We are thinking of introducing this monitor for cardiac surgery soon. Does anyone have any experience with it? Does it have a practical value (rather than just a theoretical one)?

Here is the blurb from the company (and, no, I am not associated with them  :))

QuoteThe INVOS Cerebral Oximeter

The INVOS® Cerebral Oximeter is the first and only patient monitoring system commercially available in the U.S. that noninvasively and continuously monitors changes in the regional oxygen saturation of the blood in the brain.

The INVOS Cerebral Oximeter system consists of disposable, single-patient use SomaSensors, an INVOS monitor display and associated accessories.

The INVOS Cerebral Oximeter system monitors changes in regional saturation of oxygen, or rSO2, within a sample of blood in the cerebral cortex. Changes in INVOS (In Vivo Optical Spectroscopy) values monitor the critical balance between oxygen delivery and cerebral consumption.

The INVOS Cerebral Oximeter measurement is made by noninvasively transmitting and detecting harmless, low intensity and near infrared light through SomaSensors that are placed on both sides of a patient's forehead.

Use of the patient monitoring system allows medical professionals to monitor changes in cortical blood oxygen saturation and take corrective action. Recent research and clinical experience indicates that such action can prevent or reduce neurological injuries associated with surgery and other critical cares situations, and therefore, reduce the cost of care.

The INVOS Cerebral Oximeter system is now available for adult and pediatric monitoring in the US and in many international markets.

The topic of BIS and Entropy monitors triggered me to ask my pet question that I pose to residsents:

1. When does sedation become anesthesia?

2.When does conscious sedation become awareness?

My answer to question 1 is that the sedation ---> general anesthetic spectrum has no sharp demarcation line. A GA occurs when some intervention needs to be taken to support a patient's airway. I know others have a different definition, but for me, this is a useful one because at this point of sedation, a degree of expertise (namely somebody trained in anesthesiology) is required to continue in a safe manner. Non-experts should NOT venture beyond this point!

For question 2, I do not have an answer. Sedation is tricky. It is a constant battle to balance the degree of sedation with the level of surgical stimulus while maintaining a patent airway and adequate ventilation. This degree of sedation is NOT always acheivable. Either the airway is lost, and an intervention is required (which by my answer to question 1 becomes a GA!) or the sedation is inadequate and the patient becomes aware!

Is awareness without recall (or memory or the event) true awareness? Do these insults lie buries deep in our unconscious to disturb us in the future (or revealed by hypnosis)?

I make sure that when I consent a patient for "sedation" that they understand that there MAY BE bits of the surgery that they may recall post-operatively. To do otherwise is negligent. I also reassure them that they are in charge - if they want more sedation or more local, the surgery will stop until this happens. The only way I can guarantee a lack of awareness is with a GA (and even then I cannot guarantee it!).

There is no doubt that hot air warming blankets have made a big difference in patient care under anesthesia in the last 10 years.

My institution does a lot of short cases (<1hr) where hot air warming blankets are beneficial but not cost effective. We commonly use the hot air hose without the commercial hot air blanket. Does anybody else admit to this?

Now, I must elaborate. I use it on well patients at 38^oC (there are 2 hotter settings 43^oC and 46^oC on our machines). Never for more than 1 hour. Never on ischemic skin. Always with a cotton blanket between the hose and the patient.

Anybody see any problems with this? The alternative would be to use a new blanket (at about $8 per patient or over $16,000 per year) for each patient.

George