Conductive deafness is common - probably much more common than we realise. Pressure changes within the middle ear due to nitrous oxide or simple auditory tube obstruction secondary to swelling are thought to be the cause. Usually mild and usually temporary.

A sensorineural deafness is a different kettle of cod.

Drugs are the most common cause: aminoglycazides and frusemide are most common and cytotoxic agents are also implicated.

Barotrauma can also cause sensorineural deafness. It is well-known is divers that a rapid ascent can cause bubbles of nitrogen in the cochlea, which can cause sensory deafness. Was nitrous oxide used in these cases? It is possible that an insignificant gas bubble within the inner ear could expand when nitrous is used and may cause deafness.

Ischemic injury has been shown to cause sensory deafness. Were either of these patients hypoxic or hypotensive at any time?

These are theoretical observations only. Otherwise I am at a loss.  ???

Anesthetizing children is an art. It takes more than just clamping a sevo-filled big black mask on their little terrified faces. Try as I might (and I have tried) I just can't sneak up on children with sevo as I can with halothane. I can drift the most terrified child off to sleep with halothane before they even notice anything is happening, and certainly before a mask nears their head.

I always have both halothane and sevo vaporizers on my machine for pediatric lists. I use sevo for most cases - yep its fast and convenient. But when the situation calls for it, out comes the halothane. I sing to the child, ask them questions, distract them. I cup my hand under their chin and drift halothane from above in front of their face, letting it pool into my cupped hand. Low concentrations to start, and slowly rack it up. The child yawns, eyes start to drift, halothane concentration goes up, cupped hand gets a little more mask-like, hose outlet gets closer to face. Once the child is sleepy, the hand is replaced by a mask and the hose attached. Sleeping child and very impressed parents.

Can't do that with sevo.

Never worn a face mask. Surgeons never had the balls to challenge me on it.

ECG is such a non-invasive monitor that its risk-benefit ration is hugely in favor of its use. Easy, quick, risk-free and occassionally very useful. Why would you NOT use it?

I think its probably a dose-response effect. Some nitrous causes X amount of nausea. Twice X causes twice the incidence of nausea.

Well, well, well.

In the not-so-old days (pre-propofol) it wasa well-known adage that you do not fiddle witht he airway until the patient is deeply anesthetised. Thiopentone was just the start of the induction process, not the entirety of it. After the IV induction, the patient would be deepened with volatile and then the pharynx was commonly topically anesthetized, BEFORE any stimulation of the airway.

Nowadays, we have propofol and many of us have lost the art of a true induction. Propofol gets you no deeper than thio, but it is more forgiving in terms of airways reflexes. We commonly start manipulating the airway long before the patient is deep (if you use TCI, you will note the brain concentration of propofol lags behind the IV concentration by several minutes) and rely on propofol's inate inhibition of airway reflexes to insert the LMA.

My message is this - you are inserting the LMA long before the patient is deep. Induce with propofol by all means, then use a volatile to deepen the patient (and this time allows the propofol to actually cross the blood-brain-barrier), and only then inser the LMA. No hiccups.

I still record by hand. It keeps my mind on the job. And while I dispute that I fudge the numbers, I DO filter out the artefacts that an automated recording system will record (and therefore be a point on which a lawyer will get you).

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.

I don't alter anything I do. Our hospitals have a policy of CTG monitoring for ALL patients with epidurals. The ultrasound on standby is only useful if there is somebody around who knows how to use it.

I still use it occassionally for inducing the unco-operative child. Halothane provides a longer, but smoother induction with which you can "sneak up" onto your unsuspecting child. It has a nice feature of being heavy, and pools into a hand cupped under a child's chin. By the time the child realises that something is up, they are half-stunned by the initial dose.

Sure beats forcing a sevo-filled mask onto the little mite's face.

Is morphine approved for intra-thecal use? There is certainly no mention of it on the drug insert for the brand that we use. It is approved for IV, SC, IM, intra-articular but not intra-thecal use.

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!).

Both the BIS and the Datex Entropy monitors have been closely correlated with the likelihood of both explicit and implicit recall. The actual numbers I am not experienced enough to comment on.

Of course, this leads into a discussion of consciousness, sedation and anesthesia..... the subject of a new topic I suspect!

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

Sounds like an undiagnosed cardic defect such as a VSD or ASD with a right to left shunt. Did she have an echo afterwards?