Pharmacodynamics, Pharmacokinetics, and jaw thrusts

[epidural man]

Still, after all these years, I am surprised about the huge variability from patient to patient (kinda like every time I do a spinal, I’m shocked it actually works…spinal = magic).

ASA1 45 y/o for a circ under MAC.

2 mg midazolam makes him sleepy. 50 mcg of fentanyl makes him arousable to voice with a significant shoulder tap. I’m thinking, this guy is a lightweight. My plan was to give 50mg propofol before the penile block and glans penis local (I mean, holy crap, give me the whole stick if someone is sticking a needle in my junk) - but since he was such a lightweight, I cut that in half (30mg).

For 20 minutes, I have to give this guy a jaw thrust! Super annoying because I had a great article I wanted to read about how Reagan plotted to prolong the Iran hostage situation to help him politically and hurt Carter. But no…I’m stuck working.

Work really gets in the way of living.

I’ve given 100mg to some and they keep talking to me. It’s just really interesting the variability.

We talk about the genetic variability of each individual drug - but I’ve never heard a discussion about the variability of the synergistic effects of drug combinations.

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[rowsdower88]

I get a little annoyed whenever I have to give another drug besides propofol for MAC anesthesia. >95% of MAC cases it's all I need.

de gustibus non est disputandum

 

[ambiturner]

And Nixon sabotaged a Vietnam peace plan to make Humphrey and Johnson look bad, if you’re serious about winning elections that’s what it takes!

I haven't really ever mastered prop dosing either, I think the instructions that come with it day you’re supposed to give like 10mg every 10 seconds which would help make sure you don’t over/undershoot but is totally unpractical. Also maybe this guy got drunk in the am before the circ?

 

[rowsdower88]

10mg every 10 seconds

Lol

 

[anaesthetic]

I get a little annoyed whenever I have to give another drug besides propofol for MAC anesthesia. >95% of MAC cases it's all I need.

de gustibus non est disputandum

Same, especially if I don’t want calls from PACU RNs or the GI RNs because the patient’s “too sleepy” for discharge.

e pluribus unum

 

[IMGASMD]

I just want to say I got scolded when I said that I learned to give 20cc right off the bat when I get a healthy asa1/2 patient for EGD and/or colonoscopy….. that’s 200mcg/kg/min assuming 100kg patient.

When you assuming your patient is 100kg (220lb) if you give 60ml/hr. It works out to be 100mcg/kg/min.

Both of these sound completely reasonable to me.

But I have a feeling both of the above posters are just being facetious….

I started to use ketafol much more after residency. If you really worried about them being apneic. GI nurses hate me, but would you rather be happier when I need to emergent intubate a fatty in your GI suite?!

If I had to give more than prop, I would give one or the other (fent vs versed), not both. I would usually pick fent, because my main concern after they’ve already received prop isn’t awareness (which is a reason why I would give versed). Usually it’s because they wouldn’t settle in and I don’t want to keep hammering them with more prop.

I still remember at the beginning of my ca3 year, a brand new attending had to call “anestheia stat” to cath lab…. Because he just pushed both versed and fent within mins of each then chased it with prop…. He was far away from accessing the airway, probably didn’t trust pulse ox reading for a few more seconds than he should have.

 

[abolt18]

I just want to say I got scolded when I said that I learned to give 20cc right off the bat when I get a healthy asa1/2 patient for EGD and/or colonoscopy….. that’s 200mcg/kg/min assuming 100kg patient.

When you assuming your patient is 100kg (220lb) if you give 60ml/hr. It works out to be 100mcg/kg/min.

Both of these sound completely reasonable to me.

But I have a feeling both of the above posters are just being facetious….

I started to use ketafol much more after residency. If you really worried about them being apneic. GI nurses hate me, but would you rather be happier when I need to emergent intubate a fatty in your GI suite?!

If I had to give more than prop, I would give one or the other (fent vs versed), not both. I would usually pick fent, because my main concern after they’ve already received prop isn’t awareness (which is a reason why I would give versed). Usually it’s because they wouldn’t settle in and I don’t want to keep hammering them with more prop.

