1. Department of Anaesthesia and Perioperative Medicine, Auckland City Hospital, Auckland, New Zealand
2. Department of Physiology, University of Auckland, Auckland, New Zealand
3. Department of Neurology, Auckland City Hospital, Auckland, New Zealand
4. Department of Anaesthesiology, University of Auckland, Auckland, New Zealand
5. Department of Statistics, University of Otago, Christchurch, New Zealand
6. Department of Radiology, Auckland City Hospital, Auckland, New Zealand
7. Department of Neurology, University of Auckland, Auckland, New Zealand