WHEN DOES SUX SUCK?, AND DOES ROC. ALWAYS ROCK?
Succinylcholine is a common neuromuscular blocking agent used in emergency
departments worldwide, and in systems with pre-hospital RSI capabilities. Some
systems (Layton, UT, USA) have encountered resistance when they proposed
the addition of Rocuronium to their prehospital RSI programs.
Some people feel safe using Succinylcholine, due to familiarity with the
medication, and due to the assumption (based on anesthesia algorithms)
that it is safer than Rocuronium and will wear off before profound
hypoxemia ensues in the event of a failed airway, is this true?
Critical hemoglobin desaturation will occur before return to an unparalyzed
state following 1 mg/kg intravenous succinylcholine.
Anesthesiology. 1997 Oct;87(4):979-8
This is the article where the ‘Benumof’ curves come from, detailing the variable
safe apnea durations in the healthy, young, obese, and sick. Mean time to
recovery of twitch height is 8.5 minutes. Time to desat in obese adult and normal
child is 4 min, ill adult 6.25 minutes, and normal adult 10 minutes. This debunks
the ‘succinylcholine is safe because it wears off’ myth.
Hemoglobin desaturation after succinylcholine-induced apnea: a study of
the recovery of spontaneous ventilation in healthy volunteers.
Anesthesiology. 2001 May;94(5):754-9
This evaluates the belief that patients will start breathing sufficiently rapidly to
prevent significant oxygen desaturation.
12 healthy volunteers, each pre-oxygenated, and given 1mg/kg succinylcholine.
Saturations were monitored, and when sats dropped below 80% chin lift and
assisted ventilations were provided. Six (50%) patients dropped below 95%, and
in four, below 80%. Mean values for apnea duration, eye opening on command,
and hand squeeze were 5.2, 5.7, and 7.7 minutes.
Succinylcholine dosage and apnea-induced hemoglobin desaturation in
patients Anesthesiology. 2005 Jan;102(1):35-40
This evaluates whether a lower dose of succinylcholine. would produce a faster
recovery of spontaneous ventilation. 60 patients randomized to 1/kg or 0.56/kg of
succinylcholine or saline, and then apnea time to first diaphragmatic movement
was measured. All patients received 2mg/kg propofol. Desaturation <90%
occurred in 85%, 65%, and 45% of patients, with a dose response effect
observed in those receiving succinylcholine. Time to diaphragmatic movement
was not effected, (4.7, 4.8, and 2.7 minutes respectively.)
Dose adjustment to a lower dose of succinylcholine. is not appropriate in the
ED/EMS population due to the high frequency of hemodynamically compromised
patients that will require a higher dose of succinylcholine (1.5-2mg/kg) to
achieve rapid neuromuscular blockade.
Succinylcholine is short acting, and in the setting of a difficult airway it
may need to be redosed to provide optimum intubating conditions, what
are the issues with re-dosing succinylcholine?
There are theoretical issues that the duration of action from a second dose of
Succinycholine will be significantly longer than anticipated.
Our EMS / ED / ICU patients that need airway protection still need it in a CICV
setting, 'cancelling the case' is not an option. Arguing for a medication that will
wear off in the event of failure does not resolve the physiological insult to the
patient that needs airway protection / ventilatory assistance.
Some people are resistant to changing a medication that they have used
for a decade, what are the problems with succinylcholine?
Succinylcholine has some rare but potentially life-threatening problems that
include hyperkalemia, malignant hyperthermia, bradycardia, masseter spasm
and questionable increased intracranial pressure. Some profoundly hyperkalemic
patients are not obviously identifiable prior to lab evaluation.
The US drug industry has been plagued in recent years by production shortages
of various medications, including Succinylcholine, etomidate, and sodium bicarb.
Rocuronium. proponents argue that Rocuronium. is safer, and contributes
to a prolongation of the safe apnea duration, explain:
Effect of suxamethonium vs Rocuronium on onset of oxygen desaturation
during apnoea following rapid sequence induction
Anaesthesia. 2010 Apr;65(4):358-61
Three arm trial (n=20 per group) comparing Rocuronium, or Succinylcholine with
fentanyl and lidocaine pre-med., versus Succinylcholine with propofol. Mean time
to desat <95% was 358 sec. in the Succinylcholine, Fentanyl and lidocaine
group, 378sec in the Rocuronium Fentanyl and lidocaine group, and only 248
sec. in the Succinylcholine and propofol group. Giving a Lido / fentanyl premed
could decrease the difference in safe apnea durations between Rocuronium and
Succinylcholine, however this adds to medication administration times, and does
not avoid the inherent potassium issues related to succinylcholine use.
Rocuronium proponents may argue that Suggamadex can rapidly reverse
NMB from Rocuronium and provide a layer of safety.
