Pneumonia and Metabolic Acidosis in a 35-kilogram Man

Author: V. Dimov, M.D.
Reviewer: S. Randhawa, M.D.

A 71-year-old African American male (AAM) is admitted to the hospital with the chief complaint of shortness of breath (SOB) which has had become progressively worse during the last 4-5 days.

He also has had diarrhea for one week. He has had cough productive yellow, blood-tinged sputum, night sweats and urge urinary incontinence for 3 days. He reports no fever or chills. The patient took Imodium (loperamide) over-the-counter (OTC) which helped the diarrhea.

Past medical history (PMH)

Hypertension (HTN), chronic obstructive pulmonary disease (COPD) on home O2 3 L/min, inoperable renal cancer, prostate cancer (had surgery 8 years ago).

The report of a previously done CT scan of the abdomen.


Combivent (ipratropium bromide and albuterol sulfate), Cartia XT (diltiazem), Lupron (leuprolide acetate injection), since the surgery for prostate cancer, home O2 3 L/min.

Social history (SH

Smoker (100 pck-yrs), no EtOH or drugs. Lives with his family.

What is the most likely diagnosis at this point?

AECB (acute exacerbation of chronic bronchitis).
TB (he never had a PPD test).
Lung cancer -- certainly a possibility. Also, he may have an obstructive pneumonia.
Clostridium difficile colitis, although he was not hospitalized or on antibiotic therapy recently.

What is the most likely etiology of his pneumonia?

Remember the SLIM CV mnemonic:
Strep pneumonia
Legionella -- it often causes diarrhea, more common in the elderly.
Influenzae -- Hemophilus


What would you like to do first?

Obtain vital signs and examine the patient.

Physical examination

A thin man in moderate distress. The weight is only 35 kg (5 ft tall). The patient was gradually losing weight according to his family.

VS: 35.8-112-24-161/93.
SpO2 94% on 4L.

What is your assessment at this point, from the vital signs?

Tachycardia and tachypnea. BP is not well controlled. He is mildly hypoxic but this may be his baseline due to advanced COPD. He is also on home O2.

The rest of the physical examination

Chest: (B) wheezing, right-sided crackles and dullness to percussion.
CVS: Clear S1 S2.
Abdomen: cachectic, +BS, NT, ND.
Extremities: no edema, clubbing or cyanosis.

What would you do next?

What would you like to do first?
ABG, it is quick and may help you reach the correct diagnosis.
Does he need to go to the intensive care unit?

Laboratory results.

ABG: 7.25-31-62-13-SpO2 91% on 4L of O2.

Are you surprised? Why does he have metabolic acidosis?

Is PaCO2 a little low for a patient with advanced COPD?
It certainly is.

Let's discuss the ABG results systematically, step-by-step. You have to find the answer to 6 questions remembered by the mnemonic ARMADA:

cidosis or Alkalosis?
Respiratory or Metabolic?
Anion gap?
Delta AG?
Assess compensation

These are the answers:

Metabolic acidosis.
But expected PaCO2 for this pH is 27.5, so there is some PaCO2 retention, i.e. respiratory acidosis which is not unexpected in somebody with COPD.

Anion gap (AG) = 16 (you need BMP to calculate AG).

Delta AG is 4, so there is a preexistent non-anion gap metabolic acidosis due to the diarrhea.

There are 3 disorders on this ABG: high anion gap metabolic acidosis, respiratory acidosis and initial non-AG acidosis.

What are the causes of this complex acid-base balance disorder?

There are only so many causes of high AG acidosis remembered by the mnemonic MUD PILES.

Let's get a BMP:

BUN 79 mg/dL, creatinine (Cr) 5.1 mg/dL.

Potassium (K+) 5.5 mEq/L is not high in this example of acute renal failure due to the diarrhea, secondary to the potassium loss with the multiple bowel movements.

What is his baseline renal function?
You always have to ask this question.
The creatinine (Cr) was 2.7 mg/dL just two months ago.

Chest X-ray

A previous CXR (6 months ago), left. Right-sided pneumonia, right. CXR report.

A previous lateral CXR, left. Current lateral CXR, right. CXR report.

What else would you order?

WBC is 8.6 only but the PMN are 91%. It could be just early in the course of his pneumonia.

Urinalysis (UA) showed proteinuria, blood and Trichomonas (it is never "too late" for sexual activity in this "Viagra day and age").

What happened?

The patient was started on the "pneumonia protocol" with cefotaxime and azithromycin.
Blood cultures (BCx x 2), sputum culture and urine Legionella antigen were done.
Intravenous fluids (IVF) were started for his acute renal insufficiency (ARI).
He felt better soon after the admission and the treatment/work-up continued.

Final diagnoses

Right-sided pneumonia.
Metabolic acidosis due to acute renal insufficiency (ARI) (no ketones on UA, lactic acid level was 2.2).
Acute renal insufficiency (ARI) due to fluid loss and hypovolemia.
Trichomoniasis (Flagyl 2 gm PO x 1 was given).

