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Understanding the absorptive and post absorptive states during meals

Factors other than lung hypoplasia may contribute to a poor response to initial therapy.

Absorptive state

In this scenario, ECMO may be rescuing infants with an acute deterioration in status. Other potential reasons for decrements in lung function below the physiologic potential include retained fetal lung fluid, particularly in the setting of a cesarean section delivery without labor. In translational studies in the rodent CDH lung, the investigators demonstrated a failure of perinatal transition from the fetal secretory state to the neonatal absorptive state owing to a deficiency in pulmonary epithelial sodium channel ENaC production.

It is unclear what degree of lung hypoplasia is lethal in the modern era.

Antunes and coworkers measured functional residual capacity FRC preoperatively and post-operatively in infants with CDH. It is important to note that these outcomes were not from infants specifically managed with permissive hypercapnia, although the escalation of ventilator support beyond appropriate limits to transiently achieve values below these cutoffs is unlikely to improve outcomes as Kays and colleagues previously demonstrated.

No pre-ECMO parameters differed between survivors and nonsurvivors in this cohort. We do not routinely proceed to emergency ECMO support in infants who cannot be resuscitated in the delivery room, however, and we do not recommend ECMO to families of infants in whom acceptable oxygenation has never been achieved. However, there are circumstances in which we cannot distinguish those babies with lethal lung hypoplasia from others with a reversible problem compounding respiratory insufficiency, as outlined previously, or in whom the less hypoplastic contralateral lung cannot be fully recruited.

Absorptive and Postabsorptive States

These babies may benefit from the temporary support that ECMO can provide. This protocol entails a ventilation trial while the fetus remains on placental support, followed by cesarean section delivery with or without direct cannulation for ECMO support.

The results of the use of this strategy at Boston Children's Hospital have been reported. Fetuses with liver herniated into the thorax and a low lung-to-head ratio LHR; area of contralateral lung divided by biparietal head circumference on ultrasound, a low percentage of predicted lung volume PPLV on magnetic resonance imaging MRIor the presence of significant structural heart disease were eligible for delivery by EXIT procedure.

This strategy has not been widely adopted, however. Strategies for management of the infant with CDH undergoing ECMO support are not widely published, but they seem quite variable, on the basis of informal discourse over email list servers and at ECMO-focused conferences.

However, in our experience, the small caliber of the airways in infants with CDH can increase the challenge of inflating the lungs, owing to inspissated mucous and airway debris. We use predominantly venovenous ECMO and attempt to maintain even minimal lung inflation with the conventional ventilator with the following settings: Much attention is paid to pulmonary toilet, with endotracheal suctioning and hand ventilation every 4 hours, often preceded by bronchodilator treatments and occasionally accompanied by DNase Pulmozyme treatments, both therapies administered to help clear secretions.

Infants are also not paralyzed during ECMO support unless absolutely necessary for patient care. Clotting is also exacerbated by the interventions taken to limit bleeding, particularly in circuits that have been in use for some time. Because of concerns about bleeding and clotting, if repair is to be undertaken with use of ECMO support, it is important to have a circuit with minimal evidence of consumption and clot.

  1. Other potential reasons for decrements in lung function below the physiologic potential include retained fetal lung fluid, particularly in the setting of a cesarean section delivery without labor. No pre-ECMO parameters differed between survivors and nonsurvivors in this cohort.
  2. This protocol entails a ventilation trial while the fetus remains on placental support, followed by cesarean section delivery with or without direct cannulation for ECMO support.
  3. This protocol entails a ventilation trial while the fetus remains on placental support, followed by cesarean section delivery with or without direct cannulation for ECMO support.

At times, a change of circuit and recovery from this procedure may be required before the repair is undertaken. An analysis of data from the Congenital Diaphragmatic Hernia Study Group demonstrated an increased mortality hazard of 1. For the infant undergoing surgical repair while on ECMO support, it is very important to consider placement of a thoracostomy tube, because hemothorax ipsilateral to the more hypoplastic lung may be difficult to detect postoperatively until it is severe.