TANYA'S

COMPREHENSIVE GUIDE TO

FELINE CHRONIC KIDNEY DISEASE

 

 

 

METABOLIC ACIDOSIS

(ACID-BASE BALANCE DISTURBANCE)

 

ON THIS PAGE:


What is Metabolic Acidosis?


How Common is Metabolic Acidosis?


Causes


Symptoms


Diagnosis


Goal


Treatments


 

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Home > Key Issues > Metabolic Acidosis

 


Overview


  • Metabolic acidosis means that the levels of acid in the cat's body are too high.

  • It is extremely common in CKD cats, usually cats in Stage IV, and can make the cat feel ill and the CKD progress faster.

  • It can be tricky to diagnose, but fortunately it is relatively easy to treat.


What is Metabolic Acidosis?


 

There is a delicate balance within the body known as acid-base balance (pH):

  • Blood pH is usually kept by the body within a narrow range.

  • Normal blood pH is slightly alkaline, at around 7.40.

  • A blood pH level below 7.35 is acidic.

  • A blood pH level above 7.45 is alkaline (or basic).

Metabolic acidosis means that this balance is disrupted, in that levels of acid in the cat's body are too high, so the blood pH is too low (acidic).

 

Acid is produced in the body as a result of diet. In healthy cats, the kidneys help to balance acid levels in the body in two ways:

  1. Bicarbonate ions (which are alkaline) in the kidneys help protect against acid build-up in the body;

  2. Any excess acids that do arise are flushed from the body by the kidneys.

Unfortunately the excessive urine flow of CKD washes the protective bicarbonate ions out of the kidneys. On the other hand, the damaged kidneys may no longer flush the acids from the body properly. As a result of these damaged mechanisms, acidity levels in the blood rise, and the body’s pH becomes too low. This is known as acidosis.

 

"Metabolic" means that the acidosis is caused by kidney disease. This is to differentiate it from another type of acidosis known as respiratory acidosis, which is caused by the lungs not expelling carbon dioxide properly.

 

I know a lot of people get confused by the word "acidosis" and think it is the same thing as excess stomach acid, but that is not the case. Gastrin is a gastrointestinal hormone which stimulates the secretion of gastric acid, which helps the stomach digest food. The kidneys are responsible for the excretion of gastrin, but in CKD this function may not work so well, resulting in the gastrin remaining in the stomach and potentially stimulating the production of too much gastric acid. This is what we mean by excess stomach acid.

 

Metabolic acidosis refers to the acid-base in the body as a whole (systemic pH), which is normally measured in the blood. Excess stomach acid is a separate problem with different causes and treatments, so please be sure you are dealing with the correct condition. It is possible for a CKD cat to have either excess stomach acid or metabolic acidosis, or both at the same time.

 

Metabolic acidosis is a very complex subject, and you are not alone if you find it confusing. I certainly do, and even vets can find it challenging: A practical approach to acid-base balance for small animal practitioners (2014) Parry N Online Continuing Education Indiana Veterinary Medical Association says "many practitioners find it daunting to retain the key concepts and apply them in  a meaningful way in clinical practice." Fortunately, you should only need to know the basics, i.e. what it is, what symptoms a cat might exhibit, how it is diagnosed, and most importantly, how it is treated.

The Merck Manual has a good overview of metabolic acidosis in humans.

 

Pet MD has a good overview of metabolic acidosis in layman's language.

 

Cornell University College of Veterinary Medicine has an overview of acid-base.

 

Cornell University College of Veterinary Medicine also discusses the role of the kidneys in acid-base balance.

 

Chronic kidney disease (2007) Polzin DJ Delaware Valley Academy of Veterinary Medicine discusses metabolic acidosis in rather technical terms.

 

Current concepts for the management of chronic renal failure in the dog and cat - early diagnosis and supportive care (2005), a presentation by Dr S Sanderson to the World Small Animal Veterinary Association 30th World Congress, explains more about metabolic acidosis.

 


How Common is Metabolic Acidosis?


 

Metabolic acidosis is relatively common in CKD cats, particularly as the CKD progresses. One study, Assessment of acid-base status of cats with naturally occurring chronic renal failure (2003) Elliott J, Syme HM, Reubens E & Markwell PJ Journal of Small Animal Practice 44(2) pp65-70, found that metabolic acidosis was present in 15% of the stage 3 cats in the study, but 52.6% of the cats in the top of stage 3 and stage 4 (creatinine level over 4.5 mg/dl or 400 mmol/L) had metabolic acidosis.

