Congenital Diaphragmatic Hernia

Summary
In troduction
Principles of Prenatal Care
Guidelines For Neonatal Care

Summary

if unexpected delivery occurs in a Level II nursery, resuscitation must be undertaken and supervised by the most experienced clinician available
ventilation using a bag and mask should be minimised
the baby with a best preductal pO2 <70 mmHg, or a persistent respiratory or metabolic acidosis despite 3-6 hours of expert effort to optimise ventilatory and circulatory support has a poor prognosis</p/><70 mmHg, or a persistent respiratory or metabolic acidosis despite 3-6 hours of expert effort to optimise ventilatory and circulatory support has a poor prognosis

Introduction

Congenital diaphragmatic hernia is a serious congenital abnormality associated with

pulmonary hypoplasia, worse on the ipsilateral side
structural and functional lung immaturity
a reduction in pulmonary arteriolar cross sectional area
muscular hyperplasia of remaining pulmonary arterioles
an association with other major anomalies, chromosomal and non-chromosomal, in up to 20% of cases

15 - 25 cases occur each year in Victoria corresponding to an incidence of approximately 1:3000.

In the early 1990's few were prenatally detected. With the virtual universal occurrence of mid trimester ultrasound examination for fetal abnormality more than 85% of cases are now prenatally detected.

The survival rate for all cases diagnosed is approximately 50-60%.
If a coexistent significant abnormality is present survival is <10%. This illustrates the importance of thorough evaluation, from the time of suspected fetal diagnosis, by a multidisciplinary team familiar with all aspects of the diagnosis and management of CDH.</p/><10%. This illustrates the importance of thorough evaluation, from the time of suspected fetal diagnosis, by a multidisciplinary team familiar with all aspects of the diagnosis and management of CDH

Reported survival for live born infants ranges from 50-90%. The international CDH Study Group database with over 1600 patients reports an overall survival of 66%. The experience for babies managed at RCH, Melbourne shows the survival for babies with isolated lesions to be 75% based on more than 200 infants. The difference in survival for all cases versus liveborns reflects the high rate of termination of pregnancy (TOP) where other anomalies are detected, a lower rate of TOP where an isolated lesion is present, as well as a relatively low incidence of stillbirth.

Principles of Prenatal Care

referral for tertiary level obstetric ultrasound
if the diagnosis is confirmed referral to a multidisciplinary fetal diagnostic/management team

Objectives

establish an accurate description of the abnormalities present

specify ultrasound features relevant to CDH using a standard form

degree of mediastinal shift

liver/stomach position

lung:head ratio

liquor volume

fetal echocardiogram performed by a Paediatric cardiologist, if associated congenital heart disease suspected

establish a fetal karyotype, if informed parental consent given

provide informed and supportive counselling for the family including a written summary of any discussion with the parents. This summary should include a description of the abnormalities and most likely diagnoses, management options available, and possible outcomes

Ongoing Management

referral to a Paediatric Thoracic Surgeon if not previously arranged

regular general obstetric surveillance

repeat Ultrasounds at 24, 30 and 34 weeks to assess fetal growth and features of the CDH as defined above

Intervention

prenatal steroid therapy - recommended according to usual indications. Clinical trials are under consideration for use at mature gestations

fetal operative intervention (tracheal ligation) is an unproven therapy. It is not available in Australia and is not recommended outside of clinical trials (currently in progress overseas)

Delivery Strategy

to achieve a normal vaginal delivery following spontaneous onset of labour at term

Women who live more than 1 hour from the perinatal centre are encouraged to move to Melbourne at 35-36 weeks gestation. For pragmatic reasons induction of labour at 38-39 weeks is offered to these women.
Caesarean section without labour is not recommended unless there is a clear medical indication.

Guidelines For Neonatal Care

If unexpected delivery occurs in a Level II nursery, resuscitation must be undertaken and supervised by the most experienced clinician available.

