The Brain on Ketamine

Reuben Strayer from empdates.com is our guest to discuss proper dosing of ketamine.

Take home message: At very low dose, you get analgesia with minimal effect on perception and emotion. At a very high dose, you’re going to get dissociation. In between high and low doses, you don’t know what kid of response you’re going to get.  It depends on the patient’s mood, what other drugs are on board, and the alignment of the stars in the sky. This is why using sub-dissociative ketamine as monotherapy for sedation is not a good idea- it might chill someone out, or it might take a crazy agitated patient and make them a crazy agitated patient now tripping on ketamine. Don’t use sub-dissociative ketamine alone for routine agitation; ketamine is not for routine agitation, it’s for tranquilization of the uncontrollably violent patient in full dissociative doses. For analgesia, use LOW DOSE – 10 or 15 mg in an adult. Do not push more than that or you will end up in recreational range or partial dissociation (which is not what you want).

[audio http://traffic.libsyn.com/ercast/The_Ketamine_Brain_Continuum_final.mp3]

Direct Download

Ketamine Dosing

Analgesic dose (0.1-0.3 mg/kg)

Recreational dose (0.2-0.5 mg/kg)

Partially dissociated dose (0.4-0.8 mg/kg)

Dissociative dose (>0.7 mg/kg)

Reuben’s kick ass links

Here is a detailed review of the Ketamine Brain Continuum

The Amazing Intubation Checklist

Procedural Sedation Checklist

Comments

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  2. Robert Gebei MD.

    We use Ketamine in Hungarian Ambulance service as induction at 2mg/kg for Rsi, do you think we should use midazolam also routinly with ketamine!

    1. reuben strayer

      there’s no need to use midazolam with ketamine for RSI, unless you are very concerned about increasing the patient’s blood pressure (which ketamine often does). midazolam is a great post-intubation agent, however, when the ketamine wears off (at 2 mg/kg you should dose post-intubation sedation/analgesia within 15 or 20 minutes of induction). -reub

  3. Lucas Martin, PJ, PA-C

    Hello, I am a USAF Reserve Pararescueman (PJ) currently deployed overseas. Our protocols also call for Ketamine as the induction agent of choice at 2mg/kg for RSI. We recently had a lecture by an Anesthesiologist that warned against the use of Ketamine in patients with possible elevated ICP. I understand that this is still controversial and brought that up, however the Anesthesiologist stated that it would be bad practice to administer if you suspected elevated ICP in their opinion. However, due to working in the field many of our patients can potentially have elevated ICP due to the nature of the traumatic injuries that we are treating for (blast injuries, GSW, etc), plus we are limited in the amount of things we can carry making Ketamine an excellent drug to carry for both analgesia purposes as well as an induction agent. When consulting UpToDate I had found this as well below and am wondering if you could clear things up with your thoughts on this controversy?

    ADULT RESUSCITATION

    Ketamine in patients with elevated intracranial pressure (February 2015)

    The use of ketamine as an induction agent for rapid sequence intubation (RSI) in patients with head trauma has been debated because some observational studies suggest it elevates intracranial pressure (ICP). However, a systematic review of 10 trials involving 953 critically ill patients, all managed with intubation and mechanical ventilation, concluded that the use of intravenous ketamine did not adversely affect patient outcomes, including mortality [1]. Most studies included in the review had methodological limitations, but two randomized, double-blinded controlled trials comparing the effects of prolonged ketamine and sufentanil infusions in patients with traumatic brain injury found no differences in mean daily ICP and cerebral perfusion pressures. The findings of this systematic review support our view that ketamine is an appropriate induction agent for RSI in patients with suspected ICP elevation and normal blood pressure or hypotension. (See “Sedation or induction agents for rapid sequence intubation in adults”, section on ‘Elevated intracranial pressure’.)

    Thanks!

    1. Post
      Author
      Rob Orman

      Hey Lucas!!
      Thanks so much for this question. Below is a response from Rob Bryant, an expert on the topic. Please don’t hesitate to ask for any clarification on topics discussed on the show or that you hear elsewhere. I am a big fan of the PJs and am honored to be at least peripherally involved in what you’re doing.

      Here is a little bit of stuff that might help:

      Minutes 30:10-36:40 reviews the (limited) lit on ketamine, and argues the point that if ketamine can allow for a safer preoxygenation, and intubation, then there will be less secondary brain injury.
      (excuse the funny accent, it is from my DSI talk I gave to the NACS guys in Portland last year)

      CJEM:
      link to pdf here:
      http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9629179&fileId=S1481803500012197
      LITFL post:
      http://lifeinthefastlane.com/ccc/ketamine-rsi-for-head-injury/
      Taming the SRU post:
      http://www.tamingthesru.com/blog/prehospital-medicine/ketamineintbi

      Bottom line:
      I use ketamine with the knowledge that it is extremely unlikely that I am harming my patients, and am in all likelihood helping them avoid secondary brain injury, and keeping my staff safe from my agitated patients that get DSI’d.

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