Auditory evoked responses and near infrared spectroscopy during cardiac arrest

We describe a patient who had a cardiac arrest during anaesthesia, in whom regional cerebral oxygen saturation was being measured by near infrared spectroscopy and the auditory evoked responses (AER) were being recorded. Both of these monitors provided useful information on cerebral oxygenation during cardiac arrest. Changes in the AER as the result of either reduced circulation or hypothermia are similar, and should these two situations occur simultaneously there could be difficulty in the interpretation of the AER.