Dear Puppy, Please Don't Drink So Much Water Or You Might Seizure?

So this is some interesting stuff – well, I think so anyway! I want to thank my good friend Kate Russell for raising this with me as well. The basic question at hand here is can a puppy drink so much water in a single episode as to cause water intoxication and a hyponatraemic seizure?
 

Theory Refresher

Before I get into that, a quick reminder about the theory around hyponatraemia. Essentially the clinical consequences are meant to be more related to the speed of onset than the absolute decrease. Sodium is the main osmotically active substance in the body:

  • If hyponatraemia of sufficient severity develops quickly enough ((per)acutely) water will move out of the extracellular space into the cells of the central nervous system*; cerebral oedema occurs with subsequent neurological signs. These signs can vary but seizures are possible.
  • If hyponatraemia develops more slowly (chronically) then the brain has time to ‘defend’ itself which it does by losing potassium and other osmotically active particles (organic osmolytes) from the cells; this means that there is less of an osmotic gradient and less tendency for water to move into the cells.

[*Remember ‘osmosis’? Essentially the tendency for water to move from an area of low concentration of osmotically active particles (more dilute) through a semipermeable membrane (like a cell membrane) to an area where there is a higher concentration of osmotically active particles.]

Back to the point

Phew. Okay with that theory out the way, what am I going on about in this blog? Well Kate recently saw a crossbreed puppy, a few weeks old, that by all accounts had been fine until the day of presentation; let me say from now, no other historical signs suggestive of a portosystemic shunt. On that day the puppy drank ‘a lot of water’ and then vomited a couple of times. In the hours that followed she worsened becoming more lethargic until shortly after presenting to the clinic 5 hours after drinking the water, she started to have generalised seizures. The most – and more or less only – noteworthy finding on emergency database blood tests was a marked hyponatraemia of 124 mmol/l (reference interval 139-150 mmol/l); mild hyperglycaemia – definitely no hypoglycaemia. To the best of my knowledge, plasma sodium concentration in a puppy of this age is the same as for adult dogs. Anticonvulsive therapy was implemented, the hyponatraemia was corrected, the puppy slept off the drugs (!) with no further seizure activity and as far as I know is doing fine now with no recurrence.

Kate and I are also aware of another case, that time a German Shepherd puppy, with basically exactly the same history/clinical story, diagnosed marked hyponatraemia presumed to be acute in onset, same therapy and the same progression.

So back to my question, did both these puppies drink so much water in a single episode as to cause water intoxication and a hyponatraemic seizure?

A few things to say from briefly exploring online but I guess overall I am saying that yes, in theory, this could be the case..it may not seem very probable but it certainly seems possible..to me anyway...you?

Acute water intoxication is meant to be more likely if for some reason the animal is unable to adequately excrete the excess water consumed. This was induced for example experimentally in dogs given vasopressin at the time of the water load. As far as I know puppies if anything have reduced urine concentrating ability relative to adult animals, i.e. they excrete more dilute urine, rather than retain excess water. So they should not be more prone to retaining excess water consumed.

There is one* clinical case in the literature of an adult Labrador retriever who developed acute hyponatraemia (125 mmol/l) and acute neurological signs (coma) after swimming for many hours in a lake. Marked diuresis occurred spontaneously and the patient recovered with supportive care. This suggests that the dog was able to suppress vasopressin (anti-diuretic hormone) release in response to the water load…so I guess maybe this response was delayed in onset, ‘took a while to get going’? Was this what occurred with our puppies? I am not aware of diuresis being noted in either case. But maybe the vomiting that followed the water consumption relatively caused them to lose more sodium than water??

[* Toll J, Barr SC, Hickford FH. Acute water intoxication in a dog. J Vet Emerg Crit Care 1999. 9:19.]

I did find some reports in calves that were given ad lib access to water for the first time where acute water intoxication led to clinically significant hyponatraemia; but actually red cell lysis due to changes in plasma osmolality with haemoglobinaemia/haemoglobinuria seemed to be the more notable development.

I did find plentiful mention of hyponatraemic seizures in human infants that were inadvertently given low solute drinks/feed at home, especially with concurrent vomiting/diarrhoea and hence sodium loss – but diving into the reports this was at least over a few days not a one-off episode.

