December 2018

ISOFLURANE SHORTAGE-SOME ADVICE AND TIPS

Monday, December 17, 2018

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If you need help for a specific case please do not hesitate to contact us, the question will be passed on to Karen and she will try to help you as best as she can. The following is a guide that you can use but each patient is an individual that should be assessed and a decision based on their history and clinical examination.

It is not ideal to have to change the way you anaesthetise your patients so quickly, so where at all possible keep it as similar to the way you usually do things if you can. To help vets continue to work normally during the isoflurane shortage here are some tips:

  • Use premeds, where appropriate, that will help to reduce your isoflurane consumption e.g. medetomidine combinations such as medetomidine, ketamine and methadone. This will mean that you will need less propofol or alfaxalone to induce anaesthesia and also less isoflurane to maintain anaesthesia.
    • Remember that duration of action of medetomidine will depend on dose, so if using low doses such as 1-5mcg/kg/min for longer procedures they may become lighter as this wears off
  • Use local anaesthetic blocks- if people want some info on blocks BSAVA manual is good or email me on info@eyevetclinic.co.uk and I can send you some more detailed information
  • Use low flow anaesthesia where at all possible.
    • Many circle breathing systems these days can be easily used as low as 5kg. It is better to use narrow bore tubing (15mm) for patients between 5-10kg.
    • Narrow bore tubing are available from wholesalers such as ACE veterinary and JAK
    • Circle systems should have light valves to minimise resistance, commercially available ones include the Cycloflo and the daisy wheel type
    • If using a circle at the beginning of anaesthesia have a higher flow for approximately 10 minutes to allow the removal of nitrogen that is normally in the airways of all patients
    • Then reduce down to 0.5-1L/min, the minimum is 10ml/kg/min but vaporisers become less accurate the lower the flow, so I wouldn’t go lower than 0.5L/min
    • Remember the change in depth of anaesthesia will be slower with these lower flows so if you want to rapidly change depth turn the oxygen flow up for a few minutes
  • Change to sevoflurane
    • This may be easier said than done!
    • You will need a sevoflurane specific vaporiser, this may be possible from Zoetis but they are likely to be overwhelmed at the moment.
    • Alternatively, you can buy a sevoflurane vaporiser from some of the used equipment companies such as Freelance Surgical. You will then need to source the sevoflurane.
    • It may be difficult to access sevoflurane easily as the demand will go up
  • Using Sevoflurane
    • It is very much more expensive than isoflurane!
    • It has a higher MAC- this means that you will have to have a higher level on the vaporiser dial in order to maintain an adequate depth of anaesthesia (3.5-4.5%)
    • Tailor the amount to each patient
    • Depth of anaesthesia will change a bit more rapidly than with isoflurane
    • Use LOW FLOW ANAESTHESIA to help reduce the cost to you
    • Disconnect the circle breathing systems from the machine when you are finished for the day.
  • Partial or total intravenous anaesthesia
    • IT is again going to be expensive to use total intravenous anaesthesia alone
    • Use adequate premeds to reduce the maintenance requirements
    • You may be able to combine with a CRI of methadone or a combination of drugs
    • BSAVA have some information on their website and access to the total intravenous anaesthesia chapter of the manual https://www.bsava.com/News/ArticleID/2535/Isoflurane-supply
  • Propofol
    • Don’t use the propofol with preservative!
    • You may see lower heart rates than you are used to- don’t be alarmed
    • Recovery is likely to take a bit longer as they will need to metabolize the drug to recover
    • Avoid using in cats as they have problems metabolising it and will have very prolonged recoveries
  • Alfaxlone
    • I have only used this a couple of times
    • Sometimes they can be a bit twitchy particularly in recovery
    • If they are twitchy in recovery, try to minimize stimulation. Touching them can sometimes make it worse
      • This can be used in cats

I am also putting a link to an easy way to make up CRIs including alfaxalone and propofol click here.