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SoBic trial finds no clear kidney advantage from a higher bicarbonate target

A higher blood bicarbonate target showed no clear additional kidney-function benefit in the SoBic trial, which followed 58 people with advanced chronic kidney disease and metabolic acidosis. Sodium bicarbonate raised the measured blood level, but kidney filtration declined without a significant difference between strategies. The small, open-label study compared two treatment targets over 104 weeks, leaving smaller effects uncertain.

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Two bicarbonate targets were compared in Vienna

A higher blood bicarbonate target showed no clear additional kidney-function benefit in the peer-reviewed SoBic study, a randomized trial at a renal outpatient service in Vienna, Austria. It enrolled 58 people with third- or fourth-stage chronic kidney disease and overt metabolic acidosis, an acid–base imbalance. Participants began with serum bicarbonate at or below 21 millimoles per litre. Follow-up lasted 104 weeks. The open-label design meant that patients and clinicians knew which treatment strategy had been assigned.[1], [2]

The targets were approximately 24 and 20 millimoles per litre, each with a one-millimole tolerance. Doses of sodium bicarbonate were adjusted to repeated blood measurements. In the lower-target group, levels below 19 millimoles per litre required rescue supplementation. Both strategies could therefore involve bicarbonate treatment. Aiming higher was tested for additional benefit in this population; supplementation versus no supplementation was outside the design.[1]

Blood levels separated without a clear filtration advantage

The higher-target group received a median daily sodium bicarbonate dose of 6.7 grams. Around 70 per cent of each group reached its target. Average blood-level separation reached 3.57 millimoles per litre at week 47 and 3.64 at week 104. Despite this separation, the difference in estimated kidney-filtration change was −0.98 millilitres per minute per 1.73 square metres. The uncertainty interval crossed zero and the difference was not statistically significant. Smaller treatment effects remain uncertain with the small sample.[1]

Follow-up tracked dialysis and adverse events

Follow-up was completed by 49 participants; two died and four started dialysis. Investigators also tracked blood pressure, body weight, medication changes and adverse events. Those outcomes provide a broader account of patients’ experience during the trial, but the deaths and dialysis starts do not by themselves establish harm from bicarbonate. The central kidney-function comparison remained imprecise.[1]

The results concern advanced disease with established acidosis and these particular target strategies. Rescue treatment in the comparison arm also narrows what the trial can show. Patient characteristics and treatment separation differ from earlier studies that reported other outcomes. The finding leaves broader questions about disease stage and dosing open, rather than establishing that bicarbonate supplementation has no benefit for every patient group.[1]

References

  1. News sourceScientific ReportsHigher bicarbonate target shows no added kidney benefit in a small trial↩1↩2↩3↩4↩5
  2. News sourceScienmagHigher bicarbonate target shows no added kidney benefit in a small trial↩
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