I still remember at the beginning of my ca3 year, a brand new attending had to call “anestheia stat” to cath lab…. Because he just pushed both versed and fent within mins of each then chased it with prop…. He was far away from accessing the airway, probably didn’t trust pulse ox reading for a few more seconds than he should have.

I think you missed a decimal. A bolus of 20cc (200mg) of propofol is like a 1 minute propofol drip at 2,000 mcg/kg/min for your described patient.

 

[rowsdower88]

give 20cc right off the bat

Seems very aggressive to me.

started to use ketafol

I would HATE to have to take out controlled substances and potentially waste them for 8-12 routine GI procedures, but there's a million ways to do anesthesia.

 

[anesthesiadoc]

Place a nasal trumpet? (Lubricated with a suspension of propylene glycol, propylene oxide, water, and narcan).

 

[IMGASMD]

I think you missed a decimal. A bolus of 20cc (200mg) of propofol is like a 1 minute propofol drip at 2,000 mcg/kg/min for your described patient.

Damn it. Math I have failed you.

 

[IMGASMD]

Seems very aggressive to me.



I would HATE to have to take out controlled substances and potentially waste them for 8-12 routine GI procedures, but there's a million ways to do anesthesia.

Had a patient insisted that she was allergic to propofol, for EGD. Versed and ketamine baby.

 

[GassYous]

I start egds with 5-10. 20 for very young people

 

[2Fast2Des]

100mg is my go to dose for most GI cases

 

[epidural man]

I get a little annoyed whenever I have to give another drug besides propofol for MAC anesthesia. >95% of MAC cases it's all I need.

de gustibus non est disputandum

You are obviously better at it than I.

I find propofol to be a horrible sedation drug.

It's wonderful for natural airway general anesthesia cases (like colonoscopy, EGD, etc), but I can't ever seem to find that plane where the patient is responsive enough to not be disinhibited, but sedated the right amount dictated by the procedure.

 

[rowsdower88]

You are obviously better at it than I.

I find propofol to be a horrible sedation drug.

It's wonderful for natural airway general anesthesia cases (like colonoscopy, EGD, etc), but I can't ever seem to find that plane where the patient is responsive enough to not be disinhibited, but sedated the right amount dictated by the procedure.

I thought about this more and I realized my answer is dumb and heavily dependent on my practice.

~60% of my MAC cases are egds and colons, so that's 100% propofol only.
~10% is eyeballs, again almost all propofol only
~10% cath lab/IR - almost all propofol only
~10 urology and 10% gyn - this is where I have to use othe drugs maybe half the time.

So if my practice was 100% urology and gyn cases, that would change my use dramatically.

 

[Simba1711]

I thought about this more and I realized my answer is dumb and heavily dependent on my practice.

~60% of my MAC cases are egds and colons, so that's 100% propofol only.
~10% is eyeballs, again almost all propofol only
~10% cath lab/IR - almost all propofol only
~10 urology and 10% gyn - this is where I have to use othe drugs maybe half the time.

So if my practice was 100% urology and gyn cases, that would change my practice dramatically.

I rarely give just propofol. Mostly just for colonoscopy. For egd I like to give iv lidocaine and propofol. For eyeballs I like to give just fentanyl and midazolam for conscious sedation. I don’t want patients to disinhibit and most opthamalogists want a patient that can follow directions. For eswls and vascular cases I give just versed and fentanyl as well. I occasionally have to start propofol drip for eswl if it is a big stone. For podiatry I usually have to give fentanyl versed and propofol. Their blocks are hit or miss and they want general anesthesia.

 

[Ronin786]

You are obviously better at it than I.

I find propofol to be a horrible sedation drug.

It's wonderful for natural airway general anesthesia cases (like colonoscopy, EGD, etc), but I can't ever seem to find that plane where the patient is responsive enough to not be disinhibited, but sedated the right amount dictated by the procedure.

It depends if your goal of sedation is a true MAC where they're protecting their airway. Most "sedation" where I'm at now (large academic center) are 100% GA without an airway and are billed as such.

To be honest, risk of inability to protect airway notwithstanding, it makes things much easier as far as placing airway adjuncts if necessary and not being in the death plane of awake but not responsive.

 

[Arch Guillotti]

What is this sedation thing for eswl that you speak of???

 

[GassYous]

What is this sedation thing for eswl that you speak of???

