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Fast Facts

A brief refresher with useful tables, figures, and research summaries

Acid-Base Disturbances

Acid-base disturbances are common in the critically ill. The NEJM review Physiological Approach to Assessment of Acid-Base Disturbances provides the following algorithms to guide the workup of alkalemia and acidemia and to assess for compensatory responses and etiology:

Assessment of Acidosis
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(Source: Physiological Approach to Assessment of Acid-Base Disturbances. N Engl J Med 2014.)

Assessment of Alkalosis
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(Source: Physiological Approach to Assessment of Acid-Base Disturbances. N Engl J Med 2014.)

Lactic acidosis from septic shock is the most common acid-base disturbance in the medical ICU. However, if a patient is acidemic, remember to consider other etiologies, including alternative causes of lactic acidosis and acidosis from diabetic ketoacidosis (DKA), toxic ingestions, and other causes.

The use of IV sodium bicarbonate as a buffer in lactic acidosis is controversial. In the 2021 Surviving Sepsis Campaign guidelines, a weak recommendation was made against the use of sodium bicarbonate overall to improve hemodynamics or reduce vasopressor requirements. However, its use is suggested in a subset of patients with septic shock, severe metabolic acidemia (pH ≤7.2), and AKI (with AKIN score of 2 or 3) as per the results of the BICAR-ICU trial.

Electrolyte Disturbances

Electrolyte disturbances, including hypokalemia; hyperkalemia; hyponatremia; hypernatremia; and hypomagnesemia, are common in the ICU and can occur as a result of both the underlying condition and the use of resuscitation fluids.

  • Electrolyte levels should be corrected to normal ranges in the critically ill to prevent arrhythmia, altered mental status, and other complications.

Research

Landmark clinical trials and other important studies

Research

Sodium Bicarbonate Therapy for Patients with Severe Metabolic Acidaemia in the Intensive Care Unit (BICAR-ICU): a Multicentre, Open-Label, Randomised Controlled, Phase 3 Trial

Jaber S et al. Lancet 2018.

In the open-label multicenter BICAR-ICU trial, treatment with 4.2% bicarbonate solution to increase pH >7.3 in patients with severe metabolic acidosis (pH <7.2) and SOFA score >3 or lactate >2mM did not improve mortality at 28 days or reduce organ failure at 1 week. However, patients with acute kidney injury (AKIN score, 2−3) showed improved mortality and a reduction in organ failure. Adverse effects of bicarbonate infusion included metabolic alkalosis, hypernatremia, and hypocalcemia.

Read the NEJM Journal Watch Summary

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Reviews

The best overviews of the literature on this topic

Reviews

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Integration of Acid-Base and Electrolyte Disorders

Seifter JL. N Engl J Med 2014.

Describes a method of analyzing acid-base disorders that incorporates insights from the traditional, bicarbonate-centered model and the Stewart (or strong ion) model

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Lactic Acidosis

Kraut JA and Madias NE. N Engl J Med 2014.

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Guidelines

The current guidelines from the major specialty associations in the field

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Additional Resources

Videos, cases, and other links for more interactive learning

Additional Resources

Diagnostic Use of Base Excess in Acid-Base Disorders

Berend K. N Engl J Med 2018.

This article reviews the clinical use of base excess (a measure returned on most standard blood gas machines that assesses the metabolic component of acid-base status after controlling for the respiratory component) and in particular, its uses in the acute care setting.

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Fluids and Electrolytes Challenge: Molecular Physiology of Water Balance

Ingelfinger J. N Engl J Med 2015.

A 53-year-old woman with chronic kidney disease, hypertension, and a mood disorder presented with irritability and pressured speech. Lab data include: blood pressure 130/85 mm Hg, plasma sodium 155 mmol/L, potassium 4.5 mmol/L, blood urea nitrogen 67 mg/dL, creatinine 1.99 mg/dL, glucose 90 mg/dL, and plasma osmolality 339 mOsm/L. What is the best strategy to support this patient?

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Fluids and Electrolytes Challenge: Lactic Acidosis

Ingelfinger J. N Engl J Med 2014.

A 60-year-old man with diabetes, hypertension, and chronic kidney disease presents with abdominal pain and confusion. Lab data include: blood pH 6.68, PCO2 18 mm Hg, PO2 73 mm Hg; sodium 146 mmol/L, potassium 6.3 mmol/L, chloride 83 mmol/L, and bicarbonate <2.0 mmol/L. What strategy would provide the best support for this patient?

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Fluids and Electrolytes Challenge: Physiological Approach to Assessment of Acid-Base Disturbances

Ingelfinger J. N Engl J Med 2014.

A 22-year-old woman has received 6 liters of isotonic saline and is awaiting transfer to the operating room for stabilization of injuries suffered in a car accident. The lab values include blood pH 7.28, PaCO2 39 mm Hg, sodium 135 mmol per liter, potassium 3.8 mmol per liter, chloride 115 mmol per liter, and bicarbonate 18 mmol per liter. What strategy would provide the best support for this patient?

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Interpretation of ABGs

Kaufman D. American Thoracic Society.

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