13. Total and ionized Calcium | Total and ionized Magnesium Flashcards
What are the 3 Forms of Calcium?
- Free / Ionized Calcium
- Complexed Calcium
- Plasma Protein-Bound Calcium
1| What is Free / Ionized Calcium?
Physiological ACTIVE Form
35 - 40% of Total Calcium Serum
2| What is Complexed Calcium?
Calcium that’s BOUND TIGHTLY to Variety of Anions
- Bicarbonate; Lactate; Phosphate; Citrate
40 - 50% of Total Calcium Serum
3| What is Plasma Protein-Bound Calcium?
Associated with Albumin
80% of Total Calcium Serum
What Happens to the Levels of the Calcium Forms?
and Why?
Total Serum Calcium is UNCHANGED
Relative Distribution of 3 Forms is ONLY ALTERED
DUE to pH Changes in ECF
What are the General Functions of Calcium?
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
Where is Calcium Absorbed?
Duodenum
Upper Jejunum
When Does Calcium Absorption INCREASE?
Rapid Growth in Children
Pregnancy
Lactation
When Does Calcium Absorption DECREASED?
Advancing Age
What STIMULATES the Absorption of Calcium?
Vitamin D
Growth Hormone
Increased Dietary Protein
What MUST be the Ratio of Calcium : Phosphorus in the Intestinal Contents?
2 : 1
Calcium : Phosphorous
What Does INCREASED Ratio of Calcium : Phosphorus in the Intestinal Contents, Lead to?
Formation of INSOLUBLE Calcium Phosphates
- INHIBITING Calcium Absorption
What Else INHIBITS Calcium Absorption?
Cortisol
EXCESSIVE Alkaline
How is the MAJORITY of Calcium LOST?
Urinary Excretion
What does the Plasma Concentration of Calcium Depend on?
Net Balance of Bone Mineral Deposition + Reabsorption
Intestinal Absorption
Renal Excretion
Which Hormones Regulate the Processes for Plasma Conc of Calcium?
Parathyroid Hormone, PTH
Calcitonin
1,25-Dihydroxyvitamin D
What are the Target Hormones for These Reg.Hormones?
Bone
Kidney
Intestine
What Happens when the Plasma Ionized Calcium Concentration DECREASES?
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
What is the Role of Calcitonin?
Promotes Bone Growth
DECREASES Calcium Levels in Blood
What Can Affect Calcium Metabolism
that ARE NOT ASSOCIATED
with Plasma Changes in Calcium (and Phosphate)?
Thyroid Hormone
Growth Hormone
Adrenal Glucocorticoids
Gonadal Steroids
Which Forms of Calcium are Measured in Total Calcium Investigation?
Plasma Protein-Bound Calcium
Free / Ionized Calcium (ITSELF TOO!)
What are the Analytical Method for Total Calcium Investigation?
- Spectrophotometric Determination = OF Coloured Complex
2. Atomic Absorption Spectrophotometry
What is the Analytical Method for Free / Ionized Calcium Investigation?
Ion-Selective Potentiometry
What is the Reference Range of Total Calcium Serum?
2.12 - 2.62 mmol / L
Which Specimen are Used for Total Calcium Investigation?
Serum
Heparinized Plasma
What Can INTERFERE with Total Calcium Investigation?
Citrate; Oxalate; EDTA
Hemolysis
Icterus; Lipemia
Paraproteins
Magnesium
What is the Reference Range of Free / Ionized Calcium?
1.16 - 1.32 mmol / L
Which Specimen are Used for Free / Ionized Calcium Investigation?
Whole Blood
Heparinized Plasma
Serum
How Should Specimens for, Free / Ionized Calcium Investigation, be Transported?
Collected ANAEROBICALLY
Transported on Ice + Stored at 4°C = TO PREVENT Loss of CO2 + Glycolysis; TO STABILISE pH
How does pH Changes Alter the Relative Distribution of Calcium Forms?
