timely wake ups?

[heathermed]

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Hello everyone...

Just looking for some advice once again.
I'm having a lot of trouble with wake ups.

I've been trying the following approach. I try to taper down the gas incrementally as the surgeons start closing. About this time, I turn down the RR on the vent and build up the ETCO2 on SIMV mode and have the patient start breathing. Once they start putting on the dressing, I give the reversal and turn up the flow rates.

The problems I am coming across is that most of the time, either there is too much residual gas still on board or that the pt is weak and not making adequate tidal volumes. Both result in a delayed wake up. I've tried tapering the gas earlier, but that has lead to the pt moving prematurely and me having to push propofol, which results in the same problem of delayed wake up.

I've tried using nitrous at the end but most of my attendings don't like it when I use it.

any help with successful wake up regimens would be very helpful.

thank you very much for your help

 

[lane]

Sugammadex and narcan 🙂

 

[Idiopathic]

early on, most people overdose their patients on muscle relaxant and volatile anesthetic. titrate to two twitches or something easily reversible, and realize that MAC of volatile is additive with benzos and opiates. rarely do you need more than 0.6 MAC if you have a well balanced anesthetic. as you do more cases you will appreciate the various wakeups with each agent and you will start to dial in your approach

 

[BobBarker]

Drive the gas off with the vent. If you aren't moving air, you aren't getting rid of your volatile.

 

[pgg]

Drive the gas off with the vent. If you aren't moving air, you aren't getting rid of your volatile.

That's what I do. 90%+ of the time for ordinary elective cases, I don't see any point in 'getting patients breathing again' before you wake them up. Some people like to use RR as an indicator of whether or not they've given enough opiate. In time you get a feel for how much narcotic any given patient is going to need.

Unless the patient's been spontaneously breathing the entire case with good minute volumes, like BobBarker said, drive the gas off with the vent. When you have to make an effort to get them breathing, two things happen - they get hypercarbic, and they hypoventilate, neither of which help with quick wakeups.

Also, you can turn off the volatile agent earlier than you think. Closing is not stimulating and doesn't need 1.3+ MACs of anesthesia. If you can spend the last 5-10 minutes of the case at ~ 1/2 MAC of gas it'll come off that much faster. Don't get too cute and let them ride the last 10 minutes at 2% des or 0.6% sevo until you get a better feel for it.

You don't need nitrous. It's just one more thing to complicate the wakeup. I never use the stuff unless I'm doing pediatric mask inductions or GA c-sections.

It also gets easier when you don't have random med students, interns, and residents closing ... and you can predict how soon the dressing will go on.

 

[TrustMe]

Don't wait until they are putting the dressing on to reverse the neuromuscular blockade. While they are putting the dressing on is when you should be taking out the ETT. If it is an open belly case you should start working on getting them breathing as soon as the fascia is closed. If they have twitches go ahead and reverse them and get them breathing. It can take reversal 5+ minutes to be fully effective. If they are not reversed, they won't be strong enough to make a good enough respiratory effort to blow off the volatile. The other option (as was mentioned) was use the vent to blow off the volatile and then let them breath.

Worked with a surgeon in residency that did mostly laproscopy and had a private practice mentality. He made it known that if the patient was ready we could extubate as soon as the ports were out. He used lots of local so as soon as the ports were out the only stimulation was the ETT. The patient doesn't need an ETT for them to close skin (especially if they use good local). Of course, if you have surgeons that insist that the patient be completely still while they are closing skin then they have to also understand that the wake-up may take a little longer in order to meet their other expectations.

 

[Breezee]

Consider giving your reversal after the fascia is closed. Your patient does not need to be relaxed to close the subQ and skin. I agree with lowering your agent to half MAC at this time, too. Often, the surgeon will give local. If I see this, I'll often turn off my agent entirely when they get to skin (if you have a good idea of how long it will take them to close). And I definitely agree with the aforementioned suggestions to let the vent blow the agent off for you.

 

[sevoflurane]

Turn off your gas @ 10-12 minutes before last suture is expexted to go in and run low flows.
8 minutes before last suture reverse them (you need to give it time to work maximally)
3-4 minutes before last suture, turn up your flows to 12 L/m.
If you think you are running a little ahead of your surgeon, make good use of your left over propofol.

Nice fast wake ups.

Sometimes they are extubated with great TVs and before the last suture/cast is being placed.

