Pediatric Procedural Sedation with Ketamine

The EM blogosphere has been abuzz with talk of ketamine the past week or so. We stated in the 4th LITFL Review that “an irrational fear of ketamine’s “bite” makes it  one of the most under-rated drugs in the ED doc’s arsenal.” Emergency Medicine Updates provided some great tips on Taming the Ketamine Tiger and featured a number of recent publications from the Annals of Emergency Medicine including a link to ACEP’s Clinical Practice Guideline for Emergency Department Ketamine Dissociative Sedation: 2011 Update. Also, just released, is Scott Weingart’s brilliant podcast on the use of ketamine for a controversial technique he calls Delayed Sequence Intubation — something that makes a huge amount of sense to me.

Now, this post is a Q-and-A review of last month’s article from @EBMedicine (which I finally got round to reading…) which is all about using ketamine for procedural sedation in children:

Madati PJ (2010). Ketamine: Procedural Pediatric Sedation In The Emergency Department. Pediatric Emergency Medicine Practice, 8(1). [Abstract and subscription link]

So, without further ado, here are 10 questions highlighting some of the key learning points:

Questions

Q1. Compare the IV and IM routes of ketamine administration for procedural sedation.

Ketamine for procedural sedation can be given intravenously or intramuscularly. The dose of ketamine to produce profound dissociation is:

  • 1 to 1.5 mg/kg IV
    This is given over 1-2 minutes, is effective within 1-2 minutes, results in effective sedation lasting 10-20 minutes, and if inadequate a further 0.5 mg/kg dose may be given
    or
  • 4 to 5 mg/kg IM
    This is effective within 2 to 5 minutes, results in effective sedation lasting 15-30 minutes and a repeat IM dose (2-4 mg/kg) can be given after 10 to 15 minutes if the initial effect is inadequate

The IM route is useful when IV access is problematic, but the downsides include:

  • a longer recovery time (mean of 120 minutes for IM vs. 80 minutes for IV)
  • vomiting is more likely (usually occurs during emergence)
  • sedation doses are less easily titrated

Higher doses, or even a continuous infusion, may be required in small children due to their relatively higher volume of distribution.

Q2. Should an anticholinergic agent be used with ketamine?

Atropine (0.02 mcg/kg, up to maximum of 0.6mg) or glycopyrrolate are often administered as a co-medication to reduce the hypersalivation caused by ketamine.

The weight of evidence at this time, based on meta-analyses of controlled trials, suggests that anticholinergics should not be routinely used:

  • glycopyrrolate appears to increase airway complications.
  • atropine confers no benefit.

However, atropine may be beneficial for certain procedures where having dry oral mucosae may be beneficial to the proceduralist rather than the sedationist, e.g. repair of tongue lacerations.

Q3. What are emergence reactions and how can the likelihood of them occurring be decreased?

Emergence phenomena include recovery agitation, dreams, hallucinations and depersonalisation.

They are less common in children than adults:

  • adults: 10-20% (as high as 30% in some studies), with 1-2% clinically significant.
  • children: 7.6%, with 1.4% clinically significant.

Benzodiazepines are useful for treating emergency reactions, but they do not decreased the likelihood of an emergence reaction occurring. Furthermore, co-administration of midazolam increases the risk of respiratory complications, although emesis is reduced.

In one study, involving adult patients in a non-emergency department setting, no emergence phenomena occurred if ketamine was adminstered in the following circumstances:

  • patients were interviewed in the preoperative area:
  • they were assured that the medication was safe and would provide complete analgesia during the procedure.
  • they were told that the anesthetic medication would allow them to dream about a topic of their choice
  • they were instructed to concentrate on that pleasant thought/dream during induction of anesthesia.
  • they were  encouraged to share their thoughts and feelings before undergoing ketamine sedation.
  • ambient operating room and recovery room stimuli were  minimized (e.g. noise and lighting).

Q4. What benefit does low dose ketamine with propofol offer over ketamine alone?

Studies performed in non-emergency department settings suggest that ketamine (0.5 to 1 mg/kg IV) followed by propofol (1mg/kg IV) results in more rapid recovery times (time from administration to discharge is halved in some studies) with no increase in clinically significant adverse effects.

Although ‘ketafol’ (sometimes mixed in the same syringe) is being used in emergency departments, there are currently no RCTs in an emergency department setting to support this practice.

Q5. Why might ketamine be a poor choice for the sedation of children requiring imaging (e.g. CT or MRI)?

Ketamine can cause hypertonia and semi-purposeful movements that may interfere with imaging if the patietn is required to lie still.

Q6. Is ketamine contra-indicated in head an/or ocular trauma?

