Our Anesthesia Machine Setting - Mysterious FGF debate!

[DrAmir0078]

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Good Day SDN Anesthesiologists,
My last thread was about "Perioperative Sweating", then our discussion shifted to the FGF.

Forgive me for making this fresh thread for this topic to get your attention regarding this mysterious topic to me!

I am learning a lot from you, I am far better than yesterday!

Thanks for watching my humble video about our Anesthesia Machine Setting for a patient who was undergoing Lap.
Cholecystectomy, and after the patient discharged, I've tested the machine again with 2 Lt only.

This is the video:




Your comments are valuable to make a difference!


Love and Peace
Amir

P. S.
So probably, because we do not have Soda Lime, so there is no recycling of the exhaled CO2, that is why we give 7 Lt, and because it it is a closed circuit, so our Oxygen delivered to the patient is always mixed with CO2 over the time; so why every once in a while during the surgery we disconnected the Y tube from ETT and press the Oxygen flush to release the mixture and gets only oxygen! Could be?

 

[facted]

Good Day SDN Anesthesiologists,
My last thread was about "Perioperative Sweating", then our discussion shifted to the FGF.

Forgive me for making this fresh thread for this topic to get your attention regarding this mysterious topic to me!

I am learning a lot from you, I am far better than yesterday!

Thanks for watching my humble video about our Anesthesia Machine Setting for a patient who was undergoing Lap.
Cholecystectomy, and after the patient discharged, I've tested the machine again with 2 Lt only.

This is the video:




Your comments are valuable to make a difference!


Love and Peace
Amir

P. S.
So probably, because we do not have Soda Lime, so there is no recycling of the exhaled CO2, that is why we give 7 Lt, and because it it is a closed circuit, so our Oxygen delivered to the patient is always mixed with CO2 over the time; so why every once in a while during the surgery we disconnected the Y tube from ETT and press the Oxygen flush to release the mixture and gets only oxygen! Could be?

I missed the other thread and too lazy to read through the whole thing.

For starters, what you say You're not sure about on the vent screen showing .7 looks like it's your tidal volume. Has nothing to do with fresh gas flow.

What's your actual question about the fresh gas flow? You've dialed in 7L of O2 flow. That's your fresh gas flow, though you are obviously going to deliver a diluted gas mixture secondary to rebreathing.

 

[DrAmir0078]

I missed the other thread and too lazy to read through the whole thing.

For starters, what you say You're not sure about on the vent screen showing .7 looks like it's your tidal volume. Has nothing to do with fresh gas flow.

What's your actual question about the fresh gas flow? You've dialed in 7L of O2 flow. That's your fresh gas flow, though you are obviously going to deliver a diluted gas mixture secondary to rebreathing.

OK,
So that graph in the screen is related to Tidal volume and not reflecting the how much the machine is delivered to the patient (I wondered it was between 0.0ml to 1.0 L and thought 0.7 ml is the actual FGF delivered), so we are delivering 7 L FGF and then it becomes diluted with the CO2 exhaled, is that right?
Since we don't have monitor for gas analysis, so it is difficult to assume how fresh gas mixed with volatiles in case we need to adjust the later!

 

[daneeka]

Looks like you've got a standard circle circuit, but without the soda lime. So yeah, you can't really recycle gas without causing CO2 rebreathing, so a 7L FGF is probably necessary.

The Mapleson circuits have a minimum FGF (usually a multiple of minute volume) to prevent rebreathing, and I'm sure someone somewhere has published the same for the circle circuit. Your schema for adults/kids/neonates sounds about right.

 

[deleted126335]

Despite the fact that their is no sodalime, it is a circle system so there is some rebreathing. At higher fgf rates this is minimal. At lower fgf there will be significant rebreathing of gas with CO2. Of note you have an older machine so increasing the FGF will affect the tidal volume and minute ventilation. (Newer machines in the USA don't have this issue) The data points that are relevant are the I:E ratio and change in FGF rate. You have an I:E of 1:2 so for every increase in FGF rate of 3 liters per minute will increase minute ventilation by 1 liter per minute.

 

[DrAmir0078]

Looks like you've got a standard circle circuit, but without the soda lime. So yeah, you can't really recycle gas without causing CO2 rebreathing, so a 7L FGF is probably necessary.

The Mapleson circuits have a minimum FGF (usually a multiple of minute volume) to prevent rebreathing, and I'm sure someone somewhere has published the same for the circle circuit. Your schema for adults/kids/neonates sounds about right.

That is a relief!
But if there is Soda Lime, you think we can achieve low fresh gas, like 2L is enough?
Many Thanks Dr. Daneeka

 

[DrAmir0078]

Despite the fact that their is no sodalime, it is a circle system so there is some rebreathing. At higher fgf rates this is minimal. At lower fgf there will be significant rebreathing of gas with CO2. Of note you have an older machine so increasing the FGF will affect the tidal volume and minute ventilation. (Newer machines in the USA don't have this issue) The data points that are relevant are the I:E ratio and change in FGF rate. You have an I:E of 1:2 so for every increase in FGF rate of 3 liters per minute will increase minute ventilation by 1 liter per minute.

