[toggle_box] [toggle_item title=”Which do I choose?” active=”false”]Ketamine[/toggle_item] [/toggle_box]
Ketamine is an excellent choice for moderate/procedural sedation in the pediatric ED because it has a short durtauion of action, fast onset and low risk of side effects. Its street drug cousin is PCP – but I don’t usually see kids ripping the doors off of cop cars after getting it. The drug is either effective, or it isn’t and via the binding of MDMA receptors it produces a “lights are on but nobody’s home” or trance-like state. It provides;
It doesn’t mess with;
- Upper airway muscle tone and protective reflexes
The initial IV dose is 1 to 1.5 mg/kg.with repeat doses of 0.5 to 1 mg/kg given q5-10 minutes as needed. If you are also giving Propofol, you can give 0.5 mg/kg. The IM dose is 4 to 5 mg/kg with a repeated IM dose of 2 to 4 mg/kg after 10 minutes if needed. IM dosing takes longer and has a higher risk of side effects, so I prefer IV. More on that later.
Upon administration, which is generally given over 2 minutes, you will see;
- Effect/onset withn 60 seconds after initial dose is fully given and IV is flushed
- Onset 3-4 minutes after IM dose administration
- Staring off into the distance
- Horizontal nystagmus
- Increased salivation
- Incoherent rambling/moaning
- Mild increase in blood pressure
The duration of action of a single IV dose is 5-10 minutes, whereas IM doses can last 30 minutes on average.
Overall the risk of adverse effects is low (<4%) and may be associated with age <2 years of >13 years, initial dose in excess of 2.5mg/kg, total dose >5mg/kg and coadmihstration with midazolam, atropine/glycopyrrolate. The three most common are;
This is the most common, and is the basis for making sure that patients are NPO for at least a little bit. The issue of how long to fast before ED procedures is complicated – and I’ll address it in a future post. But suffice it to say I believe that 2 hours after clears, and 4 hours after solids is fine – though others may disagree. IM increases the risk 26% vs 12% according to a RCT by Roback et al. Alhough I don’t always give it, studies have shown that premedication with ondansetron reduces the risk of vomiting with a number needed to treat of 13. The overall frequency is roughly 8% and peaks around age 12.
More common in children older than 15, and in those with a prior history of psychosis. Severe cases can resemble Godzilla rising from the ocean. MIdazolam does not decrease the risk of emergence reactions, and may increase the risk of other side effects. Therefore I do not routinely administer it with my patients, unless I have exceeded 4mg/kg of ketamine.
Apnea or laryngospasm
Very rare (1/5,000-10,000) and responds to positive pressure ventilartion with a bag valve mask, as the pressure will “pop” open the vocal cords. This appears to be an idiosynchratic reaction. With effective PPV it generally resolves in 1-2 minutes. In a single observational study the IM route was associated with an increased risk of laryngospasm OR 5.2; 95% CI 2.3-11.9. The aforementioned study by Roback did not show a significant difference in the rates of laryngospasm however.
- Younger than 3 months
- History of psychosis
- Closed head injury
- Conditions associated with elevated intracranial pressure (hydrocephalus)
- Glaucoma or other conditions associated with increased intraocular pressure an/or eye injuries – though at most the pressure increases only 1 mmHg