You don't need much, just a prop drip at like 75 and maybe a little versed/fentanyl if you're feeling nice

 

[woopedazz]

TCI gang rise up.
Marsh/Schnieder/Eleveld... Effect or plasma... 10kg or 200kg... Drunk or sober...
Propofol only for everything.
Press start, go chart.

 

[Simba1711]

What is this sedation thing for eswl that you speak of???

It’s usually just versed and fentanyl. I think that’s reasonable. Some people in my group put an Lma for these cases. There was also a thread a few years ago about doing regional for eswl. I think that’s overkill

 

[PpfSuxTube]

Still, after all these years, I am surprised about the huge variability from patient to patient (kinda like every time I do a spinal, I’m shocked it actually works…spinal = magic).

ASA1 45 y/o for a circ under MAC.

2 mg midazolam makes him sleepy. 50 mcg of fentanyl makes him arousable to voice with a significant shoulder tap. I’m thinking, this guy is a lightweight. My plan was to give 50mg propofol before the penile block and glans penis local (I mean, holy crap, give me the whole stick if someone is sticking a needle in my junk) - but since he was such a lightweight, I cut that in half (30mg).

For 20 minutes, I have to give this guy a jaw thrust! Super annoying because I had a great article I wanted to read about how Reagan plotted to prolong the Iran hostage situation to help him politically and hurt Carter. But no…I’m stuck working.

Work really gets in the way of living.

I’ve given 100mg to some and they keep talking to me. It’s just really interesting the variability.

We talk about the genetic variability of each individual drug - but I’ve never heard a discussion about the variability of the synergistic effects of drug combinations.

I had a case of awareness recently in a mid 70s female with ckd after 150 fent, 150 ppf, 20 ket, 60 remi induction. Ibw 72 kg
Et sev 2.3%

 

[coffeebythelake]

I had a case of awareness recently in a mid 70s female with ckd after 150 fent, 150 ppf, 20 ket, 60 remi induction. Ibw 72 kg
Et sev 2.3%

how reliable is the story / how likely is this true awareness?
any identifiable risk factors for awareness under GA?
some patients dream or have false memories

 

[PpfSuxTube]

Hard to deny, she remembered 3 or 4 things

 

[anesthesiadoc]

But did she remember it fondly?

 

[Arch Guillotti]

It’s usually just versed and fentanyl. I think that’s reasonable. Some people in my group put an Lma for these cases. There was also a thread a few years ago about doing regional for eswl. I think that’s overkill

would never work with the machine we have. 10,000 kidney punches.

 

[coffeebythelake]

would never work with the machine we have. 10,000 kidney punches.

your hospital should consider investing in a newer machine

 

[deleted875186]

I had a case of awareness recently in a mid 70s female with ckd after 150 fent, 150 ppf, 20 ket, 60 remi induction. Ibw 72 kg
Et sev 2.3%

Awareness after induction or during the case with sevo? How is this possible?

 

[coffeebythelake]

Awareness after induction or during the case with sevo? How is this possible?

extreme outliers exist. but i would expect some sort of identifiable risk factor or something very strange with the anesthetic delivery in the case (e.g., infiltrated PIV, vaporizer malfunction, etc) if the patient had explicit recall as @PpfSuxTube claims.

 

[PpfSuxTube]

She didnt seem to have any risk factors for awareness i noted anyway. Iv ran great. She told me she felt some pain but wasn't disturbed by it.
I think she had mild awareness for the skin incision but then was fully asleep for the majority of the procedure.

Possibly the fent was underdosed or worn off? Possibly the remi had worn off? Possibly the sevo hadnt full reached 1 mac, i use end tidal control a lot on auto flows which may have been too low flow?

Idk...

 

[jwk]

Possibly the fent was underdosed or worn off? Possibly the remi had worn off? Possibly the sevo hadnt full reached 1 mac, i use end tidal control a lot on auto flows which may have been too low flow?

Idk...

I think that's the problem, especially if you're saying she felt pain with incision.. At low flows, it might take 20 minutes or more to get to equilibrium and have a true end tidal concentration. Keep the flows up for just a few minutes and that problem goes away.

