Question 7.1

Last updated Thu, 07/25/2019 - 22:55
 Topic: Acid-Base Disorders
Pass rate
84%
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A 16 year old male has been treated all night for diabetic ketoacidosis. In the morning the blood gas printout is as follows:

Barometric pressure

760mm Hg

FiO2

0.21

pH

7.32

pO2

100 mm Hg(13.3 kPa)

pCO2

30 mm Hg (4 kPa)

HCO3-

15.0mmol/L

Standard base excess

-9.9mmol/L

Sodium

135mmol/L

(135 – 145)

Chloride

114mmol/L

(100 -110)

Potassium

3.5mmol/L

(3.2 - 4.5)

Lactate

1.3mmol/L

(0.2 - 2.5)

Glucose

14.3mmol/L

(3.6 – 7.7)

a) Describe the acid-base status.
b) Has the keto-acidosis resolved? Give your reasoning.

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College Answer

Q7.1a) Normal anion gap metabolic acidosis with appropriate respiratory compensation.

Q7.1b) Yes The anion gap is normal, indicating resolution of ketoacidosis. The persistent acidosis reflects saline fluid replacement coupled with the chloride retention during the period of ketonuria.

Discussion

Let us dissect these results systematically.
 

  1. The A-a gradient is normal.
    PAO2 = (0.21 × 713) - (30 × 1.25) = 112.2
    Thus, A-a = ( 112.2 - 100) = 12.2mmHg.
  2. There is acidaemia
  3. The PaCO2 is compensatory
  4. The SBE is -9.9, suggesting a metabolic acidosis
  5. The respiratory compensation is adequate - the expected PaCO2(15 × 1.5) + 8 = 30.5mmHg
  6. The anion gap is (135) - (114 + 15) = 6, or 9.5 when calculated with potassium. 

Has the ketoacidosis resolved? Well, there is no more anion gap, so yes- one would be forced to conclude that it has. A normal anion gap acidosis now prevails, likely due to either vigorous resuscitation with normal saline, or to the normal hyperchloraemia in the recovery phase of ketoacidosis.

References

Oh, M. S., H. J. Carroll, and J. Uribarri. "Mechanism of normochloremic and hyperchloremic acidosis in diabetic ketoacidosis." Nephron 54.1 (1990): 1-6.

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