When Does a Bicarb Drip Make Sense?

A 70-year-old woman is admitted to the intensive care unit (ICU) with a pH of 7.1, an acute kidney injury (AKI), and ketonuria. She is volume depleted and her history is consistent with starvation ketosis. This LOL truly is in NAD (that's little old lady in no acute distress, for those who haven't read The House of God). She is clinically stable and seemingly unperturbed by the flurry of activity surrounding her admission.

Your resident is concerned by the severity of the acidosis and suggests starting an intravenous (IV) bicarbonate drip. The fellow is adamantly against it. He's been taught that IV bicarbonate increases the serum pH but paradoxically causes intracellular acidosis. As the attending you elect to observe fellow autonomy — no bicarb is given. Because any debate on rounds is a "teachable moment," you decide to review the evidence and physiology behind infusing bicarbonate.

What Do the Data Reveal?

An excellent review published in CHEST in 2000 covers the physiologic effects of bicarbonate, specifically related to lactic acidosis, which our patient didn't have. Aside from that difference, the review validates the fellow's opinion. In short, the authors state that a low pH may be a marker of a dangerous systemic condition, but it need not be corrected for its own sake. It is unlikely to provoke hemodynamic or respiratory compromise outside the setting of shock or hypercapnia. IV bicarbonate can lead to intracellular acidosis, hypercapnia, hypocalcemia, and a reduction in oxygen delivery via the Bohr effect. The authors concluded that because the benefits are unproven and the negative effects are real, IV bicarbonate should not be used to correct a metabolic acidosis.

The CHEST review hardly settles the issue, though. A survey published a few years later found a majority of intensivists and nephrologists used IV bicarbonate to treat metabolic acidosis while the Surviving Sepsis Campaign Guidelines for the Management of Sepsis and Septic Shock published in 2017 recommended against bicarbonate for acidosis. It wasn't until 2018 that we reached the holy grail: a randomized controlled trial.

The BICAR-ICU study randomly assigned patients with a pH ≤ 7.20, PaCO₂ ≤ 45 mm Hg, and sodium bicarbonate concentration ≤ 20 mmol/L to receive no bicarbonate vs a sodium bicarbonate drip to maintain a pH > 7.30. There's additional nuance to the trial design and even more detail in the results. To summarize, there was signal for an improvement in renal outcomes across all patients, and those with AKI saw a mortality benefit. Post–BICAR-ICU iterations of the Surviving Sepsis Campaign Guidelines have incorporated these findings by recommending IV bicarbonate for patients with sepsis who have AKI and a pH ≤ 7.20.

That's not to say BICAR-ICU has settled the issue. Although it's far and away the best we have, there were fewer than 400 total patients in their intention-to-treat analysis. It was open-label, with lots of crossover. The primary outcome was negative for the entire population, with only a subgroup (albeit a prespecified one) showing benefit. Finally, the results weren't stratified by etiology for the metabolic acidosis. There was also evidence of alkalosis and hypocalcemia in the treatment group.

Last but not least in terms of importance, in most cases when bicarbonate is being considered, wouldn't some form of renal replacement therapy (RRT) be preferred? This point was raised by nephrologists and intensivists when we covered BICAR-ICU in a journal club at my former program. It's also mentioned in an accompanying editorial. RRT timing is controversial, and a detailed discussion is outside the scope of this piece and beyond the limits of my current knowledge base. But I do know that the A in the A-E-I-O-U acute indications for dialysis pneumonic stands for acidosis.

Our patient had AKI, a pH ≤ 7.20, and a pCO₂ well under 45 mm Hg. Does BICAR-ICU support the resident's inclination to start a drip? Sort of. The majority of patients enrolled in BICAR-ICU were in shock or were recovering from cardiac arrest, so it's not clear the results can be generalized to our LOL with starvation ketosis. Extrapolating from studies of diabetic ketoacidosis (DKA) seems more appropriate, and here the data are poor but equivocal. Reviews are generally negative but don't rule out the use of IV bicarbonate in certain patients with DKA. 

Key Takeaways

Our patient survived a 24-hour ICU stay with neither cardiopulmonary decompensation nor a need for RRT. Not sure how she did out of the ICU; presumably she was discharged soon after transfer. As is always the case with anecdotal medicine, the absence of a control prevents assessment of the counterfactual. Is it possible she may have done "better" with IV bicarbonate? Seems unlikely to me, though I doubt there would have been demonstrable adverse effects. Perhaps next time the fellow can observe resident autonomy?

Aaron B. Holley, MD, is a professor of medicine at Uniformed Services University in Bethesda, Maryland, and a pulmonary/sleep and critical care medicine physician at MedStar Washington Hospital Center in Washington, DC. He covers a wide range of topics in pulmonary, critical care, and sleep medicine.

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Cite this: When Does a Bicarb Drip Make Sense? - Medscape - Sep 01, 2023.