#430 CKD, Metabolic Acidosis, Baking Soda vs Fruits and Veggies. It’s NephMadness 2024!

March 11, 2024 | By Matthew Watto, MD

Audio

Video

Transcript available via YouTube

Is bicarbonate supplementation for metabolic acidosis in chronic kidney disease (CKD) a thing we do for no reason? We cover the pathophysiology and long-term consequences of metabolic acidosis, the history of bicarbonate use, alternative options for bicarbonate repletion including baking soda, lemon juice, fruits and veggies, whether the renal diet works, counseling patients with CKD, and common mistakes and pitfalls in managing metabolic acidosis in CKD. Our guest is Dr. Timothy Yau (@Maximal_Change, @WUNephrology, @AJKDOnline). It’s NephMadness 2024! Fill out your bracket today and check out the other podcasts participating in the NephMadness pod crawl!

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Show Segments

Time stamps refer to the ad-free version

• 00:00 Introduction and Guest Bio
• 07:46 Case Presentation
• 08:42 Initial Approach to CKD Management
• 09:10 Metabolic Acidosis in CKD
• 13:30 Consequences of Metabolic Acidosis
• 22:28 Administration of Bicarbonate
• 23:54 Alternative Options for Bicarbonate Repletion
• 24:47 Citrate and Bicarbonate
• 26:02 Sodium Bicarbonate for CKD
• 30:19 Dietary Modifications
• 33:35 Renal Diet
• 38:20 Counseling CKD Patients
• 41:39 Veverimer and Other Treatments
• 44:36 Mistakes and Pitfalls
• 46:55 Conclusion

CKD and Metabolic Acidosis Pearls

1. Don’t ‘base’ the decision to treat metabolic acidosis in CKD on a single bicarbonate value. Look at the trend.
2. Check a blood gas to make sure the low bicarbonate is not from respiratory alkalosis.
3. Amount of bicarbonate differs by formulation: 50 mEq in a 50 mL amp vs 8 mEq in one 650 mg tablet vs 8 mEq in 1/8 teaspoon of baking soda.
4. In trials, oral bicarb supplementation inconsistently prevents adverse kidney outcomes.
5. The draft 2023 KDIGO guidelines say to “consider using dietary and/or pharmacological treatment to prevent severe acidosis (e.g., bicarbonate <16 mmol/l)”, compared to the previous threshold of <22 mmol/l.
6. Base-producing fruits and vegetables offer the same GFR protection, plus improvement in cardiovascular risk profile compared to oral bicarbonate. 
7. Have a high threshold to start sodium bicarbonate and consider deprescribing for patients with near normal values.

Background and Pathophysiology

• Metabolic acidosis is most commonly seen in advanced CKD i.e. stage 4 or worse (Kim, 2021).
• Dr. Yau points out that in patients with CKD, management of metabolic acidosis is a less important factor than blood pressure or glycemic control, but still worth considering.
• Look at the serum bicarbonate trend before acting.
• The kidneys and lungs manage acid-base homeostasis. The bones act as a buffer (Faubel S and Topf J, 1999 (book)). 
• Our lungs excrete acid as carbon dioxide, but some acid must be handled by the kidneys (Faubel S and Topf J, 1999 (book)). 
• Healthy kidneys excrete excess protons as ammonium and generate new bicarbonate (Faubel S and Topf J, 1999 (book)). This ability diminishes as the number of nephrons wanes and metabolic acidosis develops and unfavorable changes in angiotensin II, and endothelin which can accelerate kidney fibrosis (Kim, 2021). 
• Though results have been inconsistent, some potential consequences of metabolic acidosis in CKD include:
  • Adverse bone health (Tabatabai, 2015) 
  • Decreased muscle mass (Visser, 2023)
  • Decline in GFR (Kim, 2021) 
  • Increased major adverse cardiac events (Collister, 2021) 

Bicarbonate replacement

• An amp of bicarbonate from the code cart has 50 mEq in 50 mL (Senewiratne, 2023).
• A liter of 5% dextrose (D5) with 3 amps of bicarbonate has 150 mEq per liter (Senewiratne, 2023).
• A 650 mg tablet of bicarbonate contains 8 mEq (Senewiratne, 2023)with a usual dose range of two (16 mEq) to four (32 mEq) tablets daily.
• Baking soda is 100 percent sodium bicarbonate and 1/8 teaspoon = one 650 mg tablet or 8 mEq. The label on most boxes says “add 1/2 teaspoon to 4 fl. Oz. of water every two hours” and cautions not to exceed “seven 1/2 teaspoons in 24 hours” or “three 1/2 teaspoons in 24 hours if you are over 60 years old” (Baking soda package label) 
• Side effects from oral bicarbonate include nausea, abdominal distension, belching, edema (Lexicomp).
• Citrate is converted to bicarbonate in the body such that every mEq of citrate generates three mEq of bicarbonate (Naka, 2004).
• Lemon juice contains potassium citrate and is often used in the management of kidney stones. It’s not commonly used in CKD due to concerns about causing hyperkalemia.