 

This is not to say that cats in earlier stages of CKD can't have metabolic acidosis. Acid-base balance of cats with chronic renal failure: effect of deterioration in renal function (2003) Elliott J, Syme HM, Markwell PJ Journal of Small Animal Practice 44(6) pp261-8 reports on a cat who developed metabolic acidosis without an accompanying increase in creatinine levels. Some cats on Tanya's CKD Support Group with early stage CKD have also had metabolic acidosis, so it is important to check for it and treat it if it is present.

 


Causes


 

Kidney disease is a very common cause of metabolic acidosis, for reasons discussed above. Other causes of metabolic acidosis include diabetic ketoacidosis, or the ingestion of toxins such as ethylene glycol (antifreeze) which can lead to acute kidney injury.

 


Symptoms


 

Metabolic acidosis can have a number of different effects on the body. All the symptoms may have other causes, so you need to look at the symptoms in conjunction with the test results for metabolic acidosis (see below). Please see the Index of Symptoms and Treatments for more information on other possible causes of these symptoms.

 

Respiratory Symptoms


Cats with metabolic acidosis are often breathless, and breathe deeply and/or rapidly. This is because metabolic acidosis leads to an excess of carbon dioxide in the body, so the body increases its breathing rate and force to try to remove some of the excess carbon dioxide (respiratory compensation).

 

Breathlessness caused by metabolic acidosis is known as Kussmaul breathing.

 

Neurological Symptoms


Chronic kidney disease (2007) Polzin DJ Delaware Valley Academy of Veterinary Medicine says that "severe acidosis may also influence... brain metabolism." Therefore you may see:

  • confusion

  • twitching

  • depression

  • seizures (or absences, spacing or zoning out)

  • coma

Cardiovascular Symptoms


Severe metabolic acidosis can also cause heart disturbances. In Renal Disease (2006) Polzin DJ Delaware Valley Academy of Veterinary Medicine, Dr Polzin says "Severe acidemia may result in decreased cardiac output, arterial pressure, and hepatic and renal blood flows and centralization of blood volume." He also mentions that metabolic acidosis may increase the risk of pulmonary oedema in cats on fluid therapy.

 

Food Metabolism Symptoms


Metabolic acidosis can adversely affect protein and carbohydrate metabolism. Poor protein metabolism can prevent the cat's body from using protein properly, which is concerning in light of a cat's relatively high need for protein. In Chronic kidney disease (2007) Polzin DJ Delaware Valley Academy of Veterinary Medicine, Dr Polzin says "Severe chronic metabolic acidosis has the potential to induce a cycle of progressive protein malnutrition and metabolic acidosis. Excessive protein catabolism may lead to protein malnutrition despite adequate dietary intake."

 

Symptoms you may see include:

  • weight loss

  • lean muscle loss or muscle wasting

  • a bony spine

  • malnutrition

 

Metabolic acidosis may also affect taurine levels. Acid-base, electrolytes and renal failure (1999) Polzin DJ, Osborne CA, James K Supplement to Compendium on Continuing Education for the Practising Veterinarian 21 11(K) states "Studies on the effects of dietary acidification in cats have revealed that chronic metabolic acidosis can cause negative potassium balance, which may in turn promote...taurine depletion."  

 

Bone Symptoms


Current concepts for the management of chronic renal failure in the dog and cat - early diagnosis and supportive care (2005), a presentation by Dr S Sanderson to the World Small Animal Veterinary Association 30th World Congress states "Inadequately controlled metabolic acidosis also contributes to renal osteodystrophy."

 

Acid-base, electrolytes and renal failure (1999) Polzin DJ, Osborne CA, James K Supplement to Compendium on Continuing Education for the Practising Veterinarian 21 11(K) states "Studies on the effects of dietary acidification in cats have revealed that chronic metabolic acidosis can cause negative calcium balance and bone demineralization."

 

Symptoms may include:

  • bone loss

  • calcification

though these symptoms are unlikely to be visible. You can read more about these problems here.

 

Other Symptoms


Metabolic acidosis may cause other symptoms:

  • weakness

  • lethargy

  • nausea and vomiting

  • mouth ulcers

  • potassium imbalances - Chronic kidney disease (2007) Polzin DJ Delaware Valley Academy of Veterinary Medicine states "severe acidosis may also influence... serum potassium concentrations."


Diagnosis


 

Although standard blood tests (blood chemistry panel and complete blood count) should be run, metabolic acidosis also requires specialised tests known as blood gas analysis for accurate diagnosis.

 

The practitioner's acid-base primer: obtaining and interpreting blood gases (2013) Waddell LS Today's Veterinary Practice 3(3) pp43-47 explains more about how to diagnose metabolic acidosis.

