Tonight on the podcast , we bust another long term medical myth. This is Part 3 of the Ketamine Mythbusters series . This episode , we cover the neuropsychiatric effects of ketamine. Does it cause dangerous psychosis? How useful is it in the agitated patient? How common is the so called emergence delirium? What can you do if it happens? What can you do to prevent it from happening?
It is listed that SCHIZOPHRENIA IS AN ABSOLUTE CONTRAINDICATION TO KETAMINE.
This is a medical myth. Like many myths it was borne out of some truth but like a lot of things in medicine and life, the truth gets distorted. Bit like ketamine and head injuries!
Early research(1,2) in patients with schizophrenia and followup studies clearly show that ketamine in subanaesthetic doses , produces increase in positive symptoms of schizophrenia ( hallucinations mainly) TRANSIENTLY.
Several case reports , case series and experimental studies(3-7) from the psychiatric and anaesthetic literature have challenged this notion that ketamine worsens schizophrenia course.
Moreover my aeromedical retrieval work in the last 6 years has found many cases of patients with schizophrenia in which I have used ketamine sedation in a wide dosing range ( 0.5mg/kg – 1.5mg/kg) with excellent results and my communication with our local psychiatrists has been positive in this regard. And remember IV ketamine is not long lasting. It has a temporary effect so any increase in hallucinations/delirium is not going to last weeks or months. This is well described in psychopharmacologic literature.
The KEY to minimising /avoiding ketamine induced hallucinations/delirium/thought disorder in patients with schizophrenia in particular is to ALWAYS USE IT AS A SECOND LINE SEDATIVE . USE ADJUNCTIVE SEDATION WITH YOUR KETAMINE! I use droperidol and midazolam. Others have used propofol. Recent study showed haloperidol also useful in preventing ketamine delirium in children(8)
Dr Friedberg, an American Anaesthesiologist describes this as “Hypnosis First, then Dissociation“. He has been using a propofol then ketamine sedation technique for cosmetic day surgery for many years with success
IN a Japanese study(10)
In this study, postoperative confusion occurred in 5 (14%) of schizophrenic patients (Group A) with small-dose ketamine and in 8 (23%) of schizophrenic patients (Group B) without ketamine. Hallucinations occurred in 1 (3%) of Group A and in 2 (6%). There was no significant difference in incidence of postoperative hallucinations between Groups A and B.
(taken from this published letter by Chief investigator Dr Kudoh)
So consider that the absolute contraindication of ketamine to patients with schizophrenia is indeed a medical myth. It is a RELATIVE CONTRAINDICATION NOT ABSOLUTE.
In emergency medicine in particular, my friend Casey Parker of BroomeDocs put it best I thought
I would rather have a patient be alive and a bit crazier than..be dead.
Moreover there is a rapidly growing body of psychiatric literature supporting the use of ketamine in refractory depressive illnesses especially with high suicidal ideation. This clearly demonstrates ketamine’s role in a positive manner in some neuropsychiatric conditions .
The above screenshot taken from this Forbe’s article
Okay but what about emergence delirium with ketamine? Sure it happens. In fact my very first use of ketamine in an emergency patient produced florid delirium with marked hallucinations. The patient was in severe pain , the ketamine fixed the pain but gave her the delirium. What did I do? 1mg Midazolam resolved the delirium quickly and the patient had no recall of the adverse event.
Scott Weingart talked about ketamine and how to reduce/manage delirium with it on one of his earliest podcasts ever!
This is a useful video showing a marked ketamine delirium at a prehospital scene. Attribution is to BBC Trauma series with Dr Dan Ellis as the prehospital doctor featured.
It used to be said that you need not give adjunctive sedation with ketamine. I dont hold this principle anymore. It is true that most patients will not have a marked delirium with ketamine. But some do. I give adjunctive sedation as routine now with ketamine sedations. Midazolam or droperidol or haloperidol..even some propofol. They all work to reduce delirium and unpleasant hallucinations(8, 14-16). Also your technique helps. Titration and quiet atmosphere help a lot. Reassurance and education before , during and after ketamine all help! Paediatric patients seem to have less delirium than adults.
here is a video of a ketamine infusion at 300mg/hr for complex regional pain condition. Note how the patient is still responsive and after infusion is not experiencing any delirium/hallucinations.Also note the author of the video explaining how its an individual response as some patients clearly can get intoxicated during the infusion and experience delirium
Take Home Key Messages:
- Ketamine can produce perceptual disturbances and an intoxication effect, dose and individual dependent
- The intoxication and perceptual disturbances are short lived and wear off after ketamine cessation
- Adverse neuropsychiatric symptoms can be minimised/prevented by adjunctive use of other sedatives e.g midazolam, haloperidol
- Ketamine has a growing role in treatment of depressive illnesses and demonstrates rapid antisuicidal properties
- My experience and the small amount of published literature is that even in psychotic conditions including schizophrenia, ketamine can be well tolerated at low dose or when combined with adjunctive sedative agents. It remains though generally accepted contraindication in psychotic conditions.
Show note references:
- The schizophrenia ketamine challenge study debate
- Psychological effects of ketamine in healthy volunteers Phenomenological study
- Uneventful total intravenous anaesthesia with ketamine for schizophrenic surgical patients.
- Preliminary evaluation of clinical outcome and safety of ketamine as an anesthetic for electroconvulsive therapy in schizophrenia.
- Ketamine Anesthesia of a Catatonic Schizophrenic Patient
Now on to the AudioPodcast ( available here and on iTunes)
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