Non-protein nitrogens

Why do we monitor NPNs?

To assess kidney functions

Where do we measure NPNs?

blood

Where do NPNs come from?

The breakdown of proteins, via consumption or muscle/enzyme breakdown

What is BUN? What is the normal concentration in blood?

BUN = blood nitrogen urea

Normal range: 7-20 mg/dL

Which organ functions may be tested using BUN?

the kidneys and liver

If we have BUN > 20mg/dL and elevated creatinine, what is the condition called?

Azotemia

What are three causes of azotemia?

pre-renal from blood filtering prior to the kidney

renal from an intrinsic kidney issue

post-renal from an obstruction of urine output

What is uremia? What are the concentrations of BUN that signal this?

when all kidney function is lost

BUN concentrations are >150 mg/dL

How do we produce urea?

Protein is broken down into ammonia

ammonia is transported to the liver and broken down into urea

What are the clinical signs of uremia?

anemia, metabolic acidosis, hyperkalemia (increased potassium) and renal osteodystrophy

What is creatinine? What is its concentration in the blood?

The breakdown product from muscles

Normal range: 0.5-1.4 mg/dL

Are creatinine concentrations affected by diet or hydration?

No

What do we typically use creatinine concentrations to calculate?

glomerular filtration rate

If creatinine levels are elevated and GFR is decreased, what is the condition of the kidney?

Poor kidney function

What is the normal range for BUN/creatinine ratios?

6-20

What do BUN/creatinine ratios help identify?

The cause of azotemia

If we have a high BUN level and normal creatinine level, what kind of ratio do we expect and what is the cause?

High ratio (ex. 68/1.4 is above 20)

Cause: pre-renal issue

If we have a low BUN level and normal creatinine level, what kind of ratio do we expect and what is the cause?

Low ratio (ex. 5/1.3 is below 6)

cause: tubular necrosis or low protein intakes

If we have a high BUN level and high creatinine level, what kind of ratio do we expect and what is the cause?

High ratio (ex. 68/3 is higher than 20)

cause: renal obstruction

If we have a high BUN level and high creatinine level that are elevated proportionally, what kind of ratio do we expect and what is the cause?

Normal ratio between 6-20

Cause: uremia, nephrotic syndrome

What is uric acid? What percentage of NPN is made up by uric acid?

Breakdown product of proteins and purines

20%

What is hyperuricemia?

Increased uric acid in the blood

What are causes of hyperuricemia?

cellular breakdown (purine degradation) and injury

What is gout? What is excreted out in the urine and secreted into joints during this condition?

Extreme levels of uric acid

Uric acid will excrete out as urate crystals in the joints and urine

What is ammonia? Where is it degraded?

The breakdown product of proteins and amino acids

It is degraded in the liver

What condition can be caused by elevated ammonia levels?

hepatic encephalopathy

What are two conditions caused by elevated ammonia?

Reye syndrome (liver and brain swelling) and end stage liver disease