Interactive ABG tool

Arterial blood gas analysis assessment tool

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Instructions

• This tool is still under development so please report any issues or feedback to s.kerr@keele.ac.uk• Work through each of the cases to determine the acid-base status of each of the patients. • For each step, select ‘ACCEPT’ to submit your response and receive feedback. • To continue to the next step, select ‘Next step’ to move to the next step in solving the case.

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Intended Learning Outcomes

This tool should enable you, the student, to:• interpret ABG results• evaluate acid-base balance disturbances• asssess the most likely cause of the acid-base disturbance & whether there is compensation

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Index

Introduction

CASE 1

CASE 2

CASE 3

CASE 4

CASE 5

(new case)

Case scenario 1

Index

Start

A patient is brought into the casualty department semi-conscious. The patient was found at home with an empty bottle of vodka and an empty bottle of sleeping pills nearby. The patient was not rousable but responded to painful stimuli. Blood gas analysis showed:

Step 1.1

First step is to check the oxygenation status of the patient

Next step

Back

Step 1.2

Next step is to determine if there is an acid-base disturbance

Next step

Back

Step 1.3

Next step

Look at whether there are changes in the PCO2 and HCO3- that could be causing the acid-base disturbance

Back

Step 1.4

Think about whether the acid-base disturbance is a change in lung function (PCO2) or is a metabolic change (HCO3-)

Next step

Back

Step 1.5

Use your knowledge of oxygenation and carbon dioxide to determine the answer

Next step

Back

Step 1.6

Check whether the PCO2/HCO3- (the one that wasn't identified as the primary disturbance) has changed in the direction that would help bring the pH back to normal

Next step

Back

Step 1.7

Check the base excess

Next step

Back

Step 1.8

Next step

Back

Congratulations, case solved!

Case 1 Completed

The patient has acute respiratory acidosis due to Type II Respiratory Failure brought on by drug-induced central neural respiratory depression

Case 2

Case scenario 2

Index

Start

A patient suffered a catastrophic stroke and following this event respiration was seen to be irregular and inadequate (rise in arterial Pco2 recorded). The patient was intubated and ventilated with an inspired oxygen concentration of 40%. Analysis of a blood sample 4 hours later showed:

Step 2.1

First step is to check the oxygenation status of the patient

Next step

Back

Step 2.2

Next step is to determine if there is an acid-base disturbance

Next step

Back

Step 2.3

Next step

Look at whether there are changes in the PCO2 and HCO3- that could be causing the acid-base disturbance

Back

Step 2.4

Next step

Think about whether the acid-base disturbance is a change in lung function (PCO2) or is a metabolic change (HCO3-)

Back

Step 2.5

Next step

Check whether the PCO2/HCO3- (the one that wasn't identified as the primary disturbance) has changed in the direction that would help bring the pH back to normal

Back

Step 2.6

Next step

Check the base excess

Back

Step 2.7

Next step

Back

Congratulations, case solved!

Case 2 Completed

The patient has acute respiratory alkalosis brought on by overventilation

Case 3

Case scenario 3

Index

Start

A patient with abdominal pain due to a duodenal ulcer was admitted to the medical ward with persistent vomiting. He was also taking large quantities of sodium bicarbonate to ease the pain. A sample of arterial blood revealed:

Step 3.1

First step is to check the oxygenation status of the patient

Next step

Back

Step 3.2

Next step is to determine if there is an acid-base disturbance

Next step

Back

Step 3.3

Next step

Look at whether there are changes in the PCO2 and HCO3- that could be causing the acid-base disturbance

Back

Step 3.4

Next step

Think about whether the acid-base disturbance is a change in lung function (PCO2) or is a metabolic change (HCO3-)

Back

Step 3.5

Next step

Check whether the PCO2/HCO3- (the one that wasn't identified as the primary disturbance) has changed in the direction that would help bring the pH back to normal

Back

Step 3.6

Next step

Check the base excess

Back

Congratulations, case solved!

Case 3 Completed

The patient has a metabolic alkalosis with respiratory compensation due to consuming large quantities of sodium bicarbonate

Case 4

Case scenario 4

Index

Start

A 52 year old man was admitted unconscious to casualty. He was a known diabetic on daily insulin. One week ago he had developed a chest infection. He stayed at home and because he stopped eating he stopped his insulin. Over the preceding 2 days he had become increasingly drowsy and in the morning of admission he was unrousable. The arterial blood gas results were:

Step 4.1

First step is to check the oxygenation status of the patient

Next step

Back

Step 4.2

Next step is to determine if there is an acid-base disturbance

Next step

Back

Step 4.3

Next step

Look at whether there are changes in the PCO2 and HCO3- that could be causing the acid-base disturbance

Back

Step 4.4

Next step

Think about whether the acid-base disturbance is a change in lung function (PCO2) or is a metabolic change (HCO3-)

Back

Step 4.5

Next step

Check whether the PCO2/HCO3- (the one that wasn't identified as the primary disturbance) has changed in the direction that would help bring the pH back to normal

Back

Step 4.6

Next step

Check the base excess

Back

Congratulations, case solved!

Case 4 Completed

The patient has a metabolic acidosis with respiratory compensation due to diabetic ketoacidosis from not taking his insulin

Case 5

Case scenario 5

Index

Start

A 48-year-old woman with a history of obesity and sleep apnea presents to the emergency department with complaints of increased shortness of breath, fatigue, and daytime sleepiness over the past week. She reports irregular use of her continuous positive airway pressure (CPAP) machine. The arterial blood gas results were:

Step 5.1

First step is to check the oxygenation status of the patient

Next step

Back

Step 5.2

Next step is to determine if there is an acid-base disturbance

Next step

Back

Step 5.3

Next step

Look at whether there are changes in the PCO2 and HCO3- that could be causing the acid-base disturbance

Back

Step 5.4

Next step

Think about whether the acid-base disturbance is a change in lung function (PCO2) or is a metabolic change (HCO3-)

Back

Step 5.5

Next step

Check whether the PCO2/HCO3- (the one that wasn't identified as the primary disturbance) has changed in the direction that would help bring the pH back to normal

Back

Step 5.6

Next step

Check the base excess

Back

Congratulations, case solved!

Case 5 Completed

The patient has a respiratory acidosis with metabolic compensation due to chronic hypoventilation related to her untreated sleep apnea

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