Anaesthesia for Feline Nephrectomy

RE: Anaesthesia for Feline Nephrectomy

Andrew Kent — Sun, 12 Apr 2020 20:42:23 GMT

[quote userid="11308" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221660"]Is any increase in ionised calcium significant? Cat is still fine in itself.[/quote]

I guess there are scales of significant. Certainly it is likely this is a contributing factor to calcium oxalate stone formation. Its not sky high and will likely represent idiopathic hypercalcaemia but it is of note.

Andy

RE: Anaesthesia for Feline Nephrectomy

Anthony Dennison — Sat, 11 Apr 2020 13:57:00 GMT

Update on the case - ionised calcium is 1.59 (ref range 1-1.4) so is confirmed high. Unfortunately we missed the weekly PTH testing run so will have to wait until next week for that.

Is any increase in ionised calcium significant? Cat is still fine in itself.

RE: Anaesthesia for Feline Nephrectomy

Andrew Kent — Thu, 02 Apr 2020 18:37:38 GMT

[quote userid="5904" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221358"]For sure, and see if you can find out the likely stone composition so you can begin dissolving it....[/quote]

They are almost invariably calcium oxalate so not dissolvable and frequently recurrent even with aggressive management.

RE: Anaesthesia for Feline Nephrectomy

Anthony Todd — Thu, 02 Apr 2020 18:18:14 GMT

[quote userid="2451" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221206"]In the first instance I get these cats onto a wet urinary tract diet + extra water.[/quote]

For sure, and see if you can find out the likely stone composition so you can begin dissolving it....

RE: Anaesthesia for Feline Nephrectomy

Anthony Todd — Thu, 02 Apr 2020 18:13:17 GMT

[quote userid="2451" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221192"] stone forming cats are at high risk of obstruction on the other side[/quote]

Not if you feed the appropriate diet......

RE: Anaesthesia for Feline Nephrectomy

paolovet — Tue, 31 Mar 2020 12:48:27 GMT

I fully subscribe to all the considerations made by Karl Bradbrook on the intensity of pain generated during kidney surgery. For analgesia, CRI of Ketamine or Fentanyl (I agree for minimum dosages) is an excellent option. Abdominal cavity washing with lidocaine or bupivacaine (maximum 2 mg / kg total) diluted, instilled and then drained after movement of the abdomen (1/4 of the total calculated as anesthesia on the incision line and the rest of the intra-cavity) could also be considered.

RE: Anaesthesia for Feline Nephrectomy

Anthony Dennison — Tue, 31 Mar 2020 12:05:22 GMT

[quote userid="12930" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221207"]What an interesting and instructive thread - thanks very much for posting, it Anthony, especially taking the time to post the xrays and your lovely detailed scans.[/quote]

Thankyou, but all the thanks go to Andy and Carl for their quick and helpful advice!

RE: Anaesthesia for Feline Nephrectomy

Beats — Tue, 31 Mar 2020 11:51:35 GMT

What an interesting and instructive thread - thanks very much for posting, it Anthony, especially taking the time to post the xrays and your lovely detailed scans.

RE: Anaesthesia for Feline Nephrectomy

Andrew Kent — Tue, 31 Mar 2020 11:44:33 GMT

Thanks for the update Anthony - we sometimes wonder in these cases with renal asymmetry if there has been a previous/resolved obstruction but I agree from what you describe it does not sound like this cat is currently obstructed.

[quote userid="11308" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221202"]Given there is no obvious obstruction or pelvic dilation, I'm hesitant to rush into any form of renal surgery at the moment - or am I missing something that needs sorting?[/quote]

No thats spot on - many nephroliths can be incidental so unless they are obstructive they do not require specific intervention. Our treatment should aim to reduce the risk of further stone formation.

[quote userid="11308" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221202"]Could the hypercalcaemia be causing the stone formation or a consequence of it, with some disruption to renal excretion?[/quote]

Certainly hypercalcaemia is a potential mechanism for stone formation (usually idiopathic hypercalcaemia) so I would investigate the calcium further (iCa, PTH +/- imaging).

In the first instance I get these cats onto a wet urinary tract diet + extra water.

Andy

RE: Anaesthesia for Feline Nephrectomy

Anthony Dennison — Tue, 31 Mar 2020 11:26:32 GMT

ps Arlo Guthrie putting the images into that post was so much easier on this new format! Thank you.

RE: Anaesthesia for Feline Nephrectomy

Anthony Dennison — Tue, 31 Mar 2020 11:25:34 GMT

Ok, so some more information.

Bloods taken this morning confirm no azotamia (Creatinine 121umol/L, Urea 10.3mmol/L, SDMA 8 ug/dL). Only abnormality is a hypercalcaemia of 3.12mmol/L (ref range1.95-2.83).

