Tasty Morsels of Critical Care 031 | Guillain-Barre Syndrome Part 2

11 Mar

Welcome back to the tasty morsels of critical care podcast. A meandering monologue through critical care fellowship exam preparation.

GBS management can be nicely split into disease specific management and ICU supportive care.

In terms of specific treatment this is something that has a reasonable evidentiary basis at this stage. The menu on offer is similar in appearance to many of the immune mediated disasters that appear in the ICU with steroids, IVIG, plasmapheresis and more recently mabs have all been studied.

IVIG is supported by a Cochrane review of randomised data and a major neuro society guideline, which is generally enough to persuade a non specialist like me mainly because I’m a very lazy man… The theory here is the usual hand wavy IVIG one – that within the massive of pool of donors (literally 1000s) that go into a bottle of IVIG there is sufficient neutralising antibody against the dodgy ones the body has produced along with a smorgasborad of other immune modulating effects we don’t really understand. Either way it works and seems to be fairly benign, if not a touch hard on the wallet.

Plasmapheresis (which involves spinning the blood in a big machine until the plasma separates out, then removing all the plasma and replacing the volume with some 5% albumin and letting the body reproduce all the other plasma components itself) is another treatment supported by a 2012 Cochrane review of randomised trials. The mechanism here is thought to be removal of the circulating antibody that is causing all the trouble. It also takes away all the associated complement that goes with it. Plasmapheresis is often delivered in 4-6 sessions. This had always confused me – why so many sessions? Is there ongoing antibody production needing treatment sessions?  The number of sessions primarily depends on the antibody type you’re going after. IgM typically spends all its time in the vascular space so after a session or two you’ve got rid of it all. IgG (which is probably what we’re going after here) has a larger Vd as such and as soon as you’ve washed it out of the vascular space it leaks back in again and plasma levels rise again. Hence the multiple sessions.

Presumably in GBS there is no ongoing antibody production as it is one of the few times in ICU plasmapheresis that you don’t need a heavy duty immunosuppressant to go along with it to stop ongoing antibody production. With regards to immunosuppression it is important to note that steroids do not work and should not be used.

The question at this stage remains as to which expensive treatment you should choose. There does not seem to be an advantage of one over the other so I think I would go for the one that does not need a 12F catheter in my neck.

Turning to supportive treatment there are a few important principles at play. Firstly is the question of when do we intubate these folk. This can be split into two parts

1) airway protection. Especially in the Miller-fisher type or if you start seeing any bulbar issues. It ould be a real shame to start a 6 week ventilation run with a bad and preventable aspiration.

2) respiratory failure. This is probably more at the fore front of our minds. Remember this is a very quiet and non distressed type of respiratory failure (unless cough goes then it’s a noisy rattly mess) where there simply isn’t any respiratory effort to increase the work of breathing. There are a few published indications for intubation and perhaps the most useful and oft quoted for exam purposes is a VC of <15ml/kg. In reality we’ll probably intubate along our usual guidance which is whenever we damn well want, especially if another team makes a polite suggestion that given the VC is less than 15ml/kg maybe we should possibly just maybe consider taking them to the ICU.

Given that the nadir of the illness is probably a month away it would seem reasonable to tube and trache and wake them up as soon as possible

A question on supportive care for GBS could be filled with FASTHUGS IN BED but a useful point to make is to look for autonomic dysfunction affecting about 10% of GBS with simple things like hypertension but it can be profound enough to need an emergent pacing wire so be prepared.

While the whole disease seems horrific it’s worth noting that 70% are independent at a year.

References:

Oh’s Manual Chapter 58

Both Deranged Physiology and LITFL have nice tables comparing GBS with other neuromuscular disorders. A favourite exam question.

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