 

[Agast]

This is what has worked for me so far as a resident at a teaching hospital:

Reversal goes in when appropriate for the case. I don't reverse a prone patient until they're flipped, I do wait for 4 twitches and I titrate my NMB accordingly by discussion with the surgeon on how long they have and what kind of closure they're planning on (sutures vs. staples). I also get a sense during the case how long it takes for twitches to come back in between NMB dosing. I know some places reverse with 2 twitches, but the culture here is 4 twitches and there's no glory in being the resident who reverses with 2 twitches and has a fat floppy patient.

I don't try to get the patient breathing right away, once the gas is off and the patient is reversed they should have the ability to breathe anyway...watching them struggle for 10 minutes of closure isn't helpful. I let the CO2 build up a little, but mostly to give me wiggle room to increase their respiratory rate at the end to blow off the gas.

I keep a little fentanyl at the end so I can slip it in as appropriate to respiratory rate, level of responsiveness so they're not writhing in pain in PACU. I also have propofol to slip in when the surgical resident is taking a while to close or they're letting the medical student take a whack at it. At this point my flows are low and the gas is off. I also base my timing on how fat the patient is. By the time my attending walks in for extubation we're ready to take the tube out.

 

[sevoflurane]

Well there are different ways to do things. I always reverse my patients prone... Waiting to flip them and then reverse them will slow you down IMO. It takes time for that neostigmine to work at full capacity. That left over propofol is a nice touch in those cases. I like to get them breathing spontaneously in the prone position with a little hand assist.

Fast and safe wake ups are what PP is all about... at least here. Surgeons and OR staff appreciate that because that extra 10 minutes equates to a lot of time over 5-10 cases.

Do what you are comfortable with... but know there are other ways. 🙂

If you really want to impress your attendings and OR staff.... get your patient to move over to the bed on their own.
Now THAT is a nice wake up! 😉

 

[Oggg]

If nitrous is an option, I will shut the volatile off and go to 6-8lpm nitrous as soon as they are closing. The residual volatile is enough to keep them asleep, but the nitrous keeps me from having to give propofol. The goal is to get sevo <0.3%. Then shut off the nitrous and the patient will stir in five minutes or less.

+1 to keeping the twitch count at 2-4 and early reversal (use propofol and outright lies when surgeon asks for paralysis during a simple wound closure)

 

[sevoflurane]

Agree with PGG on the nitrous thing. + I'm trying to keep my N/V to a minimal.

Also... you tend to blow off your inhaled agents a lot quicker if you've been running low flows for the case ....say .3-.4 l/m vs 2L/m.

 

[jwk]

I do wait for 4 twitches..... I know some places reverse with 2 twitches, but the culture here is 4 twitches and there's no glory in being the resident who reverses with 2 twitches and has a fat floppy patient.

I don't get it. Do you wait for four twitches so you can give less reversal? It's absolutely pointless to wait for 4 twitches before reversing. What if they only have 2-3 twitches and the case is done and the dressing on? Do you wait until they have 4 twitches to reverse?

 

[seinfeld]

1st question i would ask you is what gas are you using? Sevo/Des wake ups are far different than ISO wake ups.

Something that i learned early in PP is that in residency i used way too much NMB, waited too long to shut off the gas, and getting the patient breathing is not worth it 95% of the time. Another trick is to go light on opiods until they are extubated.

Most of the time patient is getting extubated as the dressings are being applied. I will tell you that being an attending means i don't have to wait for an attending to come in and supervise my extubation. I found in training that to be another factor in bad wake ups.

 

[RussianJoo]

Agree with PGG on the nitrous thing. + I'm trying to keep my N/V to a minimal.

Also... you tend to blow off your inhaled agents a lot quicker if you've been running low flows for the case ....say .3-.4 l/m vs 2L/m.

Been doing low flows lately and I love it. Plus I don't have to refill my vaporizer through out the day. A lot of times I also add a BIS and keep it in the 50's that way I am not overdosing on gas.

 

[RxBoy]

Been doing low flows lately and I love it. Plus I don't have to refill my vaporizer through out the day. A lot of times I also add a BIS and keep it in the 50's that way I am not overdosing on gas.

Love low flow. I routinely set low flow (0.25 to 0.5 L/min). It does cut down on volatile use considerably but also:
1) It helps maintains humidity and retain body temp.
2) Rapidly diagnosis a circuit leak.

