants and air.

6. Avoid N2O for fear of bowel expansion..

Perioperative care……(contd)

7. Avoid hypothermia which by virtue of increasing O2 requirements tends

to precipitate pulmonary HTN.

8. Sudden fall in lung compliance, blood pressure or oxygenation may

signal a

contra lateral pneumothorax-if present should be addressed with a

chest tube.

9. ABG monitoring preferably in the preductal artery (to pick up acidosis

early on, which otherwise can precipitate pulmonary artery HTN)

10.Surgery per se starts with a subcostal incision.

11.Once the bowel is reduced-avoid the temptation to hyperventilate

In summary, anesthetic technique depends on :

1. Size of defect

2. Probability of neonate not being extubated post operatively

3. Extent of respiratory distress

4. Expected difficulties in abdominal closure

The implications of these four points are:

A smaller defect requires a smaller surgery. Better to avoid narcotics.

It ET tube is to be left in situ, then use of narcotics & volatile agents is

accepted.

If respiratory distress is seen, regional analgesia is used in anticipation

of extubation in place of narcotics.

Use of muscle relaxation to afford better abdominal closure.

Postoperative considerations:

Post operative care is best carried out in a intensive setting.

Recovery and prognosis depend on

• Pulmonary hypertension

• Pulmonary hypoplasia

Mass effect of the viscera has no role in causing cardiovascular

compromise.

Cardiovascular compromise arises secondary to pulmonary hypoplasia

and pulmonary hypertension.

Of these, pulmonary hypertension is thought to play a vital role.

In addition to pulmonary hypoplasia, co-existing cardiac hypoplasia

(left ventricle) must be factored in while facilitating post operative

care.

Prognosis parallels the extent of pulmonary hypoplasia and presence

of other congenital defects.