 

[coffeebythelake]

She didnt seem to have any risk factors for awareness i noted anyway. Iv ran great. She told me she felt some pain but wasn't disturbed by it.
I think she had mild awareness for the skin incision but then was fully asleep for the majority of the procedure.

Possibly the fent was underdosed or worn off? Possibly the remi had worn off? Possibly the sevo hadnt full reached 1 mac, i use end tidal control a lot on auto flows which may have been too low flow?

Idk...

it sounds like the ET sevo% was way lower than 2.4% at the time of recall. 3-4 half lives mean about 12 minutes for that sevo to reach steady state in the brain. You don't even need 1 MAC of gas, just 0.7 MAC should be more than adequate especially with your other IV anesthetics which have more than just an additive effect but a synergistic one. MAC-aware is 0.3, and 0.5 should cover 98%+ of the general population. If you are going low flow immediately after intubation you need to overpressurize the system to ensure adequate sevo delivery and uptake

 

[PpfSuxTube]

Yeah I think it was the end tidal auto control. Plus I've bn doing lot of cardiac recently so im more used to snowing them with suf, midaz.

 

[coffeebythelake]

Yeah I think it was the end tidal auto control. Plus I've bn doing lot of cardiac recently so im more used to snowing them with suf, midaz.

What is "end tidal auto control"?

This? It seems like this system is supposed to do exactly what did not happen in your case -- prevent awareness

Low-flow Anesthesia Series: Part 2 - End-tidal Control

Watch this video to learn how End-tidal (Et) Control software on the Aisys™ CS2 Anesthesia Delivery System helps clinicians practice safe, low-flow anaesthesia

clinicalview.gehealthcare.com

 

[PpfSuxTube]

What is "end tidal auto control"?

This? It seems like this system is supposed to do exactly what did not happen in your case -- prevent awareness

Low-flow Anesthesia Series: Part 2 - End-tidal Control

Watch this video to learn how End-tidal (Et) Control software on the Aisys™ CS2 Anesthesia Delivery System helps clinicians practice safe, low-flow anaesthesia

clinicalview.gehealthcare.com

Yes its that. Ive used it for years and watched it algorithm. It starts around 8lpm and quickly maybe too quickly gets to 0.5lpm... idk

 

[coffeebythelake]

Yes its that. Ive used it for years and watched it algorithm. It starts around 8lpm and quickly maybe too quickly gets to 0.5lpm... idk

Is the awareness case a pending litigation case? Maybe GE healthcare should be consulted about this issue. I mean... if the failure of their product is felt to be responsible for what happened..

 

[PpfSuxTube]

Is the awareness case a pending litigation case? Maybe GE healthcare should be consulted about this issue. I mean... if the failure of their product is felt to be responsible for what happened..

I hope no, pt said she wasn't too distressed by it... she did have a lot of narcotic on boards and the sevo did eventually get her asleep so I think it was just a short window. So I hope no

Im not taking it any farther unless I have to. Great thought tho, thank you

 

[epidural man]

I had a case of awareness recently in a mid 70s female with ckd after 150 fent, 150 ppf, 20 ket, 60 remi induction. Ibw 72 kg
Et sev 2.3%

This is hard to imagine.

But she could use a lot of THC to help her sleep, and her p450 system chews up fentanyl super quick.

Still…really surprising.

When I do IVF cases, I give people Alfentanil and a mg/kg dose to start which usually is 50-60mg. Before hand, I tell them that I will be asking them afterward if they remember putting their feet in the stirrups. They all are talking to me when we put the feet in the stirrups - but to this day, zero of them ever remember doing it. It’s just hard to imagine that with all that fentanyl, ketamine, and some gas - that this 70 y/o actually had brain function of storing memories.

 

[deleted875186]

This is hard to imagine.

But she could use a lot of THC to help her sleep, and her p450 system chews up fentanyl super quick.

Still…really surprising.

When I do IVF cases, I give people Alfentanil and a mg/kg dose to start which usually is 50-60mg. Before hand, I tell them that I will be asking them afterward if they remember putting their feet in the stirrups. They all are talking to me when we put the feet in the stirrups - but to this day, zero of them ever remember doing it. It’s just hard to imagine that with all that fentanyl, ketamine, and some gas - that this 70 y/o actually had brain function of storing memories.