Psychogenic polydipsia is one of the differentials for normovolaemic hyponatraemia – but there we are talking about recurrent episodes of excessive water consumption and a chronic hyponatraemia that can be acutely decompensated by a suitable trigger. These puppies mentioned above did not have that in their life stories.

I don’t think our puppies had syndrome of inappropriate antidiuresis.

There are also lots of reports of humans drinking too much water during endurance events resulting in clinically significant acute hyponatraemia – but again I believe this is over hours-days, multiple episodes of water intake.

Anyway, that’s me done. If I am over-complicating this, if anyone knows any references I have not uncovered, if anyone can shed any more light or discussion…as always, please do!

Thanks.

ADDENDUM:

See further discussion about this HERE.

Choppy Choppy! My Top 5 Surgery Tips (N. Kulendra DipECVS)

STOP THE PRESS! This blog edition is my first ever guest blogger post! Love it. Here Nicola Kulendra, European Specialist in Small Animal Surgery and a dear friend and colleague, shares some of her top surgery tips for you. Also be sure to look out for the free PDF giveaway at the end which contains some other points relating to Soft Tissue Surgery (that is my creation, not Nicola's).
 

My top 5 surgery tips!

  1. Don't Panic! If the abdomen is pooling with blood after a bitch spay, stay calm and compose yourself.  The dog won't bleed out immediately, you have time to enlarge your incision, perform the duodenal/colonic manoeuvre to find your stump.  If you can see the caudal pole of the kidney, your bleeding vessel won’t be far away so pack some swabs in and then use a small haemostat to grab your bleeder.
  2. Never close a wound with tension. If by the time you are placing skin sutures, there is a lot of tension across your wound then it's probably the wrong decision to close it.  You can take the tension away in deeper tissues but if you are relying on the skin sutures to hold the tension then they will likely fail. It is better to leave the wound open or think about other techniques to close it, such as a local subdermal plexus flap or axial pattern flap.  Remember, it is very rare to have to do an emergency skin flap so if in doubt, take some pictures and ask a colleague/specialist for tips.
  3. Intestinal foreign bodies - always do a full ex-lap.  Any animal that eats a peach stone has a higher chance of eating another inappropriately-sized object so always do a full ex-lap with an incision from the sternum to the pubis.  Always make sure you check the stomach proximally to the level of the oesophagus and the intestinal tract caudally to the colon.  However, if an object has arrived at the colon then it is likely that it will make it to the anus. It is very rare to have to do a colotomy to remove a foreign object – if you find yourself about to do this, stop, take a moment to rethink, you sure?
  4. RTA with multiple pelvic fractures/abdominal trauma?  Don't forget the urinary tract!  Just because you can palpate a bladder doesn't mean it's not ruptured.  In addition, it can take many hours for azotaemia to develop so you may not see anything on blood work immediately.  A retrograde study is fairly easy to perform and should be performed if there is any doubt as to the integrity of the urinary tract. 
  5. Open fractures.  If you have a patient with an open fracture, give him/her analgesia and if stable perform a very wide hair clip with sterile lubricant such as KY Jelly in the wound.  Next scrub the skin with dilute chlorhexidine/iodine again with your lubricant as a barrier in the wound.  Next thoroughly lavage the wound with a green 21-gauge needle, 20 ml syringe and sterile saline/Hartmann’s solution.  Cover the wound with a sterile dressing such as Allevyn® or Melolin®. If the wound is heavily contaminated consider a wet-to-dry dressing. Place a Robert Jones if the fracture is below the elbow or stifle.


Nicola Kulendra BVetMed (Hons) MVetMed CertVDI DipECVS MRCVS
European Specialist in Small Animal Surgery

Fancy some more bits of Soft Tissue Surgery content? PLEASE CLICK HERE for a FREE PDF entitled Soft Tissue Surgery: Ten Random Points!

Syringe feeding: Yes, No, or It depends?

A while back I recorded a podcast on nutrition in sick animals with Dan Chan DACVECC DACVN, Head of Emergency and Critical Care (ECC) at the Queen Mother Hospital for Animals, Royal Veterinary College, UK. The podcast is linked to at the end of this blog post. One of the things we discussed in that podcast was the use of syringe feeding.
 

Question

I recently received an email from an RVC graduate who is now working in practice in which she wrote:

“I had a question after listening to the podcast 'Nutrition in sick animals'. It is about syringe feeding, the hospital I currently work in routinely syringe feed, being an RVC graduate I am on the fence in regards to this issue after being taught at the QMH not to syringe feed.

