Anesthesia

allnurses Guide · Dec 6, 2009

This is really interesting, thanks. Another question for you: as I understand it, sedation is fairly easy to reverse; is it the same case with paralytics?

Opioids and Benzodiazipines (Versed/Valium/Ativan etc.) can be reversed, but there is no reversal for propofol/thiopental/ketamine. So, not all the meds we use for sedation can be reversed and it is usually better to let the effect of the sedation wear off in most patients rather than try to reverse the effects of the sedation. Reversal agents have side-effects just like any other medicines, but the reversals for opioids and benzos can cause severe side-effects of MI/pulmonary edema/HTN crisis and other ill toward effects.

Paralytics can be reversed with AChesterase inhibitors which work by increasing the amount of ACh. The problem with the reversal for paralytics is that the increase ACh causes increase in the parasympathetic system (increased salivation/GI motility/lacramation/defecation/emesis, bradycardia, and bronchoconstriction), and an antimuscarnic (robinul/atropine) has to be added to be blunt the side effects of increased parasympathetic response.

Just a few things that your friendly anesthesia provider has to think about when doing sedation....lol

GilaRRT · Dec 6, 2009

This is really interesting, thanks. Another question for you: as I understand it, sedation is fairly easy to reverse; is it the same case with paralytics?

Depends, reversing non-depolarizing agents was a complicated process full of side effects. However, with the introduction of Sugammadex a newer reversal agent initially developed to reverse Zemuron, reversal can be accomplished quickly with few side effects. Sugammadex also has varying degrees of action against pancronium and vecuronium. I know of no reversal agent for depolarizing agents, Anectine being the only agent used in the United States. Being that Anectine is essentially two Ach molecules, it is degraded rather quickly by a type of cholinesterase. (Not acetylchlinesterase, however.) Assuming a phase II block is not induced or low levels of specific enzymes do not exist, the action of Anectine is rather short lived.

cmonkey · Dec 6, 2009

I think your point should be expanded upon because many people confuse what happens in the OR with what happens outside of the OR. Paralytics are common place in a procedure known as rapid sequence intubation (RSI). It is understandable to assume RSI is ~ to a "typical" OR induction. However, a paralytic has a very special place in RSI.
RSI is something we typically do in a crisis or potential crisis situation outside of the OR. In this environment it is reasonable to assume a non fasting patient who would not meet the criteria for an elective OR case. A major and often overlooked rationale for giving a paralytic in RSI is to decrease the risk of aspiration. Of course, paralysis may produce better intubating conditions; however, aspiration prevention is often regarded as one of the major traditional reasons for going down the path of RSI. However, do not always assume paralysis will make for an easier intubation. In addition, not every patient who is "critical" will require RSI. RSI is but one tool and should be used only on people who will benefit and meet strict criteria. For example, an unresponsive person who is near death would not be a RSI candidate in spite of their condition. Likewise, a morbidly obese person with spinal trauma, a Mallampati score of IV, and limited jaw mobility would also not be a good RSI candidate.
A little diversion from the OP; however, still a good topic to define in the hopes of understanding.

So in every ER-type show ever, there are situations where they could/should have used RSI but don't because it doesn't add to the drama?

loveanesthesia · Dec 6, 2009

Interesting. I'm having a procedure this month and now I'm going to pepper the anesthesiologist with questions. They love that, right?

or your CRNA......

RedCell · Dec 7, 2009

this is really interesting, thanks. another question for you: as i understand it, sedation is fairly easy to reverse; is it the same case with paralytics?

depending on what you have given, sedation is not always reversible. also, the reversals i assume you are referring to (naloxone and/or flumazenil) in and of themselves carry possible risks and consequences one must consider before blindly pushing them.

succinylcholine (other than time) does not have a reversal. typically, acetylcholinesterase inhibitors such as neostigimine or edrophonium are used if needed, to reverse nondepolarizing muscle relaxants. they are going to be useless however, if you have just given a large dose of a nondepolarizing agent. these drugs also carry huge potential consequences and risks that must be considered before administering.

one of the more interesting events on the anesthesia horizon is the eventual release of a drug called sugammadex. it is a reversal agent specifically designed to encapsulate aminosteroids such as rocuronium, vecuronium and to a lesser extent, pancuronium. due to the pharmacodynamics of this medication, it can be given immediately after dosing someone up with one of the previously mentioned nondepolarizers. various studies have demonstrated that depending on dosage, a complete reversal can be obtained in under 5 minutes (assuming hemodynamics have not been compromised).

GilaRRT · Dec 7, 2009

So in every ER-type show ever, there are situations where they could/should have used RSI but don't because it doesn't add to the drama?

Possibly, I am not big on watching the tele say for my Xbox and a few select shows that I buy on DVD.

cmonkey · Dec 7, 2009

or your CRNA......

