Lab case 378 interpretation


Question 1:

PH = 7.42, that is within normal range, more to the alkalotic side.

HCO3 = 36.8 mmol/L that is consistent with metabolic alkalosis. Next we will calculate the compensation.

To calculate the compensation for metabolic alkalosis we use the following formula:

Expected pCO2 = HCO3 x 0.7 + 20 = 45.76 (+/- 5). The value that we have is higher than that (52). SO we have additional respiratory acidosis.

It is a good practice to calculate the anion gap to exclude additional HAGMA.

AG = Na – (Cl + HCO3) = 9.2. So, we don’t have additional HAGMA.

Other abnormal findings:

K = 2.4 mmol/L. That is severe hypokalaemia.

Cl = 90 mmol/L. that is hypochloraemia.

Lactate = 3.6, that is high (moderate hyperlactataemia).

Final conclusion: This patient has Hypokalaemic, Hypochloraemic metabolic alkalosis with associated respiratory acidosis.

 Question 2:

For the differential diagnosis of metabolic alkalosis we use the mnemonic CLEVER PD

C – contraction (dehydration), possible

L – liquorice (diuretic), laxative abuse, excluded by history taking

E – endocrine (Conn’s, Cushing’s), unlikely.

V – vomiting, GI loss (villous adenoma), Patient has been vomiting.. most likely vomiting is the cause.

E – excess alkali (antacids), excluded by history taking

R – renal (Bartter’s). Unlikely

P – post hypercapnia, No

D – diuretics, excluded by history taking.

 Question 3:

The presence of alkalosis with vomiting reflects upper GI source of vomiting.

The treatment consists of correcting the physiology (electrolytes and fluid replacement) and correction of the source (Slipped lap band).

Remember, we need to check and correct Mg level prior to correcting K level.

The presence of elevated lactate can reflect possible erosion and necrosis of the stomach tissue caused by the slipped band. This require urgent surgical referral for band removal.