Radiographs from original vets are below:

Abdominal ultrasound confirms right renal enlargement. L kidney 3.11cm long, R kidney 3.92cm long. Left kidney does seem slightly hyperechoic and there is a hyperechoic lesion within it. Right kidney has an enlarged medulla, a very bright pelvis but it doesn't seem dilated at all. Small aggregate of uroliths seen within the bladder, bladder itself isn't inflamed or thickened.

Given there is no obvious obstruction or pelvic dilation, I'm hesitant to rush into any form of renal surgery at the moment - or am I missing something that needs sorting? Don't think a nephrectomy is in order anyway (especially as it looks like there are bilateral nephroliths). Could the hypercalcaemia be causing the stone formation or a consequence of it, with some disruption to renal excretion?

RE: Anaesthesia for Feline Nephrectomy

Andrew Kent — Tue, 31 Mar 2020 09:59:32 GMT

[quote userid="11308" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221198"]The owner did ask about risk of recurrence, so this is useful information thank you.[/quote]

The reported rate of reobstruction is around 40% within the first few years. Anecdotally we feel the risk is lower with bypass devices as we can flush them to reduce the risk.

[quote userid="11308" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221198"]That's the plan today - the cat isn't blocked or clinically unwell so work up today to see how the kidney is affected.[/quote]

Great - let us know what you find.

[quote userid="11308" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221198"]Would a SUB be suitable if the stone isn't in the pelvis or proximal ureter?[/quote]

Yes the location of obstruction doesn't really matter. We do (ideally) need pelvic dilation for placement which should be there if there is obstruction.

Single non-azotaemic obstructions are challenging from a decision making point of view.

Andy

RE: Anaesthesia for Feline Nephrectomy

Carl Bradbrook — Tue, 31 Mar 2020 09:48:40 GMT

A local anaesthetic "splash" or "soak" technique will certainly not be harmful and will hopefully reduce any response to nephrotomy. Lidocaine will be great for this, although if you have a longer acting local anaesthetic such as bupivacaine this will also be an option.

There is always the risk of vasodilation with an epidural but I'm usually most concerned about this if we are using a high volume or high epidural. Getting complete blockade of the whole abdomen can be a challenge without reaching the sympathetic fibres in the thoracic region and I would be looking for any changes in HR, ECG and BP during the injection. Procedures were I would not usually consider epidural anaesthesia are those patients with evidence of sepsis, especially septic abdomens and GDV and in any case were you suspect hypovolaemia or hypotension. If you are worried about using a local anaesthetic in your epidural (this is the component that leads to blockade) then you can use an opioid alone. You will not completely block nociception in this situation but will modulate the response and hopefully reduce systemic analgesia requirements. There may be times when considering fluid loading prior to epidural is appropriate and if you observe any signs of vasodilation (increase in HR and reduction in BP) during injection I would advise to stop injecting and would bolus fluid therapy at that time. From personal experience this is more of a problem in sick cases that have not had their volume status corrected prior to anaesthesia.

RE: Anaesthesia for Feline Nephrectomy

Anthony Dennison — Tue, 31 Mar 2020 09:47:34 GMT

[quote userid="2451" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221192"]I agree that I would try to avoid a nephrectomy if possible - stone forming cats are at high risk of obstruction on the other side and if that is the only kidney left then you are in trouble![/quote]

The owner did ask about risk of recurrence, so this is useful information thank you.

[quote userid="2451" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221192"]Ultrasound would be the best way to determine whether or not obstructive[/quote]

That's the plan today - the cat isn't blocked or clinically unwell so work up today to see how the kidney is affected.

[quote userid="2451" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221192"]Options include surgical intervention or bypass (we typically use a subcutaneous ureteral bypass or SUB device).[/quote]

Would a SUB be suitable if the stone isn't in the pelvis or proximal ureter?

[quote userid="6032" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221193"]I find analgesia a challenge and would consider epidural anaesthesia a very useful option if this is something you are comfortable with.[/quote]

Never done before, cat is 4.95kg so a good size but may be worth practicing on larger dogs first! I've got the BSAVA guide to procedures handy so could look at using this. Would it infiltrate that far cranially?

No fentanyl, but we are starting to build up caseloads from other local IVC practices referring things to us so it is something we should possibly consider. We do a fair amount of orthopaedic work so could be using it during those procedures more.

RE: Anaesthesia for Feline Nephrectomy

Beats — Tue, 31 Mar 2020 09:32:04 GMT

Thanks Carl Bradbrook for those excellent insights!

Can I ask if sprinkling a little lidocaine (<2mg/kg total lidocaine into cat including larynx and abdominal wound if infiltrating) over the renal hilus (and/or capsule) and letting is sit for few minutes before cutting into kidney would do any good/harm?

Also with a local anesthetic epidural, could that lead to caudal abdominal vasodilatation by blocking the sympathetic supply to blood vessels and therefore further risk decreased renal perfusion via reduced systemic blood pressure, or would that be a theoretical risk only rather than an actual real-life practical one?

