Post-surgical neurological complications of portosystemic shunt surgery in cats and dogs: prevention and management
Post-ligation neurological syndrome (PLNS) remains a major frustration. It’s gratifying that we are increasingly able to diagnose and close shunts but equally heart-breaking when everything goes pear-shaped post-op. The spectre of a horrible week of distressing, potentially very expensive and frequently-fatal seizuring in intensive care complicates the whole decision-making process. There’s an obvious need to discuss possible complications frankly with owners and, because of this, many go un-operated.
The frequency of PLNS varies considerably between reports: anything from 0-20% in dogs, 13-37% in cats. Onset of seizures may be anything up to 10 days post-op. Summarised in Heidenreich et al.:
J Vet Emerg Crit Care (San Antonio). 2016 Nov;26(6):831-836. doi: 10.1111/vec.12431. Epub 2015 Dec 18.
Successful treatment of refractory seizures with phenobarbital, propofol, and medetomidine following congenital portosystemic shunt ligation in a dog.
Heidenreich DC, Giordano P, Kirby BM
https://onlinelibrary.wiley.com/doi/abs/10.1111/vec.12431
The publication of this paper ushered in a period of optimism. A few years earlier the prospect that we might have an effective prophylactic in levetiracetam arose:
J Vet Intern Med. 2011 Nov-Dec;25(6):1379-84.
Incidence of postoperative seizures with and without levetiracetam pretreatment in dogs undergoing portosystemic shunt attenuation.
Fryer KJ1, Levine JM, Peycke LE, Thompson JA, Cohen ND.
https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1939-1676.2011.00819.x
…and now we had a means to rescue any who slipped through that net.
There’s very little published since then on how this is all working out in practice. However, our own experience reveals that before the advent of levetiracetam we operated 26 dogs with only one, non-fatal PLNS. With routine pre-op levetiracetam we have seen 2/21 suffer fatal seizures which proved uncontrollable despite the use of medetomidine.
In cats, there appears to be nothing published on the use on levetiracetam for shunt surgery but, in articles, relating to its use in this species in other scenarios there is no suggestion of untoward adverse effects.
J Vet Intern Med. 2018 May;32(3):1145-1148. doi: 10.1111/jvim.15129. Epub 2018 Apr 19.
Serum levetiracetam concentrations and adverse events after multiple dose extended release levetiracetam administration to healthy cats.
Barnes Heller H1, Granick M1, Van Hesteren M1, Boothe DM2.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5980453/
Since the publication of this article we have used levetiracetam pre-operatively in three cats undergoing shunt attentuation. 1/3 suffered fatal PLNS.
OK, so what to do when faced with a neurological post-surgical scenario?
- Check for hypoglycaemia: this usually improves once they have eaten. Prior to this it may be necessary to administer i.v. dextrose or even, anecdotally, i.v. dexamethasone 0.02-0.05mg/Kg
- If the patient received levetiracetam pre-op then it is probably sensible to continue. If they weren’t on it pre-op then add it now. Levetiracetam is available as an injectable solution for infusion.
- start a propofol CRI (dose to effect; 0.01-0.25mg/kg/min) for at least 24 hrs to maintain a semi-comatose state.
- Karen Tobias suggests mannitol infusions once or twice daily
- start phenobarbitone i.v. whilst on propofol CRI
- medetomidine/dexmedetomidine: Heidenreich used a medetomidine CRI dose of 0.016 microgrammes/kg/min in addition to a pre-existing propofol CRI.
- ACP is another option
- Benzodiazepines (diazepam, midazolam): firstly it is generally agreed that these are ineffective in PLNS scenarios. Secondly they may exacerbate hepatic encephalopathy.
- if the patient is not able to eat within 24-48 hrs then start tube feeding
- nursing care should include frequent turning and physiotherapy
It’s important to note that the dog successfully managed by Heidenreich et al. was hospitalised for 25 days!!. This is the kind of information which needs to be factored into pre-op discussion.