Disadvantages:
1) Slow to titrate gas up/down after steady state achieved.
2) Exhaust CO2 absorbers quickly.
2) Compound A (sevo) and CO buildup. Although I think this is more academic than clinical.

I don't understand how it leads to quicker wake ups other than possibly flushing out residual gas in circuit faster. Maybe less volatile absorption in circuit?

The greatest variable in elimination of volatile will be a function of alveolar MV. This will not be affected by low flows. This will be affected by reversing early and letting pt spont breath (low MV) vs. keeping pt partially paralyzed and allowing vent to do all the work (high MV sometimes more than double). My emergence strategy is usually the latter.

 

[OB1🤙]

I am also a low-flow guy. A word of caution: you have to know your machine. Some systems reroute gas from the gas analyzer back into the circuit, and some waste it out the scavenger. That 250cc/min can make a big difference if you're on the lower end of the flow spectrum.

 

[jetproppilot]

Hello everyone...

Just looking for some advice once again.
I'm having a lot of trouble with wake ups.

I've been trying the following approach. I try to taper down the gas incrementally as the surgeons start closing. About this time, I turn down the RR on the vent and build up the ETCO2 on SIMV mode and have the patient start breathing. Once they start putting on the dressing, I give the reversal and turn up the flow rates.

The problems I am coming across is that most of the time, either there is too much residual gas still on board or that the pt is weak and not making adequate tidal volumes. Both result in a delayed wake up. I've tried tapering the gas earlier, but that has lead to the pt moving prematurely and me having to push propofol, which results in the same problem of delayed wake up.

I've tried using nitrous at the end but most of my attendings don't like it when I use it.

any help with successful wake up regimens would be very helpful.

thank you very much for your help

BIS

It works man.

Wish you guys could see our awake patients in the PACU....even after an 8 hour spine case....

 

[rsgillmd]

.....I don't understand how it leads to quicker wake ups other than possibly flushing out residual gas in circuit faster. Maybe less volatile absorption in circuit?....

Yep. Nothing or essentially no new inhalational anesthetic coming in. Gas in circuit gets SLOWLY absorbed/uptaken. Off-gassing > on-gassing. When you turn up your flows it's easy to wash out. You won't even need to flush the circuit. You'll see a difference between doing it this way vs non-low flow methods.

But more than low flows it's really about knowing the procedure and knowing your surgeons. Everyone has their own style.

 

[nap$ter]

BIS

It works man.

Wish you guys could see our awake patients in the PACU....even after an 8 hour spine case....

just yuked in my mask

thought bis had whimpered away?

 

[nap$ter]

my advice for fast wake-ups -

--avoid nmb altogether if possible, or reverse as soon as fascia is closed - i often use the white muscle relaxant for surgeon requests.
--for volatile cases - turn the gas off early early early with low flows - allows slower equilibration with various compartments.
--titrate opiates to minute ventilation changes whenever possible, be ginger
--i put the induction left over propofol in line and give small bumps for premature wiggling - surgeons sometimes move faster/chat less if the pt starts to move.

bottom line - turn off the anesthesia sooner and give less opiate.

 

[OB1🤙]

My advice: use desflurane.

 

[Doctor4Life1769]

My advice: use desflurane.

It's too bad most of my attendings insist on Sevo. Only a couple have allowed me to use Des. Gotta say, amazing wake-ups with Des.

How do y'all properly time wake-ups when a pt is in stirrups? I don't want the pt to start moving while still in stirrups...

Also, fatties. My main issues with wake-ups tend to be with fat patients and those in stirrups (mainly bc I get gun-shy when they are in stirrups).

 

[HollywdAnesth]

It all depends on the kind of case. I tend to always use desflurane unless the patient has asthma or COPD.

If the case does not require muscle relaxation, then I do not give any additional NMB after the induction dose.

I treat everyone aggressively for N/V. As soon as the closure starts, I get the patient spontaneously breathing. I turn the Des (or Sevo) really low. I will do 1.5 lpm of Nitrous and 0.5 lpm of o2. If the patient needs a higher FiO2, then I do 50/50. As the closure progresses, I turn the nitrous higher (which also brings the o2 LPM higher). I titrate in narcotics to keep the respiratory rate around 10. As soon as the last stitch is in, I turn off the nitrous and max out the o2. You can usually have someone awake in less than 2 minutes.

