So recently a friend requested a second opinion on some lab tests results that she had reviewed with her doctor.
My friend is a 68 year old woman in excellent health. She exercises daily.
Her past medical history is positive for sleep apnea for which she is being treated. She had an osteoporotic wrist fracture in the past and is on blank. She had a kidney stone in the past. Here general health is excellent.
A review of symptoms was completely normal except for chronic excessive daytime sleepiness which she has had for years. She has no chest pain, no dyspnea on excertion. She has no peripheral edema. Her exercise tolerance is excellent.
Her physical examination at her doctor’s office was unremarkable. Her blood pressure in the office was 98/66 and her oxygen saturation was 98%.
Below are the results of her Basic Metabolic Panel of 6-12-2020:
|Basic Metabolic Profile|
|BUN||23.0 H||9.0-20.0 mg/dl|
|BUN/Creat||32.9 H||6.0-20.0 ratio|
|CO2||34.0 H||22.0-30.0 mmol/l|
My friend had an elevated BUN of 23.0 (N 9.0 – 20.0 mg/dl).
Her BUN/creatinine ratio was elevated at 32.9 (N 6.0 – 20.0 ratio).
And her CO2 was elevated at 34.0 (N 22.0 – 30.0 mmol/l.
The rest of her Basic Metabolic Profile was normal.
And metabolic profiles over the past ten years have been uniformly normal.
My friend has an elevated BUN/creatinine of 32.9 (N 6.0 – 20.0 ratio) with a normal serum creatinine. For a list of causes of this abnormality see Azotemia from StatPearls, updated Feb 21, 2020.
My friend’s doctor attributed the above abnormality to mild dehydration.
Next is to analyze the Basic Metabolic Profile using the method of Dr. Farkas’ method detailed in Diagnosis of metabolic acid-base disorders, September 12, 2019 as excerpted in the start of my post, Diagnosis Of And Causes Of Metabolic Alkalosis
Posted on June 19, 2020.
1. determination of the anion gap to evaluate for anion gap metabolic acidosis (AGMA)
- So my friend’s anion cap is Sodium – Chloride – Bicarb [reported as CO2 in my friend’s basic metabolic profile].
- 142 – 102 – 40 = 6
- So the patient has a normal anion gap.
2. if the anion gap is normal, just look at the bicarbonate
- Bicarbonate <22 mM with a normal anion gap indicates a pure non-anion-gap metabolic acidosis (NAGMA).
- Bicarbonate >28 mM with a normal anion gap indicates a pure metabolic alkalosis.
- A bicarbonate of 22-28 mm with a normal anion gap indicates a normal metabolic pH status.
So according to Dr. Farkas’ post, the patient has a pure metabolic alkalosis based on the elevated (CO2 which is also called – bicarbonate [above].
My friend’s doctor felt that the abnormalities were due to mild dehydration [indicated by the elevated BUN/creatinine] and that the elevated serum CO2 [bicarbonate] was due to a mildly elevated arterial CO2 from wearing a mask.
Based on using Dr. Farkas’ method, it seems more likely that the patient has a mild pure metabolic alkalosis.
I reviewed my friend’s medications and could find nothing that would account for her lab abnormalities.
Given the patient’s excellent history and normal physical exam, this result could be due to lab error. There are many other causes of metabolic alkalosis. See Metabolic Alkalosis from emedicine.medscape.com for an extensive differential diagnosis.
My interpretation is that the the abnormalities on Basic Metabolic Profile indicate mild dehydration [Elevated BUN/creatinine ratio] and a pure mild metabolic alkalosis.
So the the question is further evaluation indicated at this time.
My thought is that, given the patient’s excellent state of health, we should repeat the Basic Metabolic Profile (BMP) in two weeks to one month. If the repeat test is normal, then we are done. If the BMP is still abnormal, I’d recommend a telemedicine nephrology consult.