Fixed Dose Paralytics (Thought Experiement)
Here on FOAMfrat we do a lot of thought experiments. I would like you to consider the pro's and con's of relatively fixed dose paralytics when performing an intubation.
For the sake of this blog we will be referring to rocuronium as the primary agent. However, I feel you could substitute in succinylcholine with little variance.
Rocuronium dosing has been a point of controversy for sometime now. There are some who calculate the dose off of actual body weight, corrected body weight, lean body weight, or ideal body weight. In a study comparing these methods, the only real statistical difference was the time of onset and duration. Intubating conditions appeared to be similar when dosing at 1.2 mg/kg. Here is my thought process..
In our field we are..
1. Guessing weight.
2. Processing a lot of data.
3. Maintaining forward momentum to definitive patient care.
4. Better at guessing height.
We know that the Shoenberger J.M (2018) study showed that when rocuronium is dosed at 1.2 mg/kg, the intubating conditions were very similar to succinylcholine. If you ask most FOAMed savvy medics what the ideal dose of rocuronium is they will quote that study and say 1.2mg/kg. In reality... we have no clue how much we are giving per kilogram when someone is laying on a longboard in the back of an ambulance. Most will default to 100mg of rocuronium.
Sam Ireland did a Vodcast last year on an intubation checklist he created for the crews at Lifestar EMS. On the bottom of the checklist was a dosing guide for rocuronium based off height. I like this model because it requires no math, and a just a ball-park estimate of height. The majority of your patients will either get 100 mg or 75mg. If they lie in the middle, I always round up.
What if we give too much?
The main concern when giving a long acting paralytic is adequate sedation/analgesia. I personally think depending on the transport duration, a sedation infusion, with bumps of analgesia, is a great cognitive offload. The way levels of paralysis are measured in the post operative setting is by using a twitch monitor. The peripheral nerve stimulator will give a train of four (TOF) stimulations to the ulnar nerve. The paralysis level will be measured by how many of those shocks result in visual twitches of the hand (great blog post on this).