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Clinical Laboratory > 13. Total and ionized Calcium | Total and ionized Magnesium > Flashcards

13. Total and ionized Calcium | Total and ionized Magnesium Flashcards

1
Q

What are the 3 Forms of Calcium?

A
  1. Free / Ionized Calcium
  2. Complexed Calcium
  3. Plasma Protein-Bound Calcium
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2
Q

1| What is Free / Ionized Calcium?

A

Physiological ACTIVE Form

35 - 40% of Total Calcium Serum

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3
Q

2| What is Complexed Calcium?

A

Calcium that’s BOUND TIGHTLY to Variety of Anions

  • Bicarbonate; Lactate; Phosphate; Citrate

40 - 50% of Total Calcium Serum

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4
Q

3| What is Plasma Protein-Bound Calcium?

A

Associated with Albumin

80% of Total Calcium Serum

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5
Q

What Happens to the Levels of the Calcium Forms?

and Why?

A

Total Serum Calcium is UNCHANGED

Relative Distribution of 3 Forms is ONLY ALTERED

DUE to pH Changes in ECF

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6
Q

What are the General Functions of Calcium?

A

Skeletal Mineralisation

Blood Coagulation

Neural Transmission

Plasma Buffering Capacity

Enzyme Activity

Maintenance of Normal Muscle Tone

Excitability of Skeletal + Cardiac Muscle

Glandular Synthesis

Regulation of Exocrine / Endocrine Glands

Preservation of Cell Membrane = Integrity; Permeability

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7
Q

Where is Calcium Absorbed?

A

Duodenum

Upper Jejunum

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8
Q

When Does Calcium Absorption INCREASE?

A

Rapid Growth in Children

Pregnancy

Lactation

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9
Q

When Does Calcium Absorption DECREASED?

A

Advancing Age

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10
Q

What STIMULATES the Absorption of Calcium?

A

Vitamin D

Growth Hormone

Increased Dietary Protein

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11
Q

What MUST be the Ratio of Calcium : Phosphorus in the Intestinal Contents?

A

2 : 1

Calcium : Phosphorous

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12
Q

What Does INCREASED Ratio of Calcium : Phosphorus in the Intestinal Contents, Lead to?

A

Formation of INSOLUBLE Calcium Phosphates

  • INHIBITING Calcium Absorption
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13
Q

What Else INHIBITS Calcium Absorption?

A

Cortisol

EXCESSIVE Alkaline

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14
Q

How is the MAJORITY of Calcium LOST?

A

Urinary Excretion

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15
Q

What does the Plasma Concentration of Calcium Depend on?

A

Net Balance of Bone Mineral Deposition + Reabsorption

Intestinal Absorption

Renal Excretion

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16
Q

Which Hormones Regulate the Processes for Plasma Conc of Calcium?

A

Parathyroid Hormone, PTH

Calcitonin

1,25-Dihydroxyvitamin D

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17
Q

What are the Target Hormones for These Reg.Hormones?

A

Bone

Kidney

Intestine

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18
Q

What Happens when the Plasma Ionized Calcium Concentration DECREASES?

A

1) Parathyroid Glands Sense Change
2) Secrete PTH Immediately
3) PTH also acts on Kidney = Stimulate INCREASED Urine Phosphate Excretion + Calcium Reabsorption in Distal Nephron

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19
Q

What is the Role of Calcitonin?

A

Promotes Bone Growth

DECREASES Calcium Levels in Blood

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20
Q

What Can Affect Calcium Metabolism

that ARE NOT ASSOCIATED

with Plasma Changes in Calcium (and Phosphate)?

A

Thyroid Hormone

Growth Hormone

Adrenal Glucocorticoids

Gonadal Steroids

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21
Q

Which Forms of Calcium are Measured in Total Calcium Investigation?

A

Plasma Protein-Bound Calcium

Free / Ionized Calcium (ITSELF TOO!)

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22
Q

What are the Analytical Method for Total Calcium Investigation?

A
  1. Spectrophotometric Determination = OF Coloured Complex

2. Atomic Absorption Spectrophotometry

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23
Q

What is the Analytical Method for Free / Ionized Calcium Investigation?

A

Ion-Selective Potentiometry

24
Q

What is the Reference Range of Total Calcium Serum?

A

2.12 - 2.62 mmol / L

25
Q

Which Specimen are Used for Total Calcium Investigation?

A

Serum

Heparinized Plasma

26
Q

What Can INTERFERE with Total Calcium Investigation?

A

Citrate; Oxalate; EDTA

Hemolysis

Icterus; Lipemia

Paraproteins

Magnesium

27
Q

What is the Reference Range of Free / Ionized Calcium?

A

1.16 - 1.32 mmol / L

28
Q

Which Specimen are Used for Free / Ionized Calcium Investigation?

A

Whole Blood

Heparinized Plasma

Serum

29
Q

How Should Specimens for, Free / Ionized Calcium Investigation, be Transported?

