Case in the Spotlight 14 - answers

The Case - Young woman with asthma.

She has been treated with regular ventolin and oral steroids for 2 days by the GP, who developed an asthma action plan with her. This gave clear instructions re when to go to ED or call an ambulance, and she is in the ED.
Her HR 120 RR 30 BP 110/70

At the change of shifts you are informed that the medical registrar will see her and admit her, but it might be an hour or two because there are a number of sick patients requiring the registrar’s attention

You are asked to review the ABGs, and the doctor heading home says you should let the medical registrar know if there are any particular concerns

Arterial blood gas is performed on FiO2 0.4 (40%)
Ph   7.32 mmHg
pCO2   48 mmHg
pO2   65  mmHg
BE   -6
HCO3   18
Lactate  15.7

Na   142
K   3.2.
Cl   105
Glucose 10
Lactate 3.6

Describe the acid base disturbance and put it into the clinical context – outline the key management priorities.

• The acid base disturbance is respiratory acidosis, essentially acidosis plus high CO2.
• The anion gap is 142+3 – (105+10) = 30 so elevated
• You expect the HCO3 to be 25 (raised 1 acutely versus 4 chronic if CO2 increases by 10)

What is the likely diagnosis?

The key thing about this case is that it is severe asthma
If the CO2 is 40, or anywhere higher than that in an asthmatic, or the patient is acidotic, that is a bad sign. Clinical escalation is needed, senior input, early review with consideration of HDU/ICU.