Question 1:

PH = 7.436, that is within normal range, more to alkalaemic side

Both PCO2 and HCO3 are high. Here either we have respiratory acidosis with metabolic compensation or we have metabolic alkalosis with respiratory compensation. The third option is we have combined metabolic alkalosis and respiratory acidosis.

Usually acidosis is associated with hyperkalaemia (acidosis causes potassium to move from cells to extracellular fluid (plasma) in exchange for hydrogen ions). Also, PH is more to Alkalotic side. Accordingly…The primary process is metabolic Alkalosis.

Now, we will calculate the compensation. Expected PCO2 = 0.7 x HCO3 + 20 (+/- 5) = 44.5 (the accepted range is 39.5 to 49.5). In this case we have PCO2 of 53..So, we have combined metabolic alkalosis and respiratory acidosis.

The other abnormal finding is K = 2.4 (level less than 2.5 mmol/L = severe hypokalaemia).

No other abnormal findings in these blood gases.

Next we look at the causes of metabolic alkalosis.. for that we use the mnemonic CLEVER PD.

C – contraction (dehydration)

L – liquorice (diuretic), laxative abuse

E – endocrine (Conn’s, Cushing’s)

V – vomiting, GI loss (villous adenoma)

E – excess alkali (antacids)

R – renal (Bartter’s), severe K depletion

P – post hypercapnia

D – diuretics

Question 2:

Hypokalaemia is usually caused by reduction in potassium intake, excessive loss through kidneys or GIT or transcellular shifts.

kidneys can significantly lower potassium excretion in response to reduced intake, insufficient intake rarely causes of hypokalemia, but it might contributes to hypokalemia in hospitalized patients.

References:

• Weiner ID, Wingo CS. Hypokalemia—consequences, causes, and correction. J Am Soc Nephrol. 1997;8(7):1179–1188.
• Mount DB, Zandi-Nejad K. Disorders of potassium balance. In: Taal MW, Chertow GM, Marsden PA, Brenner BM, Rector FC, eds. Brenner and Rector’s The Kidney. Philadelphia, Pa.: Elsevier/Saunders; 2012.