What happened?

The patient became hypoxic overnight and was transferred to ICU where he was placed on non-invasive ventilation with BiPAP. The rest of treatment was continued along with the work-up for his ARI. His condition soon improved, he was transferred back to a regular nursing floor and was evaluated by physical therapy (PT) for discharge disposition.

Inpatient medications

What did we learn from this case?

Think broad -- one diagnosis is often not enough. Everybody recognized the pneumonia but what about the metabolic acidosis and the acute renal insufficiency (ARI)?

And finally, there is one last mnemonic for differential diagnosis (DDx) of weight loss - WEIGHT:

estergreen (ESR) elevation due to CTD.
Endocrine, for example new or uncontrolled diabetes.
Head, e.g. depression
Tumor, e.g. cancer


Top 10 Clinical Pearls in Acid-base Disorders. Resident and Staff Physician, Jan 2007.
Acid-base Balance Cases and Calculators. Clinical Cases and Images - Blog, Feb 2007.

Acid-base balance from Oxford handbook of clinical medicine By Murray Longmore, Ian B. Wilkinson, Supraj R. Rajagopalan:

Published: 03/12/2005
Updated: 07/28/2009


  1. This was a good informative presentation. Thanku.. but there had a wide use of abbrevations which could be confusing for freshners..

  2. Dr. Adel
    well thanks for the informations.It seems informative and refreshing.But can you tell me how the delta anion gap was 21.Is it the delta anion gap =16-12=4 and then we calculate the deta bicarb.

  3. Dear Dr. Adel, you are right -- delta AG is 4 (MD Calculator: The typo in the text has been corrected. The teaching point remains valid. Thank you for correcting this error.


  5. Well, I had some problems with the abbrevations and unfortunately I'm not a physician, but a translator. so my question is: do you know where I can find what these abbrevations stand for? Is there any website? Thank you, and congratulation for the amazing job.

  6. Complete List of Medical Abbreviations and Acronyms

    When I started (an online case-based curriculum of clinical medicine), I deliberately decided to use a lot of abbreviations. Why? Because this is how the real medicine looks like in patient charts. You have to know that "WNL" means within normal limits, otherwise you may never figure out what the note is about. Now, with EHR (electronic health records), the art of medical acronyms may come to an end. Computer-generated notes (with some human input) are infamously verbose, often with amazingly little substance. Who needs to write "WD/WN in NAD" when the computer lavishly puts "well-developed and well-nourished in no apparent distress"?

  7. This was a great case. As I start residency I'd like to build an RSS feed of educational material like cases and practice pointers as presented above, along with some journal feeds. It would be a nice format for learning because you never know what will come up next, much like in real life, and there are a wide variety of experts on the web. But it seems like there are relatively few bloggers that are doing pure education. Are you aware of any more bloggers who regularly present cases?

  8. Re: "Are you aware of any more bloggers who regularly present cases?"

    There must be some. Search on Google.

  9. Great case. Just wondering what happened to the renal problem, which was suspected of bilateral renal cancer. With inoperable situation, should we put him on chemo. And should a biopsy be done to confirm the diagnosis?

  10. This patient had Severe Sepsis. Stages of Sepsis are:
    1. SIRs is any 2 of 4 criteria. His are: 1.HR was >100 2.temp was <36.
    2. Sepsis: infection
    3. Severe sepsis: end organ damage: resp failure on bipap and renal failure (which usually improves w lots of fluids up to 15L)
    4. Septic Shock if need pressors, end organs failed
    See Surviving Sepsis which clarifies classification

    See Surviving Sepsis guidelines.

  11. pgy-3,

    You're overdoing it again... :)

    Learn to look at the big picture and the patient, not only at the numbers.

    This way, you will make it to be a good PGY-4... :)

  12. Your point is well taken that each patient needs to be individually examined and treated and may not need a lot of fluids.
    Yet this patient had pneumonia, respiratory failure, renal failure, and was acidotic. The sympathetic system can keep BP stable for hours. Early recognition is the goal since patients end up intubated and on pressors. Sepsis syndrome is an outdated term and the treatment is too late.

  13. Dear "education is key".

    Please have a look at the case again: the patient did not "end up intubated and on pressors."

    He was treated temporarily with BiPAP for several hours and transferred back to RMF. No blood pressure drop was noted either.

    Don't see sepsis everywhere -- "When you are a hammer, everything looks like a nail."

  14. so what was the etiology of the weight loss? gap acidosis? result of legionella (diarrhea + PNA) urine antigen?

  15. "so what was the etiology of the weight loss": Cancer. See above: "inoperable renal cancer"

  16. All evidence points to diagnosis of sepsis due to severe pneumonia,there are probable mets to the lungs as well from the background malignancy with secondary pneumonia

  17. Frustrating not to get the results of the blood cultures and sputum culture...Great info though...Like the breadth...acidosis and ARI..