ETCO2 and Ventilation

[Noyac]

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There is a pretty decent article in the ASA Newsletter about our current thinking when it comes to mechanical ventilation. It describes "dogma" being hyperventilating to a ETCO2 of 30-35. What's your practice currently?

I switched over from RR8, TV 10cc/kg a few years back to RR12, TV 5-8cc/kg allowing ETCO2 to rise to around 40. Anyone else doing this? ANy problems with this in the typical pt without increased ICP? Any benefits to this practice?

Just trying to stimulate discussion here.

 

[DrDre']

I run all pts without contraindications with mild permissive hypercapnea (unless they have tattoos!). I do this with lower TVs and sometimes higher rates- then I am doing protective lung ventilation as well. I use a little peep as well to decrease atelectasis.

This has been shown to increase peripheral tissue 02 saturation in morbidly obese and likely to decrease wound infections.

 

[dfk]

I run all pts without contraindications with mild permissive hypercapnea (unless they have tattoos!). I do this with lower TVs and sometimes higher rates- then I am doing protective lung ventilation as well. I use a little peep as well to decrease atelectasis.

This has been shown to increase peripheral tissue 02 saturation in morbidly obese and likely to decrease wound infections.

hey dre, bare with me for a minute. in response to your "little peep" statement, what do you consider a little? i cannot seem to find reference, but was under the assumption that during anesthesia, utilizing intrinsic (5 cm H2O) peep is not relatively effective. and that a peep of nearer 10 during GA is more comparable to 5 during SV to help eliminate atelectasis. any validity to this?

 

[Bertelman]

hey dre, bare with me for a minute....

someone gettin' nekkid????

 

[LongSnow]

If I had a choice, I'd prefer hypercapnia to hypocapnia unless otherwise contraindicated.. Acidosis better tolerated than alkalosis. oxygen unloading, enzymatic function, vasodilation(esp cerabral), etc....

My ideal end-tidal CO2(assuming healthy patient with none-minimal arterial-endtidal CO2 gradient) for a beautifully smooth wake up is ET 48 with a respiratory rate of 12. However, I always put more stake inthe RR than the ETCO2. Sometimes ETCO2 up to 60 - that would put a non otherwise stessed persons ph at 7.24 if ETCO2 =arterial co2. As the gas blow blows off and/or musle relaxation abates, can often work in little bits of fent (10-25 mcg/ 30 sec) or sufent 2.5-10 mcg to smooth it out more.

If I hypovent a healthy person to ETCO2 60 and they don't start beathing, figure I got enough narcotics on board. Using this appraoch, hover, and every now and again will will have to give small (20-40) incremental doses of Narcan. I hate giving narcan, but I would rather give narcan every third month than have patients sceam in pain as they wake up.

By the way - ever read the apneic oxygenation studies - the limiting factor was acidosis from CO2. Cardiac dysthrymias especially. Arterial CO2 were f'ing rediculous - well into the 100's+. Plus, I been called to many a code where ETCOs is 150+. ph in mid 6's, and simple ventilation resolved the entire situation. As a side nore, CO2 narcosis, I think, clinically, begins around arterial CO2 75-80.

I am very anti-dogmatic! Reflux? Yes you can have an LMA - but I won't use positive pressure ventilation, and I won't mask. Science behind it? probobly not. Cricoid? it sucks - unless utilized to opltimize you view - and it can comprimize your view and can make intubation take longer. NPO? elective stuff can wait - but what about all that grey zone stuff? I am will proceed if airwy looks decent. Beachchair shoulder hypotension - now this I really hate - but one way to hedge your bets is put on a bis montior, run propofol + desflurane to >50% burst burst supression, and everytime th surgeon bitches about bleeding reply that BP can go NO MOE LOW! Platelets for a labor epidural 98 - well that depends - were they 98 last week, or 360?

The key i think is to during residency find a way to do things swifly, smoothly efficenciently, and confidently. You do that - dogma BS will wigh less and less upon your mind.

 

[dfk]

someone gettin' nekkid????

if dre's a chick, then hell yea (but i doubt it).

 

[fakin' the funk]

This has been shown to increase peripheral tissue 02 saturation in morbidly obese and likely to decrease wound infections.

The "Does hypercapnia decrease wound infections" RCT has been done - with a negative result...I believe publication is pending. The EtCO2's were 35 vs. 50.

 

[dhb]

I usually aim for an EtCO2 around 35mmHg which sort of guarantees normocapnia.

