Management of acetaminophen toxicity

[ckent]

I have an ER related question regarding acetaminophen toxicity (I'm studying for step II). If a patient/child came in, and you knew the exact time that they took acetaminophen, would you wait until 4 hrs after before checking levels or drawing any labs? What if the patient was symptomatic? This was a question in q bank, and they are saying that you should just watch the patient for 4 hrs before drawing any labs because if you draw at any time prior to that, you risk getting falsely low levels. Also, why isn't there a knee jerk reaction to get N-acetylcysteine when you know that someone has taken a lot of acetaminophen? I know that it doesn't smell good and is difficult to ingest, but given the need for a timely administration, I don't see why they don't just administer this stuff prophylactically. It's not like it's bad for you or anything.

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[limabean]

I'm no expert but this is what I gathered from my Toxicology rotation:
1. Do you wait 4 hours before getting a level? Yes.You always wait about 4hours before getting a level because before that time you will likely get a falsely lowered level which will not help you with the patient's further management. If you know that the kid ingested the pills right before they were brought in, then you should wait four hours before getting a level. If however the parents just found an empty bottle and you have no idea when the ingestion occured (which it what you will run into more often) then this 4 hour rule does not apply-you can go ahead and get a level but will need to keep cycling it(~q 4hours) until it stabilizes(but this kind of situation probably won't show up on Step II).
2. When do you give N-acetylcysteine?
Once you get a reliable acetaminophen level(at 4 hours if you have a definite time) then if the level is above the treatment line on the standard acetaminophen nomogram then you give the antidote.
3. Wouldn't you give the antidote if the patient comes in symptamatic even if it is before 4 hours? No. If someone has just had an acute overdose, the best first step is charcoal. N-acetylcysteine is used not to prevent annoying symptoms of vomiting, nausea, etc but is it use to prevent the hepatic failure. This occurs in phase II which begins anywhere from 18-72 hrs post ingestion. Studies have shown(sorry I don't remember the citation but a good reference is Goldfranks) that N-acetylcysteine has maxium effect when given within 8-12 hours of ingestions-in other words the outcome of patients were not significantly different if they were treated at 4hrs vs 6hrs up until 8-12hours. So there should be no rush in giving it prematurely to a patient who may not need it.
FYI:
NAC is often given by docs prematurely because in a busy ED it is sometimes easier to just treat and find out that the patient didn't need it later, then it would be to try and track down an acetaminophen level especially at a large county hospital where labs can take a long time. Also very few patients will come in with an exact time of ingestion so you have to go ahead a treat because you'll never know when you've reached the 8-12 hr cut off for NAC's maximum effect and it will take awhile to get levels back.This is reality but Step II questions are based strictly on the science and "ideal situations" so you must remember them.

Hope this helps. Good luck with Step II
-limabean

 

[ERMudPhud]

Originally posted by ckent
I have an ER related question regarding acetaminophen toxicity (I'm studying for step II). If a patient/child came in, and you knew the exact time that they took acetaminophen, would you wait until 4 hrs after before checking levels or drawing any labs? What if the patient was symptomatic? This was a question in q bank, and they are saying that you should just watch the patient for 4 hrs before drawing any labs because if you draw at any time prior to that, you risk getting falsely low levels. Also, why isn't there a knee jerk reaction to get N-acetylcysteine when you know that someone has taken a lot of acetaminophen? I know that it doesn't smell good and is difficult to ingest, but given the need for a timely administration, I don't see why they don't just administer this stuff prophylactically. It's not like it's bad for you or anything.

You need to wait the four hours to get a meaningful result. If it has been less than 4 hours and the patient is symptomatic than either your time frame is wrong or you have the wrong ingestion as tylenol really shouldn't be symptomatic during that time. There is also very little need to jump right on the NAC as it has been shown to work just fine if given later-sooner isn't necesarrily better and it may prevent you from doing other more important things. NAC for instance is so nasty that it may cause your patient to keep puking up their charcoal.

If I have a patient who is a few hours out from the ingestion and I wonder if they took any tylenol at all I may go ahead and send a level but any positive level needs to be rechecked at 4 hours to rule out a significant ingestion

If I have a patient who is >8 hours out who I think has had a significant tylenol ingestion I will start NAC without waiting for the labs to come back.

By the way NAC can be given IV, you have to talk to the pharmacy about mixing it and you have to be ready to treat full blown anaphylaxis

 

[DrQuinn]

One topic that may pop up on your Step 2 is the use of an NG tube versus a large-bore Ewald tube in regards to management of OD. If a tube is the correct answer, don't ever choose the NG tube (for suctioning pill fragments).

