Syllabus · Current · V5 (2025) · Acid - Base
G1 · Acid Base Physiology
G1.iv · Henderson–Hasselbalch vs Stewart
Explain the traditional (Henderson-Hasselbach) and physico-chemical (Stewart) approaches to acid-base interpretation.
Written examination
SAQ history
Stewart Acid–Base
1 exam appearance
Outline the abnormalities in the following arterial blood gas (25% of Marks). Explain the Stewart approach to acid-base interpretation (75% of Marks).
21%
Oral examination
VIVA history
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2026A · VIVA 2
Relevant examiner prompt
Describe the abnormalities in the following arterial blood gas.
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2025B · VIVA 2
This viva will examine acid-base physiology and pharmacology. Interpret these lab values using either the traditional or Stewart (physicochemical) approach to acid-base. pH 7.20 (7.35 - 7.45) pCO2 39mmHg (5.2 kPa) (35 - 45mmHg or 4.7-6.0 kPa) HCO3- 15mmol/l (22 - 26mmol/l) Lactate 10mmol/l (0 - 2mmol/l) BE -14 mmol/l (-3 - +3mmol/l) Na 126 mmol/l (135 - 145mmol/l) K 3 mmol/l (3.7 - 4.7mmol/l) Cl 82mmol/l (101 – 110mmol/l) Cai 1.5mmol/l (1.15 – 1.30mmol/l) Mg 1mmol/l (0.7 – 1mmol/l) PO4 1.5 mmol/L (0.8 – 1.5 mmol/l) Albumin 20g/L (35 – 50 g/L)
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2024B · Day 1 · VIVA 2
This VIVA will examine acid-base and renal physiology and pharmacology. Outline the principles of the Stewart (physicochemical) approach to acid base disturbances. Using this approach interpret the arterial blood gas below. (Image removed from report.)
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2022A · Day 1 · VIVA 5
This viva will explore your understanding of acid-base physiology. List the abnormalities in this arterial blood gas analysis. FiO2 0.5 pH 7.1 PCO2 25 mmHg (3.3 kPa) PO2 100 mmHg (13.3 kPa) HCO3- 7 mmol/L Base deficit -19.9 Na+ 133 mmol/L K+ 4.5 mmol/L Cl- 105 mmol/L Anion gap 25 Lactate 7 mmol/L
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2020B · Day 3 · VIVA 6
This viva will explore your knowledge of acid-base physiology and albumin. Describe the Henderson Hassebalch Equation.
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2019B · Day 1 · VIVA 4
This viva will explore your understanding of acid base balance. What is the anion gap?
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2017A · Day 2 · VIVA 4
This viva will examine acid/base physiology. What is the Henderson–Hasselbalch equation?
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2014B · VIVA 3
This Viva tested knowledge on intravenous fluids. It explored understanding about colligative properties, anion gap and moved on to the pharmacology of frusemide.
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2013A · VIVA 7
This viva examined the physiology of acid/base and the role of the kidney in acid/base balance. The opening question was “What is the Henderson Hasselbalch equation?”
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2012A · VIVA 7
This Viva will explore your knowledge of fluids and colligative properties. What is in a bag of 0.9% Saline? Subsequent questions explored knowledge of osmolality, osmolarity, mannitol, colligative properties of fluids, anion gap, classification of diuretics and mechanism of actions.
Sources: objective text from the relevant CICM syllabus; historical SAQ and VIVA wording from CICM examiner reports.