Metabolic acidosis with aspiration pneumonia?

[greenteacloud]

Hello,

Please excuse my English. I'm from the Netherlands.

I'm trying to understand why a patient has lactic acidosis. Patient came into polyclinic to discuss medical problems that happened to manifest when cycling to the clinic against a storm. Here are her ABGs after coming in: ph: 7.31, PaCO2: 30.08 mmHg, PaO2: 92.27 mmHg, HCO3: 15 mmol/L, BE: -9.7, Lactate: 5.1mmol/L, sodium & chloride middle of range. Patient started feeling sick 1hr later.

+5 days: mild respiratory acidosis, lactate 2.1

+6 days: mild respiratory alkalosis, lactate 2.5.

Xray +48hrs shows mild aspiration pneumonia. Patent (46, f) described several such flareups over the years, always after short and intense exertion. Accompanied by lactic acidosis that seems to flare up again after short walks, shortness of breath described as 'not enough oxygen getting into blood', waking up from sleep with extreme bradycardia and weakness on left side of body, visual impairment and sometimes strong pressure in head. Duration of such flareup: 4-6 weeks with shortness of breath and bradycardia nearly every day. Patent describes being depended on carbohydrates and experiencing glycogen depletion when active before breakfast, not eating in time or eating too much protein and fats instead of carbohydrates since teens. Describes life-long muscle weakness and pain when climbing mountains or running. CK normal. Heart and lungs normal, fit enough to run 'the slowest ever' half-marathon with constant ingestion of sugar.

My thoughts: I first thought the patient might have an undiagnosed fatty acid oxidation disorder, but as far as I know they don't coincide with lactic acidosis, and glucose levels were normal, HbA1C normal on low side though, serum glucose apparently once ~11mmol/L at night 24hrs after an earlier flareup. But how does the aspiration pneumonia fit into this? I wonder if there are two separate issues that happen to coincide, both aspirated gastric acid and lactic acidosis caused by the same exertion. Any thoughts?

 

[Hannahbanana, BSN, MSN]

You look at the bicarb to see a metabolic problem. Any kind of acidosis will tend to use it up to maintain homeostasis, so it will decrease. Other acid choices on ABGs are few... CO2 is an acid. So, you might think she had a respiratory acidosis, but her CO2 is low (normal is 35-45), likely from hyperventilation. Why would she want to blow off extra acid? Because she is acidotic....and why is that, if it's not her CO2? Think other forms of acids-- lactic, ketoACIDOSIS, poisons... Lactic acidosis is your choice, because hers is high.

So, she has a metabolic acidosis that is uncompensated by her respiratory rate.

If she has an aspiration pneumonia, her PaO2 would likely decrease. If she has a lower hematocrit (not known here) she could be cellularly hypoxic with any exertion even if at rest she has a normal PaO2 and saturation. Increased work of breathing might do it. Can't guess much beyond this, but does this make sense?

BTW, your English is a lot better than my Dutch.

 

[Hannahbanana, BSN, MSN]

Quick ABG chart to help you decide respiratory? Metabolic? Compensated? Not compensated? Remember: Compensation approximates but never quiiiiite gets into the normal range! And note that oxygenation is a separate decision!  Answers?      (pH / CO2 / Bicarb)

A. 7.29 / 50 / 25       C. 7.52 / 50 / 25

B. 7.29 / 28 / 19        D. 7.52 / 29 / 26