Neuroprotective Effects of Hypothermia Combined With Inhaled Xenon Following Perinatal Asphyxia

The study hypothesis is that: Following perinatal asphyxia treatment with a combination of hypothermia and inhaled xenon preserves cerebral metabolism and structure. Following informed parental consent, infants that continue to require endotracheal tube ventilation following resuscitation will be randomised to treatment with hypothermia only or hypothermia and xenon. All infants in both groups will be treated with hypothermia for 72 hours started within 6 hours of delivery and infants allocated to hypothermia and xenon will also receive 30% xenon (balanced with oxygen and air) for 24 hours through a purpose designed delivery system. Structured neurological examination will be done daily during the 1st week after birth and at discharge. MRS and MRI will be performed once between 4-10 days of age. MRS/MRI data analysis will be by investigators blinded to the allocated intervention.

Inclusion criteria

Infants will be eligible for enrolment into the trial if each of the following criteria is fulfilled:

• Infants 36 to 43 weeks gestation with at least one of the following:

• Apgar score of <5 at 10 minutes after birth;
• Continued need for resuscitation, including endotracheal or mask ventilation, at 10 minutes after birth;
• Acidosis defined as pH <7.00 and/or base deficit >15 mmol/L in umbilical cord blood sample or any blood sample within 60 minutes of birth (arterial or venous blood).
• Moderate to severe encephalopathy consisting of altered state of consciousness (reduced or absent response to stimulation) and hypotonia, and abnormal primitive reflexes (weak or absent suck or Moro response). Clinical severity of HIE will be assessed by Thompson encephalopathy score, and modified Sarnat score.
• At least 30 minutes duration of amplitude integrated EEG (aEEG) recording that shows moderately abnormal or suppressed background aEEG activity or seizures

Exclusion criteria

• If treatment with hypothermia is delayed beyond 6 hours, or infants are expected to be >12 hours of age at the time of randomisation; Infants with ventilatory oxygen requirement > 70%; Attending clinician considers infant not suitable to participate because of other serious congenital abnormalities, or the infant's condition appears terminal.