Question

Conrad Jackson is a 28-year-old man who presents to the emergency department with severe fatigue and dehydration secondary to a 4-day history of vomiting. During the interview, he describes attending a family reunion and states that perhaps he “ate something bad.” Upon admission his vital signs are a temperature of 102.7°F, heart rate of 116 bpm, respiratory rate of 18 breaths/min, and blood pressure of 86/54 mm Hg. The nurse also notes the patient has dry mucous membranes and tenting of skin. The physician orders an IV to be started with 0.45% normal saline, and orders a serum electrolytes and an arterial blood gas. (Learning Objective 7)

The following results are returned from the laboratory:

Sodium (Na+) 150

Potassium (K+) 5.5

Chloride (Cl¯) 110

BUN 42

Creatinine 0.8

Glucose 86

pH 7.32

PaCO2 35

HCO3¯ 20

PaO2 90

O2 Sat 98%

What is your interpretation of this arterial blood gas sample?

Explain the high potassium in this patient.

Calculate the patient’s anion gap:

What is the interpretation of this anion gap?

Answer 1

1. Interpretation of arterial blood gas (ABG) :-
- pH is low at 7.32, but normal is around 7.4.
- HCO3 (bicarbonate) is low at 20. Normal range for HCO3 is around 22-28.
- patients is in acidosis.

2. Cause of high potassium:-
- Because of Mr. Jackson’s symptoms of tenting of the skin and dry mucous membranes, represent being dehydrated.
- Dehydration can lead to higher potassium levels.

3. Patient's anion gap:-
- The anion gap is the difference between primary measured cations (sodium and potassium) and the primary measured anion (chloride and bicarbonate) in serum.
=> Na – (Cl+HCO3) = x.d.
=> 150 – (110+20) = 20.

4. Interpretation of anion gap:-
- patient's anion gap is over 16, which is indicative of having metabolic acidosis.