It takes alot of vigilance and awareness. You just get used to it. You develop tricks for different kinds of procedures. I have my tricks for carotids and choles. They tend to work well most of the time. In residency, I developed a technique for pedi dental cases and breast augmentations that people still do at my program.

Just experiment. Find out what works for you. If the patient jumps while they are suturing an appendectomy incision, it isn't the end of the world.

 

[dhb]

If you can't wake up a patient on your terms with any kind of gas then you are probably not very good at what you do.
Nitrous, propofol... it's fine if you don't have anything better to do than play around, the bottom line the less stuff you use the easier the wake up.

 

[leaverus]

There is no science, rhyme, nor reason to it. As any fool can plainly see, there are a thousand different ways to do it. It's part of the "art" of anesthesia. And even then it's hard to get right 100% of the time - i challenge anyone who claims every single one of their patients wakes up right on time.

 

[codeb1ue]

Turn off your gas @ 10-12 minutes before last suture is expexted to go in and run low flows.
8 minutes before last suture reverse them (you need to give it time to work maximally)
3-4 minutes before last suture, turn up your flows to 12 L/m.
If you think you are running a little ahead of your surgeon, make good use of your left over propofol.

Nice fast wake ups.

Sometimes they are extubated with great TVs and before the last suture/cast is being placed.

What do you do with the vent settings once turning gas off and putting them to low flow? Do you increase it slightly to help them breathe off gas faster or leave them as is?

I've tried the tactic of cutting down on my gas sooner but recently realized that I also instinctively turn my vent settings way down around the same time to start building up the CO2. And I always wondered why I have so much gas still on board when drapes come down.

 

[jetproppilot]

my advice for fast wake-ups -

--avoid nmb altogether if possible, or reverse as soon as fascia is closed - i often use the white muscle relaxant for surgeon requests.
--for volatile cases - turn the gas off early early early with low flows - allows slower equilibration with various compartments.
--titrate opiates to minute ventilation changes whenever possible, be ginger
--i put the induction left over propofol in line and give small bumps for premature wiggling - surgeons sometimes move faster/chat less if the pt starts to move.

bottom line - turn off the anesthesia sooner and give less opiate.

That last line you wrote is

BIBLICAL

 

[Oggg]

+1 to less opiates. RR of 10 is too low. If the surgery is not too painful, I'm ok with RR 18. You can always give narcotic after wakeup or in the PACU. High dose narcotics at induction to blunt the sympathetic response to laryngoscope are over rated.

 

[nap$ter]

What do you do with the vent settings once turning gas off and putting them to low flow? Do you increase it slightly to help them breathe off gas faster or leave them as is?

I've tried the tactic of cutting down on my gas sooner but recently realized that I also instinctively turn my vent settings way down around the same time to start building up the CO2. And I always wondered why I have so much gas still on board when drapes come down.

leave the vent as is. as you've already observed, turning the gas and minute ventilation down at the same time won't get you anywhere. if you want to wake the pt up on spont vent, they have to be breathing very early ie usually not possible in a belly case.

the reason for going to low flow with gas off super early can be illustrated by the following example which i used to see often with junior residents.

get called to room for wake-up - fat (american average) patient for belly case, gas kept somewhere around 3/4 mac until fascia is closed, then resident turns flows way up, gas off, keeps vent on (MV 5L/min).

at around 0.5-0.6 ET volatile pt sputters and coughs. resident turns vent off, pt slowly starts to breathe (MV 2-3L/min).

ET volatile on spont vent comes up at 0.8-0.9?!? resident makes comments about novel patient quality of spontaneous generation of volatile anesthesia - where's that gas coming from?!

patient takes another 10-15min to breathe the rest of the volatile off. 15min x 4patients can be an extra hour for that room.

for the residents - how is possible that the same pt will have an et iso of 0.5 on the vent with MV of 5L/min, but when they start breathing on their own with MV of 2L/min the et iso comes back at 0.8?

 

[deleted9493]

Balanced anesthetic is the key. Opioids don't have to delay your wake-ups: I find long acting opioids allow a lower MAC on closure without as much periodic respiratory depression as seen with the more potent synthetics. There is good evidence that lidocaine down the endotracheal tube can mitigate coughing at the end of a case--you can easily find several studies that speak to this. It seems to be dose dependent.

I am underwhelmed by the literature re: nitrous oxide and PONV and still find it useful for emergence in some.

There is one good reason to like Desflurane that I can think of but beyond its insolubility, are there any other pros to using Desflurane as opposed to Sevoflurane?