Ketamine is traditionally contra-indicated in situations where raised intra-cranial or intra-ocular pressure may be harmful or poorly tolerated.

These contra-indications are largely based on data from the 1970s. More recent studies in animals and ICU patients have undermined the belief that ketamine causes clinically significant increases in either intra-cranial or intra-ocular pressures. Indeed, some believe ketamine may be neuroprotective as a result of maintaining a stable ICP but with increased cerebral blood flow.

At present, it is probably best to choose an agent other than ketamine in these settings, unless other agents are less suitable for other reasons.

Q7. How are the dissociative effects of ketamine related to the dose administered?

The dissociative state is a lack of response to external stimuli due to ‘disconnection’ of the thalamoneocortical system from the limbic system, as a result of non-competitive antagonism at NMDA receptors.

Above a dose of about 1mg/kg IV the dissociative effects of ketamine  do not exhibit dose-responsive effects. Once a patient is fully dissociated, higher doses do not result in a deeper level of sedation.

‘Sub-dissociative’ doses (<1mg/kg IV or <2 mg/kg IM) of ketamine provide potent analgesia, due to agonism of mu, delta, and kappa opioid receptors.

Q8. What are the effects of ketamine on the airway and respiration?

Airway effects:

  • maintenance of airway reflexes
  • risk of laryngospasm — rare (~0.4%)
  • excessive salivation

Respiratory effects:

  • no suppression of respiratory drive
  • bronchodilation

Q9. How long should a patient be fasted before they are sedated with ketamine?

Most guidelines state that patients should be fasted for 4-6 hours prior to procedural sedation. However, no relationship between adverse respiratory events and fasting times has been found in any studies thus far.

Fasting time should be tailored to the risks of aspiration versus the benefit of an early procedure. Fasting times should not be an issue in true emergencies (e.g. neurovascular compromise due to a displaced fracture).

Q10. Why is ketamine contra-indicated in children less than 3 months of age?

For two main reasons:

  • increased rates of respiratory complications
  • animal studies implicate NMDA antagonists as a cause of apoptosis and neurodegeneration in developing brains.

Ketamine is also absolutely contra-indicated in patients with a history of overt psychosis.

Want to test your knowledge some more?

Other stuff the proceduralist/ sedationist needs to know is explored in a case-based Q&A called Nasal foreign body, ketamine and laryngospasm.

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Comments

  1. Gerard Fennessy says

    Great post Chris,
    We used ketamine as our main anaesthetic on Mt Ruapehu Skifield -- used mainly for relocating knees and elbows, and removing skiboots from tib/fib fractures. It was used particularly because of the positive effects it had on respiration (bronchodilation, airway reflex preservation), cardiovascular stability, and additional analgesic and anmetic effects, unlike propofol or benzidiazepines.

    I would throw support behind the above methods of preventing emergence phenomena. Although we can throw all sorts of medications at pain, there is a whole lot of psychology involved in pain relief, and before I give anyone ketamine, I tell them to think of a nice safe place or a favourite holiday.

    I was only flumoxxed by one gentleman who said he had never had a decent holiday. He got a quite a severe case of emergnece phenomena and asked to never be given ketamine again! Interestingly, some people advocate a further dose of ketamine for emergence….

    • says

      My favourite ketamine experience involved a rodeo bull rider (probably not a very good one) who was in agony after being stomped on by his unwilling steed. He had a psoas hematoma on CT. 30 mg of morphine hadn’t done anything. I gave him 0.2mg/kg ketamine as an analgesic -- but I gave it a bit too fast. He looked like he was on a roller coaster and held onto the bed rails for dear life. Then with a huge grin on his face he asked, “what was that?”. I replied, “it might be best if you don’t know…”
      C

  2. says

    G’day Paddy,

    3 hours fasting looks to be adequate (could still be overkill given that airway reflexes are preserved) for ketamine in children according to this BestBet: http://www.bestbets.org/bets/bet.php?id=866
    Also when vomiting does occur, its usually after the sedation wears off, so aspiration is less likely.

    I think fasting times are more of a tradition rather than being based on any firm evidence, at least for procedures in the emergency setting. Aspiration is rare, and in GAs tends to happen during intubation and extubation -- which we don’t do for procedural sedation. Hard to see a definitive study ever being done. The ACEP Clinical Policy ‘Critical Issues in the Sedation of Pediatric Patients in the Emergency Department’ is worth a look for a summary of what evidence there is: http://www.ncbi.nlm.nih.gov/pubmed/18359378

    C

  3. says

    Anyone noticed behaviour changes after a dose of Ketamin. 2 Pediatric patients in our hospital reported and since then there is ban for Ketamine. Not at all evidence but !

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