Lab case 385 interpretation


 Question 1:

PH = 7.344, that is mild acidaemia.

HCO3 = 18.4 mmol/L (less than 24). So, we have metabolic acidosis.

Next, we need to calculate the compensation and the anion gap.

To calculate respiratory compensation, we use Winter’s formula, that is

Expected CO2 = 1.5 x HCO3 + 8 (+/- 2). For this patient, expected CO2 will be:

1.5 x 18.4 + 8 (+/-2) = 33.75 – 37.75. Since this patient’s pCO2 is within the expected range then the patient doesn’t have an additional respiratory process.

Next, we will calculate the anion gap, that is Na – (Cl + HCO3) = 20.6, so we have HAGMA here.

Since we have HAGMA, then we need to calculate the Delta Ratio to exclude the presence of additional metabolic process.

Delta Ratio is calculated as AG-12/24-HCO3 = 1.53. This means that we have pure HAGMA (ratio between 0.8 and 2.0 means pure HAGMA).

Other abnormal findings:

Glucose = 20.7, that very high. High level of glucose interferes with Na level and leads to pseudo-hyponatraemia. To calculate the corrected level, we use the following equation:

Corrected Na = Measure Na – (Glucose -5)/3 = 143 mmol/L.

Other significant abnormality is the lactate level of 9.5 mmol/L. This lactate level is unusual for cases of DKA or dehydration. Most probably this patient has an additional metabolic process that interferes with the metabolism of lactate. (Type B Hyperlactataemia).

This patient had Ketones level of 0.2 mmol/L.

 Question 2:

With dehydration, injected insulin (SC) tends to accumulate in the subcutaneous tissue. With rehydration it starts to distribute to the systemic circulation then to the target organs.

Because This patient had injected 10 units of fast acting insulin about 2 hours before these results were obtained, we decided to hydrate the patient first before deciding on further treatment. The patient received 1L of normal saline over 30 minutes. Repeat blood sugar after 1 hour was 6 mmol/L.

We started to worry about cerebral oedema due to rapid osmolar shift, thankful the patient remained stable.