1. New developments in cerebral monitoring Tariq Alzahrani Demonstrator College of Medicine King Saud University

2. Classification Cerebral perfusion monitoring. Cerebral metabolism monitoring. Cerebral function monitoring.

3. Cerebral perfusion monitoring Global cerebral perfusion monitoring : - cerebral blood flow measurements. - transcranial Doppler ultrasonography. - near-infrared spectroscopy. - jugular bulb oximetry. Regional cerebral perfusion monitoring : - brain tissue partial oxygen tension monitoring.

4. Global cerebral perfusion monitoring Cerebral blood flow measurements : -Methods : -Kety-Schmidt Inert-gas Saturation Technique. -(TCID) transcerebral double-indicator dilution technique. TCID may become a feasible & clinically useful alternative method fore measurement of global cerebral blood flow.

6. Transcranial Doppler ultrasonography (TCD) : - its noninvasive, used for the diagnosis of cerebral vasospasm by measurement of blood flow velocity. - 200 cm/s -Transcranial colour-coded sonography

7. Near-infrared spectroscopy (NIRS) (brain oximetry) : - continuous noninvasive monitoring of cerebral oxygen saturation. - measures arterial, venous & capillary blood oxygen saturation. - accuracy (emitter-detector separation).

9. Jugular bulb oximetry (SjO2) : - continuous invasive monitoring of jugular bulb oxygen saturation - has been applied in neuroanesthesia & neurological intensive care management since the 1980s as an indirect measure of the adequacy of cerebral perfusion.

10. Regional cerebral perfusion monitoring Brain tissue partial oxygen tension monitoring (PbtO2) : - invasive catheter measures oxygenation in very localized area of the brain - catheter (probe) need guidance to help place into areas of brain by xenon computed tomography or single-photon emission computed tomography. - ischaemia threshold SjvO2 50% = PbtO2 8 mmHg.

11. - major differences : 1. SjvO2 more reduction during hyper ventilation. 2. PbtO2 was more affected by changes in arterial partial oxygen tension. 3. during global ischaemia - PbtO2 decreas to 0 & remained at 0 - SjvO2 initially decreased, but then increased again as cerebral blood flow ceased, & the only blood in the jugular bulb was of extracerebral origin.

12. Cerebral metabolism monitoring Cerebral microdialysis : - Molecules in the extracellular space extracted & measured. - catheters inserted into the temporal & subfrontal cortex at the end of cerebral aneurysm surgery. - samples extracted & analyzed by microdialysis apparatus (which can analyze glucose, lactate, glutamate, glycerol & urea concentrations within minutes of collection.

13. - revealed that lactate & glutamate appeared to be sensitive markers of impending ischaemia - whereas increased glycerol levels were associated with sever ischaemic deficits.

14. Cerebral function monitoring Bispectral index (BIS). Approximate entropy. Auditory evoked potential (AEP).

15. BIS : - is a processed electroencephalographic parameter that is obtained by discriminate analysis of a set of electroencephalographic features. - is known to have a high correlation with clinical signs of anaesthesia & with the concentrations of most hypnotic agents.

16. - is a dimensionless scale from 0 (complete EEG suppression) to 100 (awake). - BIS values of 65-85 have been recommended fore sedation - BIS values of 40-65 have been recommended fore GA - BIS values lower than 40, cortical suppression becomes discernible in raw EEG as a burst suppression pattern.

19. Approximate entropy : - BIS + EMG (facial muscle). - as a measure of anaesthetic depth.

20. AEP : - used for measuring hypnotic drug effects. - is better discriminatory power in describing the transition from the conscious to the unconscious state in the individual patient. - in the future, further studies are required that apply other anaesthetic drugs before any conclusions on the general utility of the AEP index can be drawn.

21. Conclusion The future of cerebral monitoring looks more promising than ever. The recent introduction of regional cerebral monitoring techniques such as PbtO2 & cerebral microdialysis, might allow a better understanding of pathophysiological events.

22. Future studies to compare global with these regional cerebral monitoring techniques might yield unique information with regard to targeted management of, for example, intracranial hypertension.