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Clinical Biochem > ISE and Electrolytes > Flashcards

ISE and Electrolytes Flashcards

(75 cards)

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1
Q

Sodium reference range

A

133-146 mmol/L
critical: <125 or >155 mmol/L

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2
Q

Potassium reference range

A

3.5-5.0 mmol/L
critical: <2.6 or >6.2 mmol/L

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3
Q

Chloride reference range

A

96-109 mmol/L

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4
Q

Bicarbonate reference range

A

23-31 mmol/L

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5
Q

Calcium reference range

A

2.10-2.60 mmol/L
critical: <1.65 or >3.25 mmol/L

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6
Q

Magnesium reference range

A

0.70-1.00 mmol/L
critical: <0.40 or >1.90 mmol/L

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7
Q

Phosphorus reference range

A

0.80-1.45 mmol/L
critical: <0.40

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8
Q

Anion gap reference range

A

4-16 mmol/L

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9
Q

Osmolality (serum) reference range

A

280-300 mmol/Kg

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10
Q

Osmol gap reference range

A

<10 mmol/L

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11
Q

Activity

A

the proper term for the concentration of an electrolyte measured in an electrochemical cell used in the Nernst equation

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12
Q

Activity Coefficient

A

the activity of an electrolyte divided by molar concentration, a measurement of the interaction of the selected electrolytes with other species in the solution

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13
Q

Potentiometry

A

an electrochemical technique that measures the electric potential between two electrodes under equilibrium conditions

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14
Q

Potentiometric electrode

A

consists of a reference electrode and an indicator electrode

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15
Q

Reference electrode

A

stable and has a constant potential relative to the sample solution, has a junction to allow electrical ionic conductivity between the sample solution and the internal filling solution

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16
Q

Indicator electrode

A

has an ion selective membrane where a potential difference occurs when there is a difference in the activity of ions on either side of the membrane

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17
Q

Nernst equation

A

Ecell=Eind-Eref + Ejxn

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18
Q

Classes of ion-selective membranes

A

glass, liquid/polymer, solid state, gas sensing

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19
Q

Glass membranes

A

used to measure H and Na
commonly composed of SiO2, Na2O, CaO or Al2O3

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20
Q

Liquid/Polymer membranes

A

composed of an ion exchanger or ionophore (lipophilic) dissolved in a viscous, water insoluble solvent

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21
Q

Solid state membranes

A

composed of a single type of crustal or pressed pellet of salts of the ion of interest
membrane potential is created by the movement of ions from the sample into vacancies in the crystal lattice

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22
Q

Gas permeable membranes

A

has a thin outer membrane that is permeable to the gas of interest and an internal pH electrode

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23
Q

What are limitations to ISE

A

temperature, ionic strength, pH, biofouling, cross-reacting ions, electrolyte exclusion effect

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24
Q

What is the electrolyte exclusion effect

A

indirect ISEs dilute the patients sample with an aqueous solution. Sodium levels will by falsely low in samples that have a high solid proportion (ie. hyperlipidemia or hyperproteinemia)