My question is in certain circumstances I can see why syringe feeing can be useful and I was just wondering how the QMH overcome these situations without syringe feeding.
My main example is if a patient in the hospital is too nervous or sometimes scared to eat, you have tried hand feeding and encourage the owners to come in and feed them, possibly even attempting appetite stimulators (e.g. mirtazapine). What would be the next step if the animal still refused to eat? In this instant would placing a feeding tube be the next step?”

My response

To which I replied focusing only on enteral (not mentioning parenteral) nutrition:

“Nice to hear from you and glad you are listening to the podcasts. In answer to your questions, what I would say is the following...

So obviously the reason that one might be considering syringe feeding is because you are worried that the patient is not receiving sufficient nutrition and that this carries potential adverse effects - as discussed in the podcast. Then you have to ask yourself whether syringe feeding is a strategy that will be able to improve this situation as always using a risk/harm-benefit assessment:

  • So on the benefit side, it may result in the patient receiving more nutrition; it is also cheap and does not require any fancy equipment or much in the way of skilled training to do - although clearly people need to know what they are doing.
  • On the risk/harm side, it is extremely unlikely that you will be able to give the patient their calorific requirement via this route - but you could say, reasonably, "well something is better than nothing".
  • But even more on the risk/harm side is the negative experience for the patient: if as you say the patient is already too nervous or scared to eat on their own, will syringing food into them help their state of well-being more than if they just did not get any nutrition? If the patient is really not compliant and requires restraint/forcing clearly this is even worse - but I am sure (most) people would not push it that far. And of course they may not be eating because they feel too ill or nauseous so making them is not very pleasant and they can develop food aversion - as Dan says, whenever having food is a negative experience this is a risk.
  • And then there is the risk - albeit I don't think a very big one - of aspiration. And we need to bear contraindications in mind, e.g. facial injuries, inability to swallow etc.


BUT there are certainly animals where one or two episodes of syringe feeding seems to prompt them to start eating on their own - whether it is because they overcome their nervousness or some other psychological or physiological 'block'. And so in suitable cases where all you are trying to do is to see if you can kick-start the patient to eat themselves, then trying this once or twice at a push does not seem unreasonable - but very much on an individual case by case basis bearing in mind everything I have said above about that individual patient's circumstances, what your intended purpose is and what the risk/harm-benefit assessment is.

What I would do if the patient was not willing/able to nourish him/herself adequately would depend on the patient in question...Options:

1. If the patient is doing well in all other respects other than lack of nutrition, then although we understand and support the need for early nutrition, on this individual occasion we may choose to just tolerate the status quo. This would typically be a patient that we anticipate sending home very soon and in which the morbidity was not significant (e.g. say a post-TPLO patient or something like that).

2. Same as option 1. but actually can we send the patient home sooner than we maybe would have otherwise to see whether things improve? This might for example mean a different analgesia strategy to go home with but can we make it happen? Are the clients willing to provide more home care than originally discussed?

3. And yes in a number of cases where nutrition is insufficient and the patient is nowhere near ready to even trial home discharge, feeding tube.

I might be wrong but I imagine there are more patients in category 1. or 2. where you work in first opinion than say at a tertiary referral centre like the QMHA.

Feeding tubes of whatever sort are obviously going to cost more than syringe feeding but there may also be some cost-saving in quicker healing and recovery. Also the vast majority of patients tolerate the tubes and the feeding well. Naso-oesophageal less so than oesophageal/gastric but even so. And placement will require anything from mild sedation to general anaesthesia depending on the tube in question.

Often we will place feeding tubes - especially oesophageal - pre-emptively if the patient is having anaesthesia for a procedure and we anticipate that they are unlikely to eat and nutrition will be an issue. So for example the surgeons might place an oesophagostomy tube when they are fixing fractures in RTA cats on the basis that the benefits of having the tube there outweigh the fact that we may not use it. BUT we also have cases where the patient is eating something on their own but not enough and we can then use the tube to top up their intake.

Does that help at all?”

I am as always very interested to hear your thoughts on this.

The podcast episode in question can be accessed here.

AND if you would like a PDF document entitled Top Ten Tips on Nutrition in Sick Animals derived from this podcast PLEASE CLICK HERE