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CC 2 LAB > Serum Potassium Test > Flashcards

Serum Potassium Test Flashcards

1
Q

is the major intracellular cation.

A

Potassium

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2
Q

Major intracellular cation in the body

A

Potassium

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3
Q

concentration____ times greater inside the cell than outside

A

20

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4
Q

only___% of total body K+ circulates in the plasma (___% is intracellular)

A

2%

98%

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5
Q

FUNCTIONS

A

• Regulation of neuromuscular excitability
• Contraction of the heart
• Intracellular fluid (ICF) volume
• H+ (hydrogen ion) concentration

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6
Q

Tissue buffering in acidosis can lead to

A

^ plasma [K*]

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7
Q

Tissue buffering in alkalosis can lead to

A

v plasma [K*]

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8
Q

Causes of artifactual hyperkalemia (false increase):

A
  1. Coagulation process & Thrombocytosis
  2. Prolonged tourniquet application
  3. Excessive clenching of fists during blood collection
  4. Storage of blood sample in ice
  5. Hemolysis (most common)
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9
Q

Coagulation process & Thrombocytosis: During clot formation, platelets release______, and in thrombocytosis (elevated platelet count), the excess platelets further contribute to the release of potassium, leading to_____

A

potassium

falsely elevated levels.

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10
Q

Prolonged tourniquet application: Prolonged pressure from a tourniquet can trap blood and reduce circulation, leading to ______from cells, which____ potassium in the sample.

A

potassium leakage

elevates

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11
Q

Excessive clenching of fists:

The cause of this______ potassium during fist clenching is a local effect caused by release of potassium from muscle during muscle contraction in the forearm.

A

increased

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12
Q

Storage of blood sample in ice:

Cold temperatures can cause red blood cell damage, leading to the release of intracellular potassium, resulting in _____potassium levels.

A

falsely elevated

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13
Q

The rupture of red blood cells during sample collection or handling releases intracellular potassium into the plasma, the most common cause of falsely high potassium readings.

A

Hemolysis:

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14
Q

• Slight hemolysis (______): increases..

A

50mg/dL of Hgb

^ 3%

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15
Q

• Gross hemolysis (_____): increases…

A

> 500mg/dL of Hgb

^ 30%

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16
Q

How is falsely increased results prevented (due to clotting reasons)

A

situation may be avoided by using a
heparinized tube to prevent clotting of the specimen

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17
Q

How is falsly incrrased results prevented (due to hemolysis)

A

by using proper care in the drawing of blood.

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18
Q

How is falsely increased results prevented (due to improper storage)

A

storing blood on ice promotes the release of K+ from cells, whole blood samples for K+ determinations should be stored at room temperature (never iced) and analyzed promptly or centrifuged to remove the cells.

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19
Q

• Specimen:

A
  1. Serum
  2. Plasma (AOC: Heparin)
  3. Urine (24-hour urine)
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20
Q

_______is the anticoagulant of
choice.

Whereas serum and plasma generally give similar K+ levels,_____ reference intervals tend to be slightly
higher.

A

Heparin

serum

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21
Q

Why is potassium higher in serum than in plasma?

A

Because clotting promotes release of potassium

22
Q

Significantly elevated platelet counts may result in the release of K+ during clotting from rupture of these
cells, causing a spurious hyperkalemia. In this case, _______is preferred.

A

plasma

23
Q

T or F

Whole blood samples may be used
with some analyzers. Consult the instrument’s opera-
tions manual for acceptability.

A

True

24
Q

Urine specimens should
be collected over a____-hour period to eliminate the influence of diurnal variation.

A

24

25
Q

METHODS

A

Colorimetric Methods

Ion Selective Electrode (ISE)

26
Q

Colorimetric Methods

A

Lockhead and Purcell Method

27
Q

Lockhead and Purcell Method
• Potassium is reacted with_____ to produce_______

A

sodium cobaltinitrite

sodium potassium cobaltinitrite

28
Q

Lockhead and Purcell Method

With the addition of_____ (color developer), a____ color is produced and determined spectrophotometrically

A

phenol

blue

29
Q

Ion Selective Electrode (ISE)
• Uses_____ and ______ as inner electrolyte solution

A

valinomycin membrane and KCI

30
Q

• Current method of choice

A

Ion Selective Electrode (ISE)

31
Q

REFERENCE RANGES FOR POTASSIUM

Serum

A

3.5-5.1 mmol/L

32
Q

REFERENCE RANGES FOR POTASSIUM

Plasma

A

Males: 3.5-4.5 mmol/L
Females: 3.4-4.4 mmol/L

33
Q

REFERENCE RANGES FOR POTASSIUM

Urine

A

25-125 mmol/d

34
Q

Principle

Agappe

A

Sodium Tetraphenylborate + Potassium –—> Potassium Tetraphenylborate + Sodium

35
Q

Agappe

Potassium is estimated by_____ method.

The extent of turbidity is____ to the potassium concentration and is measured photometrically at
_______nm

A

Turbidimetric

proportional

578 nm (570-620 nm)

36
Q

Potassium Reagent

A

Sodium tetraphenylboron (TPB-Na) 0.2 mol/1

37
Q

Potassium standard

A

Potassium Standard Concentration 5 mmol/L

38
Q

Agappe

Reagent Preparation

A

Potassium Reagent and Standard are ready to use.

39
Q

Agappe

Reagent Storage and Stability
The sealed reagents are stable up to the expiry date stated on the label, when stored at______ and_____

A

2 - 8°C and protected from light

40
Q

Agappe

Open Vial Stability
Once opened, the reagent is stable up to_____, if contamination is avoided.

A

4 weeks

41
Q

Agappe

Standard and sample amount

A

25 microliters

42
Q

Standard and sample amount

A

25 pL

43
Q

Agappe amount of reagent

A

1000 microliters

44
Q

Agappe

Mix well and incubate ____for ___ minutes.
Measure the absorbance of Standard (Abs.S) and test sample (Abs.T) against_____ at____ with in____

A

at room temperature

5

distilled water

578 nm

10 minutes

45
Q

Agappe

Reference Range
It is recommended that each laboratory should establish its own reference values.
The following value may be used as guide line.
Serum/Plasma: ______

A

3.6 - 5.5 mmol/L

46
Q

Agappe

Linearity
This reagent is linear up to______

A

14 mmol/L.

47
Q

Agappe

If the concentration is greater than linearity (14 mmol/L), dilute the sample with…

A

normal saline and repeat the assay. Multiply the result with dilution factor.

48
Q

Potassium is the most abundant

A

Intracellular cation

49
Q

Name the Colorimetric method for Potassium determination?

A

Lockhead & Purcell Method

50
Q

What is the color developer used in the Lockhead & Purcell Method?

A

Phenol

51
Q

What are the causes of artifactual hyperkalemia?

A

Thrombocytosis
Prolonged tourniquet application
Excessive clenching of fists
Storage of blood sample in ice
Hemolysis

52
Q

What is the reference range for serum potassium?

A

3.5-5.1 mmol/L

CC 2 LAB (35 decks)

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