A

Collected ANAEROBICALLY

Transported on Ice + Stored at 4°C = TO PREVENT Loss of CO2 + Glycolysis; TO STABILISE pH

30
Q

How does pH Changes Alter the Relative Distribution of Calcium Forms?

A

INCREASED pH = DECREASED Free / Ionized Calcium

DECREASED pH = INCREASED Free / Ionized Calcium

31
Q

What can Cause LOW pH Levels?

and How?

A

Leaving Tourniquet on for TOO LONG!

  • This can INCREASE Value of Calcium Serum
32
Q

What is the MOST COMMON Cause of HYPER-Calcemia (INCREASED Calcium Levels)?

A

Overproduction of PTH = Hyperparathyroidism

33
Q

What Can Confirm the INCREASE of Calcium, in Urine?

A

24Hr Urine Examination

34
Q

What Genetic Factor Causes INCREASED Calcium Levels?

A

Hypocalciuric Hypercalcemia

  • Where Individuals DO NOT Excrete Normal Amounts
  • HENCE INCREASED Levels of Calcium in Serum
35
Q

What are the Other Causes of INCREASED Calcium Levels?

A

EXCESSIVE Vitamin D

Immobilization

Kidney Failure

Hyperthyroidism

Medications = Thiazide Diuretics

36
Q

What are the Symptoms of HYPO-Calcemia (DECREASED Calcium Levels)?

A

Weakness

Muscle Spasms

Heart Rhythm Disturbance

GI Disorders

Impaired Growth = In Children

37
Q

How Much of Total Magnesium is in Extracellular Fluid?

A

1%

38
Q

How Much Magnesium is Ionized / Free Magnesium?

A

55%

39
Q

How Much Magnesium is Plasma Protein-Bound Magnesium?

A

30% Associated with Albumin

40
Q

How Much Magnesium is Complex Magnesium?

A

15% WITH

  • Phosphate
  • Citrate
  • Other Anions
41
Q

How Much of Total Magnesium is in Intracellular Fluid or Bone Matrix?

A

99%

60% = Bone Matrix

40% = Skeletal Muscles, Blood Cells, Other Cells

42
Q

What is the General Function of Magnesium?

A

Essential for MORE than 300 Cellular Enzymes

  • Transfer of Phosphate Groups;
  • Require ATP:
  • ## Transcription + Translation of DNAMembrane Stabilisation

Nerve Conduction

Ion Transport

Calcium Channel Activity

43
Q

How is Magnesium Regulated?

A

GI Absorption

Renal Excretion

44
Q

What is the MAJOR Regulator of Magnesium?

A

Plasma Mg2+

45
Q

What Happens in Magnesium DEFICIENCY?

A

1) LEADS to REDUCED Urinary Excretion

Plasma Electrolyte Abnormalities

Cardiac Arrhythmias

46
Q

Which Specimen are Used for Total Magnesium Investigation?

A

Serum

NOT Plasma

47
Q

Why is Plasma an UNACCEPTABLE Specimen for Total Magnesium Investigation?

A

Anticoagulant in Plasma INTEFERES with Most Procedures

48
Q

What Analytical Method is Used for Total Magnesium Investigation?

A

Photometry = Absorbance of 520 nm

49
Q

What is the Reference Method for Total Magnesium Investigation?

A

Atomic Absorption Spectrophotometry

50
Q

How is Free / Ionized Magnesium Measured?

A

Magnesium Ion-Selective Electrodes, ISE

51
Q

How does pH Changes Alter the Relative Distribution of Magnesium Forms?

A

INCREASED pH = DECREASED Free / Ionized Magnesium

DECREASED pH = INCREASED Free / Ionized Magnesium

52
Q

What is the Reference Range of Total Magnesium Serum?

A

0.75 - 0.95 mmol / L

53
Q

What is the Reference Range of Free / Ionized Magnesium ?

A

0.44 - 0.6 mmol / L

54
Q

What Conditions are Associated with HYPER-Magnesemia? (INCREASED Magnesium Levels)?

A

Impaired Kidney Function

Diabetic Ketoacidosis

Adrenal Insufficiency

Hyperparathyroidism

Hypocalcaemia (LOW Calcium Levels)

Hyperkalemia (HIGH Potassium Levels)

55
Q

What are the Symptoms of HYPER-Magnesemia? (INCREASED Magnesium Levels)?

A

Heart Rhythm Disturbances

Muscle Weaknesses

Nausea + Vomiting

Breathing Difficulties

56
Q

What Conditions are Associated with HYPO-Magnesemia? (DECREASED Magnesium Levels)?

A

Dietary Deficiencies / Malnutrition

Absorption Insufficiency

Increased Excretion

Alcoholism

Diarrhoea

Medical Diuretics

57
Q

What are the Symptoms of HYPO-Magnesemia? (DECREASED Magnesium Levels)?

A

Heart Rhythm Abnormalities

Muscle Weakness + Cramps

Confusion; Hallucination; Seizures

Clinical Laboratory (31 decks)

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