Thread by @GasNovice

This thread is all about Monitoring Neuromuscular Blockers (NMBs) for anaesthetic novices

I think this is often underplayed in clinical practice and we can be lazy

I’ll start with this summary infographic and elaborate as we go along.

#anaesthesia #novice
1/n

NMBs are not benign drugs. Their use (or lingering effect) is associated with:
- Risk of awareness (NAP5)
- Laryngeal weakness
- Aspiration
- Patient distress
- Adverse airway events
- Reduced hypoxic drive

…all of which we want to avoid and shouldn't leave for the PACU

2/n

The duration of action quoted for NMBs is the duration until recovery to 25% of original twitch height (roughly just after the 4th twitch is visible as far as I can tell)

Not time to full function
Not time to elimination
Not time to extubation
doi.org/10.1213/000005…

3/n

Don't assume the NMBs have just “worn off”.
Left to their own destiny, around 30% of patients will have a level of NMB that is not suitable for extubation even after 2 hours
doi.org/10.1093/bja/ae…

4/n

Clinical signs for resolution of blockade:
- Sustained head lift for 5s
- VC breaths of 10ml/kg
- 25cmH2O inspiratory pressure generation

…are unreliable

5/n

We can’t accurately measure the train of 4 fade by eye.
doi.org/10.1097/000005…
So don’t try to do it yourself

6/n

We therefore need qualitative ways to measure the NMJ function – so we use nerve stimulators to assess the response of certain muscle groups to depolarisation – "train of 4"

Counting To4 will determine when we can give reversal. qualitative means will determine extubation

7/n

Accepted practice is to give neostigmine (+glycopyrronium) when we can see at least 3 twitches
doi.org/10.1097/000005…
If using suggamadex and Roc, then give either:
16mg/kg to reverse immediately,
4mg/kg when at least 1 PTC or
2mg/kg if To4>2
From doi.org/10.1111/anae.1…

8/n

The mean time for neostigmine to have an effect is 17mins!! (8.3 – 46.2min range). So you have to time it
doi.org/10.1097/000005…

Extubation only when To4 ratio is 90%

9/n

It matters where you put the electrodes.
Put cathode (black) distally, closest to nerve - to depolarise rather than hyperpolarise.
Ulnar nerve correlates best with upper airway muscles.
Using max mA current may stimulate the muscle directly (false positive)

10/n

So compelling is the evidence for quantitative monitoring that it is a monitoring requirement per the 2021 AAGBI guidelines to monitor throughout anaesthesia
Before giving NMB
Before waking and extubation
doi.org/10.1111/anae.1…

11/n