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CC finals readings > AMMONIA > Flashcards

AMMONIA Flashcards

1
Q

produced in the deamination of amino acids during protein metabolism. It is removed from the circulation and converted to urea in the liver.

A

Ammonia

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2
Q

however, ammonia is present in the plasma in low concentrations

A

Free ammonia is toxic

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3
Q

-produced in the catabolism of amino acids and by bacterial metabolism in the lumen of the intestine
-excreted as ammonium ion by the kidney and acts to buffer urine.

A

Ammonia (NH3)

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4
Q

ammonia is consumed by the parenchymal cells of the liver in the___________________________a nontoxic compound that is excreted in the urine.

A

KrebsHenseleit or urea cycle to produce urea

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5
Q

Clinical conditions in which blood ammonia concentration provides useful information are

A

hepatic failure, Reye’s syndrome, and inherited deficiencies

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6
Q

most common cause of disturbed ammonia metabolism

A

Severe liver disease

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7
Q

The monitoring of blood ammonia may be used to determine prognosis, although correlation between the extent of ______________________________________ is not always consistent.

A

hepatic encephalopathy and plasma ammonia concentration

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8
Q

better indicator of the severity of disease

A

Arterial ammonia concentration

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9
Q

-occurring most commonly in children, is a serious disease that can be fatal. Frequently, the disease is preceded by a viral infection and the administration of aspirin.
-an acute metabolic disorder of the liver, and autopsy findings show severe fatty infiltration of that organ.

A

Reye’s syndrome

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10
Q

can be correlated with both the severity of the disease and prognosis.

A

Blood ammonia concentration

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11
Q

Ammonia is of use in the diagnosis of inherited deficiency of urea cycle enzymes. Testing should be considered for any neonate with unexplained

A

nausea,
vomiting, or
neurological deterioration associated with feeding

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12
Q

can be used to monitor hyperalimentation therapy and measurement of urine ammonia can be used to confirm the ability of the kidneys to produce ammonia

A

Assay of blood ammonia

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13
Q

The accurate laboratory measurement of ammonia in plasma is complicated by its

A

low concentration, instability, and pervasive contamination

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14
Q

which ammonia is isolated from the sample and then assayed.

A

two-step approach

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15
Q

involves direct measurement of ammonia by an enzymatic method or ion-selective electrode

A

second approach

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16
Q

-One of the first analytic methods for ammonia, developed by
-exploited the volatility of ammonia to separate the compound in a microdiffusion chamber

A

Conway in 1935

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17
Q

The amount of ammonia is determined by

A

titration

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18
Q

-Ammonia can be measured by an enzymatic method using
-this method is convenient and the most common technique used currently

A

GLDH

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19
Q

-preferred coenzyme because it is used specifically by GLDH

A

NADPH

20
Q

NADH will participate in reactions of other endogenous substrates, such as

A

pyruvate

21
Q

added to the reaction mixture to increase the rate of the reaction and to stabilize GLDH. This method is used on many automated systems and is available as a prepared kit from numerous manufacturers.

A

Adenosine diphosphate

22
Q

-uses a thin-film colorimetric assay
-In this method, ammonia reacts with an indicator to produce a colored compound that is detected spectrophotometrically

A

dry slide automated system

23
Q

The electrode measures the change in pH of a
solution of___________as ammonia diffuses across a semipermeable membrane

A

ammonium chloride

24
Q

extremely important for plasma ammonia assays

A

Careful specimen handling

25
Q

increases rapidly following specimen collection because of in vitro amino acid deamination

A

Whole blood ammonia concentration

26
Q

should be obtained without trauma and placed on ice immediately

A

Venous blood

27
Q

are suitable anticoagulants

A

Heparin and EDTA

28
Q

should be evaluated for ammonia interference before a new lot is put into use

A

Commercial collection containers

29
Q

Samples should be centrifuged at ____°C within 20 minutes of collection and the plasma removed

A

0-4

30
Q

Specimens should be assayed as soon as possible or frozen.
Frozen plasma is stable for several days at ___°C

A

-20

31
Q

contain two to three times as much ammonia as plasma; hemolysis should be avoided

A

Erythrocytes

32
Q

significant source of ammonia contamination. It is recommended that patients do not smoke for several hours before a specimen is collected

A

Cigarette smoking by the patient

33
Q

Many substances influence the in vivo ammonia concentration.
-may increase ammonia in plasma

A

Ammonium salts, asparaginase, barbiturates, diuretics, ethanol, hyperalimentation, narcotic analgesics, and some other drugs

34
Q

several antibiotics decrease concentrations

A

Diphenhydramine, Lactobacillus acidophilus, lactulose, levodopa

35
Q

interferes in dry slide methods

A

Glucose at concentrations greater than 600 mg/dL (33 mmol/L)

36
Q

potential problem in the laboratory measurement of ammonia

A

Ammonia contamination

37
Q

must be taken to minimize contamination in the laboratory in which the assay is performed

A

Precautions

38
Q

Elimination of sources of ammonia contamination can significantly improve the accuracy of ammonia assay results. Sources of contamination include

A

tobacco smoke, urine, and ammonia in detergents, glassware, reagents, and water

39
Q

ammonia content of serum-based control material is

A

unstable

40
Q

Frozen aliquots of human serum albumin containing known amounts of________________________ Solutions containing known amounts of ammonium sulfate are commercially available.

A

ammonium chloride or ammonium sulfate

41
Q

Values obtained vary somewhat with the method used.8 Higher concentrations are seen in

A

newborns

42
Q

in which there is significant collateral circulation (as in cirrhosis) or if parenchymal liver cell function is severely impaired, ammonia is not removed from the circulation and blood concentration increases.

A

severe liver disease

43
Q

High concentrations of NH3 are

A

neurotoxic and often associated with encephalopathy

44
Q

Ammonia alters metabolic processes in the brain, which results in accumulation of

A

toxic species, and impairs astrocyte function

45
Q

associated with inherited deficiency of urea cycle enzymes. Measurement of plasma ammonia is important in the diagnosis and monitoring of these inherited metabolic disorders

A

Hyperammonemia

CC finals readings (16 decks)

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