III. Physiology
A. Indications/Contraindications
As with any support technique used in emergent settings, it is critical to
continuously review the experience in order to identify those patients who
predictably have a poor outcome and those who survive with solely conventional
modalities. Many of the “absolute” exclusion criteria have been relaxed as
experience with ECLS has allowed refinement and standardization of various
aspects of the technique. Inclusion criteria are broadly defined to those who fail
or are likely to fail conventional therapy for cardiac and pulmonary support.
To further define neonates that are likely to need ECLS for respiratory
failure, an oxygen index and alveolar-arterial oxygen difference have been used.
Oxygen index (OI), based on arterial oxygenation and mean airway pressure
(MAP), is calculated thus: OI = (MAP x FiO 2 x 100)/PaO 2 .[ 15 ] An OI greater than
40 consistently on several blood gases is highly predictive of mortality; therefore,^
“early” initiation of ECLS based on an O.I. > 25 can be considered. The alveolar-
arterial oxygen difference [(A-a)DO 2 ] value of > 610 torr despite several hours of
maximal medical management is associated with a very high mortality.[ 16 ]
Patients on high frequency jet or oscillatory ventilation and newborn patients with
CDH are frequently placed on ECLS at lower criteria.
Criteria for high mortality risk among non-neonatal children with respiratory
failure and for children of all ages with cardiac failure have been less well-
defined. A combination of ventilation index (respiratory rate PaCO2 peak
inspiratory pressure / 1000) > 40 and an oxygen index > 40, or a combination of