That is right , Adrian
Ketamine differs from other sedatives as it lacks tha charasteristic
dose-response when titrated. Once a critical dose is used (3-5 mg/Kg IM) the
dissociative state appears. Once achieved there is not a change in the depth
just in the duration of the sedation. Some authors, and Ray McGlone could
tell us more about that, use lower doses 2-2.5 mg/Kg , but the jury still
out about reduction in incidence of complications.
The reporting of laryngospam has been minimal with only 4 cases reported in
the literature (all the cases in the same series 1022 patients using IM
ketamine as a dose of 4 mg/Kg, easily reversed and no sequelae) but other
studies using similar dose or larger has not reported such complication.
This could mean, as you said , that laryngospasm is related to laryngeal
stimulation due to secretions or instruments.An agitated child due to
unadequate sedation is potentially more at risk.
The dose appears to have a wide safe range (2-10 mg /Kg Im) Severe
overdoses has been reported with no sequelae, just transient respiratory
depression. This should not be a reason to drop the guard when using this
drug, (or any other sedative) as the only dead recorded in children was
published in 1997, a 2 months old baby was given an IV overdose of 10 times
the intended dose during rapid sequence induction performed by anasthetists
in ITU after heart surgery (as we can see plenty of "other factors") .
Andres Izquierdo Martin
SpR Emergency Medicine
North East Thames Region
[log in to unmask]
--- Original Message -----
From: "Adrian Fogarty" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, February 15, 2001 12:24 AM
Subject: Re: chemical restraint
> Actually Charlie, I would have thought that the most dreaded complication
of
> ketamine sedation would be laryngospasm (which is probably the most
dreaded
> complication of just about any anaesthetic/sedative next to "can't
> intubate/can't ventilate" scenario). But laryngospasm is not seen in deep
> anaesthesia (or in full consciousness), it's a feature only seen in the
> "twilight zone" of semi-sedation, and precipitated by surgical stimulus or
> laryngeal stimulation from secretions or instrumentation. So your
> generalisation that "complications are dose related" doesn't quite hold
> water for laryngospasm, I feel. One huge advantage of ketamine is that
it's
> extremely difficult to overdose on it! The drug doesn't cause airway
> obstruction or cardiovascular instability, so not much goes wrong with big
> doses. If one wishes to avoid laryngospasm, I would err on a bigger dose
of
> ketamine, allow the patient to get nice and deep, and keep them dry
> (secretions), before surgically stimulating them.
>
> Best wishes
>
> Adrian Fogarty
>
> > -----Original Message-----
> > I also agree that Ketamine - an agent for which I have the greatest of
> > respect - is a very valuable drug when correctly used in A/E
> > practice and I
> > think we must see ourselves as capable of using it safely. This means
> > knowledge and experience not just if its actions but the ability
> > to deal with
> > the potential complications which in my experience are strongly
> > dose related.
> >
> > Charlie Fee,
> > Craigavon
> > N.Ireland
>
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