Sat27November0556PM 3

A 45-year-old woman is admitted to the medical admissions unit with a provisional diagnosis of a diabetic ketoacidosis.

Her biochemistry results are as follows.

pH 7.21 (7.35-7.45)

PaCO2 11 mmHg (38-42)

PaO2 98 mmHg (75-100)

BE -17 (-3 to +3)

Bicarbonate 8 mEq/L (22-28)

SpO2 98%

Glucose 25.8 mmol/L (3.5-5.5)

Na 139 mmol/L (135-145)

K 6 mmol/L (3.5-5.1)

Cl 105 mmol/L (99-101)

Bic 8 mmo/L (22-29)

Urea 10.4 mmol/L (1.7-8.3)

Creat 101 µmol/L (44-80)

Which one of the following values approximates best to the calculated anion gap (mmol/L) ?

(Please select 1 option)

32 Correct

28

22

16

36

Explanation

The anion gap is a method of assessing the contribution of unmeasured anions to acidosis. It is calculated by adding the values of the principal measured cations and subtracting the values of the principal measured anions.

Anion gap = [K+] + [Na+] - [Cl-] l- [HCO3-] (plasma concentrations in mmol/L).

The normal range for the anion gap is 8-16 mmol/L.

In this example, the anion gap = [6] + [139] - [105] - [8] = 32 mmol/L

Causes of an elevated anion gap include:

Ketoacid overproduction (diabetes, alcohol, starvation)

Lactic acid overproduction

Inability to excrete acids (sulfate and phosphate) secondary to acute kidney injury

Dehydration, and

Poisoning with salicylates, ethylene glycol, methanol, paraldehyde and propyl alcohol.

Answer Statistics

1

82%

2

5%

3

10%

4

2%

5

3%

Times answered: 267