 

Diagnostic tree: blood gas analysis (2012) Waddell LS NAVC Clinician's Brief Jan 2012 pp18-19 is a diagnostic tree to help your vet measure and treat metabolic acidosis.


Blood Gas Analysis


 

The main way of assessing metabolic acidosis is via blood gas analysis. There are two types of blood gas analysis, arterial (using blood taken from an artery) and venous (using blood taken from a vein).

 

It is easy to make mistakes with blood gas analysis because if the blood sample is exposed to air, the dissolved gas escapes and makes the reading look lower than it really is.

 

Arterial and venous blood gases: indications, interpretations, and clinical applications (2009) Irizarry R & Reiss A Compendium: Continuing Education for Veterinarians Oct 2009 ppE1-E7 discusses blood gas testing.

 

Arterial Versus Venous Blood Gas Analysis


Arterial blood gas analysis is the most accurate, particularly for checking respiratory function, but the equipment is expensive and not widely available. The cat also needs to be sedated, so in practice you are more likely to be offered venous blood gas analysis.

 

Although arterial measurements are better for assessing respiratory function, for most CKD cats blood taken from a vein (venous blood), ideally from the jugular vein, will suffice to check for metabolic acidosis.

 

Global RPh explains how to interpret arterial blood gas tests (the ranges are for humans).

 

Blood pH


Normal blood pH is usually slightly alkaline (also referred to as basic) at around 7.40 (the level for your laboratory may be a little different).

  • If blood pH is below 7.35, it is acidic and you are probably dealing with metabolic acidosis.

  • If blood pH is above 7.45, it is alkaline and you are probably dealing with the opposite problem of metabolic alkalosis.

Diagnostic tree: blood gas analysis (2012) Waddell LS NAVC Clinician's Brief Jan 2012 pp18-19 has a table of typical feline measurements on page 2, which indicate that venous pH values tend to be a little lower than arterial (around 7.34 arterial versus 7.3 venous).

 

HCO3- (Bicarbonate)


Bicarbonate levels in a blood gas analysis test are usually reduced in metabolic acidosis, but you need to look at them in conjunction with the pH level. If bicarbonate levels  are below normal, and so is the blood pH level, the cat probably has metabolic acidosis.

 

The normal range for bicarbonate is around 16-24, depending upon which laboratory is used.

 

Diagnostic tree: blood gas analysis (2012) Waddell LS NAVC Clinician's Brief Jan 2012 pp18-19 has a table of typical feline measurements on page 2, which indicates that venous bicarbonate levels tend to be a little higher than arterial ones (17.5 arterial versus 19.4 venous).

 

TCO2


If TCO2 or total carbon dioxide levels are low, it can be a sign that bicarbonate levels are also low. However, TCO2 may also be lowered for other reasons, such as anaemia.

 

Not every blood gas analysis will include TCO2.

 

BEecF Base Excess of the Extra Cellular Fluid)


The bicarbonate figure above is actually a calculated figure. The BEecF value considers all the metabolic acid-base disturbances, with a normal value being 4 mEq/L. A lower value points to metabolic acidosis.

 


Blood Chemistry


 

Cats with suspected metabolic acidosis should have a blood chemistry panel and a complete blood count run as well as blood gas analysis (you will not be able to check the anion gap without a chemistry panel). Cornell University College of Veterinary Medicine says "To detect an acid-base disturbance, both a blood gas analysis and chemistry panel should be performed...The blood gas analysis and chemistry panel provide information on most of the variables responsible for acid-base disturbances and the results should be used together for interpretation."

 

You may see changes in the following in particular:

 

TCO2


TCO2 or total carbon dioxide in the blood is a way of measuring levels of bicarbonate (HCO3) in the body. If TCO2 is low, it can be a sign that bicarbonate levels are low. However, it may also be lowered for other reasons, such as anaemia.

 

The usual range for TCO2 is about 17 to 23. Renal Disease (2006) Polzin DJ Delaware Valley Academy of Veterinary Medicine, says "we recommend that blood gas analysis be performed to confirm metabolic acidosis whenever total CO2 decline below 15 mmol/L." This is because it is very common to get false readings for TCO2, so it often looks lower than it really is. Because of this some laboratories, such as Antech in the USA, may only measure it on request (with Antech, you need to ask for Test No. T115. If you are using MSU, ask for the electrolytes expanded serum panel).

 

If your vet or his/her laboratory cannot measure TCO2 at all, ask your vet if it is possible to test for carbon dioxide (CO2) levels instead - if they are low, they may also indicate metabolic acidosis. But ideally you want blood gas analysis tests as discussed above.

