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Acid-Base Disorders: Identification and Causes

In this course, we explain physiological concepts which will help you interpret acid-base disturbances detected on the ABG. We explain the clinical importance of calculation of the anion gap in the presence of a metabolic acidosis. We explain the link between extracellular fluid (ECF) electrolyte levels and ECF pH.

1.5 x AMA PRA Category 1 Credits™
Available on the Pro Plan



In this course, we teach you how to identify acid-base disturbances on the arterial blood gas (ABG). We begin by dealing with important physiological concepts which will help you interpret changes in parameters on the ABG relevant to acid-base balance. We will teach you the differential diagnosis of metabolic and respiratory pH disturbances. We explain the concept of the ‘anion gap’ and show you how calculation of this variable can guide investigation in the presence of a metabolic acidosis. We explain the link between extracellular fluid (ECF) electrolyte levels and ECF pH with particular reference to metabolic alkalosis.


Planner and Author: Dr John Seery MB PhD

  • Consultant Physician at St. Vincent's University Hospital, Dublin, Ireland
  • Lecturer at the School of Medicine and Medical Science, University College Dublin, Ireland
  • Studied medicine at the University of Cambridge, United Kingdom
  • A Natural Sciences graduate of Trinity College Dublin, Ireland
  • PhD in Cell Biology from University College London, United Kingdom

Planner: Dr Karen Strahan PhD (University of Cambridge), Head of Editorial
Planner: Tommy O'Sullivan, CME Manager

Estimated Time to Complete

1.5 hours

Target Audience

  • Physicians
  • Nurses
  • Nurse Practitioners
  • Physician Assistants
  • Paramedics

Learning Objectives

Upon successful completion of this activity, you will be able to:

  • Explain physiological compensation and mass action in the context of pH disturbances
  • Explain the bicarbonate buffer equilibrium
  • Calculate and interpret the anion gap in cases of metabolic acidosis
  • Identify abnormalities of serum potassium and or chloride concentration as the cause of a metabolic alkalosis

Course Content

  • Introduction
  • Mass Action
  • Physiological Compensation
  • Bicarbonate Buffer System
  • Patterns of pH Disturbance
  • Metabolic Acidosis - Causes
  • The Anion Gap
  • Metabolic Alkalosis - Causes
  • Respiratory pH Disturbances - Causes
  • Quiz
  • Essential Reading

Release date


Expiration date


Instructions for Participation

Participants must complete the online activity during the valid period as noted above.
Follow these steps:

  1. View videos in sequence
  2. Read the papers on the essential reading list
  3. Complete the quiz
  4. Complete the activity evaluation form to provide feedback for continuing education purposes and for the development of future activities
  5. Download the Certificate of Completion

Relevant Financial Disclosures

Acadoodle adheres to the ACCME's Standards for Integrity and Independence in Accredited Continuing Education. Any individuals in a position to control the content of a CE activity, including faculty, planners, reviewers or others are required to disclose all relevant financial relationships with ineligible entities (commercial interests). All relevant conflicts of interest have been mitigated prior to the commencement of the activity.

Planners and faculty for this activity have no relevant financial relationships with commercial interests to disclose.


Brandis K. Acid-Base Physiology.

Seery JP. 10 Things You Need to Know about Arterial Blood Gas (ABG): Identifying Simple pH Disturbances.

Higgins C. Clinical aspects of the anion gap.

Rutledge TE. Acid-base disturbances in the emergency department. Part 2: Making the diagnosis. Can Fam Physician. 1991:37:2469-75.

Galla JH. Metabolic Alkalosis. J Am Soc Nephrol. 2000;11:369-75.

Additional Reading

Story DA. Bench-to-bedside review: A brief history of clinical acid-base. Crit Care. 2004;8(4):253-8.

Story DA. Stewart Acid-Base: A Simplified Bedside Approach. Anesth Analg. 2016;123(2):511-5.

Cove M and Kellum JA. The End of the Bicarbonate Era? A Therapeutic Application of the Stewart Approach. Am J Respir Crit Care Med. 2020;201(7):757-8.

Zanella A et al. Extracorporeal Chloride Removal by Electrodialysis. A Novel Approach to Correct Acidemia.  Am J Respir Crit Care Med. 2020;201(7):799-813.

Stewart PA. Modern quantitative acid-base chemistry. Can J Physiol Pharmacol. 1983;61(12):144-61.

Brandis K. Acid-Base Physiology.

Kraut JA and Madias NE. Serum Anion Gap: Its Uses and Limitations in Clinical Medicine. Clin J Am Soc Nephrol. 2007;2(1):162-74.

ACCME Accreditation Statement

Acadoodle, Ltd is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.

Credit Designation Statement

AMA Physician’s Recognition Award

Acadoodle, Ltd designates this enduring material activity for a maximum of 1.5 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

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