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1. Function and
Measurement of
Electrolytes
1

2. Learning Objectives
2
 Upon completion of the lecture, the student will be able to:
 Define electrolytes and related terms.
 Discuss the intracellular and extracellular distribution of
electrolytes
 Explain the typical relationship (balance) of water and
electrolytes
 Discuss typical Na, K, blood gas, phosphorous, magnesium,
iron, Cl, CO2/HCO3 levels in body fluids based on
pathophysiological responses.
 Describe the principle of analysis of Na, K, iron, magnesium,
phosphorous, Cl and total CO2 (HCO3-), in terms of
electronic components, reagents and endpoint detection.
 Discuss typical Na, K, blood gas, phosphorous, magnesium, iron, Cl,
CO2/HCO3 3 levels in body fluids based on pathophysiological responses.
 Describe the principle of analysis of Na, K, blood gas,
phosphorous, iron, Cl, CO2/HCO3 and total CO2 (HCO3-), in

3. Outline
3
 Introduction
 Source
 Clinical Significance
 Methods of Analysis
 Specimen
 Interpretation
 Quality Control
 Sources of Error
 Documentation and Reporting
 Summary

4. Terminology
4
 Partial pressure of Oxygen (PO2):
dissolved oxygen gas in the blood
 Partial pressure of Carbon dioxide
(PCO2): dissolved carbon dioxide in the
blood
 pH: potential of H+ concentration
 Bicarbonate (HCO3-): part of major
buffer system; salt form of carbon
dioxide

5. Electrolytes
Body Fluid Compartments
5
 In lean adults, body fluids constitute
 55% of female and 60% of male total body mass
 Intracellular fluid (ICF) inside cells
 About 2/3 of body fluid
 Extracellular fluid (ECF) outside cells
Interstitial fluid between cell is 80% of ECF
Plasma in blood is 20% of ECF
Also includes lymph, cerebrospinal fluid, synovial fluid,
aqueous humor, vitreous body, endolymph, perilymph, and
pleural, pericardial, and peritoneal fluids

6. Body Fluid Compartments
6

7. Fluid Balance
7
 Body is in fluid balance = when required amounts
of water and solutes are present and correctly
proportioned among compartments
 Water is by far the largest single component of the
body making up 45-75% of total body mass
 Process of filtration, reabsorption, diffusion, and
osmosis all continual exchange of water and solutes
among compartments

8. Sources of Body Water Gain and
Loss
8
 Fluid balance related to electrolyte balance
 Intake of water and electrolytes rarely proportional
 Kidneys excrete excess water through dilute urine or
 excess electrolytes through concentrated urine
 Body can gain water by
 Ingestion of liquids and moist foods (2300mL/day)
 Metabolic synthesis of water (200mL/day)
 Body loses water through
 Kidneys (1500mL/day)
 Evaporation from skin (600mL/day)
 Exhalation from lungs (300mL/day)
 Feces (100mL/day)

9. Daily Water Gain and Loss
9
Feces

10. Regulation of body
water gain
during dehydration
10
 Mainly by volume of
water intake/ how much
you drink
 Dehydration – when
water loss is greater
than gain
 Decrease in volume,
increase in
osmolarity of body
fluids
 Stimulates thirst
center in
hypothalamus

11. Regulation of water and solute loss
11
Elimination of excess body water through urine
Extent of urinary salt (NaCl) loss is the main factor
that determines body fluid volume
Main factor that determines body fluid osmolarity is
extent of urinary water loss
3 hormones regulate renal Na+ and Cl- reabsorption
or excretion
Angiotensin II and aldosterone promote urinary Na+ and
Cl- reabsorption of (and water by osmosis when
dehydrated)
Atrial natriuretic peptide (ANP) promotes excretion of
Na+ and Cl- followed by water excretion to decrease blood
volume

12. Major hormone regulating water loss is
antidiuretic hormone (ADH)
12
Also known as vasopressin
Produced by hypothalamus, released
from posterior pituitary
Promotes insertion of aquaporin-2 into
principal cells of collecting duct
Permeability to water increases
Produces concentrated urine

13. Intoxication
13

14. Electrolytes in body fluids
14
Ions form when electrolytes
dissolve and dissociate
4 general functions
Control osmosis of water between
body fluid compartments
Help maintain the acid-base balance
Carry electrical current
Serve as cofactors

15. Electrolytes
15
Electrolytes are charged particles
or ions when in solution .
 Cations are positively charged ions.
 Anions are negatively charged ions.
List of the four Major
Electrolytes:
Sodium (Na+)
Potassium (K+)
Chloride (Cl-)

16. 16
 Minor electrolytes or minerals include
calcium
phosphorus
Magnesium
 Iron is a trace electrolyte of clinical significance.
 Blood gases are sometimes measured with
electrolytes.
 Blood gas analysis includes
pH
dissolved carbon dioxide (pCO2) and
dissolved oxygen (pO2).