RE: Anaesthesia for Feline Nephrectomy

Carl Bradbrook — Tue, 31 Mar 2020 09:20:09 GMT

Hi Anthony,

I find nephrotomy or nephrectomy a challenging anaesthetic for a number of reasons and would consider nociception (due to manipulation of abdominal contents, handling of the kidney itself and abdominal retraction), haemorrhage, hypotension and hypothermia as potential complications. I find analgesia a challenge and would consider epidural anaesthesia a very useful option if this is something you are comfortable with. A ketamine infusion is a great alternative or addition in cats, and suitable even in cats with reduced renal function. I would use doses on the lower end of the range and consider that the effect may be prolonged if renal excretion is reduced. As suggested in the thread I would avoid lidocaine as an infusion in cats. If an epidural is not possible then either a fentanyl infusion, methadone tops ups or a methadone infusion are good opioid options. I would avoid NSAIDs until you are happy with the patients stability well into the recovery period.

I would be monitoring BP closely, as hypotension is something to look out for and ensure you have good IV access if you need to bolus fluid therapy or give any other fluids or drugs. If you are using multiple infusions a second IV will be useful. As its a cat and an abdominal procedure hypothermia is a significant risk, and active warming should commence as soon as anaesthesia is induced.

Maropitant may prove useful in terms of reduction in vomiting and PONV but unfortunately we do not have the evidence currently to support its antinociceptive properties, but there is the potential to be able to use lower inhalant agent vaporiser settings.

Very happy to discuss further when you have a plan for the procedure

Carl

RE: Anaesthesia for Feline Nephrectomy

Andrew Kent — Tue, 31 Mar 2020 09:07:51 GMT

I agree that I would try to avoid a nephrectomy if possible - stone forming cats are at high risk of obstruction on the other side and if that is the only kidney left then you are in trouble!

Ultrasound would be the best way to determine whether or not obstructive - in general if it is then some procedure to salvage the kidney can be worth considering. Options include surgical intervention or bypass (we typically use a subcutaneous ureteral bypass or SUB device).

Happy to chat further once you know the situation.

Andy

RE: Anaesthesia for Feline Nephrectomy

Anthony Dennison — Tue, 31 Mar 2020 07:45:01 GMT

Thanks David. Just reading about it in Fossum. I'll assess where the stone is, may be able to get away with a pyelolithotomy if it's far enough down. I'll get images from the scan and post the outcome later.

RE: Anaesthesia for Feline Nephrectomy

David Mills — Tue, 31 Mar 2020 07:24:24 GMT

Yes just skin glue. Use a sterile syringe and needle to draw it up and dribble over the cut edge. Have used non sterile glue before without apparent issues, it's not a good medium for microbial growth. Suturing the kidney leads to more scar tissue and impaired function compared to simply glueing the outside edge.

Normally they're in the renal pelvis so you may need to cut that deep. Other ones in parenchyma are normally palpable from outside. Use a scalpel to incise.

RE: Anaesthesia for Feline Nephrectomy

Beats — Tue, 31 Mar 2020 07:11:35 GMT

[quote userid="8991" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221181"]Consider nephrotomy. Simply slice along the long axis to pelvis and remove stone. They bleed. Once stone is out squeeze the two halves together and glue over the exterior. Simple and quick and rarely interferes with function. Kidneys can recover. [/quote]

Have never done this - thanks for tip!

RE: Anaesthesia for Feline Nephrectomy

Anthony Dennison — Tue, 31 Mar 2020 01:12:37 GMT

[quote userid="9239" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221182"]I'm not sure I would use Lidocaine CRI in a cat due to potential cardiac effects.[/quote]

Of course, didn't think of that thanks.

[quote userid="8991" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28999/anaesthesia-for-feline-nephrectomy/221181"]Once stone is out squeeze the two halves together and glue over the exterior[/quote]

Just skin glue? We don't have any sterile packs of this, but cat is quite stable so could postpone the op for 24hrs whilst we source a sterilised version.

Thanks for the really useful information!

RE: Anaesthesia for Feline Nephrectomy

Dinu Catilina — Mon, 30 Mar 2020 22:40:14 GMT

I'm not sure I would use Lidocaine CRI in a cat due to potential cardiac effects. I would premedicate with medetomidine/methadone.

RE: Anaesthesia for Feline Nephrectomy

David Mills — Mon, 30 Mar 2020 22:26:24 GMT

Consider nephrotomy. Simply slice along the long axis to pelvis and remove stone. They bleed. Once stone is out squeeze the two halves together and glue over the exterior. Simple and quick and rarely interferes with function. Kidneys can recover.

Methadone infusion at maintenance. Rarely need ket. Use a quad induction then start cri. Usually home the next day. Msropitant useful for analgesia in cats and melox is not contraindicated.