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CLINICAL CHEM 2 LEC > P2.4-CHLORIDE + BICARBONATE + MAGNESIUM > Flashcards

P2.4-CHLORIDE + BICARBONATE + MAGNESIUM Flashcards

1
Q
  • is the major extracellular anion
A

CHLORIDE

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2
Q

it is significantly involved in
the maintenance osmolality, blood volume, and
electric neutrality

A

CHLORIDE

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3
Q

Chloride ingested route in the body

A

almost completely absorbed
by the intestinal tract,

is filtered by the glomerulus,

and is passively reabsorbed by the PCT

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4
Q

– Excess Cl- is excreted in the

A

urine and sweat.

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5
Q
  • Cl-maintains electrical neutrality in two ways:
A

– Na+ is reabsorbed along with Cl- in the proximal tubules.
– Chloride shift (Hamburger Phenomenon)

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6
Q

may occur when there is an excess loss of bicarbonate as a result of GI losses, RTA, or metabolic acidosis

A

Hyperchloremia (> 107 mmol/L)

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7
Q
  • excessive loss of Cl from prolonged vomiting, diabetic ketoacidosis, aldosterone deficiency, or salt-losing renal diseases such as pyelonephritis
  • high serum bicarbonate concentrations
A

Hypochloremia (< 98 mmol/L)

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8
Q

Specimen used for Chloride determination

A

▪ Serum or plasma (lithium heparin)

24-hour urine sample

▪ Sweat chloride analysis

▪ Fecal chloride analysis

(sometimes whole blood with certain analyzers)

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9
Q

Chloride - ▪ with marked hemolysis, levels may be ______as a result of a dilutional effect

A

decreased

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10
Q

Fecal chloride analysis is used when suspecting what disease

A

congenital hypochloremic
alkalosis with hyperchloridorrhea

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11
Q

congenital hypochloremic
alkalosis with hyperchloridorrhea laboratory results

A

may reach 180 mmol/L in feces , with undetectable Cl− in urine

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12
Q

Methods for chloride determination

A

Ion Selective Electrode

Mercurimetric Titration (Schales and Schales)

Spectrophotometric Methods

Amperometric-Coulometric Titration (Cotlove Chloridometer)

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13
Q

Ion Selective Electrode
▪ membrane used for chloride

A

tri-n-octylpropylammonium chloride decanol

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14
Q

❑A protein-free filtrate of specimen is titrated
with mercuric nitrate solution in the presence of diphenylcarbazone as an indicator.

A

Mercurimetric Titration (Schales and Schales)

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15
Q

Indicator used for Mercurimetric Titration (Schales and Schales)

A

diphenylcarbazone

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16
Q

End product of Schales Schales

A

mercuric chloride (blue-violet color complex)

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17
Q

Spectrophotometric Methods for chloride

A

▪ Mercuric Thiocyanate (Whitehorn titration
Method) - reddish complex
▪ Ferric Perchlorate = colored complex

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18
Q

Reference ranges for Chloride

A

Plasma, Serum: 98-107 mmol/L

Urine: 110-250 mmol/D

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19
Q
  • second most abundant anion in the ECF
A

BICARBONATE (HCO3-)

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20
Q

What percentage of total CO₂ does HCO₃⁻ account for at physiological pH?

A

More than 90%

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21
Q

What are the three components of total CO₂ in the blood?

A

Bicarbonate ion (HCO₃⁻), carbonic acid (H₂CO₃), and dissolved CO₂

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22
Q

What is the major buffering system in the blood?

A

The bicarbonate (HCO₃⁻) buffering system

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23
Q

Where is bicarbonate reabsorbed in the kidneys?

A

85% in the proximal convoluted tubule (PCT), 15% in the distal convoluted tubule (DCT)

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24
Q

What acid-base imbalance is associated with decreased HCO₃⁻?

