Case #2

The patient is a 54 year-old male with a history of coronary artery disease who was admitted to the hospital for increasing lower extremity edema, abdominal swelling and shortness of breath. The patient had noted an ~30 pound weight gain over the past month and during the past week has had three pillow orthopnea.

On physical exam the patient is a well-developed, well nourished male in moderate respiratory distress. Blood pressure 140/80, pulse 95, respirations 28 and labored. Body weight 101 kg. HEENT was unremarkable. Cardiac exam had an S1, S2 and S3 without S4 or murmur. Pulmonary exam was remarkable for bilateral rales 2/3rd up both lung fields. Abdomen was enlarged with a positive fluid wave. Lower extremities were remarkable for 3+ pitting edema.

Laboratory Data

 

 June July 1    July 2 July 3 Normal Values
Sodium    130 133  134  133  136-140 mmol/L
Potassium  4.9   5.7  5.8  6.0  3.5-5.3 mmol/l
Chloride  100   90   91  93  98-108 mmol/L
Total CO2   22   20   17  15  23-27 mmol/L

BUN

   20   87   94  101  7-22 mg/dl
Creatinine  0.9   3.0   3.5  3.7  0.7-1.5 mg/dl

 

Renal ultrasound- Right kidney 10 x 5.5, Left kidney 10.5 x 6.0. Both kidneys demonstrate normal echogenicity and are without masses or cysts. There is no hydronephrosis.

 

Urine lytes- (July 2nd) sodium 10 mmol/L
                              creatinine 130 mg/dl

Case #2 Questions

  1. Is the cause of this patient’s renal failure acute or chronic? 
    The recent onset and rapid rise in bun and creatinine are consistent with acute renal failure.

  2. Calculate the fractional excretion of sodium. 
    (10 mmol/l/134 mmol/l)     x 100= .075/37 x     100=.20% 
    (130 mg/dl)/(3.5 mg/dl)
  3. Is this patient’s renal failure consistent with a prerenal cause or acute tubular necrosis?
    Prerenal

  4. What is the patient’s volume status?
    This patient is clinically volume overloaded because of congestive heart failure. The kidney perceives itself as being in a low volume state due to the decreased effective circulating arterial volume.

  5. Which of these methods would you recommend to improve renal perfusion in this case?

i. Intravenous sodium chloride
   This would worsen the congestive heart failure.
ii. Intravenous pressure support- 
    This patient is already hypertensive.
iii. Inotropic support with afterload reduction (i.e. Dobutamine)
     This would improve cardiac output and renal perfusion.

  1. When is it appropriate to order urine lytes to determine the fractional excretion of sodium in a patient with renal failure? 
    When the renal function is deteriorating. If function is     improving one would expect to see an elevated fractional excretion of sodium as the excess salt and water is removed by the kidney.

On July 3rd the patient had a hypotensive episode associated with a myocardial infarction.

Laboratory Data

  July 4th Urine lytes
 Sodium 50 mmol/L
Creatinine 40 mg/dl

Sodium 

 135 mmol/L 
Potassium  6.3 mmol/L 
Chloride  92 mmol/L 

Total CO2  

 14 mmol/L

BUN

  120 mg/l

Creatinine

  4.7 mg/dl
 
  1. Calculate the fractional excretion of sodium on July 4th. 
    (50 mmol/l35 mmol/l)     x 100=0.37/8.5 x 100= 4.3% 
    (40 mg/dl/4.7 mg/dl)

  2.  Is this patient’s renal failure consistent with a prerenal cause or acute tubular necrosis? 
    ATN

  3. What is the most likely etiology of renal failure in this patient on July 4th? 
    This is probably due to the hypotensive episode associated with the myocardial infarction.