What vegans should know pre-operatively

Most people will have surgery at some point in their life, vegans included.  Whether elective or an emergency, this can be a difficult and frightening time with many people being anxious about both the operation and their anaesthetic. Therefore it is not surprising that the last thing on a patients mind is the type of anaesthetic they will receive.

Many people consider “anaesthetic” to be just one thing. In fact, an anaesthetic comprises several different types of drug of which numerous different varieties exist. 

When I first began my anaesthetic training a senior colleague explained this to me using the analogy of baking. Giving an anaesthetic is very much like baking a cake. Broadly speaking, a cake requires three things; flour, sugar and fat.  A general anaesthetic usually also requires three things; 1) a drug to render the patient unconscious, 2) a pain killer and 3) a muscle relaxant- the latter being optional depending on the procedure. This is known within the profession as “the triad of anaesthesia”1. 

To expand the analogy further, just as you can bake a cake with many different types of flour/sugar/fat, which all have different flavours and textures, are vegan or not, it is possible to give an anaesthetic using different types of drug. They all have their differing properties with regards to their onset times, duration of action, side effects etc but on the whole they are quite similar. The number of combinations of anaesthetic drugs is beyond count, almost like the number of types of cakes are innumerable. Then added to the basic mix, there are the non-essential, but good to have, extras too. With cake it might be chocolate, fruit or icing, with anaesthetic it is often intravenous fluids, anti-sickness drugs and local anaesthetic.

So, you’re thinking, just tell me which drugs are and aren’t vegan! Well, whilst I could do that, and I will,* unfortunately, it is not as simple as just substituting “X” for “Y”. Following five years of undergraduate medical school training and two years of general junior doctor training, anaesthetists train for a minimum of seven or more years and take several specialist post-graduate exams in anaesthesia to be able to navigate the subtleties of the speciality.  Both patient factors and surgical factors have to be taken into account when making these decisions and so I’m hoping that this article will give vegans simply a starting point to discuss their options with their anaesthetist. This is particularly important as many anaesthetists have a selection of favourite “recipes” they like to follow and they will need some notice, at the pre-operative stage, if they are to modify these.

To start with let’s talk about which anaesthetic drugs are vegan friendly, which thankfully is the majority of them:

*Please bear in mind that no drug currently in use in the UK is technically fully vegan given they will all have been tested on animals during their development. If you are interested in supporting the move away from this practice- visit Animal Free Research (formerly Dr Hadwen Trust). 

So, with so many vegan options available, what is the problem? Well, firstly the most commonly used anaesthetic agent is called propofol 2. It is the default position for most anaesthetists and it is highly unlikely you will be asked your views on the use of animal products in anaesthesia prior to the operation. It can be used as an “induction agent” to put you to sleep or as maintenance to keep you asleep as a continuous infusion. It’s a good drug in that it works very quickly and reliably to put people to sleep. Also, it is the best drug to have for minor procedures as it is well cleared from the body but also because it depresses laryngeal reflexes (those that cause coughing and gagging) and allows for the placement of a supra-glottic airway (a breathing tube that sits above the vocal cords as opposed to one that goes through the cords and thus usually requires the use of a muscle relaxant.) Unfortunately the drug is carried in a mixture containing egg, as is another anaesthetic drug called etomidate, although this is much more rarely used due to its depressant effects on adrenal gland function.  Knowing the pharmaceutical industry I highly doubt they would use free range egg, thus affecting vegetarians too. So, what are the options to avoid propofol? 

1. Use a different intravenous induction agent e.g. thiopentone/ketamine. This is no problem if your operation or medical history already requires you to have muscle relaxant. 
2. Have a “gas induction” to go to sleep i.e. deep breath on anaesthetic gas e.g. sevoflurane. A good option if your operation/medical history allows you to have a supra-glottic airway tube. It takes longer (a couple of minutes rather than a few seconds) to go to sleep- and has a bit of a funny chemical smell but it’s a common choice for kids. Note this can be unsafe in emergency situations or if you suffer from acid reflux. 
3. Have your operation awake using a local anaesthetic technique e.g. a spinal anaesthetic/ epidural/regional block +/- sedation e.g. midazolam. This is a good option if you operation is expected to last less than a few hours and is on the periphery of the body i.e. this is not really an option for most heart/lung/bowel/brain surgery.