A

Metabolic acidosis

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25
What is the compensatory mechanism for metabolic acidosis?
Hyperventilation (to expel CO₂)
26
What acid-base imbalance is associated with increased HCO₃⁻?
Metabolic alkalosis
27
What is the compensatory mechanism for metabolic alkalosis?
Hypoventilation (to retain CO₂)
28
What specimens are used for bicarbonate testing?
Serum or plasma (lithium heparin)
29
Why should the sample be capped before analysis?
To prevent CO₂ loss, which can decrease levels by 6 mmol/L per hour
30
What are the common methods for measuring bicarbonate?
Ion-selective electrode (ISE) pCO₂ electrode Enzymatic method Carboxylate phosphoenolpyruvate (PEP) & malate dehydrogenase method
31
Carboxylate Phosphoenolpyruvate (PEP) and Malate Dehydrogenase (MDH) Reaction Pathway
Phosphoenolpyruvate + HCO₃⁻ → Oxaloacetate + H₂PO₄⁻ Oxaloacetate + NADH + H⁺ → Malate + NAD⁺ (MDH catalyzes this step)
32
Reference Range for Venous CO₂
23 to 29 mmol/L (Plasma, Serum)
33
What is the fourth most abundant cation in the body and the second most abundant intracellular ion?
Magnesium (Mg²⁺)
34
What is the role of magnesium as an enzyme activator
Magnesium binds to enzymes to increase enzymatic activity.
35
How much magnesium does an average 70 kg human body contain?
1 mole (24 g) of Mg²⁺
36
Where is magnesium distributed in the body?
- 53% in bones 46% in muscle, organs, and soft tissue <1% in serum and red blood cells
37
What percentage of serum magnesium is bound to albumin?
About 1/3 (33%)
38
What is the fourth most abundant cation in the body and the second most abundant intracellular ion?
Magnesium (Mg²⁺)
39
What is the role of magnesium as an enzyme activator?
Magnesium binds to enzymes to increase enzymatic activity.
40
How much magnesium does an average 70 kg human body contain?
1 mole (24 g) of Mg²⁺
41
Where is magnesium distributed in the body?
53% in bones, 46% in muscle, organs, and soft tissue, <1% in serum and red blood cells
42
What percentage of serum magnesium is bound to albumin?
About 1/3 (33%)
43
What is the physiologically active form of magnesium in the body?
The free (ionized) Mg²⁺
44
Magnesium is an essential cofactor for how many enzymes?
More than 300 enzymes
45
Name three metabolic processes where magnesium is important.
1. Glycolysis, 2. Carbohydrate, protein, and lipid metabolism, 3. Neuromuscular transmission
46
Name dietary sources of magnesium.
Nuts, dry cereals, vegetables, fruits, fish, meats, and hard drinking water.
47
How is magnesium regulated in the kidneys?
25–30% reabsorbed in the PCT, 50–60% in the ascending loop of Henle, 2–5% in the DCT, 6% excreted in urine daily
48
What hormone increases plasma magnesium concentration and renal reabsorption?
Parathyroid hormone (PTH)
49
What hormones increase renal excretion of magnesium?
Aldosterone and thyroxine
50
What is hypomagnesemia?
A decreased magnesium level below the normal range.
51
Name three causes of hypomagnesemia due to reduced intake.
1. Starvation, 2. Chronic alcoholism, 3. Magnesium-deficient IV therapy
52
What are some causes of hypomagnesemia due to increased excretion?
Renal tubular disorders, hyperparathyroidism, hyperthyroidism, hyperaldosteronism, diabetes, diuretics, gentamicin, cisplatin, cyclosporine, digoxin
53
What is the primary treatment for hypomagnesemia?
Oral magnesium supplements (Mg lactate, oxide, chloride) or IV magnesium sulfate for severe cases.
54
What is hypermagnesemia?
An increased magnesium level above the normal range.
55
What is the most common cause of hypermagnesemia?
Renal failure (decreased excretion of Mg²⁺).
56
Name three causes of hypermagnesemia due to increased intake.
1. Excessive antacid or laxative use, 2. Magnesium-containing enemas or cathartics, 3. IV magnesium therapy
57
What are the symptoms of hypermagnesemia at levels >1.5 mmol/L?
Cardiovascular, neurological, gastrointestinal, metabolic, and neuromuscular abnormalities.
58
What is the treatment for hypermagnesemia?
Stop magnesium intake, IV fluids and diuretics (if renal function is normal), Hemodialysis in severe cases
