In this episode, I’ll first review how Sux and Roc stack up in terms of onset, duration, efficacy, and safety. Then, I’ll explain the reason why Roc only rocks when you, Pharmacy Nation, are around. This discussion will be framed around the urgent need to establish an airway in a critical care setting. Elective and preoperative airway concerns are not a relevant part of this discussion. I’ve also included some links to other people debating the use of these 2 drugs for RSI at the end of this post.

The debate

For over a decade there has been a debate on whether it is better to use succinylcholine (Sux) or rocuronium (Roc) for rapid sequence intubation (RSI) in emergency settings.

I’m surprised when reading these debates by the lack of attention given to the time it takes for the patient to receive sedation after RSI.

Onset

As long as the right dose is used, Sux and Roc have essentially the same onset of action.

Sux is dosed at 1 to 1.5 mg/kg and works within 45 seconds.

Roc works within 45 seconds too but only if you give 1.2 mg/kg. Published dosing ranges from 0.6 mg/kg to 1.2 mg/kg but the lower doses have an onset that becomes progressively unmanageable for RSI the lower you get. Go big or go home.

Duration

Paralysis from Sux should be over in 10 minutes.

Paralysis from Roc may last up to 90 minutes.

The shorter duration of Sux is often touted as a safety benefit. The claim is that if the airway can’t be placed, the patient can be bagged and ventilated until the Sux wears off. This sounds reasonable and I used to believe it. But hearing others debate the 2 drugs made me look closer at whether the shorter duration of Sux was in fact a safety benefit:

Even with perfect pre-oxygenation conditions, a healthy patient will go at most 8 minutes before hypoxia sets in from the apnea caused by a paralytic. Your patient isn’t healthy though – they are critically ill and need an airway. And chances are high that because of this illness pre-oxygenation conditions are far from perfect. There is no such thing as “bagging them until the paralytic wears off” because after the paralytic wears off, they are still critically ill and still need an airway. So in this context there is no difference between Sux and Roc – once you paralyze the patient you are committed to establishing an airway within the next few minutes.

Neurologic exams are very limited until the paralytic wears off, so Sux does have an advantage over Roc here, but that is a very rare concern.

I’ll talk more about the duration in regards to time to sedation later but first let’s compare efficacy & safety.

Efficacy

Both Sux and Roc allow for a good chance at airway placement on the first try – there are no differences if you use the doses we discussed earlier.

Safety

I thought I had the safety differences between these two drugs straight until I got a bewildered stare from an anesthesiologist. Anesthesia was called to help intubate someone in my ICU and I had drawn up Roc in advance because the potassium was high. This is exactly what I told the doc when he asked for Sux. He asked how high the K was (5.2) and then gave me a puzzled look and asked again for the Sux. Why did he give me that strange look? I figured it out after I went back and reviewed the contraindications and precautions of these two drugs.

Roc doesn’t have a contraindication apart from allergy. It carries the same warnings/precautions as any other paralytic.

Sux on the other hand does have a list of contraindications: history of malignant hyperthermia, myopathies with elevated CPK, Acute phase of injury following burns, multiple trauma, denervation (stroke), crush injury, intra-abdominal sepsis.

Sux also has some additional warnings beyond the standard ones for a neuromuscular blocker such as hyperkalemia, bradycardia, and increased intraocular pressure.

I found that these contraindications were overblown in the Sux vs Roc debate. The potential risk from using Sux in these contraindications is catastrophic hyperkalemia unresponsive to resuscitative efforts. A reference that I know and trust, Rosen’s Emergency Medicine (Rosen’s), discusses these contraindications in detail. It turns out the period of concern for fatal hyperkalemia is >5 days after the burn, crush injury, denervation or intra-abdominal sepsis. This really narrows down the potential population with contraindications to Sux.

It also turns out that using Sux in the setting of preexisting hyperkalemia or renal failure doesn’t cause a problem (this is also covered in Rosen’s). Regular vanilla hyperkalemia from Sux gets treated the same as any other hyperkalemia.

After reading Rosen’s, I now understand why the anesthesiologist wasn’t impressed with a potassium of 5.2 as a reason to choose Roc over Sux. His assessment was that since problems are so rare outside of the specific contraindications for Sux, he would rather use what he was comfortable with (Sux) than switch to Roc for no good reason.