Thanks,
I am getting what you were saying, and it helps with other comments to resolve this mystery!

In other hospitals, they have different versions of Anesthesia Machine like Datex Ohmeda...
I hope in my residency next few days will show you what we got, hopefully newer versions!

 

[coffeebythelake]

That is a relief!
But if there is Soda Lime, you think we can achieve low fresh gas, like 2L is enough?
Many Thanks Dr. Daneeka

With a co2 absorber u dont even need 2lpm. We routinely run at 0.5 lpm or less in maintenance phase. In other words, your lack of a co2 absorber is causing a huge waste of inhaled anesthetic gas

 

[pgg]

every once in a while during the surgery we disconnected the Y tube from ETT and press the Oxygen flush to release the mixture and gets only oxygen! Could be?

This isn't really necessary with FGFs of 7 L; CO2 is easily washed out with that much fresh gas. And by disconnecting the Y you're putting a bunch of volatile into the operating room for everyone to breathe. Our OSHA has rules about that.

Is there a scavenging system, or at least a waste hose from the machine leading out of the room?


Those unsecured O2 tanks would get cited in a US hospital. If one falls over and the regulator gets broken you could have a violent torpedo. That may be a logistic or facility issue you don't have the power to fix, but be careful.

 

[pgg]

Do you ever use that halothane vaporizer? Inhalation inductions?

 

[pgg]

So probably, because we do not have Soda Lime, so there is no recycling of the exhaled CO2, that is why we give 7 Lt, and because it it is a closed circuit,

To be precise with terms, it's a circle system but not closed.

You've got 7 L going in every minute, and 7 L has to come out every minute. It's either leaving through a vacuum assisted scavenging system, or a waste hose going somewhere, or into the air in the operating room.

Since there is some recirculation of gasses, yours is a semiclosed circle system. This is a good summary:

https://www.openanesthesia.org/anesthesia_delivery_systems_anesthesia_text/

 

[deleted697535]

It seems like false economy to me. You don't have soda lime, capnography or temp probes.
In it's place you have 7 litres fgf. O2 and volatile is expensive. I guess iso is cheap compared to Des that we have but still.

Medical air and ow can cost 100$ of thousands per year in a big hospital. I know it isn't your issue. It's understandable to some degree...
It would be very hard to practice like this. It couldn't happen really in the eu or north america. We'd be straight up closed down

 

[DrAmir0078]

With a co2 absorber u dont even need 2lpm. We routinely run at 0.5 lpm or less in maintenance phase. In other words, your lack of a co2 absorber is causing a huge waste of inhaled anesthetic gas

Well, it is because of budget issues, probably they found Soda Lime vs Oxygen supply feasibility, Oxygen won of course !
I heard they had before Soda Lime, but what to do with the austerity of the government !

 

[DrAmir0078]

This isn't really necessary with FGFs of 7 L; CO2 is easily washed out with that much fresh gas. And by disconnecting the Y you're putting a bunch of volatile into the operating room for everyone to breathe. Our OSHA has rules about that.

Is there a scavenging system, or at least a waste hose from the machine leading out of the room?


Those unsecured O2 tanks would get cited in a US hospital. If one falls over and the regulator gets broken you could have a violent torpedo. That may be a logistic or facility issue you don't have the power to fix, but be careful.

Dr. Pgg,
Thanks for your valuable comment, that behavior of disconnecting Y (I heard, some Attendings used to do this) and the technicians sometime perform it (sure, it is wrong), sometimes we get leaks from those tubes, and we could smell the volatiles !

The problem which is I am not sure about the Scavenging system, a waste hose (Probably there is none, as we can move the machines sometimes between the rooms) and this is my question to the Technicians today too, if there a release valve or exhaust we've could smell the volatiles, aren't we? (I am calling the head of technicians to see!)

Yes, we are very careful with those Oxygen tanks, it is scary! Thanks for the reminder!

 

[DrAmir0078]

Do you ever use that halothane vaporizer? Inhalation inductions?

This question for you Dr. Pgg?
When was the last time you ever used Halothane?
Indeed, until 4 months ago, we run out the Halothane, and our Ministry of Health banned the use of Halothane !
I've seen how awesome Halothane in induction, especially for the kids, if you compare it with Isoflurane !

 

[DrAmir0078]

To be precise with terms, it's a circle system but not closed.

You've got 7 L going in every minute, and 7 L has to come out every minute. It's either leaving through a vacuum assisted scavenging system, or a waste hose going somewhere, or into the air in the operating room.

