Answers lab case 221
Question 1:
PH = 7.59, that is alkalaemia.
PCO2 = 23, that is low ( less than 40 mmHg) So we have respiratory alkalosis.
Next step is we look for the compensation, from the story the condition looks acute. The compensation equation for acute respiratory alkalosis is
Expected HCO3 = PCO2 – [(40-PCO2)/10] x 2 = 21.6….. that is slightly less than 22. It can be considered fully compensated or there is an associated metabolic acidosis.
Always calculate the anion gap,
AG = Na – (Cl + HCO3 ) = 19. So, we have associated high anion gap metabolic acidosis.
Next step we calculated delta ratio.
Delta ratio = AG – 12/ 24 – HCO3 that is 7/2 = 3.5. Accordingly we have HAGMA and metabolic alkalosis.
Calculated osmolarity = 2 x Na + urea + glucose = 312, osmolarity is high.
Na = 127, that is low. Before considering hyponatraemia we need to make sure it is not factitious due to hyperglycaemia. So, we need to calculate corrected Na level for high glucose.
Corrected Na = Na + [(glucose – 5)/3] = 135 mmol/L that is within normal range.
Urea = 27.8, that is high in it reflects renal failure. Now we need to calculate Urea – creatinine ratio to know what type of renal failure we have (Pre-renal, renal or post-renal).
Urea-Creatinine ratio = Urea x 1000 / Cr = 201. So we have pre-renal renal failure.
Next we build our differential diagnosis.
Acute respiratory alkalosis = CHAMPS (Central/CNS, Hyperventilation, Anxiety, mechanical ventilation, pregnancy/ progesterone or Sepsis/salicylate)…. From this list we can consider Anxiety or sepsis.
High Anion Metabolic acidosis = (lactate is high, ketones are high and urea is high), all these can contribute.
Metabolic acidosis (Clever PD):
Contraction Alkalosis
Liquorice
Endocrine causes (Conn’s/Cushing’s)
Excess alkali
Vomiting, NG suction
Renal (Barter’s)
Post-hypercapnia
Diuretics
From this list we can consider contraction alkalosis.
Final conclusion, is Acute respiratory alkalosis with HAGMA and metabolic alkalosis associated with hyperglycaemia and elevated plasma osmolarity and pre-renal renal failure. Also factitious hyponatraemia due to hyperglycaemia.
Question 2 Answer,
On arrival to ED this patient was very anxious in a panic state. Once she calmed down her PH improved to 7.32. However, her blood Pressure dropped further (74/51).
First step in the management is resuscitation:
The patient was given 500 ml of N/S immediately then she needed further 4 doses of 250 ml N/S before her blood pressure improved to 100/70. The patient was extremely dehydrated.
Second Step in the management is Fluids, electrolytes and insulin replacement and monitoring:
This patient was considered to have DKA rather than HHS for the following reasons.
1- Serum osmolarity is 312 (for HHS the osmolarity must be more than 320).
2- Ketones level = 3.5 ( for HHS ketones should be less than 3, as elevated ketones reflects insulin deficiency.)
Accordingly patient was put on DKA pathway for fluids/ insulin and electrolytes replacement.
With 1 hourly monitoring of glucose level, K+ level and urine output.
Third step in the management is treating the cause:
The cause can be adjustment of diabetes medication however in such cases we can’t exclude infection as a potential cause (temp is toward the low side and she was in respiratory alkalosis). Accordingly, patient was given a dose of broad spectrum antibiotics (as per goal directed approach).
Fourth step in the management was preventing thrombosis/ DVT:
For that we can give Heparin 5000 Units S/C twice daily or Enoxaparin 0.5 mg/kg S/c once daily.