Neuroprotection

There has been considerable interest in the development of novel neuroprotective strategies to prevent the delayed neuronal cell death. To date moderate cerebral hypothermia is the most promising treatment: experimental studies show that a reduction of body temperature by about 3°C following global hypoxic-ischaemic injury preserves cerebral energy metabolism, reduces cerebral tissue injury and improves neurological function(Amess PN et al., Ped Res, 1997; Bona E et al., Ped Res, 1998). A meta-analysis of the major randomised trials in full term and near full term infants shows that moderate hypothermia for perinatal hypoxic-ischaemic encephalopathy reduces death or severe disability and improves neurological outcome in survivors (Edwards et al. BMJ 2010;340:c363).

Below are the criteria, contraindications and outline protocol for infants who are being cooled.

Criteria:

Infants with suspected HIE who meet the following criteria may be considered for treatment with cooling:

A. Infants ≥36 completed weeks gestation admitted to the NICU 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 within 60 minutes of birth (defined as any occurrence of umbilical cord, arterial, venous or capillary pH <7.00).
  • ? Base Deficit ≥16mmol/L in umbilical cord or any blood sample (arterial, venous or capillary) within 60minutes of birth.

Infants that meet criteria A should be assessed for whether they meet the neurological abnormality entry criteria (B):

B. Seizures (clinical or sub clinical*) or moderate to severe encephalopathy, consisting of:

  • Altered state of consciousness (reduced or absent response to stimulation).?
  • Abnormal tone (focal or general hypotonia, or flaccid).
  • Abnormal primitive reflexes (weak or absent suck or Moro response).

*seizures may be apparent on clinical examination (abnormal rhythmic movement of limbs, lip smacking etc) but can sometime be difficult to diagnose. The CFM is able to detect seizure activity not apparent clinically –known as sub clinical seizures. The CFM should be recorded in all infants with suspected birth asphyxia, preferably before cooling is started. However, cooling need not be delayed until the aEEG is initiated.

A normal CFM record (confirmed by assessing the underlying EEG and excluding artefact distortion of CFM) indicates a high probability of normal outcome, and clinicians may consider that treatment with cooling is not required.

If criteria A and B (above) are met, treatment with cooling may be considered. Cooling is unlikely to be effective if commenced more than 12 hours after birth. The decision to offer cooling will be made by the attending consultant who must be in included in ALL discussions regarding cooling. ‘Borderline’ cases who are marginally outside the original trial criteria should be discussed with the local Network Cooling Centre.

EoE HEALTH FOUNDATION NCP1

EoE HEALTH FOUNDATION NCP2

EoE HEALTH FOUNDATION NCP3

Contraindications for Cooling:

Cooling is not appropriate if:

  • The infant is likely to require surgery during the first 3 days after birth.
  • There are other abnormalities indicative of poor long-term outcome.

Ongoing therapeutic hypothermia may not be appropriate if the infant appears moribund or has persisting extremely severe encephalopathy such that further treatment is likely to be futile, for example if the CFM/EEG is isoelectric beyond 12-24 hours of age.