Written by Jeffrey A DeChellis, MA, MICP

All practitioners who perform Rapid Sequence Induction (RSI) are probably familiar with the term defasciculation.  The degree of importance you give to defasciculation may depend on when you were first introduced to RSI and the protocols in place at that time.  The origins of prehospital RSI are rather vague, but whether you believe this is a procedure adapted from Peter Safar’s seminal piece from the 1970s or you feel RSI has its origins in OB-GYN anesthesia from the 1940s, defasciculation was probably a standard part, from its conception.  This discussion of RSI references that performed with the neuromuscular blocking agent (NMBA) Succinylcholine and not necessarily that performed with a non-depolarizing agent, though it may speak to these in a slightly different vein.

RSI is utilized on a subset of patients for whom increases in ICP, even transient ones, have been deemed potentially deleterious. Many practitioners have developed differing strategies to attenuate the rise in ICP associated with RSI for these patients.  The three main methods utilized in the prehospital setting tend to be Lidocaine, Fentanyl, and defasciculation.  Initially, these were incorporated in the mnemonic LOAD (Lidocaine, opioid, Atropine, defasciculation) for pretreatment of RSI patients.   It was theorized that by administering a defasciculating agent, you could prevent the fasciculations induced by Succinylcholine, thus preventing the associated rise in ICP.  Several agents have been recommended for this, such as Lidocaine, Magnesium or any NMBA.  The consensus early on was that 1/10th the intubating dose of any NMBA should be appropriate to decrease the degree of fasciculations cause by Succinylcholine administration, in hopes of attenuating any rise in ICP associated with fasciculations.   Many prehospital practitioners incorporated this dose of a nondepolarizing NMBA, typically Vecuronium, into their protocols for patients with suspected increased ICP, requiring RSI.

As RSI progressed into the prehospital setting, there were several studies presented questioning its effectiveness and utility, causing many to take another look at RSI in the prehospital setting.  Upon reexamination, many who realized just how labor intensive this procedure was felt simplification was needed to increase the effectiveness and success of this procedure.  One of the first areas to be modified was the practice of defasciculation.  At this point, some practitioners had incorporated defasciculation as a part of their protocols for all RSI intubations, while others limited it to those patient with increased ICP.  As experts re-examined this procedure, they felt as though the evidence in support of defasciculation was lacking.  Since fasciculations could not be directly demonstrated to be causative in the rise in ICP in patients with TBI, they felt this step could be eliminated, in an attempt to simplify the procedure, without any significant risk to the patient.

Several steps in the RSI procedure were eliminated by removing defasciculation from our protocols: (1) there was no need to decide which patients would benefit from this and for whom it was unnecessary; (2) the calculation of 1/10th the intubating dose was no longer needed; (3) having to reconstitute the Vecuronium and, and (4) calculating the actual milliliters to be delivered was now out of the mix as well.  The labor-intensive task of prehospital RSI was now a little less labor intensive, and perhaps patients would be better off for it.  Coming from a project who routinely defasciculated all RSI patients, the effects of removing this from our protocols were immediately evident. The actual fasciculations I have witnessed range from almost unnoticeable to those mimicking tonic-clonic seizure activity.   Now that fasciculations are often witnessed while performing RSI, I am not convinced these are actually better for my patients.  I realize the data may be lacking, demonstrating a causal effect of fasciculations on the rise in ICP associated with this procedure; however, I am not convinced.  If we are to believe that something as subtle as any needle stick, suctioning or even turning the light on in a room are factors associated with an increase in ICP, I find it hard to accept that somehow, particularly exaggerated fasciculations, could be exempt from this.

Why defasciculation?  In the 1960s, it became apparent that the fasciculations associated with the use of Succinylcholine produced some negative effects, particularly post-operative myalgias, increased intragastric pressure and a release of catecholamines.  So the world of anesthesia has spent the last several decades looking for ways to address this issue.  Additionally, it was noted that Succinylcholine caused an increase in ICP for patients with brain tumors undergoing elective neurosurgery. That increase was reduced by pretreatment with nondepolarizing NMBAs, creating further interest in RSI defasciculation pretreatment.  Whether or not we could extrapolate that Succinylcholine-induced increased in ICP from patients with brain tumors to those with acute TBI is a question that would be best answered by a prospective randomized controlled study.  So while the myalgias may well not top anyone’s list of concerns, from the administration of Succinylcholine, increased intragastric pressure along with increase in circulating catecholamines in the patient with an acute TBI under the guise of the “full stomach” theory may be cause for concern, and what about “safe apnea”?

Over the last few years FOAM and social media have brought to light the concern for increasing the “safe apnea” period during RSI.  Denitrogenation, preoxygenation, reoxygenation and apneic oxygenation have all received quite a bit of press due to increased research in this area, as has safe apnea time.  We go to great lengths to ensure increased safe apnea times for RSI.  15lpm via nasal cannula & NRB has become an integral part of many protocols for both preoxygenation and apneic oxygenation for prehospital RSI; this, without a secure evidence base, in support thereof.  Additionally adding this step to an already labor-intensive procedure must increase its cognitive load, especially in light of the fact that we typically only have one oxygen source, initially, in the prehospital setting; the very same cognitive load we tried to decrease by eliminating pretreatment with defasciculation.  I am in full support of this added step, however, fascinated by how it was so quickly implemented with little concern for the added cognitive load.  With all this concern for increasing safe apnea time, why would we then force a patient’s musculature to fasciculate, knowing this action must consume oxygen and potentially decrease our safe apnea time, as suggested by studying Rocuronium versus Succinylcholine?

All of these factors taken into consideration, I propose we should incorporate routine defasciculation, or a variation thereof, into our protocols for most of our prehospital RSI cases, excluding those who endorse a “crash airway” situation.  If we made defasciculation a standard part of our protocols, utilizing a universal dose for all patients, we could incorporate this at the same time we are adding the 15lpm nasal cannula, with little increase in cognitive load or labor for this procedure.  Additionally, since there appears to be an interest in eliminating Succinylcholine from this procedure altogether [or at least limiting its use], the universal defasciculating dose of the non-depolarizing NMBA should be an adequate substitute for a “priming dose” in this alternative situation, leaving it a universal part of the protocol regardless of which type of NMBA is utilized.

I propose that instead of “dumbing down” this procedure, in an attempt to simplify it under the guise of patient safety; we attempt to decrease the cognitive load and labor intensity of RSI through the following. First, increase the prehospital providers’ foundational knowledge base in the realm of RSI through education.  Second, the use of cognitive offloading techniques such as standardization and universal dosing, in our protocols and training, to decrease the intensity of this procedure.   Replacing Vecuronium with Rocuronium too would remove the additional steps created by reconstitution.  These few simple steps could afford our patients safe RSI without compromising safe apnea time, potentially deleterious increases in  ICP or increased risk of aspiration.

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