# Lab case 370 Interpretation

PH = 7.481, That is mild alkalaemia.

pCO2 = 21 mmHg, so we have metabolic alkalosis.

Next, we will calculate the compensation. It is not clear from the history if the respiratory alkalosis is acute or chronic.

For Acute respiratory alkalosis, we expect HCO3 to decrease by 2 mmol for every 10 pCO2 below 40. Accordingly, the expected HCO3 to be around 20 mmol if the case was pure acute respiratory alkalosis.

For chronic respiratory alkalosis, we expect HCO3 to decrease by 5 mmol for every 10 pCO2 below 40. Accordingly, the expected HCO3 to be around 14 mmHg. (Chronic respiratory alkalosis can be caused by chronic pulmonary diseases, congestive cardiac failure or severe anaemia), Hb of 98 is not severe enough to cause respiratory alkalosis.

In the presence of high lactate, high ketones and high creatinine, most probably we have metabolic acidosis. This patient has high blood glucose level. So, the patient has DKA.

Because of the above we are going to consider the respiratory alkalosis to be acute, and because HCO3 is lower than expected then the patient has additional metabolic acidosis.

Once we find that there is metabolic acidosis then we need to calculate the anion gap. That is Na – (Cl+HCO3) = 133 – (98 + 15.6) = 19.4. That is high.  (HAGMA).

In the presence of high glucose level, Na level will be falsely reduced (Pseudohyponatraemia). The corrected Na level is calculated as:

Corrected Na= measure Na + (Glucose level – 5)/3 = 141. That will give us a higher AG of 28.

Because we have HAGMA then we need to calculate the delta ratio to exclude the presence of additional metabolic process. Delta ratio is calculated as:

Delta ratio = (AG – 12) / (24 – HCO3) = 1.7 (Level between 0.8 and 2 indicates pure HAGMA).

So, we have combined acute respiratory alkalosis and HAGMA.

As discussed earlier, this patient has high glucose level, high lactate and high ketones. In the presence of HAGMA then this patient has DKA. (Especially with ketones level higher than 3 mmol/L).

Treatment should commence according to local DKA protocols.

For the causes of respiratory alkalosis, we use the mnemonic CHAMPS

• C = CNS diseases
• H = Hypoxia
• A = Anxiety/Pain
• M = Mechanical ventilation/ over ventilation
• P = Progesterone
• S = Salicylates / sepsis

This patient was extremely anxious and that was the cause of her respiratory alkalosis.

Special thanks to Dr Shane Collis for providing the details for this case