Ketamine for Pain Management: Writing an article, your opinions?

[Medic27]

So, as am EMT I don't understand very complex medicine like what you guys deal with. From what I understand Morphine doesn't last as long or as strong as Fentanyl. Why would you use Ketamine over these 2? Ketamine could also be used as sedative?

 

[SpecialK]

So, as am EMT I don't understand very complex medicine like what you guys deal with. From what I understand Morphine doesn't last as long or as strong as Fentanyl. Why would you use Ketamine over these 2? Ketamine could also be used as sedative?

Morphine and fentanyl aren't really that complex; ketamine is a wee bit more, but not that hard.

The differences between morphine and fentanyl aren't really that significant and probably don't mean much in the real world. Fentanyl is a bit more lipophillic so has a faster onset and shorter duration of action; but honestly, it's probably only about 30 seconds to one minute or so which isn't that big of a deal when you think about it. The "big" selling point for fentanyl is it releases less histamine so those who feel yuck with morphine have less of this effect with fentanyl but by-and-far the number of people who report feeling "yuck" with morphine to such a significant degree to justify giving them fentanyl is probably one in a zillion.

Fentanyl is about 10x more expensive than morphine so unless there's a very, very strong indication to give it, I don't see it as being overly necessary personally.

Ketamine is not an opioid analgesic but has some opiate receptor affinity so produces some analgesia but the main effect, IIRC, is to disconnect the sensory areas of the thalamus from the cerebral cortex by increasing release of GABA. This means the patient still may have pain but their brain is not aware of the pain. It is also advantage because it maintains airway and breathing.

 

[E tank]

Fentanyl in the US is cheaper than Kool-Aide...it works faster than MS and is therefore more easily titratable for pain. It has a far shorter half-life so is more forgiving in an overdose scenario. It has less side effects.

Ketamine is a useful analgesic for it's temporary dissociative effects but can cause severe dysphoria and distress in some patients at even small doses (20-50 mg)

 

[Medic27]

Morphine and fentanyl aren't really that complex; ketamine is a wee bit more, but not that hard.

The differences between morphine and fentanyl aren't really that significant and probably don't mean much in the real world. Fentanyl is a bit more lipophillic so has a faster onset and shorter duration of action; but honestly, it's probably only about 30 seconds to one minute or so which isn't that big of a deal when you think about it. The "big" selling point for fentanyl is it releases less histamine so those who feel yuck with morphine have less of this effect with fentanyl but by-and-far the number of people who report feeling "yuck" with morphine to such a significant degree to justify giving them fentanyl is probably one in a zillion.

Fentanyl is about 10x more expensive than morphine so unless there's a very, very strong indication to give it, I don't see it as being overly necessary personally.

Ketamine is not an opioid analgesic but has some opiate receptor affinity so produces some analgesia but the main effect, IIRC, is to disconnect the sensory areas of the thalamus from the cerebral cortex by increasing release of GABA. This means the patient still may have pain but their brain is not aware of the pain. It is also advantage because it maintains airway and breathing.

Thank you so much for the detailed response, I appreciate it.

 

[Carlos Danger]

The differences between morphine and fentanyl aren't really that significant and probably don't mean much in the real world. Fentanyl is a bit more lipophillic so has a faster onset and shorter duration of action; but honestly, it's probably only about 30 seconds to one minute or so which isn't that big of a deal when you think about it. The "big" selling point for fentanyl is it releases less histamine so those who feel yuck with morphine have less of this effect with fentanyl but by-and-far the number of people who report feeling "yuck" with morphine to such a significant degree to justify giving them fentanyl is probably one in a zillion.

I think most people who use both drugs routinely would agree that clinically, the differences between morphine and fentanyl are actually quite substantial. Nausea, itching, and other side effects are much more common with morphine. Fentanyl is much easier to re-dose since its onset and duration are shorter. A significant percentage of the action of morphine is due to its active metabolites, whereas fentanyls metabolites are not clinically active.

Fentanyl is just a much "cleaner" and useful drug all the way around.

 

[RocketMedic]

IIRC, fentanyl also has a significantly lesser rate of allergic reactions than morphine.

 

[NUEMT]

Nerve blocks, guys, really? Nerve blocks. Things done by specialized anesthesiologists with years of training you want to do in the field? I haven't ever seen a nerve block done even in the ER except for minor things like finder dislocations. Pain management is not as big an issue as y'all are making it out to be to need pain blocks pre-hospitally.

It is being done for finger and hand injuries. In the field.

 

[TXmed]

i have read a little about, but still very curious, on ketamine's effects on temporal summation (pain wind up). could any of the anesthetists elaborate on that?

 

[Carlos Danger]

i have read a little about, but still very curious, on ketamine's effects on temporal summation (pain wind up). could any of the anesthetists elaborate on that?

I don't know that ketamine is any better at preventing wind up than any other technique. Opioids, systemic lidocaine, and of course nerve blocks all prevent the painful stimulus from being transmitted to the brain, which is where central sensitization occurs. What is interesting about ketamine is both the way that it works to prevent wind up, and also that it is being used to successfully treat these central pain syndromes.

Unlike opioids, whose analgesic effect is primarily centered in the spinal cord, where they block the painful stimulus from being transmitted to the brain, and local anesthetics, which primarily block the stimulus from being transferred from the periphery to the spinal cord, ketamine works at the NMDA receptors in the brain, which is where windup happens. As a non-competitive antagonist, ketamine books other ligands and apparently slows down the fast rate of ionic transmission to the post-synaptic nerve, which of course is what causes summation. Not unlike the way that non-depolarizing NMB's works, except in the brain rather than at the neuromuscular junction. Or at least that is my understanding.