9.1 The following arterial blood gas and biochemistry results are from a patient with cardiac and respiratory disease and recent profuse vomiting
- a) Describe the acid-base disturbance(s)
- b) List the potential causes of the acid-base abnormalities in this patient
9.2 A 35-year-old woman with pre-eclampsia is admitted to ICU following an emergency Caesarian section under general anaesthesia for failure to progress during labour at 38 weeks gestation. Arterial blood gas, full blood count and electrolytes post extubation are as follows:
- a) Describe and explain the acid-base status
- b) Calculate and interpret the A-a gradient
- c) What is the likely significance of the anaemia and the leukocytosis?
Answer and interpretation
9.1 a) Describe the acid-base disturbance(s)
- Metabolic alkalosis with respiratory compensation
9.1 b) List the potential causes of the acid-base abnormalities in this patient
Possible causes in this patient:
- Diuretic therapy
- Steroid therapy
- Vomiting from gastric outlet obstruction Post hypercapnoeic alkalosis
9.2 a) Describe and explain the acid-base status
- Acute respiratory acidosis
- At 38 weeks pregnancy the normal PaCO2 is <30 mmHg with a compensatory reduction in bicarbonate. The blood gases therefore indicate acute CO2 retention probably due to pain and narcotics. In the non-pregnant patient these results would indicate an uncompensated normal anion gap metabolic acidosis.
9.2 b) Calculate and interpret the A-a gradient
- A-a gradient – this is raised at 154 mmHg, suggesting shunt and/or V/Q mismatch.
- Possible explanations are the loss of FRC after abdominal surgery, segmental collapse/consolidation or aspiration
9.2 c) What is the likely significance of the anaemia and the leukocytosis?
- Hb and WCC – the mild anaemia is physiological in pregnancy and the neutrophil leukocytosis is a normal feature during labour and early post-partum
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.