ABG changes in Cardiac Arrest and CPR


The degree of acid-base abnormality during cardiac arrest and cardio-pulmonary resuscitation (CPR) is dependent on a number of variables, which include:

  1. cause of arrest
  2. duration of arrest when arterial blood gas (ABG) is taken
  3. the quality of the CPR and ventilation the patient is receiving
  4. temperature of the patient when ABG taken
  5. drugs administered during arrest (ie. Adrenaline and NaHCO3)


  • lactic acidosis from hypoperfusion (Type A) and/or B2-agonist effect of adrenaline administration (Type B2)


  • may be inadequately ventilated leading to acidaemia (especially if not intubated)
  • iatrogenic hyperventilation is common during cardiac arrest, causes respiratory alkalosis


  • from combined metabolic and respiratory acidosis


  • if patient only receiving air (FiO2 0.21)
  • aspiration, pulmonary oedema, pulmonary embolus, primary respiratory pathology


  • quantifying degree of metabolic acidosis


  • from cell death and loss of cell membrane integrity and acidosis


  • stress response

References and Links


CCC 700 6

Critical Care


Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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