Ketamine - disadvantages in trauma pts.

[IVAN HRONEK]

not sure if this is OK, but thought it would be easiest just to go to the main source - Miller's Anesthesia textbook...
 
Ketamine increases cerebral metabolism, CBF, and ICP. Because of its excitatory CNS effects, which can be detected by generalized EEG development of theta-wave activity,[463] as well as by petit mal seizure-like activity in the hippocampus,[482] ketamine increases CMRO2. Whereas theta-wave activity signals the analgesic activity of ketamine, alpha waves indicate its absence. There is an increase in CBF that appears to be higher than the increase in CMRO2 would mandate. With the increase in CBF as well as the generalized increase in sympathetic nervous system response, there is an increase in ICP after ketamine administration.
 
Ketamine in vitro probably has negative inotropic effects. Myocardial depression has been demonstrated in isolated rabbit hearts,[530] intact dogs,[531] chronically instrumented dogs,[532] and isolated canine heart preparations.[533] However, in isolated guinea pig hearts, ketamine was the least depressant of all the major induction drugs.[534] The finding that ketamine may exert its myocardial effects by acting on myocardial ionic currents (which may exert different effects from species to species or in diverse tissue types) may explain the tissue and animal model variance in direct myocardial action.[535]. The centrally mediated sympathetic responses to ketamine usually override the direct depressant effects of ketamine. Ketamine can produce hemodynamic depression in the setting of deep anesthesia when sympathetic responses do not accompany its administration.
 
 Ketamine-anesthetized patients have profound analgesia but keep their eyes open and maintain many reflexes. Corneal, cough, and swallow reflexes may all be present but should not be assumed to be protective.[457]
 
A potential respiratory problem, especially in children, is the increased salivation that follows ketamine administration (also see Chapter 60 ). Such salivation can produce upper airway obstruction, which can be further complicated by laryngospasm. The increased secretions may also contribute to or may further complicate laryngospasm. In addition, although the swallow, cough, sneeze, and gag reflexes are relatively intact after ketamine administration, there is evidence that silent aspiration can occur during ketamine anesthesia.[457]. Personally I see it in adults quite often....
 
I understand in Africa Ketamine is used all the time, also because they don't have intubation devices and ETTs. What is their aspiration rate though, do we know ? Aspiration is rare by itself, however can be a devastating or lethal iatrogenic complication.
 
In trauma pts. I would be most concerned with the increased ICP - i know we get away with a lot in this respect, but the last thing I like to see is a patient herniating and ending his life just after my intubation....
personally I am crazy about all the little things, including raising the head of the bed, modified rapid sequence with hyperventilation, giving Lidocaine, using a drug that vasoconstricts cereberal vasculature rather than increases CBF (Propofol, Thiopenthal)
Thanks for the stimulating discussion, I love it !
Ivan Hronek MDChief, Critical Care & Trauma AnesthesiaSFMC Gas, Inc.St. Francis Medical CenterLynwood, CA



> From: trauma at emergencyunit.com> To: trauma-list at trauma.org> Date: Fri, 3 Aug 2007 00:15:05 +0100> Subject: RE: Ketamine vs. Etomidate in trauma pts.> > Well...> > > Disadvantages of Ketamine:> > 1. tachycardia - many trauma pts. are tachycardic enough already> > Not necessarily a disadvantage; the tachycardia is actually as a result of a> direct sympathomimetic action.> > 2. negative inotropic effect (that gets uncovered if catecholamines are> depleted and there is an insufficient sympathetic response to the> stimulation by Ketamine). > > It is my understanding that catchecholamine release does not mediate this> action so I do not understand that. K MIMICS the action, not releases it.> > 3. seizures (like Etomidate) and increase brain tissue O2 consumption> (unlike Etomidate)- problem e.g. in head traumas etc. > > No clinical effect from these - they are theoretical. I have used ketamine> extensively in head trauma with no apparent ill effect. Anyone else seen> trouble?> > 4. increased secretions everywhere> > Usually only a problem with under 3s and can be dealt with using> glycopyrrholate or atropine.> > If used as analgesic unclear when transition to general anesthesia with> aspiration risks ..> > The whole point about ketamine (found in the earliest studies by Dundee) is> that even at anaesthetic doses aspiration is really rare. Hence its huge> popularity in Africa for single operator LSCS.> > If you don't use Midazolam the seizures are more likely, too...> > <shrug> Ditto with alfentanil. If it happens deal with it. As it happens I> have never seen it, but I probably will tomorrow having said that! > > I agree though that it is good in all these other situations, just it cannot> be used in a number of situations where Etomidate can.. Ivan Hronek MDChief,> Critical Care & Trauma AnesthesiaSFMC Gas, Inc.Lynwood, CA> > > > --> trauma-list : TRAUMA.ORG> To change your settings or unsubscribe visit:> http://www.trauma.org/index.php?/community/