Since there is some recirculation of gasses, yours is a semiclosed circle system. This is a good summary:

https://www.openanesthesia.org/anesthesia_delivery_systems_anesthesia_text/

Got it Dr. Pgg,
I am so thankful !

Probably, it is the operating room air! (but so curious to see where is that in the machine)

So our machine is semiclosed circle system, but if we activate the Soda Lime will be closed?

What a wonderful article to read !

 

[pgg]

It seems like false economy to me. You don't have soda lime, capnography or temp probes.
In it's place you have 7 litres fgf. O2 and volatile is expensive. I guess iso is cheap compared to Des that we have but still.

Medical air and ow can cost 100$ of thousands per year in a big hospital. I know it isn't your issue. It's understandable to some degree...
It would be very hard to practice like this. It couldn't happen really in the eu or north america. We'd be straight up closed down

Thee are good points but even in the US there are different grades and costs to O2 depending on the application, e.g. aviation, medical, welding, research. A significant portion of the cost of medical O2 in the US is the paperwork, need to vacuum empty tanks before refilling them, etc.

I bet they aren't paying anything near our costs for their O2. And it looks like their machines don't have a medical air supply.

CO2 absorbent can be costly, and honestly much of the volatile cost savings from low flow techniques is eaten up by the much faster consumption of absorbent.

 

[DrAmir0078]

It seems like false economy to me. You don't have soda lime, capnography or temp probes.
In it's place you have 7 litres fgf. O2 and volatile is expensive. I guess iso is cheap compared to Des that we have but still.

Medical air and ow can cost 100$ of thousands per year in a big hospital. I know it isn't your issue. It's understandable to some degree...
It would be very hard to practice like this. It couldn't happen really in the eu or north america. We'd be straight up closed down

At least this Hospital Dr. Newtwo and most of the other hospitals in the provinces away from the Teaching centers in the big cities!
No Soda Lime (they used to have them before), No capnography (Thanks that opportunity, I used to place the nasal cannula and put the extension to the monitor while I was at GWUH, so I know what that is), no Temp probes (Only in the wards)

WOW ... I wish I am able to write a good paper to the Secretory of Health of Iraq to raise the awareness of such issues, but as you know, I am just very small in my power size compared with the Professors or others; that is why I need this residency to build up the knowledge, and in a better position, so when I will say something, at least somebody will hear me!
----

 

[pgg]

When was the last time you ever used Halothane?

I'm not sure I've ever used it. We had some halothane vaporizers when I was an intern in 2002. I've seen it used at hospitals in Afghanistan. I don't believe I've ever used it myself though.

I've
seen how awesome Halothane in induction, especially for the kids, if you compare it with Isoflurane !

My knowledge of halothane is just book knowledge, but it has some undesirable features. It's therapeutic window is narrow, and dysrhythmmias are a higher risk. Halothane hepatitis is a thing but I don't really know how big that issue really is. I'd use it for inhalation inductions if I didn't have sevoflurane, but I'd switch to isoflurane as soon as the kid was asleep.

 

[DrAmir0078]

I'm not sure I've ever used it. We had some halothane vaporizers when I was an intern in 2002. I've seen it used at hospitals in Afghanistan. I don't believe I've ever used it myself though.

wow, it is a history Dr. Pgg !

My knowledge of halothane is just book knowledge, but it has some undesirable features. It's therapeutic window is narrow, and dysrhythmmias are a higher risk. Halothane hepatitis is a thing but I don't really know how big that issue really is. I'd use it for inhalation inductions if I didn't have sevoflurane, but I'd switch to isoflurane as soon as the kid was asleep.

It is the same as many new agents now for us are in the book!
True, I've experienced so many times dysrhythmias in our middle age patients and we have to stop giving it (the miracle is, rapidly correction of dysrhythmias once we close the dial and to switch to Isoflurane)
My Senior Attending, he used to induct kids with Halothane and then switch to Isoflurane, but the other day I saw him induct right away with Isoflurane and kid is crying and the technician was holding tight the mask on him!

 

[pgg]

Probably, it is the operating room air! (but so curious to see where is that in the machine)

So our machine is semiclosed circle system, but if we activate the Soda Lime will be closed?

Simply put, open/closed/semi-closed depends on what percent of your FGF exits the circuit (100%, 0%, and 1-99% respectively).

A circle system can be closed or semi-closed. It can functionally approach open if FGFs are high enough.

A mapleson circuit is open - but note that rebreathing of CO2 can still occur if FGFs are too low. How low depends on the specific type of Mapleson, and whether breathing is spontaneous or controlled.

Absorbent is a separate issue.

CO2 absorbent is required for closed circuit anesthesia (because the CO2 can't otherwise leave the circuit). It is also required for semi-closed circuit anesthesia IF the fresh gas flow is too low (roughly under 3-5 LPM for an adult) to wash out the CO2. It is not required for open circuit anesthesia because the CO2 exits the circuit with the rest of the gas.

