first of all, you've stated the units incorrectly. saunders lists normal serum ammonia as 35 to 65 mcg/dl
, that's micrograms
, not milligrams (page 116). actually, the parameters are much wider than you are being quoted.
ammonia levels rise when there are large amounts of protein being catabolized and the liver is unable for some reason to convert it into urea so it can be excreted through the kidneys. anything that interferes with the breakdown of ammonia in the system will increase serum levels. that includes such conditions as:
- hepatic encephalopathy
- hepatic coma
- hepatocellular disease
- portal hypertension
- severe heart failure with congestive hepatomegaly
- gi bleeding and/or obstruction with mild liver disease
- erythroblastosis fetalis of the newborn
- reye syndrome
- asparagine intoxication
- a genetic metabolic disorder of the urea cycle
most information came from pages 41-42, mosby's diagnostic and laboratory test reference
, 4th edition, by kathleen deska pagana and timothy james pagana except where noted. when there is such wide variety in lab values there are two things the testing administrators are likely to do: (1) actually list the lab values they want you to apply to these kinds of questions in the test information instruction booklet which you should have already downloaded and read very carefully (they did this with our national crni exam where we were extensively tested over fluid and electrolytes), or (2) they will give you answer choices with lab values that are so widely spread out that it will be unmistakable which answers are right and which are wrong. they will not deliberately trick you with picayune answer choices like this on the nclex. it is better for you to know that ammonia levels are elevated in the diseases listed above, why and to know the broad range of test results than to try to determine which text is giving you absolute correct lab range results. the test makers are aware that there can be large variation in the lab ranges, so they are not likely to specifically question on this. an exception would be potassium. it is well-known and standard that 3.5 to 5.0 meq/liter is a normal level in adults. anything above or below results in grave consequences for the patient. normal potassium level is something you should know off the top your head.