 

Anion Gap


A CKD cat with metabolic acidosis would normally have an increased anion gap. The anion gap is a calculated measurement, being the difference between measured concentrations of cations (pronounced "cat-eye-ons") and anions (pronounced "an-eye-ons") in the blood. It is calculated as follows:

AG = [Na+ + K+] - [Cl- + HCO3]

which in English means:

anion gap = [sodium + potassium] – [chloride + bicarbonate].

Touch Calc will calculate it for you if you input the appropriate values from your cat’s bloodwork. 

 

The normal range for cats is around 10-27, though it does vary greatly from lab to lab.

 

Sometimes a cat has metabolic acidosis yet has a normal anion gap. This is because the anion gap is a calculated figure, and if one of the figures used for the calculation is well out of normal range, this can affect the result. For example, if bicarbonate is lost, chloride increases to offset it, which means the anion gap remains normal. This may happen in cats with severe diarrhoea.

 

The practitioner's acid-base primer: differential diagnoses and treatment (2013) Waddell LS Today's Veterinary Practice 3(6) pp25-30 has a clear explanation of the anion gap.

 

Cornell University College of Veterinary Medicine has detailed information on the anion gap.

 

Limitations of the Anion Gap


There are other causes of metabolic acidosis with an increased anion gap (e.g. diabetic ketoacidosis), so an elevated anion gap alone does not necessarily mean the cat has metabolic acidosis caused by CKD.

 

Conversely, a cat may have an elevated anion gap yet not have metabolic acidosis. For example, cats with metabolic alkalosis (the opposite problem to metabolic acidosis) may also have a high anion gap (these cats often also have low potassium levels).

 

Therefore it can be helpful to also check blood pH.

  • If the anion gap is high but blood pH is below normal, you are probably dealing with metabolic acidosis.

  • If the anion gap is high but blood pH is above normal, you are probably dealing with metabolic alkalosis.

 

Elevated phosphorus levels (hyperphosphataemia), which are often a concern in CKD cats, may also be a factor if the anion gap is high. Serum anion gap: its uses and limitations in clinical medicine (2007) Kraut JA& Madias NE Clinical Journal of the American Society of Nephrology 2(1) pp162-174 states that "Elevated values most commonly indicate metabolic acidosis but can reflect laboratory error, metabolic alkalosis, hyperphosphatemia, or paraproteinemia."

 

BUN and BUN:Creatinine Ratio


Since severe metabolic acidosis affects protein metabolism, it may increase BUN levels and contribute to a high BUN:creatinine ratio. Chronic kidney disease (2007) Polzin DJ Delaware Valley Academy of Veterinary Medicine says "The combined effects of reduced protein synthesis due to uremia and accelerated proteolysis due to acidosis promote elevations in blood urea nitrogen."

 

Potassium Imbalances


If a cat has metabolic acidosis, the cat's potassium levels may appear high or normal in blood tests, but may subsequently fall after the metabolic acidosis is treated. You should therefore ensure that your cat's potassium levels are monitored.

 


Urine Tests: Urine pH


Some vets diagnose metabolic acidosis from the pH levels of the urine but in Renal Disease (2006) Polzin DJ Delaware Valley Academy of Veterinary Medicine, Dr Polzin says "Because urine pH is often insensitive as a means of assessing the need for or response to treatment, it is not recommended for this purpose."

 


Goal


 

As you can see, metabolic acidosis is not something to ignore. What are your goals, should you need to treat it?

 

Feline CKD: Current therapies - what is achievable? (2013) Korman R & White J Journal of Feline Medicine and Surgery 15(S1) pp29–44 says "Bicarbonate concentration should be maintained between 15 and 22 mmol/l and blood pH between 7.2 and 7.4."

 

ISFM consensus guidelines on the diagnosis and management of feline chronic kidney disease (2016) Sparkes AH, Caney S, Chalhoub S, Elliott J, Finch N, Gajanayake I, Langston C, Lefebvre H, White J & Quimby J Journal of Feline Medicine & Surgery 18(3) pp219-239 states "aiming to maintain a blood bicarbonate or total Co2 in the range of 16–24 mmol/l."

 

The International Renal Interest Society (2015) has the same recommendation: "Maintain blood bicarbonate/ total CO2 in the range of 16-24 mmol/l."

 

Your goals are therefore:

  • TCO2 or bicarbonate in the blood between 16 and 24.

  • Blood pH between 7.2 and 7.4.

