Jugular Venous Oximetry

Jugular Venous Oximetry (JVO)

-It provides insight into the metabolic and oxygenation state of the brain.

-It provides information about the balance of oxygen supply and demand, for a larger portion, if not the complete brain.

Indications:

-During cardiopulmonary bypass

-Neurosurgery

-After traumatic brain injury.

Figure 1: JVO Catheterization Technique

Technique:

-A catheter is inserted into the jugular vein in a retrograde fashion (using Seldinger’s technique) so that its tip sits at the base of the skull in the jugular bulb. This allows continuous pressure monitoring as well as intermittent withdrawal of a jugular venous blood sample for gas analysis (Fig. 1).

-Continuous monitoring: can be achieved using an oximetry catheter inserted via a conduit sheath.

-Confirmation of location: can be made with a lateral cervical spine x-ray (Fig. 2).

Figure 2: JVO Catheter Lateral Cervical Spine X-Ray 

Identification of the dominant Jugular vein:

For the best representation of the metabolic state of the brain, the catheter should be placed in the dominant jugular vein, most commonly the right side. Confirmed by:

-In patients who have had a cerebral angiogram, the venous phase of the study will provide information on dominant venous drainage.

-The intra-arterial contrast will drain almost exclusively through one jugular vein, regardless of the side of injection.

-Side dominance can also be predicted using ultrasound where the dominant vein may be larger. In the absence of this information, the right side is preferred.

The pressure gradient between the jugular venous pressure and the central venous pressure:

-Pressure transduction of the jugular bulb catheter allows comparison with the central venous pressure to rule out potential venous obstruction.

-In a supine patient with a neutral neck position, there should be no pressure gradient between the tip of the jugular bulb and the central venous catheter.

-Although rare, a significant gradient (> 4 mmHg) can occasionally develop during positioning if there is significant twisting or bending of the neck.

-This gradient indicates venous obstruction, potentially causing brain edema or ischemia.

-The head should be repositioned until the gradient resolves.

Interpretation of blood gas analysis of jugular venous blood sample:

-The saturation of jugular venous blood (SjvO₂) demonstrates whether cerebral blood flow (CBF) is sufficient to meet the cerebral metabolic rate for oxygen (CMRO₂) of the brain (Lower values of SjvO₂ reflecting greater uptake by the brain and therefore less blood flow).

-It is essential that blood samples from the retrograde catheter be drawn slowly to avoid contamination from non-cerebral venous blood.

-A normal value is between 65-75 %. Desaturation (SjvO₂ < 55 %) indicates impending cerebral ischemia (e.g., caused by hypotension, hypocapnia, increasing cerebral edema).

-In traumatic brain injury, SjvO₂ below 50% for more than 10 min. is undesirable and associated with poor outcomes. However, it has low sensitivity, (a relatively large volume of tissue must be affected, approximately 13 % before SjvO₂ levels decreased below 50 %).

-Intraoperative hyperventilation will lower SjvO₂ as it decreases CBF.

-In the setting of a non-traumatized brain that is exposed to moderate hyperventilation for the duration of a neurosurgical procedure, the acceptable level for SjvO₂ is unknown.

-In the absence of other demands, it is reasonable to guide intraoperative hyperventilation by maintaining SjvO₂ > 50%.

-Measurement of simultaneous arterial and jugular venous samples allows the determination of lactate output from the brain, the presence of which indicates the occurrence of anaerobic metabolism.

Disadvantages & Limitations:

-It is a global monitor that could easily miss small areas of regional ischemia.

-If CBF & O₂ consumption both decreased (e.g., in severe brain injury, SjvO₂ may be unchanged.

Categories: Monitoring