charting...dialed in or end tidal?

Quick question for SRNA's or CRNA's...When charting concentration of the anesthetic agent, do you chart what's dialed in or end tidal concentration? ..... What's the right way?

As with so many aspects of clinical technic, IMHO there is no 'right' way, but a thousand different ways to skin the cat. Different strokes for different folks. For one thing, of course not all machines will feature agent analysis. In that case, personally, I chart the indicated % on the vaporizer. When I do have a machine with agent analysis, I chart that, usually the inhaled %.

deepz

I use end tidal to gauge the depth of my anesthetic and so that is the # I chart. My reasoning is that the dialed number has no relationship on what the patient is getting especially at low flows. Also, the end tidal is what I look at during emergance. If my end tidal is adequate, I'm sure the brain is getting at least that concentration. I am always concerned with awareness as that is my personal nightmare. Charting end tidal is the worst case scenerio so I have a "fudge factor' built in. Same goes for CO2 and O2, since I like to run low flow, I feel a little better charting these numbers.

End-tidal concentration is a better representation of brain concentration while inspired concentration represents that amount in the lungs.

endtidal. it just makes more sense to me, like wntrmute says, it's what i look at to gauge how much gas is still on board.

End-tidal concentration is a better representation of brain concentration while inspired concentration represents that amount in the lungs.

Isn't this the opposite of what is really happening?

From Barash "At equilibrium the CNS partial pressure equals the blood partial pressure, which equals alveolar partial pressure."

From this, it is evident that it takes time for the blood compartment to saturate, which in turn will allow the Brain compartment to equilibiate. So over the course of a long case, in tidal would eventually equal brain concentration. But this would take a long time to happen.

As a result of this, I was taught that the end tiidal reading is more reflective of brain concentration.

Craig

the brain is part of the vessel rich group and should equilibrate with the alveolar partial pressure pretty quickly

Isn't this the opposite of what is really happening?

From Barash "At equilibrium the CNS partial pressure equals the blood partial pressure, which equals alveolar partial pressure."

From this, it is evident that it takes time for the blood compartment to saturate, which in turn will allow the Brain compartment to equilibiate. So over the course of a long case, in tidal would eventually equal brain concentration. But this would take a long time to happen.

As a result of this, I was taught that the end tiidal reading is more reflective of brain concentration.

Craig

nilepoc,

i'm confused at first i thought you were disagreeing w/ kscrna, but then your last sentence is agreeing with what he had said originally.

ET%=brain

the brain is part of the vessel rich group and should equilibrate with the alveolar partial pressure pretty quickly

I figured I would word that in a way that did not convey everything I was trying to say. Anyway, back to my question, am i correct in saying that the Et Agent is more reflective of brain concentration of agent?

The original poster I quoted said it the other way.

Craig

I agree monitoring end-tidal concen. during a case is more of a reliable indicator of the brain p.p. as opposed to the dialed in concen. A CRNA (charts dialed in) gave this example: If a pt claims to have been awake/aware during surgery, case goes to court, and anesthesia records indicate agent concen. (end-tidal) throughout the case was considerably less than MAC, then the fingers would be pointed at you. However, if the dialed in concen. was charted that that is closer to an "appropriate" anesthetic level then it would CYA more. I am still in my first semester of school and new to the clinical setting, so I hope I'm making sense.

I figured I would word that in a way that did not convey everything I was trying to say. Anyway, back to my question, am i correct in saying that the Et Agent is more reflective of brain concentration of agent?

The original poster I quoted said it the other way.

Craig

The original poster said it the same way. End tidal is more reflective of brain concentration.

Oh wow, I composed a whole reply, based on a miss reading of someones post, and then quoted it. Boy I need some sleep. I feel utterly stupid.

humbly slinking off to the corner, to collect my dunce cap.

Hahaha

:-)

End tidal is the most accurate method; however, the dialed in will be more easily defended in a lawsuit. An example is an end tidal of 2.5 and the patient's CO drops from 5.0 to 1.2. You want to lighten the anesthetic immediatly, but because of the diminished uptake of agent, your end tidal never changes. If you charted dialed in then you would note that you turned agent down signifigantly. It may not be the most accurate, but is a more accurate record of what you are acctually doing and is easier to defend without going into FA and FI, solubility coefficients, and physiology.