 

[drfeelgood]

I leave 0.4 et Sevo and give mini propofol boluses at the end of the case. Everyone wakes up within 30 secs or 1.5 minutes....which is expected by our surgeons in my busy practice. There is also less coughing and bucking..... My surgeons love me..... I know this because they tell me at least once a week.... I see their smiles when They see me setting up in their room in the morning. I learned this from Dr. Sutton at Brown University in Rhode ISland.🙂

 

[codeb1ue]

.

 

[codeb1ue]

for the residents - how is possible that the same pt will have an et iso of 0.5 on the vent with MV of 5L/min, but when they start breathing on their own with MV of 2L/min the et iso comes back at 0.8?

redistribution from fat?

 

[cchoukal]

I am blessed, I suppose, with LONG closing times, being at an academic VA most of the time. As such, I have the luxury of a long landing pattern. I also have the following beliefs:

V/Q matching during spontaneous ventilation is superior to that during positive pressure ventilation, thereby increasing the rate of elimination of agent.

People wake up "better" (less delirium, bucking, thrashing, punching; maybe this is a VA thing!) with a slower, gradual landing.

With that in mind, most of the time, I get the patient spontaneously ventilating. This allows titrating of long-acting opiates to comfort. I turn off the agent very early (for ex-laps, while closing fascia, for cranis, once the skull is closed, for hips and knees, while closing the capsule) and control the elimination with flows.

For a typical ex-lap, I'll turn the agent off during fascia, let the CO2 rise, reverse as the last fascial stitch is tied, and let the patient breath. (If it's for a big midline hernia and the surgeons make a big stink about not wanting bucking, I'll do a DL and LTA before reversing). Dose opiate to RR 8-12, and let them slowly breathe off the agent at flows of 0.3-0.5 L/min. When they're finally putting on dressings, I'm typically able to awaken and extubate under the drapes without much fuss.

The art is controlling the agent by increasing and decreasing the flows, as the pace of closure becomes apparent.

I think that at the end of a case, your goals are amnesia, analgesia, and immobility, and so you can tailor your mix to achieve these goals with things that don't also prolong emergence. In other words, low amounts of residual agent will handle amnesia, and opiates will basically take care of the rest. But every case is different, and as you progress, you'll find ways to make things work.

 

[pgg]

If it's for a big midline hernia and the surgeons make a big stink about not wanting bucking, I'll do a DL and LTA before reversing

Do you let the cuff down and slide the LTA alongside the ETT?

I used a bunch of LTAs during residency and lost interest in them simply because a lot of those cases were so ridiculously long that by the time wakeup rolled around, the effect was gone. I tried reconstituting some tetracaine in with the lidocaine and that seemed to help for the cases that were done in a couple hours.

One of my attendings swore by squirting lidocaine down the ETT at the end of the case, but it never seemed to work for me, and no wonder, since it wouldn't get the cords or even the bit of trachea under the cuff ... I think he was just getting the equivalent effect of 100 mg of IV lidocaine.

Frankly never occurred to me to use an LTA at the end of a case. 🙂

 

[cchoukal]

Yup. Little prop, suction, hold the vent, DL, cuff down, LTA. It helps to keep the patient relatively paralyzed til the end, so I do the LTA while they're on fascia, before I reverse. It's probably overkill, and it's as much to show the residents it can be done, but it does seems to prevent any bucking at the end.

 

[sevoflurane]

What do you do with the vent settings once turning gas off and putting them to low flow? Do you increase it slightly to help them breathe off gas faster or leave them as is?

I've tried the tactic of cutting down on my gas sooner but recently realized that I also instinctively turn my vent settings way down around the same time to start building up the CO2. And I always wondered why I have so much gas still on board when drapes come down.

Hard to say. This is where the art of anesthesia comes in. Every patient is a little different and you respond differently depending on hemodynamic data, how the patient has responded during the case, et gas concentration, peak perssuers, etc. In general, building up CO2 is a good thing when getting patients to breathe. If you have too much gas on board at the end of the case, you need to turn off your vaporizer earlier and turn up your flows earlier as well....

In some patients, I have no problem waking them up with .5 mac on board prior to extubation.

 

[pgg]

If you're using the Drager Apollo machines, you can build up CO2 without decreasing minute ventilation just by taking the CO2 absorbant out of the circuit. Click the absorbant canister out like you were replacing it. Those machines will seal themselves, and the patient will rebreathe CO2.

