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Mixed Acid-Base Disorders

In clinical practice, mixed acid-base disorders are frequently missed by healthcare professionals. In this course, you will learn how to identify mixed acid-base disorders on the ABG and how to delineate the likely contributing causes of such disturbances.

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



Mixed acid-base disorders are commonly encountered in clinical practice. They are frequently missed by healthcare professionals. On occasion, this has implications for patient management with lost opportunities for therapeutic intervention. In this course, we explain the significance of the ‘derived values’ (base excess and standard bicarbonate) reported on the arterial blood gas (ABG). In case studies, we show you how these values can help us detect the presence of mixed acid-base disturbances on the ABG and facilitate the diagnosis of unsuspected pathologies. We explain the limitations of the derived values. We demonstrate the application of the so-called ‘bedside rules’ in the detection of mixed acid-base disturbances on the ABG. We explain the role of ‘Winter’s formula’ in the assessment of the adequacy of respiratory compensation in metabolic acidosis and illustrate the clinical application of this formula. We show you how to apply and interpret the ‘delta ratio’ in cases of metabolic acidosis and illustrate how this value allows us distinguish between two major categories of causes of metabolic acidosis. We explain the nomenclature used on the ABG readout.


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

2.0 hours

Target Audience

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

Learning Objectives

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

  • Explain the nature of the ‘derived values’ reported on the ABG
  • Identify mixed acid-base disturbances on the ABG by applying the ‘bedside rules’
  • Identify mixed acid-base disturbances on the ABG by analysis of the ‘derived values’, base excess and standard bicarbonate
  • Use ‘Winter’s formula’ to assess the adequacy of compensation in a metabolic acidosis
  • Calculate the delta ratio to identify mixed causes of acidosis
  • Use appropriate terminology in the description of acid-base abnormality

Course Content

  • Introduction
  • Indentification of Mixed Acid-Base Disorders - Clues
  • The Bedside Rules
  • The Bedside Rules in Action
  • Base Excess & Standard Bicarbonate
  • Base Excess in a Clinical Case
  • Derived Values - Terminology
  • Derived Values - Limitations
  • The Delta Ratio
  • ABG Nomenclature
  • 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. The Great Trans-Atlantic Acid-Base Debate.

Yartsev A. Assessment of Compensation: Boston and Copenhagen Methods.

Rastegar A.  Use of the ΔAG/ΔHCO3 Ratio in the Diagnosis of Mixed Acid-base Disorders. J Am Soc Nephrol 2007;18(9):2429-31.

Additional Reading

Brandis K. Acid-Base Physiology. 9.6 Clinical Examples

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 2.0 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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