Cerebral function monitoring during therapeutic hypothermia in a tertiary neonatal centre
Introduction Therapeutic hypothermia is a standard of care in the UK for neonates with hypoxic ischaemic encephalopathy. Meeting neurological criteria are essential for recruitment of neonates for treatment. Neurological symptomatology may be subtle and the role of cerebral function monitoring (CFM) though not essential for starting treatment has been endorsed by the BAPM in its position statement.
Method An audit to review the management of neonates with suspected hypoxia ischaemia who underwent therapeutic hypothermia was carried out in a tertiary neonatal centre. Information was taken from the patient record and TOBY forms regarding recruitment as per standard criteria, and neurological symptoms. A confidential review of the CFM traces was performed where available and they were classified as being continuous normal voltage, discontinuous normal voltage, burst suppression, low voltage or inactive.
Results 29 cases underwent therapeutic hypothermia during the period August 2009-August 2011 with a total of 1979 cooling hours provided. Traces were reviewed in 28 out of 29 cases with one not obtainable. 4 cases had continuous normal voltages, 14 cases had discontinuous normal voltage, 3 had burst suppression, 6 were low voltage or inactive. 2 cases had only seizures. Of 29 cases 2 had neonatal encephalopathy which may have been attributable to other causes. All the cases with burst suppression, low voltage or inactive trace that normalised their CFM records within 72 hours were discharged feeding orally. Cases with burst suppression, low voltage, or inactive trace that didn't normalise their trace all died.
Conclusion All neonates undergoing therapeutic hypothermia should have cerebral function monitoring initiated if available. Used adjunctively with the presentation, clinical course and neuroimaging it may be a prognostic indicator of survival and outcomes in such neonates. Cerebral function monitor traces need cautious interpretation for artefacts. Background and improvement of the trace in neonates may be affected by antiepileptic medication. It is important to investigate other causes for neonatal encephalopathy in neonates undergoing therapeutic hypothermia. It is inevitable that some neonates with borderline neurology and continuous normal voltage appearance will be cooled. This work highlights the pitfalls of interpreting CFM traces of neonates being cooled for trainees.