Bicarb studies

• Early trials of oral bicarbonate repletion were encouraging for prevention of major adverse kidney events aka MAKE (Brito-Ashurst, 2009, Di Iorio, 2019.). 
• A subsequent randomized placebo controlled, double-blind study did not find a difference in MAKE (BiCARB study group, 2020). 
• The BASE trial (Raphael, 2020) looked at the safety and tolerability of two sodium bicarbonate doses compared to placebo, but found an increase in albumin:creatinine ratio. Dr. Yau speculates this was from probably from the sodium load (expert opinion).
• Veverimer, a hydrochloric acid binder, was unable to show a difference in major adverse kidney outcomes (VALOR CKD, 2023).

KDIGO guidelines 

• Compared to 2012, the most recent KDIGO guideline from 2023 takes a big step back from bicarbonate supplementation for metabolic acidosis in CKD.
• KDIGO 2012 (section 3.4.1) recommends oral bicarbonate supplementation for serum bicarb under 22 with correction to the normal range, a 2b recommendation. 
• A KDIGO guideline draft update from 2023 (section 3.9) suggests consideration for treating a bicarbonate under 16, using dietary and/or pharmacologic therapy, as a “practice point” (a final version will be released in early 2024).

Diet

• A “renal diet” restricts sodium, potassium, and phosphorous. 
• In general, animal proteins are metabolized to acid, and plant proteins are metabolized to base (Noce, 2021).
• Base-producing fruits and veggies include apples, apricots, oranges, peaches, pears, raisins, strawberries, carrots, cauliflower, eggplant, lettuce, potatoes, spinach, tomatoes, and zucchini (Goraya, 2013).
• Fruits and vegetables have been compared to oral bicarbonate supplementation in treating metabolic acidosis in CKD, first showing similar improvements of serum bicarbonate levels without increasing hyperkalemia (Goraya, 2013). 
• A follow up study showed fruits and vegetables improved cardiac risk factors compared to sodium bicarbonate or usual care (Goraya, 2019).
  • As compared to placebo, five year net GFR decrease was lower and serum bicarb was higher in both the fruits & vegetables and the sodium bicarb groups; no GFR or bicarb difference was found between the two interventions
  • Metabolic markers like weight loss, blood pressure and cholesterol were improved in the fruits and veggies group. 
• Dr. Yau notes that dietary interventions are reasonable for patients aside from those with baseline hyperkalemia (potassium above 5.5) –expert opinion.

A few more random pearls

• Dr. Yau has a high threshold to start sodium bicarbonate and even mentions that deprescribing is reasonable for patients with a serum bicarb of 20 or more (expert opinion).
• Avoid these mistakes!
  • Don’t base the decision to treat on a single bicarbonate value. Look at the trend. 
  • Check a blood gas to make sure the low bicarbonate is not from respiratory alkalosis.

Links

1. Dark Souls is Dr. Yau’s “comfort” videogame
2. Skyrim is Paul’s “comfort” videogame
3. boygenius “the record” (album)

Goal

Listeners will effectively treat metabolic acidosis in chronic kidney disease (CKD)

Learning objectives

After listening to this episode listeners will…

1. Recall the mechanism for metabolic acidosis in CKD
2. Describe adverse consequences associated with chronic metabolic acidosis
3. Choose an appropriate management plan for patients with CKD and metabolic acidosis

Disclosures

Dr. Yau reports no relevant financial disclosures. The Curbsiders report no relevant financial disclosures. 

Citation

Watto MF, Yau T, Okamoto E, Williams PN. “#430 Chronic Kidney Disease & Metabolic Acidosis, NephMadness 2024”. The Curbsiders Internal Medicine Podcast. thecurbsiders.com/category/curbsiders-podcast Final publishing date March 11, 2024.