A 41 year old man is admitted to your Emergency Department, unconscious, with the first set of blood results. The second set of blood gases are taken  1 hour later.

Parameter

Initial values

1 hour later

Normal range

pH

7.05

7.35

7.35-7.45

PaCO2

34 mmHg (4.6
kPa)

39 mmHg (5.2 kPa)

35-45 mmHg (4.7-6.0
kPa)

PaO2

203 mmHg (33.6 kPa)

94 mmHg (12.5 kPa)

75-98 mmHg (10.0-
13.0 kPa)

Actual bicarbonate

9 mmol/l

21

22-26 mmol/l

Sodium

137 mmol/l

134-145 mmol/l

Potassium

4.2 mmol/l

3.5-5.1 mmol/l

Glucose

11.2 mmol/l

Ionised
Calcium

1.21 mmol/l

2.15-2.55 mmol/l

Chloride

105 mmol/L

95-105 mmol/L

a. Describe the initial acid-base  disturbance
b. List 3 clinical scenarios which may produce such a pattern of arterial blood gas derangement?

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College Answer

3.2a. The initial acid-base disturbance is a mixed metabolic and respiratory acidosis with a raised anion gap.

3.2b. Seizures
Resuscitated cardiac arrest
Near drowning
Near hanging

Discussion

This question is identical to Question 15.2 from the second paper of 2009.