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25
pH ISE
composed of glass, ion exchange between sodium and hydrogen occurs altering the potential of the electrode which correlates with hydrogen ion activity temperature dependent, if temperature increases, pH decreases exposure to atmospheric air will decrease CO2 and increase pH
26
Sodium ISE
composed of glass or PVC with crown ether
27
Preferred specimen for sodium ISE
serum or heparin plasma
28
Interferences with sodium ISE
hyperlipidemia (false decrease if indirect ISE) hyperproteinemia
29
Potassium ISE
composed of PVC and valinomycin or polymers containing crown ether bis heptanedioate
30
Preferred specimen for potassium ISE
separated serum or heparin plasma at 4C potassium will increase in unseparated samples due to leakage from RBCs at RT or 37C potassium can decrease due to glycolysis serum samples have higher potassium than plasma because platelets release potassium during clotting
31
Interferences for potassium ISE
hemolysis incorrect torniquet use may falsely increase excessive fist clenching or forearm exercise may falsely increase leukocytosis may falsely increase if not immediately separated thrombocytosis may falsely increase
32
Chloride ISE
composed of polymer and incorporated quaternary ammonium salt anion exchanges
33
Preferred specimen for chloride ISE
serum or lithium heparin
34
Interferences for chloride ISE
may lack selectivity in the presence of other halides and organic ions (thiocyanate/lactate)
35
Carbon dioxide ISE
composed of teflon or silicone, carbon dioxide passe through the membrane and dissolves within an inner electrolyte solution, ions are detected by an interior pH ISE
36
Preferred specimen for carbon dioxide ISE
arterial heparinized blood, serum or plasma
37
Interferences for carbon dioxide ISE
exposure to atmospheric air decreases CO2 build up of protein on the ISE membrane will cause errors temperature, barometric pressure and erroneous calibration
38
Bicarbonate testing
carbon dioxide and carbonic acid are converted to bicarbonate by an alkaline pH, it goes through a series of reactions and then NAD production is measured spectrophotemetrically
39
Preferred specimen for bicarbonate testing
serum or lithium heparin whole blood or plasma
40
Interferences in bicarbonate testing
CO2 will decrease if exposed to atmospheric air
41
Calcium ISE
consists of a calcium ionophore membrane case on a solid support, measures ionized calcium
42
Preferred sample for calcium ISE
collect anaerobically, dry heparin, maintain temperature at 4C, avoid fist pumping as it will cause blood pH to decrease and ionize calcium
43
Interferences of calcium ISE
ethanol, proteins, phosphate, lactate
44
Calcium O-Cresolphthalein testing
calcium is freed from albumin via acidification, then under alkaline conditions calcium binds to O-Cresolphthalein causing a colour change
45
Preferred specimen for Calcium O-Cresolphthalein testing
serum or lithium heparin plasma
46
Interferences for Calcium O-Cresolphthalein testing
hemolysis (EGTA can be added to dissociate complex, any colour left will be due to hemolysis and can be accounted for), icterus, lipemia, magnesium ions (reduced by addition of 8-hydroxyquinoline and at pH 12 and read at 570-580nm), gadolinium compounds and paraproteins
47
Phosphorus testing
inorganic phosphorus binds to ammonium molybdate in acidic solution to form a complex measured at 340 nm
48
Preferred specimen for phosphorus testing
serum of lithium heparin in unseparated specimens phosphate can increase upon storage at RT of 37C
49
Interferences of phosphorus testing
hemolysis, icterus, lipemia EDTA, citrate and oxalate monoclonal free light chains complex can be reduces with naphthol sulfonic acid and measured at 600-700nm to reduce interferences at 340nm
50
Magnesium testing
magnesium binds to calmagite to form a stable chromogen which is measured at 532nm
51
Preferred sample for magnesium testing
serum of lithium heparin plasma
52
Interferences in magnesium testing
hemolysis, bilirubin, lipemia EDTA, potassium oxalate, sodium citrate EGTA can be used to decrease calcium interferences
53
Anion gap
the gap between measured cations and anion, due to unmeasured anions such as proteins, sulphates and phosphates
54
Anion gap equation
Na - (Cl - HCO3)
55
What causes increased anion gap
diabetic ketoacidosis, lactic acidosis, renal failure, renal tubular necrosis, diarrhea, decreased reabsorption of bicarbonate, intoxication with organic compounds (ethanol, methanol or ethylene glycol)
56
What causes decreased anion gap
hypoalbuminemia, hypercalcemia, hypermagnesemia or hypergammaglobulinemia
57
What regulates sodium
renal angiotensin aldosterone system (kidney)
58
What causes hypernatremia
primary aldosteronism, cushings syndrome, secondary aldosteronism, damage to the hypothalamus (causing decreased thirst), diabetes insipidus
59
What causes hyponatremia
(normal osmolality) electrolyte exclusion effect (high osmolality) hyperglycemia, uremia or mannitol (low osmolality) liver, kidney or heart disease, SIADH, Addisons disease, diuretics, extrarenal fluid loss
60
What regulates chloride
renin angiotensin aldosterone system (kidney) excess is found in sweat and excreted in urine
61
What causes hyperchloremia
similar to hypernatremia respiratory alkalosis where HCO3 is excreted alongside Na rather than ClWa
62
What causes hypochloremia
similar to hyponatremia furosemide inhibits Cl reabsorption in the kidneys
63
What regulates potassium
the kidneys, aldosterone and insulin
64
What causes hyperkalemia
preanalytical variables cause pseudohyperkalemia (hemolysis, thrombocytosis, leukocytosis) redistribution occurs during acidosis, IVH, rhabdomyolysis, burns and tissue hypoxia increased retention due to Addisons disease, hypoaldosteronism and treatment with ACE inhibitors
65
What causes hypokalemia
redistribution can cause due to insulin therapy and alkalosis renal tubular acidosis, tubular necrosis, corticoid hormone excess with metabolic acidosis decreased intake excessive loss
66
What regulates bicarbonate
kidneys and lungs
67
What regulates calcium
Parathyroid hormone, PTH, Calcitriol (synthesized from vitamin D)
68
What causes hypercalcemia
primary hyperparathyroidism malignancy (breast cancer) tumours that invade bone and stimulate reabsorption renal failure and endocrine disorders
69
What causes hypocalcemia
hypoalbuminemia lower total calcium levels with normal free calcium liver, renal and heart disease chronic renal failure proteinuria resulting in hypoalbuminemia hyperphosphatemia hypoparathyroidism neck surgery that destroys the parathyroid gland
70
What regulates phosphate
parathyroid hormone and calcitriol
71
What causes hyperphosphatemia
hyperparathyroidism pseudohypoparathyroidism acromegaly
72
What cause hypophosphatemia
a shift from ECF to ICF due to respiratory alkalosis, glucose administration or insulin renal wasting hyperparathyroidism, Fanconis syndrome, inherited rickets, osteomalacia
73
What regulates magnesium
no specific mechanism
74
What causes hypermagnesemia
excessive administration of antacids, enemas and fluids containing magnesium
75
What causes hypomagnesemia
shift from ECF to ICF intestinal origin (diarrhea, vomiting, bowel surgery) kidney origin (diabetes mellitus, diuretics, antibiotics, alcoholism)

Clinical Biochem (15 decks)

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