 

[positraction]

Hello everyone...

Just looking for some advice once again.
I'm having a lot of trouble with wake ups.

I've been trying the following approach. I try to taper down the gas incrementally as the surgeons start closing. About this time, I turn down the RR on the vent and build up the ETCO2 on SIMV mode and have the patient start breathing. Once they start putting on the dressing, I give the reversal and turn up the flow rates.

The problems I am coming across is that most of the time, either there is too much residual gas still on board or that the pt is weak and not making adequate tidal volumes. Both result in a delayed wake up. I've tried tapering the gas earlier, but that has lead to the pt moving prematurely and me having to push propofol, which results in the same problem of delayed wake up.

I've tried using nitrous at the end but most of my attendings don't like it when I use it.

any help with successful wake up regimens would be very helpful.

thank you very much for your help

There is a device out there to improve emergence. I have used it. It works.

http://www.anecare.com/Physicians/index.html

Operating room time is the most expensive time in the building!

 

[Doctor4Life1769]

I leave 0.4 et Sevo and give mini propofol boluses at the end of the case. Everyone wakes up within 30 secs or 1.5 minutes....which is expected by our surgeons in my busy practice. There is also less coughing and bucking..... My surgeons love me..... I know this because they tell me at least once a week.... I see their smiles when They see me setting up in their room in the morning. I learned this from Dr. Sutton at Brown University in Rhode ISland.🙂

I did this for my general case today, in addition to Rx's idea.

LMA placed, I was given a lunch, I return and the patient was on Sevo 0.4 and Nitrous (pt with hx of PONV), but it helped me keep sevo low, so I kept it BUT i also decreased flows from 2.4L/min to 0.35L/min. Patient was off the vent. I saw they were suturing up, so I turned off Sevo and turned off Nitrous. Sevo and Nitrous still circulating due to low flows. Gave ondansetron (had received scop patch during preop) and then began giving 10mg propofol bolus each minute for 3 mins. Patient was still breathing on her own. I did not give opiates even though RR was 18-19. It was not a painful procedure (port-a-cath placement) and we'd given 50mcg up front. By the time drapes were off, I turned up flows to 15L/min and put on 100% O2, sevo and nitrous immediately went to 0 and all I had to do was call her name out and tell her to open her eyes, which she did, and she had great tidal volumes and had good head lift, so I removed the LMA. No coughing/bucking or spasm. Patient denied having pain or nausea. Patient did real well in PACU as well. Probably my best wake-up yet.

 

[BobBarker]

I dont think you were meeting her oxygen requirement with .35L total flow of nitrous/o2 mixture. Not to mention that 2L of flow/compound A thing.

 

[cchoukal]

I dont think you were meeting her oxygen requirement with .35L total flow of nitrous/o2 mixture. Not to mention that 2L of flow/compound A thing.

Depends. There are several liters of circuit filled with oxygen from which the patient can draw. And the number of MAC-hours that you're below 2L/min of flow for the few minutes atthe end of the case is probably of little consequence.

 

[soonerfrog]

Agreed. Compound A should be bottom of your decision tree with such short amount of time for exposure. It's all about MAC hrs and even then, it's still largely Academic. Congrats on the wake up. Best part of the job in my opinion is the happy, eyes open on name calling, no bucking, no pain, no PONV, smiling & chatting pt.

 

[dhb]

I did this for my general case today, in addition to Rx's idea.

she had great tidal volumes and had good head lift, so I removed the LMA. No coughing/bucking or spasm.

🤣 Now that is some academic anesthesia right there!

(don't mean to pick on you but this was just too funny)

 

[BobBarker]

What are you guys thoughts on the oxygen requirement component of my post? I agree, about the compound A thing being a relative non-issue, but I could see many of my attendings freaking out over it.

 

[sevoflurane]

What are you guys thoughts on the oxygen requirement component of my post? I agree, about the compound A thing being a relative non-issue, but I could see many of my attendings freaking out over it.

This is a good low flow anesthesia topic.

BB is correct. If you have a 50/50 mixture of O2 and N2O you are likely not meeting metabolic needs.

VO2 (oxygen consumption) is around 4-7 cc/kg/min in a normal healthy resting adult. Probably more like 4 cc/kg/min under GA as it decreases 02 consumption.

Take a 70 kg patient. 70kg x 4cc/kg/min = 280cc of O2 consumption per minute.