The other non-vegan thing you are likely to be given if unwell is a group of fluids called colloids. These can crop up in any hospital setting not just anaesthesia. They contain big molecules thought to increase blood pressure when given intravenously. One group contains vegan friendly starches but the other contains gelatines. They have trade names like gelospan® and gelofusin. These are a group of fluids you can fully and easily avoid. They have no proven benefit over and above the above named crystalloid fluids and in fact there is evidence to suggest harm 3 including problems with kidney injury, bleeding and chronic itching. Interestingly, this is also true of the vegan friendly starches which have largely been removed from clinical practice.4 

Crystalloids are therefore the mainstay of most hospitals fluids. Traditionally normal (0.9%) saline has been the commonest fluid used, however, it can cause a raised chloride level in the blood which is an acid and leads to problems with a low pH. Therefore manufacturers have moved to “physiologically balanced” solutions such as Plasma-Ltye148® and Hartmanns solution. The former is vegan but the latter may not be depending on the manufacturer. Baxters Hartmanns solution is safe but others may not be. A fact even I did not know prior to writing this article so do not expect your anaesthetist to be aware of this either. Hartmanns solution is also called “lactated  ringers solution” and as the name suggests it contains lactate (as does the anti-sickness drug cyclizine) created using a base which can sometimes be milk. Whilst the two fluids are roughly equal in efficacy, sadly it is unlikely to be as simple as requesting Plasma-Lyte148®, as most hospitals bulk buy to keep costs low and each institution is likely to have an exclusive contract for one or another of the fluids. Your choice may be between a balanced solution (including non-Baxters Hartmanns) or normal saline. This is a judgement call as whilst normal saline is considered to be inferior to a balanced solution, most operations only lead to the administration of small amounts of fluid, and it is generally only large volumes that lead to problems. 

Ok, now a word about intensive care- ICU. If someone is critically ill and on a ventilator they are nearly always sedated with propofol.  Its advantage in this situation is that it doesn’t accumulate much in the tissues meaning it wears off relatively quickly when you switch the infusion off.  So, what’s the alternative?  Well, we can go back to using what we used prior to propofols relatively recent invention (1977). We can sedate with midazolam and an opiate (see above table). This combination has a long safety record and as such is still the first choice in paediatric (childrens) intensive care. It is inferior in its offset time, however it does have the advantage of avoiding the risk of “propofol infusion syndrome5 (where fatty lipids build up in the blood and lead to liver, kidney and heart damage.) that can occur after prolonged infusions. 

The other common issue I have come across on ICU is feeding the unconscious patient. We usually give a liquid feed down a tube in the nose down into the stomach. The vast majority of these feeds contain cows’ milk. There is a soya based alternative- Nutrison-Soya®. However, this will probably have to be ordered in as it won’t be kept in stock. Also, because of how its vitamin D is sourced it is not vegan. I would argue the latter is better than the former, however, each individual must make their own decision about what is acceptable to them. I have heard that there have been instances where soya milk was used in isolation instead for those wishing to remain strictly vegan, however, this is nutritionally inferior which could impair recovery.

In summary, The Vegan Society states that being vegan should be “as far as is possible and practicable”6. I feel that it is perfectly reasonable to want to avoid animal products in this context, it is also perfectly practicable in the anaesthetic context, as all these drugs live in the same cupboard, it just requires a conversation about what you are and are not willing to accept. As an anaesthetist I know I could achieve an animal product free anaesthetic for myself and I hope this article will help you achieve this too. Every patient who has mental capacity has an absolute legal right to refuse any treatment they wish even if the doctor considers this refusal to be unwise, this is the ethical principle of autonomy, and any doctor who overrides this could be prosecuted for assault. Just make sure you are clear about what you are and are not happy with and ask for this to be documented in your notes and on your drug chart. 

Dr Charlotte Houltram MBChB FRCA (Fellow of the Royal college of Anaesthetists) ST5 in anaesthesia & Intensive Care Medicine, Reviewed by Samantha Fry MRPharmS (Member of the Royal Pharmaceutical Society) Clinical diploma, Hospital Pharmacist.

All enquiries to cmhoultram[at]doctors.net[dot]uk

References

1. http://www.frca.co.uk/article.aspx?articleid=100504

2. https://www.medicines.org.uk search- SPC Diprivan

3. Cochrane Review: Are colloids more effective than crystalloids in reducing death in people who are critically ill or injured? Published: 28 February 2013 Authors:  Perel P, Roberts I, Ker K

4. www.gov.uk/drug-safety-update/hydroxethyl-starch-intravenous-infusions

5. https://bnf.nice.org.uk/drug/propofol.html#medicinalForm

6. https://www.vegansociety.com/go-vegan/definition-veganism