INCREASED pH = DECREASED Free / Ionized Calcium
DECREASED pH = INCREASED Free / Ionized Calcium
What can Cause LOW pH Levels?
and How?
Leaving Tourniquet on for TOO LONG!
- This can INCREASE Value of Calcium Serum
What is the MOST COMMON Cause of HYPER-Calcemia (INCREASED Calcium Levels)?
Overproduction of PTH = Hyperparathyroidism
What Can Confirm the INCREASE of Calcium, in Urine?
24Hr Urine Examination
What Genetic Factor Causes INCREASED Calcium Levels?
Hypocalciuric Hypercalcemia
- Where Individuals DO NOT Excrete Normal Amounts
- HENCE INCREASED Levels of Calcium in Serum
What are the Other Causes of INCREASED Calcium Levels?
EXCESSIVE Vitamin D
Immobilization
Kidney Failure
Hyperthyroidism
Medications = Thiazide Diuretics
What are the Symptoms of HYPO-Calcemia (DECREASED Calcium Levels)?
Weakness
Muscle Spasms
Heart Rhythm Disturbance
GI Disorders
Impaired Growth = In Children
How Much of Total Magnesium is in Extracellular Fluid?
1%
How Much Magnesium is Ionized / Free Magnesium?
55%
How Much Magnesium is Plasma Protein-Bound Magnesium?
30% Associated with Albumin
How Much Magnesium is Complex Magnesium?
15% WITH
- Phosphate
- Citrate
- Other Anions
How Much of Total Magnesium is in Intracellular Fluid or Bone Matrix?
99%
60% = Bone Matrix
40% = Skeletal Muscles, Blood Cells, Other Cells
What is the General Function of Magnesium?
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
How is Magnesium Regulated?
GI Absorption
Renal Excretion
What is the MAJOR Regulator of Magnesium?
Plasma Mg2+
What Happens in Magnesium DEFICIENCY?
1) LEADS to REDUCED Urinary Excretion
Plasma Electrolyte Abnormalities
Cardiac Arrhythmias
Which Specimen are Used for Total Magnesium Investigation?
Serum
NOT Plasma
Why is Plasma an UNACCEPTABLE Specimen for Total Magnesium Investigation?
Anticoagulant in Plasma INTEFERES with Most Procedures
What Analytical Method is Used for Total Magnesium Investigation?
Photometry = Absorbance of 520 nm
What is the Reference Method for Total Magnesium Investigation?
Atomic Absorption Spectrophotometry
How is Free / Ionized Magnesium Measured?
Magnesium Ion-Selective Electrodes, ISE
How does pH Changes Alter the Relative Distribution of Magnesium Forms?
INCREASED pH = DECREASED Free / Ionized Magnesium
DECREASED pH = INCREASED Free / Ionized Magnesium
What is the Reference Range of Total Magnesium Serum?
0.75 - 0.95 mmol / L
What is the Reference Range of Free / Ionized Magnesium ?
0.44 - 0.6 mmol / L
What Conditions are Associated with HYPER-Magnesemia? (INCREASED Magnesium Levels)?
Impaired Kidney Function
Diabetic Ketoacidosis
Adrenal Insufficiency
Hyperparathyroidism
Hypocalcaemia (LOW Calcium Levels)
Hyperkalemia (HIGH Potassium Levels)
What are the Symptoms of HYPER-Magnesemia? (INCREASED Magnesium Levels)?
Heart Rhythm Disturbances
Muscle Weaknesses
Nausea + Vomiting
Breathing Difficulties
What Conditions are Associated with HYPO-Magnesemia? (DECREASED Magnesium Levels)?
Dietary Deficiencies / Malnutrition
Absorption Insufficiency
Increased Excretion
Alcoholism
Diarrhoea
Medical Diuretics
What are the Symptoms of HYPO-Magnesemia? (DECREASED Magnesium Levels)?
Heart Rhythm Abnormalities
Muscle Weakness + Cramps
Confusion; Hallucination; Seizures