11 guidelines for conservatively treating chronic kidney disease (2007) Polzin D, Veterinary Medicine Dec 2007, Dr Polzin states "Once therapeutic targets have been attained, re-evaluate dogs and cats receiving alkalinizing therapy every three to four months to ensure continued compliance and therapeutic success at maintaining the target."

 


Treatment



Benefits of Treatment


 

If metabolic acidosis is present, it is important to treat it because it can make the CKD progress faster, and can cause problems with weight and muscle loss. 11 guidelines for conservatively treating chronic kidney disease (2007) Polzin D, Veterinary Medicine Dec 2007, Dr Polzin states 'the clinical effects of metabolic acidosis may include progressive renal injury and increased protein catabolism with loss of lean tissue." Plus it can make cats just feel plain ill: in Chronic kidney disease (2007) Polzin DJ Delaware Valley Academy of Veterinary Medicine, Dr Polzin says "Chronic metabolic acidosis may promote a variety of adverse clinical effects including anorexia, nausea, vomiting, lethargy, weakness, muscle wasting, weight loss, and malnutrition."

 

Conversely, treating metabolic acidosis can slow down the progression of CKD, according to Current concepts for the management of chronic renal failure in the dog and cat - early diagnosis and supportive care (2005) Sanderson S Presentation to the World Small Animal Veterinary Association 30th World Congress, which says "correcting metabolic acidosis has the potential to not only slow down the progression of CRF, but it also has the potential to minimize protein catabolism and renal osteodystrophy."

 

You are unlikely to see improved kidney values after treating metabolic acidosis, but you will be helping avoid continued kidney injury and treatment should help your cat feel much better.

 


Why Some Vets Do Not Rush to Start Treatment


 

Despite the many risks and side effects of metabolic acidosis, sadly some vets do not want to  treat it - in Current concepts for the management of chronic renal failure in the dog and cat - early diagnosis and supportive care (2005) Presentation to the World Small Animal Veterinary Association 30th World Congress, Dr S Sanderson states that "at least in veterinary medicine, it appears that metabolic acidosis tends to be undertreated in patients with CKD."

 

Some vets may be reluctant to treat metabolic acidosis for a surprising reason: A practical approach to acid-base balance for small animal practitioners (2014) Parry N Online Continuing Education Indiana Veterinary Medical Association says "many practitioners find it daunting to retain the key concepts and apply them in  a meaningful way in clinical practice."

 

In many cases, however, vets are reluctant to act because they are worried about overtreating and causing the opposite problem of metabolic alkalosis. This is not an unreasonable approach in some cases. The cat's body will always try to achieve a state of balance, so if metabolic acidosis is present, it will be trying to remedy it. This is called a compensatory response. The practitioner's acid-base primer: obtaining and interpreting blood gases (2013) Waddell LS Today's Veterinary Practice 3(3) pp43-47 says "The kidneys compensate more slowly, with compensation beginning within a few hours and maximum compensation taking 4 to 5 days." It is possible that damaged CKD kidneys would need longer.

 

Therefore it is normally recommended to start with dietary changes for mild acidosis (see below). ISFM consensus guidelines on the diagnosis and management of feline chronic kidney disease (2016) Sparkes AH, Caney S, Chalhoub S, Elliott J, Finch N, Gajanayake I, Langston C, Lefebvre H, White J & Quimby J Journal of Feline Medicine & Surgery 18(3) pp219-239 state that if cats are fed a therapeutic kidney diet and are kept properly hydrated, "Additional therapy is rarely needed."

 


When to Start Treatment


 

The recommendations on when treatment should be begun vary a little, but the general consensus seems to be that treatment should normally be started if blood bicarbonate remains below 16 mEq/L or mmol/l despite dietary therapy (though please see the caveats in the previous paragraphs).

 

If your vet does not want to treat confirmed, chronic metabolic acidosis, it may help to show some of these references:

 

Renal dysfunction in small animals (2016) Brown SA Merck Veterinary Manual states that even for cats in Stage 1 CKD, "The identification and supportive treatment of developing complications (eg, systemic hypertension, potassium homeostasis disorders, metabolic acidosis, bacterial urinary tract infection) should be aggressively pursued." Dr Brown goes on to say that treatment "may be indicated if the animal is severely acidotic (plasma bicarbonate <15 mEq/L) or remains acidotic 2-3 wk after diet change."

 

ISFM consensus guidelines on the diagnosis and management of feline chronic kidney disease (2016) Sparkes AH, Caney S, Chalhoub S, Elliott J, Finch N, Gajanayake I, Langston C, Lefebvre H, White J & Quimby J Journal of Feline Medicine & Surgery 18(3) pp219-239 state that if cats are fed a therapeutic kidney diet and are kept properly hydrated, treatment probably won't be necessary, but it may be needed "if clinical concerns exist and blood bicarbonate or total CO2 concentrations are below 16 mmol/l."