Now, clinically, you'll see both sides of the fence, Ewald or just going ahead with the charcoal. But on Step 2 make sure you just pick the Ewald over the NG (I had this choice on my Step 2).

Q, dO

 

[ERMudPhud]

I should have added that you see many, many tylenol ingestions for everyone that ends up needing NAC. Thats alot of smelly NAC and a lot of vomit to clean up if we gave it prophylactically

 

[ERMudPhud]

Originally posted by QuinnNSU
One topic that may pop up on your Step 2 is the use of an NG tube versus a large-bore Ewald tube in regards to management of OD. If a tube is the correct answer, don't ever choose the NG tube (for suctioning pill fragments).

Now, clinically, you'll see both sides of the fence, Ewald or just going ahead with the charcoal. But on Step 2 make sure you just pick the Ewald over the NG (I had this choice on my Step 2).

Q, dO

Also keep in mind that the data showing that lavage ISN'T very useful is reasonably good. The best data shows that it probably only helps in people with altered mental status and potentially lethal ingestions (tricyclics, aspirin, calcium channel blockers,...) not tylenol, benzo's, SSRI's etc... I reserve it for rare cases where the ingestion could easily kill you and we don't have a good antidote. The complications of large bore tubes are significant and more common than many of us are comfortable with. I use NGT tubes for patients that need NAC or golytely but won't/can't take it.

 

[Apollyon]

One early morning around 3am we were discussing this, and the attending (who'd trained at Jacobi) said the ONLY time he lavages is if the patient (almost literally) choked down the pills while rolling in the door - otherwise, it's well-nigh useless.

PS and that Ewald was the way to go (pills won't get through the NG)

 

[BCE]

In children who have swallowed paediatric syrup only (not tablets) we do levels at 2 hours. Several papers now showing that in this sub-group peak occurs by 2 hours.

BCE

 

[jawurheemd]

ah -- one of my favorite topics -- tox

as it stands, 4 hours is standard as we base apap toxicity on the matthew-rumack normogram and the normogram starts at 4 hourse (you can't extrapolate the line back to time zero -- you'll get into trouble). however, with coingestants that delay gut motility, the peak may be shifted to the right, so who knows if the 4 hour level is valid for those patients -- also, now with the longer acting tylenol formulation, the normogram may not apply as well.

if you have a known time of ingestion, and the source is reliable (i.e. mother who saw the patient ingest the medicine), i would be comfortable waiting 4 hours to get the level. however, this doesn't preclude you from getting other labs on the patient to evaluate for coingestions earlier.

in terms of NAC administration, there's an 8 hour window from time of ingestion before you need to give it -- if you suspect ingestion >8 hours ago, give NAC right away.

when you give NAC, use an NG tube if needed and lots of Reglan. mix it in ginger ale or something. it tastes and smells awful due to the sulfur component

in the US, NAC administration via IV should be done in consultation with your regional poison control center. in general, it requires a 50 micron filter to administer -- which is essentially the filter used to administer blood products. dosing is the same. administer slowly to avoid most reactions.

i could go on and on, but it's best if you read a standard toxicology text -- acetominophen toxicity is a very significant poisoning in the US and should be well appreciated as it's the major reason for a liver transplant.

-James

 

[Sessamoid]

I've only ever had to give NAC IV once, on a patient that couldn't tolerate the stuff even via NG with pretty healthy doses of antiemetics. The pharmacy bitched and moaned about providing it for IV administration since it's not approved for IV in the US, but I pretty much told them that if the patient died, I'd be writing in my chart that the pharmacist refused to provide the antidote. His resistance pretty much crumpled on the spot.

 

[ckent]

Thanks guys. So NAC doesn't work if it's given too early? I actually chose giving the child activated charcol as my answer (given that OD's of one substance may mean OD with other substances, but Kaplan said that wasn't correct because charcol doesn't do anything with acetaminophen). If I were in the ER, I'd definitely draw levels on people as soon as they enter and then ~4 hrs post ingestion, even though I still think that it must be a rare occurence for you to know exactly what time they ingested.

 

[Sessamoid]

There's no such thing as too early for NAC, since the full course of NAC involves 17 doses. In real life, AC is generally what I'd do first, then wait for the levels to come back. As previously noted, NAC is really disgusting. Smells and presumably tastes like rotten eggs.