rats with very low urine SG

Re: rats with very low urine SG

Mark Rowland — Tue, 07 May 2013 08:37:47 GMT

I wasnt allowed a pm, but a radiograph several hours after venepuncture demonstrated lots of consolidation on 1 side of the thorax. What we have to remember is that obese rats are used as a model for studies in type 2 diabetes in humans. Disorders in the coagulation pathways are documented with this condition as is the increases propensity for strokes. So with obese rats I warn the owners and try other sites first.. If I have to go fro the cvc I use an insulin syringe with rats. Carpenters Formulary gives a venepuncture volume of 5.5ml/kg as a safe draw for rats.

Re: rats with very low urine SG

CatherineThomas — Mon, 06 May 2013 22:05:30 GMT

[quote user="Mark Rowland"]

I have had 1 animal die following cranial cava puncture and it was a rat.

[/quote]

Do you know why? Do you do anything differently since?

Re: rats with very low urine SG

Mark Rowland — Mon, 06 May 2013 21:14:48 GMT

I have had 1 animal die following cranial cava puncture and it was a rat.

Re: rats with very low urine SG

John Flynn — Mon, 06 May 2013 20:18:58 GMT

Thanks Marie - that's interesting, especially about the increased circulating volume with obesity - I didn't know about this.

Re: rats with very low urine SG

Marie Kubiak — Sun, 05 May 2013 18:07:23 GMT

[quote user="John Flynn"]

Knowing next to nothing about rats (but I think they are great pets!) I find this fascinating stuff. Some questions though:

10ml sounds like a lot of blood from a rat - certainly way more than I would have assumed safe... assuming this is extrapolation from the 1% bodyweight rule, do you really see rats weighing a kg!
I appreciate that the 1% sounds like an arbitrary rule-of-thumb, but surely being obese doesn't increase the circulating volume and therefore the amount of blood that can safely be taken; do you mean that if you see an obese rat and want a blood sample you take 1% of your estimation of its lean bodyweight?
Sampling from the cranial vena cava - I've seen this kill the odd pig (admittedly done conscious) - does this ever happen if done in anaesthetised small furries?
Regarding dynamic testing, I don't see the need to give ACTH iv if that's the stimulating agent you're talking about; I do this out of habit in dogs, but as far as I know the intramuscular route is just as acceptable?

[/quote]

I agree - fantastic pets, much better for kids than rabbits or guinea pigs, if only people could get over the stigma of them being rats!

1. Yes, I have seen 1kg rats, and not just the giant Gambian pouched rats, just hideously obese dumbo rats. Fortunately they are rare, most are in the 300-600g bracket.

2. It is slightly arbitrary but appears to be a good rule of thumb and I take it as true bodyweight not lean bodyweight. Being obese does apparently increase the circulating blood volume quite significantly and certainly in humans this increased volume is cited as a contributing factor to obesity-related cardiac disease with increased preload +/- afterload putting greater strain on cardiac function.

3. I sample under sedation/anaesthesia to access the vena cava as I don't feel comfortable accessing a large vein in a very wriggly animal that is too small to fully restrain, and I like to make sure I can apply decent pressure after sampling without having to wrestle a conscious animal. We do this on a daily basis in a variety of small mammals and I have yet to have one die.

4. I'm not very clued up on dynamic testing as haven't done any canine/feline medicine for a good few years so will admit to having to go and look that up on the Synacthen data sheet and it does say that it can be given IM in humans so presumably this is a valid route in other mammals.Thanks for pointing that out, it does make the ACTH stimulation testing more feasible in smaller animals too.

Marie

Re: rats with very low urine SG

Suzanne Kelly — Mon, 29 Apr 2013 00:12:47 GMT

In dogs and cats if urine SG is < 1.008 it means the kidney is functioning well enough to dilute the urine. Is this the case in rats?

Suzanne

Re: rats with very low urine SG

John Flynn — Sat, 27 Apr 2013 16:53:31 GMT

[quote user="Marie Kubiak"]

So many pet rats are obese that I don't tend to heed this as a symptom any more! The SG is low and I've found that renal pathology (particularly amyloidosis) is a common histopathological finding with failure to concentrate. Unfortunately most pet rats don't get histo funded post-mortem so we don't have that many as confirmed diagnoses.

You can get blood from the tail vein in a conscious well-behaved rat, or also jugular or cranial vena cava in a sedated rat and can collect 1% body weight (so anywhere from 3-10ml depending on level of obesity!). The problem with dynamic testing is that you would need to be able to catheterise and give the stimulating agent IV which is tricky. You could look at measuring ALP (a supportive marker of Cushingoid disease in hamsters) and doing basal cortisol and urine cortisol:creatinine, as well as assessing renal function with bloods and urinalysis.

[/quote]

Knowing next to nothing about rats (but I think they are great pets!) I find this fascinating stuff. Some questions though:

10ml sounds like a lot of blood from a rat - certainly way more than I would have assumed safe... assuming this is extrapolation from the 1% bodyweight rule, do you really see rats weighing a kg!
I appreciate that the 1% sounds like an arbitrary rule-of-thumb, but surely being obese doesn't increase the circulating volume and therefore the amount of blood that can safely be taken; do you mean that if you see an obese rat and want a blood sample you take 1% of your estimation of its lean bodyweight?
Sampling from the cranial vena cava - I've seen this kill the odd pig (admittedly done conscious) - does this ever happen if done in anaesthetised small furries?
Regarding dynamic testing, I don't see the need to give ACTH iv if that's the stimulating agent you're talking about; I do this out of habit in dogs, but as far as I know the intramuscular route is just as acceptable?

Re: rats with very low urine SG

Marie Kubiak — Sat, 27 Apr 2013 14:56:05 GMT

Marie