 

The International Renal Interest Society (2015) has the same recommendation to commence treatment "If metabolic acidosis exists (blood bicarbonate or total CO2 <16 mmol/l) once the patient is stabilized on the diet of choice."

 

Because cats with metabolic acidosis are too acidic, the treatments used aim to make the body more alkaline. This can be very effective: in Chronic kidney disease (2007) Polzin DJ Delaware Valley Academy of Veterinary Medicine, Dr Polzin says "Alkalization therapy is often of value in reversing these signs."

 


Diet


 

The first step to prevent metabolic acidosis or to treat mild metabolic acidosis is to try to feed a therapeutic kidney diet. Most renal diets are pH neutral or even slightly alkalinising. They also contain potassium citrate, which can help with metabolic acidosis (see below).  ISFM consensus guidelines on the diagnosis and management of feline chronic kidney disease (2016) Sparkes AH, Caney S, Chalhoub S, Elliott J, Finch N, Gajanayake I, Langston C, Lefebvre H, White J & Quimby J Journal of Feline Medicine & Surgery 18(3) pp219-239 state "Panel recommendations: Feeding a renal diet formulated to minimise acidosis, and maintaining good hydration, are likely to be beneficial in preventing clinically significant metabolic acidosis in cats with CKD.

 

If your cat will not eat such a food, at least try to avoid foods for urinary tract health, which are acidified and therefore not suitable for CKD cats generally and cats with metabolic acidosis in particular.

 


Fluid Therapy: Lactated Ringers Solution


 

Most CKD cats will eventually be receiving subcutaneous fluids regularly to maintain hydration, and these may also help with metabolic acidosis if you are using lactated ringers solution (LRS) (which is the most commonly used sub-Q fluid for CKD cats).

 

LRS helps because the lactate is metabolised by the liver where it is converted to bicarbonate, which  may be sufficient to correct mild acidosis.

 

However, sub-Qs are not normally given solely to assist with metabolic acidosis.

 

If you are giving your cat sodium chloride fluids, these may exacerbate metabolic acidosis, so speak to your vet about switching fluids.

 

Please see Subcutaneous Fluids for more information on fluid choices.

 


Potassium Citrate


 

Cats with metabolic acidosis who also have low potassium levels can be given potassium citrate. In fact, other treatments for cats with both conditions may only be of limited use: 11 guidelines for conservatively treating chronic kidney disease (2007) Polzin D, Veterinary Medicine Dec 2007, Dr Polzin states "Metabolic acidosis when accompanied by potassium or magnesium depletion may respond poorly to alkali therapy alone."

 

Potassium citrate is an effective treatment for both problems but you may need to watch for crystals forming in your cat's urine. Dr Polzin says "since potassium doses required for adequate correction of hypokalemia may exceed the citrate dose required to correct acidosis, there is a risk of excessive alkalinization. Starting doses of 40 to 60 mg/kg given orally every eight to 12 hours are recommended."

 

Managing fluid and electrolyte disorders in renal failure (2008) Langston C Veterinary Clinics Small Animal Practice 38 pp677–697 recommends "Potassium citrate (40–60 mg/kg/d divided into two to three doses) is an alternative to potassium gluconate that also helps to correct acidosis."

 

ISFM consensus guidelines on the diagnosis and management of feline chronic kidney disease (2016) Sparkes AH, Caney S, Chalhoub S, Elliott J, Finch N, Gajanayake I, Langston C, Lefebvre H, White J & Quimby J Journal of Feline Medicine & Surgery 18(3) pp219-239 state "Additional therapy is rarely needed, but if clinical concerns exist and blood bicarbonate or total Co2 concentrations are <16 mmol/l, oral supplementation with potassium citrate (40–75 mg/kg q12h as a starting dose) may be used, aiming to maintain a blood bicarbonate or total Co2 in the range of 16–24 mmol/l."

 

If you are using potassium citrate, you should give it at least two hours apart from any phosphorus binders containing aluminium, because citrate may increase the absorption of aluminium.

 

Potassium citrate should also not be used or its usage should be stopped for cats with high potassium levels. 

 


Bicarbonate of Soda


Bicarbonate of Soda Overview


Bicarbonate of soda, also known as sodium bicarbonate, may be used to treat metabolic acidosis if the above treatments are not sufficient. It works by replenishing the bicarbonate ions lost from the body. Since bicarbonate is alkaline, giving it helps offset the excess acidity of metabolic acidosis.

