Can it ever go wrong with ketamine?
Ketamine has a wide therapeutic range which means there is a pretty reasonable margin for error when you overshoot. It is a forgiving drug. However yes, there are occasional well recognised complications.
The important ones:
- Emergence Phenomena
- Apnoeas
- Airway obstruction (usually resolves with basic airway manoeuvres/adjuncts
- Laryngospasm (DOESN’T always resolve with basic airway manoeuvres)
Emergence Phenomena
This is an excited delirium, often with severe hallucinations, that occurs as the dissociative effect of ketamine wears off. It can happen in as many as 1 in 3 adults (as per RCEM).
It can be quite dramatic, but is fairly straightforward to treat with an IV benzo. 1mg IV midazolam in a normal sized adult male would be an appropriate initial dose.
Apnoeas
This very rare. But it does happen.
The risk can be easily mitigated by slow bolusing the ketamine over 60 seconds… when you have the luxury of giving it IV of course (e.g. in a controlled procedural sedation). However, when giving an IM ketamine sedation (for example when rapid tranq-ing an ABD patient) slow bolusing is not an option.
Basic airway repositioning/manouvres, with a bit of BVM ventilation is usually all that’s required. However, occasionally the apnoeas are persistent, and may compromise the patient if BVM is difficult… which of course necessitates proceeding to an RSI.
This is a essential video from Reubin Strayer demonstrating the optimal technique for BVM ventilation in the ED (use two hands, both thumbs down…. every time).
Airway obstruction
This is usually easily resolved by doing the basics well:
- Re-positioning (try to get the external auditory meatus to align with the sternal notch)
- A good jaw thrust
- Appropriately sized airway adjuncts
Doing the above will almost always be sufficient to de-obstruct the airway. However, again, if you are not winning you should be prepared to perform RSI.
Here is a quality online module from Cliff Reid on how to optimise positioning for BVM (and laryngoscopy).
Laryngospasm
This is the scariest complication of ketamine. It happens in 0.3% of cases. Much more common in kids.
Laryngospasm is a reflex involving the superior laryngeal nerve that induces closure of the glottis (vocal cords slamming shut).
It is induced by stimulation of the airway. There is a risk of it in a ketamine sedation because the airway reflexes are preserved and there are increased secretions. If secretions drip into the larynx this can precipitate laryngospasm, as can sticking the suction tube too far down (“suction where you can see”).
Classically you will hear a high-pitched inspiratory stridor (a “crowing” sound). However, the stridor isn’t always that obvious and you may only pick it up by noticing an increased work of breathing or desaturation. In complete airway obstruction you will lose the ETCO2 waveform and be unable to BVM ventilate (even with perfect technique).
The good news is that the vast majority of cases are sorted with a good jaw thrust, 100% oxygen (delivered via mask with a tight seal), and BVM ventilation (ie PPV) with PEEP.
How can we deliver emergency PEEP?
In my place we don’t have the adjustable PEEP valves that attach to the expiratory port of the ambubag (self-inflating) BVM. I’d imagine most UK EDs are the same.
However, we do have readily available Mapleson C (“Waters”) circuits in resus which have adjustable pressure limiting (APL) valves. These allow us to deliver PEEP, albeit less precisely than with a PEEP valve (where you can select a specific number)… but they do the trick.
Check out this video which explains how to use the Mapleson C circuit.
Refractory laryngospasm
If 100% FiO2/PPV/PEEP don’t rapidly break the laryngospasm… do the following:
- Call 2222 (or equivalent phone number to rapidly activate a MET call/cardiac arrest call). Assistance from anaesthetics/ICU will be needed ASAP.
- Ensure the difficult airway equipment is next to you.
- Deepen the sedation with some propofol (0.5mg/kg is reasonable). This will often be the key intervention in the more severe laryngospasm cases.
- Larson’s manoeuvre can be effective. Wedge your middle fingers (both sides) between the mastoid process and ramus of the mandible (easily found by feeling just behind the earlobe). In there somewhere is the styloid process which is your target. Press really hard medially and anteriorly. Think of it like a particularly brutal jaw thrust.
- Start setting up for an RSI, though hopefully the laryngospasm will break before the paralytic is needed.
In the most severe laryngospasm cases where a full RSI is indicated, suxamethonium is preferred over rocuronium due to its faster onset. Give the full dose (1-2mg/kg IV or 3-4mg/kg IM) to optimise intubating conditions.
Of course, management of the patient with refractory laryngospasm will be an MDT effort. Close collaboration with anaesthetics/ICU is essential.
Cheers all,
Robbie
@robbielloyd.bsky.social