@ .35 l/m with 50/50 N20/O2 mixed in you are only delivering about 175 cc/min. 175 cc's is 105 cc/min. off the calculated VO2.

Keep in mind there is some variability. Super healthy, fit people with a low VO2 may only need 3cc/kg/min. Those with more issues such as obesity, PVD, cardiac shunts, will need a higher delivery of fresh O2.

For adults, I don't usually go under 3L/M of fresh gas flow.

Great topic to discuss as it is very clinical.

 

[RussianJoo]

I did this for my general case today, in addition to Rx's idea.

LMA placed, I was given a lunch, I return and the patient was on Sevo 0.4 and Nitrous (pt with hx of PONV), but it helped me keep sevo low, so I kept it BUT i also decreased flows from 2.4L/min to 0.35L/min. Patient was off the vent. I saw they were suturing up, so I turned off Sevo and turned off Nitrous. Sevo and Nitrous still circulating due to low flows. Gave ondansetron (had received scop patch during preop) and then began giving 10mg propofol bolus each minute for 3 mins. Patient was still breathing on her own. I did not give opiates even though RR was 18-19. It was not a painful procedure (port-a-cath placement) and we'd given 50mcg up front. By the time drapes were off, I turned up flows to 15L/min and put on 100% O2, sevo and nitrous immediately went to 0 and all I had to do was call her name out and tell her to open her eyes, which she did, and she had great tidal volumes and had good head lift, so I removed the LMA. No coughing/bucking or spasm. Patient denied having pain or nausea. Patient did real well in PACU as well. Probably my best wake-up yet.

Great Job! I've been doing this for a while now, I like to pull my LMA's deep so I do this mostly for ETTs. I also squirt 3 ml of 4% lidocaine down the ETT which helps a lot with them tolerating the tube. Did a 5hr carniotomy the other day, without monitoring, the surgeon actually wanted paralysis. Low flows all the way, didn't give any fentanly during the last 2hrs of the case, I had to bolus some propofol during the last 20min because the intra-operative CT scanner wasn't working very well, kept him on the vent and didn't reverse till the last minute. But like you I called the dudes name he opened his eyes, I asked him to take a big breath, tidal volume of 800+, and I pulled the tube. The nurses got the roller ready, but I said hold on, and asked him if he could move over, and he did. It was great, during my CA-1 year all of my GETA pt's had to be rolled over and were very drowsy. Now with low flows my pt's move over by themselves and are a lot more alert. Oh and we mostly use Iso, like 99% of the cases, and our surgeons are very very slow, and I still get very quick wake ups.

 

[sevoflurane]

I agree, about the compound A thing being a relative non-issue, but I could see many of my attendings freaking out over it.

Didn't compound A come out of a rat study back in the day?

I have to review the literature, but I remember thinking that the newer studies kinda laughed at this and showed little to no difference in renal dysfunction btw/ low flow des/iso vs sevo.

I belive Baxter says that you get 2 MAC hours of sevoflurane @ low flows.

Now if you are running a .5 MAC case @ low flows... that buys you considerable time under low flow anesthesia.

Best way to warm the patient during a big spine case when the ambient temp is 56 degrees is NOT with a bair hugger or a hot dog... Low flows is considerably better. If I find condensed water vapor in my circuit... it means I've done a good job @ low flows.

 

[cowboy71]

Stop anesthesia when surgeon starts closing, get patient breathing spontaneously. When patient moves tell the surgeon they better hurry because they are clearly not timing their operation to your anesthetic. 😉

Seriously though, if you ask a thousand anesthesiologists you would hear a thousand different ways to do it. Residency is the time to learn and if the patient moves at the end it is usually not that big of a deal, unless their head is pinned or something similar. I learned this early as a CA1. I was waking up an ortho case and the residents were putting on the dressing. A senior anesthesia resident walked in just as the patient moved. The surgery residents said the "the patient is moving" I reached for the propofol, the CA3 looked at them and said "your finished aren't you?" The said "were just putting on dressings" He said "well hurry up, the patient is waking up"

I personally don't like des because patients seem to move when the level drops below about 1.5% but they are ready to extubate until lower. With sevo or iso they usually don't move with minimal stimulation until they are ready to extubate at about 0.2%. I don't think narcotics delay wakeups as long as they are breathing. It is the residual gas, benzo, etc. that delays wake-ups.