Papademetriou, M.D.; (2011) Multichannel near infrared spectroscopy to monitor cerebral oxygenation in infants and children supported in extracorporeal membrane oxygenation (ECMO). Doctoral thesis , UCL (University College London).

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Abstract

Extracorporeal membrane oxygenation is a life support system for infants and children with intractable cardiorespiratory failure. The risk for developing neurological injuries in this group of patients is considerable. The causes are multifactorial and are not yet fully understood. Induction of ECMO involves ligation of the major neck vessels – common carotid artery and internal jugular vein – which may cause lateralised cerebrovascular injury. Physiologic changes such as hypoxia, hypotension and hypercarbia associated with ECMO can disrupt cerebral autoregulation. Near infrared spectroscopy (NIRS) offers the advantage of continuous non invasive means of monitoring cerebral oxygenation at the bedside. To date, NIRS systems used clinically are single or dual channel systems and do not allow evaluation of the status of cerebral circulation in the extended cerebral regions. This work involves the development of a multichannel NIRS system for use in paediatric cardiothoracic intensive care with specific application on patients supported on extracorporeal circulation. A novel flexible neonatal cap was designed and constructed to accommodate an array of sources and detectors that provide measurements of multisite cerebral oxygenation from 12 channels. Multimodal data collection (systemic and ECMO circuit parameters) simultaneous with multichannel NIRS was established to allow monitoring of multisite cerebral oxygenation and haemodynamics. A novel method of analysis, wavelet cross-correlation, was generated to study the concordance between multisite oxyhaemoglobin concentration (HbO2) and mean arterial pressure (MAP) as a means to investigate regional variations in cerebral circulation and assess cerebral autoregualtion. Group data of 6 patients showed statistically significant differences in WCC between right and left hemispheres during sequential changes in ECMO circuit blood flow. WCC between HbO2 and MAP provides a useful method to investigate the dynamics of cerebral autoregulation during ECMO. Modest manipulations of ECMO flows are associated with regional changes in cerebral autoregulation which may potentially have an important bearing on clinical outcome.

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