Ketamine: Not Always Magic (Attention, Kiwi)

[Eydawn]

Dear Kiwi,

I know you have this great love of Ketamine used to facilitate RSI. You think it is, to put it bluntly, THE SHIT.

Please read the following blog entry, written by some nice Scandinavian anaesthesia registrars... I believe it says that their patient was given 300mg of Ketamine with NO EFFECT. (@_@)

http://www.scancrit....ketamine-match/

Therefore, "special K" is not in fact, always that special...

Lots of Love,

Wendy

On a serious note, HOLY HELL. Apparently, as far as the writer could figure out, lamotrigine (Lamictal) may block the effects of ketamine by blocking the action of glutamate on non NMDA glutaminergic receptors. Hence, how a 60kg psych patient could get 300 mg of IV Ketamine and still be fighting...

YIKES!

Wendy

CO RN-ADN Student

Edited June 2, 2012 by Eydawn

[Arctickat]

hmmm, kinda like Narcan as an opoid antagonist....I wonder if it would work,,,,,

[Kiwiology]

I confuze (*puts away valiums) ... great, now I haz to face stupid bastard reality, and am still confuze

A very interesting case report thank you for sharing however are you trying to say that a n=1 case report with a clearly established pharmacodynamically reasonable drug-to-drug interaction somehow means ketamine is not as good?

I do not for one second think you are trying to say that cos you has too much intellectigence for that

[snoopy911]

Wow! What an interesting story Wendy! You would think that 400 mg would be enough to take out an elephant! I guess not in all circumstances. This story is of particular interest to me, since I am about to start low dose, outpatient Ketamine infusions for the disease I have, CRPS/RSD. I am going to be infused for 4 hours a day, for 10 days. The dose is suposed to be about 80mg an hour. So I just cant imagine what 400 would be like!

[Kiwiology]

The typical dosage for analgesia is 0.5mg/kg IV or 1mg/kg IM/oral, or for induction 1.5mg/kg IV or 2-4mg/kg IM

So somebody who is 60kg getting 300mg of ketamine wow they should be asleep pretty damn good, interestingly a case report from Australia recently said a patient was given 30mg/kg (instead of 3mg) with no adverse side effects, they just slept a little longer than expected

Ketamine is a very safe and very desirable medicine, it does not have the hypotensive or hypoadrenal side effects of benzos/propofol or etomidate respectively and maintains airway and circulation very well

[chbare]

Unfortunately, it has many side effects and potential interactions. You deal with it enough and you end up appreciating it is a risk versus benefit issue as is the case with most medications and procedures. Bradycardia, dysrhythmias, hypersecretion and both hyper and hypotension are known side effects. It is generally a good medication, but not a silver bullet.

[Kiwiology]

Any medication has side effects it's as you say, a balance/tradeoff between the good, the bad and the alternate

Certainly it is extremely popular for procedural sedation particularly in paediatric patients and for anaesthesia in "sick" people who have sepsis, hypotension etc

[chbare]

Actually, propofol is very popular for procedures. You can administer it, monitor during the procedure and recover the patient in minutes. With ketamine, I'm stuck monitoring the patient for an extended period that is even longer because of the benzos they receive. Clearly, a suboptimal situation when I have patients lining the hallway and I'm stuck doing a 1:1 recovery on a status post dislocated shoulder. Logistics and resource utilisation are critical in the real world.

Edited June 3, 2012 by chbare

[Kiwiology]

Yep, propofol is also quite popular here as well but so is the fentanyl/midaz combo. Propofol is restricted here to vocational scopes of practice requiring the administration of anaesthesia; so emergency medicine, anaesthesia and intensive care medicine, maybe at a stretch rural hospital medicine I am not sure about that one. So fentanyl/midaz means you do not require an anaesthetist to be present and is used for things like colonoscopy which are often performed in the outpatient, non hospital setting which are not accredited by ANZCA for anaesthesia.

Anyway, ketamine has its place, but so does etomidate, thiopentone, sevoflurane, propofol, midazolam etc.

My strong bias toward preference towards ketamine is exclusively in the domain of prehospital rapid sequence intubation and analgesia as this is where its extremely low cardiorespiratory risk has a big advantage over benzos, propofol, etomidate etc as a good proportion of prehospital RSI patients are physiology where hypotension, respiratory depression, supression of adrenal function or baroreceptor reflexes etc would be bad. It is also an excellent analgesic in low dosages and a brilliant tool to have when you've emptied your morphine snapoules but the patient is still screaming in pain.

To extrapolate the usefulness of ketamine in these situations to an elective anaesthetic is not appropriate

Edited June 3, 2012 by Kiwiology

[chbare]

Perhaps you should not have mentioned procedural sedation if your bias is specific toward pre-hospital use in RSI?

In addition there has been much discussion about etomidate and the adrenal suppression concern leading to increased mortality has not been validated inspite of fairly large amounts of evidence. Perhaps in the future; however, it still remains a viable option even in septic shock patients. I'm certainly not convinced by the evidence at this point.