Well, yeah, that's what I meant, but if I stopped to think about that I'd have lost the question I wanted to ask. I have a one-thought mind lately. Won't school be fun. :eek:

cmonkey · Dec 7, 2009

Meds like Ketamine are very fast acting, IIRC. I know the vet used it when she neutered my mom's dog, and she said we had to be careful not to stimulate him (I was patting him) because of the fast reversal and I think because it doesn't completely sedate to unconsciousness... So using meds like that would be for something fast like a colonoscopy? Or is that more a use for Versed? THAT'S a funny med; my son had it for some dental work and I have some of the funniest home movies of EVER. He turns out to be a happy drunk. lol

This is really fascinating, thanks so much for indulging my curiosity.

allnurses Guide · Dec 7, 2009

Meds like Ketamine are very fast acting, IIRC. I know the vet used it when she neutered my mom's dog, and she said we had to be careful not to stimulate him (I was patting him) because of the fast reversal and I think because it doesn't completely sedate to unconsciousness... So using meds like that would be for something fast like a colonoscopy? Or is that more a use for Versed? THAT'S a funny med; my son had it for some dental work and I have some of the funniest home movies of EVER. He turns out to be a happy drunk. lol
This is really fascinating, thanks so much for indulging my curiosity.

Ketamine as a single dose like most sedation medications is relatively short acting as a single dose. When giving multiple doses of medications or running a drip the duration of action and elimination half-life change. The reason your vet probably didn't want you to stimulate your dog is because ketamine is a dissociative anesthesitic that can cause delirium for a short time especially as it is wearing off/the patient is waking up. Ketamine is structarlly related to PCP.

There is no right med for every procedure. You have to pick the right med(s) for the right patient for that procedure/surgery.

By the way ketamine is non-reversable. Its' duration of action ends, like most medications, when it redistributes in the body.

loveanesthesia · Dec 7, 2009

with the introduction of Sugammadex a newer reversal agent initially developed to reverse Zemuron, reversal can be accomplished quickly with few side effects. Sugammadex also has varying degrees of action against pancronium and vecuronium.

Sugammadex has not been released by the FDA, they have asked for further studies on hypersensitivity, and in the OB, pediatric, and renal failure populations. It'll be great if there are few side effects, but we've been told that before-Raplon. Another issue is recurarization-return of paralysis-at least one patient in the Phase II trials experienced recurarization.

GilaRRT · Dec 8, 2009

Sugammadex has not been released by the FDA, they have asked for further studies on hypersensitivity, and in the OB, pediatric, and renal failure populations. It'll be great if there are few side effects, but we've been told that before-Raplon. Another issue is recurarization-return of paralysis-at least one patient in the Phase II trials experienced recurarization.

It is being used in Europe, however. We can only hope they continue to have good experiences with sugammadex and it obtains FDA approval. However, IV paracetamol has been used safely and with success for what, 20 years in Europe, and we still do not use it in the United States?

I am aware of isolated cases of recurarization; however, I am not sure of the context of these cases. While sugammadex has varying degree of effectiveness on aminosteriod based non-depolarizing agents, it was designed specifically to reverse Zemuron. Zemuron being a rather short duration NDNMB, should not have recurarization issues with sugammadex. However, did these issues develop with a longer acting agent such as pancronium, was a small dose of sugammadex given, or were there contributing factors present? I suspect this will come out with future trials.

With that, I am not really sure sugammadex will cause extensive changes to the anesthesia community. I am not positive; however, reversal do not seem like an extensively utilized practice in anesthesia? I would not want to frequently reverse patients with agents known to have multiple side effects. Where sugammadex may be popular is in emergency rooms and in pre-hospital care, where reversal of a paralytic during an RSI gone bad may be a good option. However, with the effectiveness of current supraglottic rescue technology, even reversing a paralytic in such a situation may not be the first consideration. Still a great option to have available IMHO.

loveanesthesia · Dec 8, 2009

I am aware of isolated cases of recurarization; however, I am not sure of the context of these cases.
With that, I am not really sure sugammadex will cause extensive changes to the anesthesia community. I am not positive; however, reversal do not seem like an extensively utilized practice in anesthesia? I would not want to frequently reverse patients with agents known to have multiple side effects. .

The context was with rocuronium, so the concern.

I think sugammadex has the potential to be great addition for difficult airway management, not so much for routine muscle paralysis. It would be nice to give a 1.2 mg/kg dose of Zem, get a nice quick relaxation (approaching sux) and then have the option of quick reversal in the Can't intubate Can't ventilate case. It's too expensive to use for routine management. As for side effects, not many drugs have as many serious SE as sux does. It probably wouldn't get through the FDA today.