 

11 guidelines for conservatively treating chronic kidney disease (2007) Polzin D, Veterinary Medicine Dec 2007, Dr Polzin states "Oral sodium bicarbonate is the most commonly used alkalinizing agent for patients with metabolic acidosis of chronic renal insufficiency or failure."

 

The International Renal Interest Society (2015) says "once the patient is stabilized on the diet of choice, supplement with oral sodium bicarbonate (or potassium citrate if hypokalaemic) to effect to maintain blood bicarbonate / total CO2 in the range of 16-24 mmol/l."

 

One human study, Bicarbonate supplementation slows progression of CKD and improves nutritional status (2009) de Brito-Ashurst I, Varagunam M, Raftery MJ & Yaqoob MM Journal of the American Society of Nephrology 20(9) pp2075-2084 found that " bicarbonate supplementation slows the rate of progression of renal failure to ESRD and improves nutritional status among patients with CKD."

 

Sodium bicarbonate to slow the progression of chronic kidney disease (2011) Rossier A, Bullani R, Burnier M & Teta D Revue médicale suisse 7(284) pp478-82 investigated this further and reports that three trials with CKD indicated that sodium bicarbonate may slow the progression of CKD in humans.

 

ISFM consensus guidelines on the diagnosis and management of feline chronic kidney disease (2016) Sparkes AH, Caney S, Chalhoub S, Elliott J, Finch N, Gajanayake I, Langston C, Lefebvre H, White J & Quimby J Journal of Feline Medicine & Surgery 18(3) pp219-239 state "bicarbonate therapy has been shown to improve nutrition (calorie and protein intake, lean body mass), and slow progression in humans with CKD."

 

It is not clear whether treating the metabolic acidosis generally or the use of bicarbonate of soda specifically helped in these studies.

 

I know  this treatment sounds great but it is not a benign treatment when used inappropriately, so never give your cat bicarbonate of soda without your vet's knowledge and approval: too much can cause the opposite problem of excess alkalinity, which can be very dangerous. 

 

Drugs has some information about bicarbonate of soda.

 

Bicarbonate of Soda Formulations


In the USA, bicarbonate of soda (sodium bicarbonate) is also known as baking soda.

 

In some countries such as the UK, you will see baking powder but do not buy this, because although it contains sodium bicarbonate, it also contains other ingredients which you do not want.

 

Wherever you live, you should be able to find bicarbonate of soda in powder form in the baking section of most supermarkets. In the USA, you can also buy it in pill form, in which case (since cat-sized doses are tiny) you would probably have to crush it before use.

 

Bicarbonate of Soda Dosage


It is not that easy to find specific dosing recommendations for bicarbonate of soda because it needs to be tailored to the individual patient. In 11 guidelines for conservatively treating chronic kidney disease (2007) Polzin D, Veterinary Medicine Dec 2007, Dr Polzin says "Because the effects of gastric acid on oral sodium bicarbonate are unpredictable, the dosage should be individualized for each patient."

 

Dr Katherine James of the Veterinary Information Network suggests an initial dose:

  • 5-10mg per kg of body weight every twelve hours.

In 11 guidelines for conservatively treating chronic kidney disease (2007) Polzin D, Veterinary Medicine Dec 2007, Dr Polzin suggests a similar but slightly higher initial dose:

  • 8 to 12 mg/kg body weight every 8 to 12 hours.

Current concepts for the management of chronic renal failure in the dog and cat - early diagnosis and supportive care (2005), a presentation by Dr S Sanderson to the World Small Animal Veterinary Association 30th World Congress, makes the same recommendations as Dr Polzin.

 

Here is a table showing the recommended dosages for cats of various sizes at the lowest and highest ends of these ranges. Remember, these dosages are in mg.

 

 

Dose per kg

(2.2 lb) of cat in mg

Dose

Frequency

Cat Weight

2.25kg 3.65kg 4.55kg
5 lbs 8 lbs 10lbs
Dr Katherine James 5

Twice daily

11 18 23
10 22 36 45
 

Dr David Polzin/

Dr S Sanderson

8

2-3 times daily

18 29 36
12 27 43 55

 

As you can see, Dr James recommends giving these amounts twice daily while Drs Polzin and Sanderson recommend giving these amounts 2-3 times a day. I would start at twice a day and increase only if needed. Be guided by your vet.