Can sugammadex save a patient in a simulated ‘cannot intubate, cannot
ventilate’ situation? Anaesthesia. 2010 Sep;65(9):936-41
This was a manikin based ‘cannot intubate, cannot ventilate’ scenario where the
total time taken for anesthetic teams to prepare and administer suggamadex was
studied. The mean time to administration of sugammadex was 6.7 min, following
which a further 2.2 min (8.9 min total) should be allowed to achieve a train of four
ratio of 0.9. Multiple dosing errors occurred. This highlights that suggamadex
might not have saved this patient in a CICV situation.
Rocuronium may delay appropriate post intubation analgesia, what is the
solution to this?
Effect of paralytic type on time to post-intubation sedative use in the
emergency department. Emerg Med J. 2013 Nov;30(11):893-5.
Retrospective case review of 200 intubations. 77% of patients were started on a
propofol or midazolam infusion, the remainder received bolus dosing of sedative
agents. Mean time to sedative administration was 27 vs 15 min for Rocuronium
vs Succinylcholine.
Long-acting neuromuscular blocker use during prehospital transport of
trauma patients. Air Med J. 2013 Jul-Aug;32(4):203-7.
51 trauma patients intubated in the prehospital setting. 42% of these patients
received a long acting neuromuscular blocker. Time to sedative use following
intubation was recorded. The LA-NMB group received sedatives less promptly
after intubation compared with those who did not receive LA-NMBs (16 vs. 7
minutes, respectively; P = .04).
Poor post intubation sedation and analgesia can easily be avoided by the use of
fentanyl with induction agent / neuromuscular blockade dosing, and a post
intubation checklist that includes identification of appropriate analgesia and
sedation administration.
What situations is succinylcholine still better than Rocuronium?
In situations where a rapid and timely neurological evaluation might change
management, the shorter duration of succinylcholine is preferred.
Examples include patients intubated for seizure control, patients with traumatic
intracerebral bleeds, stroke patients, and patients who have been intubated
following a cardiac arrest that need a neuro assessment to determine eligibility
for Targeted Temperature Management. EEG monitoring is essential for any
intubated seizure patient, and non-convulsive status is well described. Most
surgical intervention decisions for traumatic intracerebral bleeding are based on
available imaging studies, and not the clinical exam. Patients with strokes who
need intubation are likely to have higher NIHSS scores, and may be more likely
to have poor outcomes from TPA administration.
Securing a safe airway without desaturation or inducing hyperkalemic
complications trump these arguments. For short (30 min) transport times, it is
conceivable that the duration of neuromuscular blockade from Rocuronium
alone, compared to succinylcholine and then vecuronium would produce a more
favorable duration of paralysis with a patient emerging from their neuromuscular
blockade at the time of hospital arrival.
Have there been any prehospital studies, or emergency department based
studies comparing intubation success with Rocuronium vs
Succinylcholine?
Rocuronium versus succinylcholine in air medical rapid-sequence
intubation. Prehospital emergency care 2011;15:457-463
1045 intubations, 46% received Succinylcholine. There was an overall 59% First
pass success rate, 31% required 2 attempts and 7% required 3 or more
attempts. After propensity score adjustment, Succinylcholine was associated with
a higher incidence of first pass success (odds ratio 1.4 (1.1-1.8). First attempt
success with Rocuronium was 55% (50-59%) and 64% (59-68%) for
succinylcholine.
One possible explanation for the decreased first pass success could be the
potential impatience of the intubator to wait for optimum intubating conditions
before the first attempt. This could occur if the Rocuronium was taking longer to
achieve neuromuscular blockade than the succinylcholine. The first pass success
rates seem low in this study compared to a rate of 76% in a 2012 HEMS study.
Prehosp Emerg Care. 2012 Apr-Jun;16(2):293-8
Summary.
Rocuronium can produce optimum intubating conditions in a similar timeframe to
succinylcholine and has no significant contra-indications. Succinylcholine is not
safer than Rocuronium as its duration of action is likely to exceed the safe apnea
duration of most EMS / ED patients. Rocuronium has beneficial effects on the
safe apnea duration in our sick EMS and ED patients, and has the added benefit
of avoiding long acting neuromuscular blockade.
The use of Rocuronium with Ketamine provides an additional mathematical
benefit of similar weight-based dosing, decreasing the cognitive load of multiple
medication calculations during the preparation phase of RSI.
Final word:
Anaesthesia, 2009, 64 (suppl. 1) 73-81, Goodbye Suxamethonium!
A review intended to offer a eulogy for suxamethonium .
Additional References:
Is Rocuronium as effective as succinylcholine at facilitating laryngoscopy
during rapid sequence intubation?
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