59
What specimen is required for magnesium testing?
Non-hemolyzed serum or plasma (lithium heparin); 24-hour urine (acidified with HCl).
60
Which anticoagulants are unacceptable for magnesium testing?
Oxalate, citrate, and EDTA (they bind Mg²⁺).
61
What are the common methods for magnesium measurement?
1. Calmagite method (532 nm), 2. Formazan dye method (660 nm), 3. Methylthymol blue method
62
What percentage of magnesium in serum exists in the free (ionized) state?
0.61
63
What percentage of magnesium in serum is complexed with other ions?
0.05
64
What is the physiologically active form of magnesium in the body?
The free (ionized) Mg²⁺
65
How does PTH affect magnesium absorption?
Enhances intestinal absorption and renal reabsorption of magnesium
66
How does PTH respond in hypomagnesemia?
Increases renal and intestinal absorption of magnesium
67
What are some causes of decreased magnesium absorption?
Malabsorption syndromes, intestinal resection, pancreatitis, prolonged vomiting, diarrhea, laxative use
68
How does intestinal resection or bypass surgery cause hypomagnesemia?
It reduces magnesium absorption by removing sections of the bowel responsible for absorption.
69
What is neonatal hypomagnesemia?
A condition associated with diabetic mothers or maternal hypoglycemia
70
What is primary hypomagnesemia?
A selective malabsorption disorder of magnesium in infants
71
What is chronic congenital hypomagnesemia?
A condition linked to a protein defect in the intestine that leads to poor magnesium absorption
72
What magnesium level is associated with cardiovascular, neuromuscular, psychiatric, and metabolic abnormalities?
< 0.5 mmol/L
73
What are the most severe causes of hypermagnesemia?
Decreased renal function combined with excessive magnesium intake (e.g., antacids, enemas, cathartics)
74
What conditions can cause pseudohypermagnesemia?
Dehydration, multiple myeloma, bone metastases
75
How does multiple myeloma or bone metastases lead to hypermagnesemia?
Increased bone loss releases magnesium into the bloodstream.
76
What is the treatment for hypermagnesemia due to excessive intake?
Discontinue magnesium sources
77
What is the treatment for severe hypermagnesemia?
Immediate supportive therapy for cardiac, neuromuscular, respiratory, or neurologic issues
78
What is the treatment for hypermagnesemia in renal failure?
Hemodialysis
79
How is hypermagnesemia treated in individuals with normal renal function?
Diuretics and IV fluids
80
What are the colorimetric methods for magnesium measurement?
Calmagite method (532 nm), Formazan dye method (660 nm), Methylthymol blue method
81
What is the reference method for magnesium measurement?
Atomic Absorption Spectrophotometry (AAS)
82
What dye is used in the Dye-Lake method for magnesium measurement?
Titan Yellow Dye (Clayton Yellow or Thiazole Yellow)
83
What is the reference range for serum magnesium using colorimetric methods?
0.63–1.0 mmol/L (1.26–2.10 mmol/L)
84
What are the cardiovascular symptoms of hypomagnesemia?
Arrhythmia, hypertension, digitalis toxicity
85
What are the neuromuscular symptoms of hypomagnesemia?
Weakness, cramps, ataxia, tremor, seizures, tetany, paralysis, coma
86
What are the psychiatric symptoms of hypomagnesemia?
Depression, agitation, psychosis
87
What are the metabolic symptoms of hypomagnesemia?
Hypokalemia, hypocalcemia, hypophosphatemia, hyponatremia
88
What are the cardiovascular symptoms of hypermagnesemia?
Hypotension, bradycardia, heart block
89
What are the neuromuscular symptoms of hypermagnesemia?
Decreased reflexes, dysarthria, respiratory depression, paralysis
90
What are the dermatologic symptoms of hypermagnesemia?
Flushing, warm skin
91
What are the gastrointestinal symptoms of hypermagnesemia?
Nausea, vomiting
92
What are the neurologic symptoms of hypermagnesemia?
Lethargy, coma
93
What are the hemostatic symptoms of hypermagnesemia?
Decreased thrombin generation, decreased platelet adhesion

CLINICAL CHEM 2 LEC (17 decks)

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