Resuscitation

Resuscitation will be individualised according to the condition of the baby and the response to initial steps in resuscitation.

Ventilation using a bag and mask should be minimised.

If endotracheal intubation is required make sure the tube is not inserted too far.

Positive pressure ventilation should be accompanied by inspiratory pressure or volume monitoring, when available.

IPPV, if required, should be provided by a mechanical ventilator at the earliest opportunity.

A large bore nasogastric tube (Ryles tube 10F) should be passed once the baby has been stabilised in the delivery room.

Physical contact with the parents should be facilitated before transfer.

Preductal saturation monitoring should be undertaken during any transfers. Saturations in the 70's and 80's are satisfactory provided sufficient ventilatory support is provided to ensure adequate tidal volume. This is the most difficult situation to get right and in the absence of portable volume monitors a highly experienced clinician must be supervising this period.

Stabilisation - immediate priorities

achieve acceptable gas exchange

saturations > 75%

pCO₂ at a level that allows the pH to be > 7.20 while minimising the chances of inducing lung injury or air leak.

monitor preductal saturations

apply a transcutaneous pCO2 monitor

consult with NETS and level 3 centre

Units reporting very high survival concentrate on minimising lung injury especially in the initial hours after birth and rarely exceed PIP of 25.
If available use a synchronised mode of ventilation

Ongoing Stabilisation

establish venous access - if the baby's condition is poor and the circulation compromised rapidly place a UV catheter

measure blood pressure and assess the circulation to determine the need for volume support

obtain a chest X Ray

if the baby's condition remains poor obtain a blood gas by the most expedient route (arterial stab) and adjust support accordingly

arterial access

if urgent - cannulate the UA

if non urgent then either the procedure can be deferred until the baby has been transferred, or a right radial (i.e. preductal) line sited

do not waste time (and arteries) if the first attempt is unsuccessful

sedate and muscle relax the baby who remains in poor condition despite attempts at optimising ventilation. In particular muscle relaxants should be considered if the baby requires high pressure IPPV (e.g. a mean airway pressure of > 14)

surfactant administration (survanta, one ampoule) is optional. Some babies with CDH tolerate this procedure very poorly

The baby with a best preductal pO2 <70 mmHg, or a persistent respiratory or metabolic acidosis despite 3-6 hours of attempting to optimise ventilatory and circulatory support has a very poor prognosis.</p/><70 mmHg, or a persistent respiratory or metabolic acidosis despite 3-6 hours of attempting to optimise ventilatory and circulatory support has a very poor prognosis

Continuing Management

requires a team of neonatologists, paediatric surgeons and paediatric intensivists

continuous monitoring of transcutaneous pCO₂, tidal and minute volumes

the lowest FiO₂ that results in a preductal saturation > 85% is maintained, especially in the initial hours of care. Permissive hypercarbia is strongly advocated

preductal arterial access is desirable if the infant's condition is marginal

assessment for dysmorphism - including echocardiography, renal and cranial sonography, a karyotype should be considered

an ongoing metabolic acidosis requiring repeated large doses of base suggests myocardial ischaemia, sepsis or strangulated bowel

the principles of management and escalation of therapy include

use of muscle relaxants and sedatives

synchronised ventilation (SIMV or A/C) with tidal/minute volume monitoring

HFOV +/- Inhaled nitric oxide if the baby has unsatisfactory gas exchange after a reasonable trial of conventional ventilation, or there is an ongoing need for high ventilatory pressures or FiO₂

jet ventilation if there is overt gas trapping or air leak

ECMO - less than 10% of babies need this

surgery - after ventilatory and circulatory support weaned to satisfactory levels (e.g. FiO₂ < 0.4 and mean airway pressure < 14)

discharge to a level II unit considered after

full enteral nutrition established for at least one week

respiratory status indicates significant reserve

audiology - arranged prior to discharge if possible

long term follow up required

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