It is true that there are a handful of horror story-like case reports of Sux gone bad, and there are not any for Roc that don’t involve anaphylaxis. So using Roc for RSI is certainly the risk averse strategy, and as a pharmacist I do like being risk averse! But the contraindications and risks with Sux are so rare that the likelihood of anything going wrong with a specific patient is infinitesimal.

Why Roc only rocks when a pharmacist is in the house

There is one specific thing you should look out for as a pharmacist when Roc is being used for RSI: The time to sedation after RSI.

The duration of Sux matches up nicely with the duration of popular RSI induction agents such as etomidate, propofol, or ketamine. If you forget to administer continuous sedation, it won’t be long before the patient prompts you to do so; the vent will alarm, you’ll see movement, etc… But this is not the case with Roc – there will be no patient reminder to start sedation until up to 90 minutes has passed!

Is this just another minuscule difference blown up for the sake of winning a Roc vs. Sux argument? It turns out there is some actual data on this issue. Let’s review 4 studies on the issue:

Estimates of sedation in patients undergoing endotracheal intubation in US EDs

Published in 2013 in American Journal of Emergency Medicine, this retrospective cohort analysis found that less than half of patients in US emergency departments who underwent endotracheal intubation received sedation afterwards. Yikes! They may have been so sick they weren’t showing signs of needing sedation, but if they were paralyzed with Roc they wouldn’t have the chance to.

Long-acting neuromuscular paralysis without concurrent sedation in emergency care

This single center retrospective cohort described the frequency of patients receiving Roc without sedation afterwards as 18%!

Effect of paralytic type on time to post-intubation sedative use in the emergency department

This single center retrospective cohort showed that the time to sedation after Sux was 15 minutes, and the time to sedation after Roc was 27 minutes.

These 3 previous studies paint a disturbing picture of patients paralyzed after RSI but without sedation. In the only study that looked at Sux vs Roc, the time to sedation was almost double with Roc!

With that background, a very curious article was published in July 2015.

Impact of rocuronium and succinylcholine on sedation initiation after rapid sequence intubation

This article was the subject of a recent journal club at my hospital and was presented by pharmacy student Nicole.

It was another retrospective review but this time an extra variable was evaluated – the presence of a pharmacist during the RSI.

The mean time to sedation for the entire cohort was more than twice as long for Roc compared to Sux (34 min vs 16 min). But things get much more interesting when you examine the time to sedation based on whether or not a pharmacist was present. For Sux, a pharmacist being present reduced the time to sedation from 28 minutes to 12 minutes, and for Roc the pharmacist being present reduced time to sedation from 55 minutes to 23 minutes.

None of these studies attempted to look at hard end points such as whether the patient could recall being paralyzed but not sedated, or the onset of PTSD.

Now we have what appears to be a very clear difference between Roc & Sux, and a pharmacist at the bedside appears to mitigate that difference.

If you’ve ever been present for intubation of a critically ill patient, it becomes clear why having a pharmacist present would make a difference in time to sedation. Immediately after intubation the team is focused on confirming tube placement. After that the patient often has other management priorities, like addressing the hypotension that often follows endotracheal intubation, and addressing the underlying cause of the patient’s need for an airway. The pharmacist’s unique focus on the duration of action of the drugs given for RSI, and the need for continued sedation is just another way we can help take care of patients in critical care areas. Rather than waiting for the patient to move, buck the vent, or attempt to self extubate, the pharmacist can reach for the continuous sedation at the same time the rest of the team is looking at the end tidal CO2 detector.

Now we know – Roc only rocks if there is a pharmacist in the house!

Roc vs. Sux debate links:

Does Roc rock? Does Sux suck?

Sux vs Roc – why Sux still holds an edge in RSI

ROC ROCKS AND SUX SUCKS! WHY ROCURONIUM IS THE AGENT OF CHOICE FOR RSI

And many, many more…

If you like this post, check out my book – A Pharmacist’s Guide to Inpatient Medical Emergencies: How to respond to code blue, rapid response calls, and other medical emergencies.

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