17. 17

18. The Function of Electrolytes
18
Electrolytes participate in:
enzyme activation,
coagulation and complement cascades
contribute to plasma osmolality
participates in cardiac rhythm
neuromuscular excitation

19. Function of electrolytes
conti..
19
Maintenance of osmotic pressure and water
distribution in body fluid compartment
Maintenance of correct pH
Regulation of the proper function of the
heart and other muscles
Involvement in oxidation-reduction
reactions
Participate in catalysis as cofactors for
enzymes

20. Distribution of Electrolytes
20
 Intracellular versus Extracellular
distributions vary
Na+, Ca++ and Cl- = extracellular
K+, Mg++ and CO3- = intracellular
 Effect of hemolysis: release of
intracellular
ions

21. 21

22. Water and Electrolyte Balance
22
 Intracellular Fluid (ICF)
More protein, K +, Mg2+, phosphates,
HCO3-
 Extracellular Fluid (ECF)
Less protein
More Na+, Cl- , Ca++
 ECF could be subdivided into:
Interstitual Fluid (extravascular)
Intravascular Fluid (plasma)

23. Concentrations in body fluids
23
 Concentration of ions typically expressed
in milliequivalents per liter (mEq/liter)
 Chief difference between 2 ECF
compartments (plasma and interstitial
fluid)
 plasma contains many more protein anions
Largely responsible for blood colloid osmotic
pressure

24. ECF
24
ECF most abundant cation is Na+,
anion is Cl-
ICF most abundant cation is K+,
anion are proteins and phosphates
(HPO4
2-)
Na+ /K+ pumps play major role in
keeping K+ high inside cells and Na+
high outside cell

25. Water Balance
25
Total water intake = total water out-
put
Osmotic Pressure (Na + water)
Hormonal Influences
Aldosterone: conserves Na and Cl
Anti-diuretic Hormone (ADH):
conserves water

26. Condition of Fluid Imbalance
26
Loss of Water
Dehydration
Lack of ADH
Loss of Water and Electrolytes
 GI loss
 Excessive sweating
 Burns
 Excess urine excretion

27. Edema
27
 Fluid accumulates in tissue space (interstitial space)
Lead to salt & water depletion when extreme
 Causes of Edema:
Low plasma protein levels =insufficient osmotic pressure
Block lymphatic vessels= preventing the removal of
protein from interstitial fluid e.g. filariasis

28. Electrolytes and Acid Base
Balance
28
 Major electrolyte involved in acid
base balance is HCO3-
(bicarbonate salt).
Source:
 H2CO3 HCO3
 HCO3 +H H2O+ CO2
 The resulting bicarbonate is
reabsorbed to help maintain acid
base balance in blood plasma.
carbonic anhydrase

29. Overview of Acid-Base Balance
29
Neutral blood pH 7.4 is maintained
by
Bicarbonate salt = controlled by
kidney
carbonic acid = controlled by lungs

30. Renal Control of Electrolytes
• Renal Control of Acid Base Balance
• Distal convoluted tubules perform 2 main
functions. They are:
1) secrete H and NH
+
4
+
2) secrete Na , HCO
+ 3
-
& H PO
2 4
-
30

31. Disturbances of Electrolyte and
Acid Base Balance
31
 Metabolic Acidosis
 Indicated by decreased blood pH and
decreased bicarbonate/ total CO2
 Causes of Metabolic Acidosis are: diarrhea,
diabetic ketoacidosis and renal failure
 Compensation: Respiratory system
attempts to normal blood pH by eliminating
more carbon dioxide and decreasing blood
pCO2 levels

32. Disturbances of Electrolyte and
Acid Base Balance
32
 Metabolic Alkalosis
 Indicated by increased blood pH and
increased bicarbonate/ total CO2
 Causes of Metabolic alkalosis: excess
treatment with bicarbonate salts, prolonged
vomiting and renal causes of K depletion.
Compensation: Respiratory system
attempts to normal blood pH by retaining
carbon dioxide and blood pCO2 levels