Agreed, true etSevo had to be lower than 2.3% …

 

[Hoya11]

Agreed, true etSevo had to be lower than 2.3% …

i often see the strategy of only giving a few breaths/min after induction in order to quicken the return of spontaneous breathing, but then the gas doesnt get on fast enough and the induction agents wear off and you have a very light/temporarily awake situation. thats why i put the flows at 8 and the gas at 4 for the first minute or so and give 18-20 breaths per minute to attain a good sevo level, then can back off..

 

[GassYous]

i often see the strategy of only giving a few breaths/min after induction in order to quicken the return of spontaneous breathing, but then the gas doesnt get on fast enough and the induction agents wear off and you have a very light/temporarily awake situation. thats why i put the flows at 8 and the gas at 4 for the first minute or so and give 18-20 breaths per minute to attain a good sevo level, then can back off..

Why not gas at 8 and flow at 1-2

 

[Hoya11]

Why not gas at 8 and flow at 1-2

1-2 not enough, high gas, high flow, get in on board - im not concerned about saving sevo for one minute at the risk of awareness

 

[Dantrolene FC]

1-2 not enough, high gas, high flow, get in on board - im not concerned about saving sevo for one minute at the risk of awareness

Just inject sevo directly into the expiratory limb of the circuit and keep the flows low.

 

[nimbus]

Just inject sevo directly into the expiratory limb of the circuit and keep the flows low.

Reminds me of this article.

“Free Standing Vaporizers Can Tip Over​

Case #2​

The 3 y.o. child was undergoing a cleft lip repair, intubated and breathing spontaneously with assistance. An unsecured freestanding halothane vaporizer sat on the tabletop, attached to an oxygen source and circuit. About 30 minutes into the case, as the anesthesiologist reached behind the machine to retrieve a fallen laryngoscope, he accidentally knocked over the vaporizer. Liquid Halothane entered the circuit. The child suffered immediate cardiac arrest. The anesthesiologist could not resuscitate the child.

Volunteer groups will sometimes encounter free-standing vaporizers, either at the site or brought by your own team. Regardless of agent, secure such free standing vaporizers to prevent spillage of liquid agent into the circuit, and from there into the patient. The resulting massive overdose, especially of an agent like Halothane, can instantly produce cardiac arrest.”

Halothane: Avert Volunteer Anesthesia Mishaps 1

Anesthetic mortality during volunteer medical missions is 20X higher than US. Discuss volunteer anesthesia mishaps inhalation anesthesia/Halothane.

airwayjedi.com

I go on trips with a group. One of their sevo vaporizers delivers 12% sevo when dialed all the way up. Everybody loves it for inhalation inductions.

 

[anbuitachi]

agree with aboves. blast flows and put sevo to 3 and then come back down later

 

[Maz777]

Think of the environment. Do zero-flow anesthesia. Turn off the monitors. It gives surgeons the perfect operating conditions.

Donate those deadly vaporizers to the local orphanage. Take away the central supply of nitrous. Think of the polar bears, you ingrates! Those baby seals aren't going to eat themselves. You want baby seals crossing the border and invading your house? I don't think so.

 

[coffeebythelake]

Think of the environment. Do zero-flow anesthesia. Turn off the monitors. It gives surgeons the perfect operating conditions.

Donate those deadly vaporizers to the local orphanage. Take away the central supply of nitrous. Think of the polar bears, you ingrates! Those baby seals aren't going to eat themselves. You want baby seals crossing the border and invading your house? I don't think so.

spinals for everyone. we even have a PP guy who does the high spinals for eye surgeries.

 

[Dantrolene FC]

spinals for everyone. we even have a PP guy who does the high spinals for eye surgeries.

I think a cervical epidural would make more sense since you could get some sparing of the cardiac fibers.

 

[GassYous]

I think a cervical epidural would make more sense since you could get some sparing of the cardiac fibers.

I prefer to just inject the optic nerve directly. There's really no point in blocking the other nerves. Remember c3 4 5 keeps you alive.

 

[coffeebythelake]

I prefer to just inject the optic nerve directly. There's really no point in blocking the other nerves. Remember c3 4 5 keeps you alive.

A total spinal by knocking out the brainstem? A light GA will still be needed here.