 

[btbam]

wow, it is a history Dr. Pgg !



It is the same as many new agents now for us are in the book!
True, I've experienced so many times dysrhythmias in our middle age patients and we have to stop giving it (the miracle is, rapidly correction of dysrhythmias once we close the dial and to switch to Isoflurane)
My Senior Attending, he used to induct kids with Halothane and then switch to Isoflurane, but the other day I saw him induct right away with Isoflurane and kid is crying and the technician was holding tight the mask on him!

An inhalational induction with Iso sounds worse than getting waterboarded.

 

[DrAmir0078]

Simply put, open/closed/semi-closed depends on what percent of your FGF exits the circuit (100%, 0%, and 1-99% respectively).

A circle system can be closed or semi-closed. It can functionally approach open if FGFs are high enough.

A mapleson circuit is open - but note that rebreathing of CO2 can still occur if FGFs are too low. How low depends on the specific type of Mapleson, and whether breathing is spontaneous or controlled.

Absorbent is a separate issue.

CO2 absorbent is required for closed circuit anesthesia (because the CO2 can't otherwise leave the circuit). It is also required for semi-closed circuit anesthesia IF the fresh gas flow is too low (roughly under 3-5 LPM for an adult) to wash out the CO2. It is not required for open circuit anesthesia because the CO2 exits the circuit with the rest of the gas.

Got it Dr. Pgg !

Regarding Mapleson, we use either Mapleson F or Modified (Jaskson Rees) for children or infants, we never used it for Adult, although both of them for Spontaneous Anesthesia (no Paralytics) and sometimes we assist with OP airways / rarely LMA !

So, we got definite washing out of CO2 with that 7 Lt !

 

[DrAmir0078]

An inhalational induction with Iso sounds worse than getting waterboarded.

Indeed ! !
I was really astonished !
95% (not a study) but just assuming from my experience, why we induct kids on Volatiles because we couldn't get an IV on them, because they cry ! You need an army to hold one kid over here !

 

[deleted59964]

would be nterested to know the cost for you of

Current isoflurane use vs (1/14 x current iso cost plus soda lime cost)
Your oxygen (and medical air if you have it) cost would also decrease ... but harder to quantify

Thanks for your perspective... I’ll stop whining about equipment I use now

 

[DrAmir0078]

would be nterested to know the cost for you of

Current isoflurane use vs (1/14 x current iso cost plus soda lime cost)
Your oxygen (and medical air if you have it) cost would also decrease ... but harder to quantify

Thanks for your perspective... I’ll stop whining about equipment I use now

I'll have to ask tomorrow someone who knows about the prices!

Oxygen is always available, most of the hospital has their own Oxygen manufacturing factory, so it is always available in cylinders!

Medical air is not available!

This hospital used to be a Military hospital constructed by a Yugoslavian company that has a central gas system, but they deactivated after 2003 when it is changed to be civilian, probably due to malfunctioning !

Soda Lime as I said, it used to be available!

We need to know the price!

Thanks Dr. Jobsfan, you have to whining and we do the same all the time, we sigh a lot, we damn a lot, we all want a safe practice field!

We have a say
"each one pull his fitted blanket"
That means, your blanket is longer than mine, so you can cover your whole body to get warm, while our blanket is shorter but at least can cover our legs, so both get warm differently!

 

[coffeebythelake]

with the constant high FGF how do u prevent pt airway from drying out? I doubt the HME is enough

 

[DrAmir0078]

with the constant high FGF how do u prevent pt airway from drying out? I doubt the HME is enough

Thanks a lot,
I just knew HME (Heat Mositure Exchanger) which is a device attached to tube - hose system!
I saw some hoses has HMEs, but I believe they are not working (I believe they need to be periodically changed) beside this machine has no HME connected!
I don't know how to answer your question, and never heard that our machines provide humidified gas!
What are the consequences of dried airways?
Are these manageable?
Patients mostly complain of sore throat, and we blame the ETT, so what else?

 

[daneeka]

It's not important, but for exam purposes:

Open circuit = dropping ether onto a handkerchief
Semi-open circuit = running a circle or Mapleson at high FGF
Semi-closed circuit = running a circle at low FGF
Closed circuit = only enough FGF to replenish uptake of O2/volatile (tends to be sophisticated machines with end-tidal control etc)

 

[DrAmir0078]

It's not important, but for exam purposes:

Open circuit = dropping ether onto a handkerchief
Semi-open circuit = running a circle or Mapleson at high FGF
Semi-closed circuit = running a circle at low FGF
Closed circuit = only enough FGF to replenish uptake of O2/volatile (tends to be sophisticated machines with end-tidal control etc)

Lots of thanks Dr. Daneeka