Multimodality monitoring allows using a combination of jugular venous bulb oximetry and transcranial doppler ultrasound allows a greater understanding of the state of the cerebral circulation and oxygen consumption. Jugular Venous Bulb Oximetry Jugular venous bulb oximetry involves placing a sampling catheter in the internal jugular vein, directed upwards, so that its tip rests in the jugular venous bulb at the base of the brain. The SjO 2 will fall when there is an imbalance between oxygen consumption and delivery. Vascular spasm and a rise in CVR are very common after brain injury and are significantly worsened by hyperventilation. Jugular venous bulb oximetry should be employed whenever there is prolonged hyperventilation Burst suppression to reduce CMRO 2 may be used in patients who have presistent intracranial hypertension not responsive to standard therapy.
Barbiturates are the most commonly used agents.
Multimodality monitoring should probably be employed when such therapy is instituted. Transcranial Doppler Ultrasound Transcranial doppler is a non-invasive method of assessing the state of the intracranial circulation. The velocity of flow can be measured in the middle, anterior and posterior cerebral arteries, the opthalmic artery and internal carotid. Flow cannot be measured from velocity because the cross-sectional area of the arteries cannot be measured directly. . However the doppler shift measured is inversely proportional to the diameter of the vessel, so that, all other factors remaining constant, vascular spasm leads to an increase in flow velocity.