Question 1:

PH = 7.451 that is a very mild alkalaemia

PCO2 is 26 mmHg (less than 40), so we have respiratory alkalosis.

Next step is to check for compensation. From the information available, we cant tell if the condition is acute or chronic.

For acute respiratory alkalosis, we expect the HCO3 to drop by 2 for every 10 of CO2 below 40. Accordingly, the expected HCO3 should be “24 – (14 x 0.2)” = 21.2. HCO3 in this case is 18. So we have additional metabolic alkalosis.

For chronic respiratory alkalosis, we expect HCO3 yo drop by 5 for every 10 of CO2 below 40. Accordingly, the expected HCO3 should be “24 – (14 x 0.5)” = 17, that is very close to the value that we have 18

Other findings:

Na = 129, Moderate hyponatraemia.

K = 3.0, Moderate hypokalaemia

Hb = 80 g/dL = anaemia

Glucose = 9.2, mild hyperglycemia

Lactate – 5.1, severe hyperlactataemia. Lactate level more than 5 is usually associated with metabolic acidosis. To confirm that we will calculate the anion gap (Na – (Cl +HCO3) = 14 (>12). So, we have might have additional HAGMA.

In this case the patient had Chronic respiratory acidosis with high anion gap metabolic acidosis. The cause of the respiratory alkalosis was the massive ascites, this will cause abdominal distention and reduced the breathing capacity and the tidal volume. The body will compensate by increasing the respiratory rate which causes respiratory alkalosis. The HAGMA is due to hyperlactataemia secondary to liver failure. The hyponatraemia and hypokalaemia are due to the dilution associated with fluid retention.

 Question 2:

For the differential diagnosis of respiratory alkalosis we use the mnemonic CHAMPS.

C = CNS causes

H = Hypoxia (pulmonary causes).

A = Anxiety or Pain

M = Mechanical ventilation

P = Progesterone or Pregnancy

S = Salicylate or sepsis.

 

Question 3:

Lactic acidosis is usually divided into 2 categories

Type A, usually occur in association with clinical evidence of poor tissue perfusion or oxygenation of blood.

Type B lactic acidosis, occur with no evidences of impaired tissue oxygenation or perfusion. Type B is subdivided into 3 categories.

Type B1 usually occur in association with systemic disease like hepatic failure, renal failure, diabetes or malignancy

Type B2 is caused by several classes of medication or toxins, examples: Biguanides, alcohols, iron, INH, zidovudine and salicylates.

Type B3 is due to inborn errors of metabolism.