 

[jwk]

If I had a choice, I'd prefer hypercapnia to hypocapnia unless otherwise contraindicated.. Acidosis better tolerated than alkalosis. oxygen unloading, enzymatic function, vasodilation(esp cerabral), etc....

My ideal end-tidal CO2(assuming healthy patient with none-minimal arterial-endtidal CO2 gradient) for a beautifully smooth wake up is ET 48 with a respiratory rate of 12. However, I always put more stake inthe RR than the ETCO2. Sometimes ETCO2 up to 60 - that would put a non otherwise stessed persons ph at 7.24 if ETCO2 =arterial co2. As the gas blow blows off and/or musle relaxation abates, can often work in little bits of fent (10-25 mcg/ 30 sec) or sufent 2.5-10 mcg to smooth it out more.

If I hypovent a healthy person to ETCO2 60 and they don't start beathing, figure I got enough narcotics on board. Using this appraoch, hover, and every now and again will will have to give small (20-40) incremental doses of Narcan. I hate giving narcan, but I would rather give narcan every third month than have patients sceam in pain as they wake up.

By the way - ever read the apneic oxygenation studies - the limiting factor was acidosis from CO2. Cardiac dysthrymias especially. Arterial CO2 were f'ing rediculous - well into the 100's+. Plus, I been called to many a code where ETCOs is 150+. ph in mid 6's, and simple ventilation resolved the entire situation. As a side nore, CO2 narcosis, I think, clinically, begins around arterial CO2 75-80.

I am very anti-dogmatic! Reflux? Yes you can have an LMA - but I won't use positive pressure ventilation, and I won't mask. Science behind it? probobly not. Cricoid? it sucks - unless utilized to opltimize you view - and it can comprimize your view and can make intubation take longer. NPO? elective stuff can wait - but what about all that grey zone stuff? I am will proceed if airwy looks decent. Beachchair shoulder hypotension - now this I really hate - but one way to hedge your bets is put on a bis montior, run propofol + desflurane to >50% burst burst supression, and everytime th surgeon bitches about bleeding reply that BP can go NO MOE LOW! Platelets for a labor epidural 98 - well that depends - were they 98 last week, or 360?

The key i think is to during residency find a way to do things swifly, smoothly efficenciently, and confidently. You do that - dogma BS will wigh less and less upon your mind.

It's really kind of strange the range of EtCO2 that we allow. Many hyperventilate when using the vent down into the low 30's, but those same people allow spontaneously breathing LMA patients to go along in the upper 60's. We just got some vents with pressure support - they are da bomb and PERFECT for use with LMA's.

And as far as beachchair shoulders - we put the fear of God into our surgeons about the evils of hypotension, and we simply don't do controlled hypotension on shoulders (or spines or anything else) any more. I'm glad to see someone else using the BIS as somewhat of a guide with those cases. If I've got someone with questionable pressures but a BIS of 40, I'm not too worried. If the BIS is 10, then I've got problems.

 

[dfk]

It's really kind of strange the range of EtCO2 that we allow. Many hyperventilate when using the vent down into the low 30's, but those same people allow spontaneously breathing LMA patients to go along in the upper 60's. We just got some vents with pressure support - they are da bomb and PERFECT for use with LMA's.

And as far as beachchair shoulders - we put the fear of God into our surgeons about the evils of hypotension, and we simply don't do controlled hypotension on shoulders (or spines or anything else) any more. I'm glad to see someone else using the BIS as somewhat of a guide with those cases. If I've got someone with questionable pressures but a BIS of 40, I'm not too worried. If the BIS is 10, then I've got problems.

funny you say the fear of god is put into the surgeons about HOTN, but what we are taught these days is the fear of VAE with beach chair. much easier to tx hotn than vae. IMO of course.

 

[dhb]

funny you say the fear of god is put into the surgeons about HOTN, but what we are taught these days is the fear of VAE with beach chair. much easier to tx hotn than vae. IMO of course.

😕 If you're saying what i think you're saying then you're missing an important concept.

 

[periopdoc]

funny you say the fear of god is put into the surgeons about HOTN, but what we are taught these days is the fear of VAE with beach chair. much easier to tx hotn than vae. IMO of course.

It is much easier to take a concept that ortho dude understands somewhat (blood pressure) and make an argument than it is to try to introduce a new concept (VAE). Of course if you call it a pulmonary embolism instead of VAE, ortho dude would probably get more excited.

- pod