 


Bicarbonate of Soda How to Measure


 

It is difficult to measure bicarbonate of soda dosages for cats because the amounts involved are tiny. It doesn't help that teaspoons vary so much in size. Let me try to make this a little easier:

  • First of all, you need some tiny measuring spoons. The measuring spoons I am talking about are discussed here and available from Amazon in most countries.

  • Let's take Dr James's recommendation for an 8lb (3.65kg) cat receiving 10 mg per kg of cat twice a day.

  • According to the table above, this cat would receive 36 mg of bicarbonate of soda every 12 hours:

  • This gives a total daily dose of 72mg (i.e. 36mg twice a day).

  • I understand that many boxes of baking soda available in the USA (e.g. Arm and Hammer) state that 1/8 teaspoon contains 0.6g of sodium bicarbonate. Check the product you are using to ensure it is the same.

  • 0.6g is the same as 600mg. So an eighth of a teaspoon holds 600mg.

  • You, however, only need 72mg for the day. So you need a little under an eighth of an eighth of a teaspoon, which is 1/64 of a teaspoon.

  • As it happens, this is what the drop spoon in the set I link to hold. It holds about 75mg, i.e. around your total daily dose.

  • So you would give half the drop spoon amount twice a day. This is a flat, not a heaped, measure.

  • If your cat needs a different dose, it may help to know that the smidgen spoon apparently holds about 150mg of bicarbonate of soda.

  • The safest thing is to get your vet to tell you the correct dose for your cat and help you measure it.

Bicarbonate of Soda How to Give


So you have your tiny amount of bicarbonate of soda at the ready, but how best to give it to your cat?

 

I used to provide a recipe from my vet outlining how to give it in your cat's drinking water, but that is not necessarily the easiest way of ensuring your cat receives the full daily dose, and it can be tricky if you have more than one cat (you definitely don't want healthy cats receiving bicarbonate of soda).

 

It may be possible to mix a solution to keep in the fridge for easier measuring and giving. Chronic Renal Failure (2001) Polzin DJ Delaware Valley Academy of Veterinary Medicine advises "A solution containing approximately 84 mg of sodium bicarbonate per ml (1 meq/ml) of solution can be prepared by adding 2.5 ounces of sodium bicarbonate to 1 quart of water." If you find it easier to think metric, you would add 84g of bicarbonate of sodium to 1 liter of water.

 

Dr Polzin goes on to say "This solution may be stored capped and refrigerated for several months. This solution may be administered at a starting dose of 1 to 1.5 ml per 10 kg of body weight." This is broadly in line with his recommendations above, where he advises giving 8 to 12 mg/kg body weight every 8 to 12 hours (his solution is a slightly higher strength of 8.4 to 12.6 mg).

 

I expect your head is spinning now. Many people find it easiest just to dissolve the day's dose of bicarbonate of soda in some water and give it via syringe into their cat's mouth twice or three times day (giving a half or a third each time, as appropriate). It doesn't taste very nice, so some people pop the powder (without any added water) into a gelcap and give it that way.

 

If you work, you may want to make up enough to last a week. For example:

  • For a cat receiving a total of 75mg of bicarbonate of soda a day.

  • 75mg is a drop spoonful each day.

  • Measure out seven drop spoonfuls of bicarbonate of soda and place in a jar.

  • Add 14 ml of water and stir.

  • Give the cat 1 ml of the mixture twice a day. Shake or stir before drawing the water into a syringe.

Bicarbonate of Soda Risks


Bicarbonate of soda is usually a safe treatment for most cats with confirmed metabolic acidosis. It can be problematic if you give it to a cat who does not have metabolic acidosis, or if you give too much. The usual dosages sound so small that people assume it is safe to be relaxed about dosages but that is not the case.

 

Bicarbonate of soda should not be given to cats with low potassium levels because it may reduce potassium levels further. In this case, potassium citrate (see above) is a better choice anyway for most cats, because it treats both problems simultaneously.

 

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This page last updated: 11 April 2017

Links on this page last checked: 11 April 2017

 

 

 

   

*****

 

TREATING YOUR CAT WITHOUT VETERINARY ADVICE CAN BE EXTREMELY DANGEROUS.

 

I have tried very hard to ensure that the information provided in this website is accurate, but I am NOT a vet, just an ordinary person who has lived through CKD with three cats. This website is for educational purposes only, and is not intended to be used to diagnose or treat any cat. Before trying any of the treatments described herein, you MUST consult a qualified veterinarian and obtain professional advice on the correct regimen for your cat and his or her particular requirements; and you should only use any treatments described here with the full knowledge and approval of your vet. No responsibility can be accepted.

 

If your cat appears to be in pain or distress, do not waste time on the internet, contact your vet immediately.

 

*****

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