Electrolytes 2 Flashcards by Gay Amor Tipolo Gacang

Distribution of calcium in blood:

45% = Free Ca2+ ions (ionized Ca2+)
40% = bound to protein (albumin)
15% = bound to anions (HCO3-, citrate, lactate)

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5000 - 10,000 times higher concentration in the cytosol of cardiac or smooth muscle cells

Ionized calcium

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Vital for muscle contractility

Ionized calcium

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Mean concentration in humans of ionized calcium

1.18 mmol/L

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more sensitive and specific marker for Ca2+ disorders

Ionized Ca2+

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TOTAL CA2+ MEASUREMENT

Reference m e t h o d

Atomic Absorption spectrophotometry (AAS)

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TOTAL CA2+ MEASUREMENT

Acidification prior to dye-binding to release Ca2+ from its protein carrier

Orthocresolphthalein Complexone (CPC) method

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Orthocresolphthalein Complexone (CPC) method uses this to form complex with Ca2+

CPC or Arsenazo III dye

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Orthocresolphthalein Complexone (CPC) method uses this to prevent Mg2+ interference

8-hydroxyquinoline

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IONIZED/FREE CA2+ MEASUREMENT

lon-selective electrode (ISE)

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REFERENCE RANGES FOR CALCIUM

Total Calcium - Serum, Plasma:
lonized Calcium - Serum (Adult):
lonized Calcium - Whole blood (Adult):

Total Calcium - Serum, Plasma:
Child, <3 yrs old : 2.13-2.63 mmol/L
Adult: 2.24-2.53 mmol/L

lonized Calcium - Serum (Adult): 1.15-1.33 mmol/L
lonized Calcium - Whole blood (Adult): 1.15-1.27 mmol/L

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Ine 4th most abundant cation in the body

MAGNESIUM

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It is the 2nd most abundant intracellular ion after potassium (K+)

MAGNESIUM

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it is a n essential cofactor for over 3 0 0 enzymes

MAGNESIUM

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The average 70 kg human body contains about how many Mg2+

1 mol (24 g)

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Distribution of magnesium in the body

~ 5 3 % - b o n e
~46% - muscle, other organs, and soft tissue
<1% - serum and red blood cells (RBCs)

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Distribution of magnesium in the serum

~1/3 of Mg2+ is protein-bound (mostly to albumin)
~2/3 is unbound:
• ~61% is in the free (ionized) form - physiologically active
• ~5% is complexed with other ions (e.g., phosphate, citrate)

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Sources of Magnesium

Raw nuts
Dry cereal
Hard drinking watse

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Renal reabsorption of Mg2+:

25%-30% - РСT
50%-60% - ALH → major regulator site
2%-5% - DCT

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Renal threshold of Magnesium

0.60-0.85 mmol/L (=1.46-2.07 mg/dL)

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Increases renal reabsorption of Mg2+ and enhances intestinal absorption of Mg2+

Parathyroid hormone (PTH)

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common in ICU patients or those on diuretics or digitalis due to tissue depletion, affecting about 15% of nonhospitalized individuals, while hypermagnesemia is much less frequent

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Hypomagnesemia

Colorimetric methods in measuring total Mg2+

Mga forms reddish-violet complex (read at 532 nm)

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Calmagite

Colorimetric methods in measuring total Mg2+

Mg2+ forms colored complex (read at 660 nm)

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Formazan Dye

Colorimetric methods in measuring total Mg2+ Mg2+ forms colored complex with the chromogen

Methyl Thymol Blue

Reference method for Magnesium Determination

AAS

REFERENCE RANGES FOR MAGNESIUM Serum, colorimetric

Serum, colorimetric: 0.66-1.07 mmol/L or 1.7-2.4 mg/dL

Main intracellular anion

PHOSPHATE

Integral part of DNA and RNA as phosphodiester linkages

PHOSPHATE

Major energy storage molecules:

ATP, creatine phosphate, and phosphoenolpyruvate (PEP) contain phosphate

Phosphate affects the concentration of 2,3-bisphosphoglycerate (2,3-BPG) in red blood cells: promotes oxygen release from hemoglobin

Increased 2,3-BPG

Phosphate affects the concentration of 2,3-bisphosphoglycerate (2,3-BPG) in red blood cells: oxygen is held more tightly by hemoglobin.

Decreased 2,3-BPG

Factors affecting renal regulation of Phosphate:

1. Parathyroid Hormone 2. Vitamin D 3. Calcitonin and acid-base status 4. Growth hormone

most important regulator of Phosphate

Parathyroid hormone

Decreases blood phosphate by increasing renal excretion

Parathyroid hormone

Increases phosphate level

Vitamin D

Can increase blood phosphate by reducing renal excretion

Growth hormone

Body distribution of Phosphate

• 80% of total body phosphate is in bone • 20% is in soft tissues • <1% is found in serum/plasma as active phosphate

Phosphate levels follow a circadian rhythm: Highest in: Lowest in:

Highest in: late morning Lowest in: evening

Common principle of phosphate determination

Ammonium phoshpmolybdate complex

REFERENCE RANGES FOR INORGANIC PHOSPHORUS (SERUM) Neonate: Child ≤15 y : Adult: Urine (24hr):

Neonate: 1.45-2.91 mmol/L Child ≤15 y : 1.29-2.26 mmol/L Adult: 0.81-1.45 mmol/L Urine (24hr): 13-42 mmol/day

Result of anaerobic metabolism, occurring when oxygen delivery is severely diminished

LACTATE

the normal end product of glycolysis under aerobic conditions

Pyruvate

Elevation in blood is an early, sensitive, and quantitative marker of oxygen deprivation or Tissue hypoxia

Lactate

Lactate In normal (aerobic) conditions

Pyruvate is converted to acetyl-CoA ➡️ Acetyl-CoA enters the citric acid cycle (TCA). 1 mole glucose = 38 mole of ATP

Lactate In hypoxic (anaerobic) conditions:

Pyruvate is converted to lactate due to high NADH levels ➡️ Lactate is released into the blood 1 mole glucose = 2 mole of ATP

Primary regulator of Lactate

Liver

Additives recommended in lactate determination as they inhibit glycolysis and do not interfere with coagulation

iodoacetate and fluoride

REFERENCE RANGES FOR LACTATE Venous: Arterial:

Venous: 0.3-1.2 mmol/L Arterial: 0.3-1.6 mmol/L

The difference between measured cations and measured anions in serum

ANION GAP

It reflects the presence of unmeasured anions or cations in the blood

ANION GAP

Routine Electrolytes Used in anion gap

Sodium (Na*), Potassium (K*), Chloride (CI*), and Bicarbonate (HCO* or total CO2).

Anion gap Without potassium formula and reference range

AG = Na+ - (Cl- + HCO3-) Reference range: 7-16 mmol/ L

Anion gap with potassium formula and reference range

AG = (Na+ + K+) - (Cl- + HCO3-) Reference range: 10 - 20 mmol L

Electrolytes 2 Flashcards

(54 cards)