33. Balance
33
Respiratory acidosis – abnormally high
PCO2 in systemic arterial blood
Inadequate exhalation of CO2
Any condition that decreases movement of
CO2 out – emphysema, pulmonary edema,
airway obstruction
Kidneys can help raise blood pH
Goal to increase exhalation of CO2 –
ventilation therapy

34. Balance
34
 Respiratory Acidosis
Indicated by decreased blood pH and increased dissolved
carbon dioxide/ pCO2
Causes of respiratory acidosis are:
Respiratory illnesses that cause hypoventilation
and hypercapnia (too much carbon dioxide in
blood)
Emphysems = diseases control breathing system of lung
Chronic Bronchitis
Medications that depress respiration

35. Disturbance of Acid Base Balance
35
Respiratory alkalosis
 Indicated by increased blood pH and decreased
dissolved carbon dioxide/ Abnormally low PCO2 in
systemic arterial blood
 Cause is hyperventilation due to oxygen deficiency from
high altitude or pulmonary disease, stroke or severe
anxiety
Renal compensation can help to normalize
One simple treatment to breather into paper bag for
short time

36. Sodium Na+
36
 Most abundant ion in ECF
 90% of extracellular cations
 Plays vital role in fluid and electrolyte
balance also osmotic pressure maintain
 Level in blood controlled by
Aldosterone – increases renal reabsorption
ADH – if sodium too low, ADH release stops
Atrial natriuretic peptide – increases renal
excretion

37. 37
 Normal daily diet contains 130-260 mmol of
NaCl, but the body requires only 1-2mmol/day;
the excess is excreted by kidney.
 70%-80% of Na is reabsorbed actively in the
PCT, with Cl & water passively.
 Another 20% to 25% is reabsorbed in the LH.

38. Clinical Significance Hypernatremia
38
 Na gain or water loss cause hypernatremia
 Caused by renal and non-renal disorders.
 Common non-renal causes:
Dehydration
Burns
Excessive Sweating
 Renal:
 Nephrogenic diabetes insipidus

39. Clinical Significance
Hyponatremia
39
 Water gain or Na loss cause hyponatremia.
 Renal Causes:
Salt losing nephritis
Chronic renal failure can cause water overload:
Nephrotic syndrome can cause fluid imbalances and
edema with resulting hyponatremia.
Urine Na levels are normal or decreased in hyponatremia
due to edema.
 Non-renal causes:
 psychogenic water overload

40. Potassium K+
40
 Most abundant cations in ICF
 Also helps maintain normal ICF fluid volume
 Maintains cardiac rhythm and contributes to
neuromuscular conduction.
 Imbalances, hyperkalemia or hypokalemia, will result in:
 Cardiac arrhythmia and weakness

41. Clinical Significance of
Hyperkalemia
41
 What are causes of hyperkalemia?
 Renal failure (renal tubular acidosis )
 Drugs: potassium-sparing diuretics
 Diabetic ketoacidosis :
 Hemolytic or Leukemia
Endocrine causes: hypocortisolism, Hypoaldosteronism
GI absorption: increased intake (e.g., fresh fruits)
Release from cells: myolysis, tumor lysis, hemolysis

42. Clinical Significance Hypokalemia
42
 What causes it?
 Renal tubular acidosis
 Hyperaldosteronism:
 Endocrine causes: Hyperaldosteronism,
hypercortisolism; K lost and Na retained
 Drugs: diuretics
Vomiting or GI loss
Gastrointestinal loss: vomiting, diarrhea, laxatives
 Intracellular shift
 Alkalosis
 Insulin therapy

43. CHLORIDE CL-
43
 Most prevalent anions in ECF
 Moves relatively easily between ECF and ICF because
most plasma membranes contain Cl- leakage channels
and antiporters
 Can help balance levels of anions in different fluids
 Chloride shift in RBCs
 Regulated by
 ADH – governs extent of water loss in urine
 Processes that increase or decrease renal reabsorption of
Na+ also affect reabsorption of Cl-

44. Clinical Significance of Chloride
44
Contributes to the acid-base balance
by the isohydric shift
Chloride shift is:
Movement of Cl opposite to HCO3-

45. Clinical Significance Hyperchloremia
45
Dehydration: severe diarrhea or
burns
Hyperaldosteronism: Na and Cl
retention

46. Clinical Significance
Hypochloremia
46
Excessive urination
Excessive sweating
Hypoaldosteronism: Na and Cl
lost, K retained

47. Bicarbonate HCO3
-
47
 Second most prevalent extracellular anion
 Concentration increases in blood passing through
systemic capillaries picking up carbon dioxide
 Chloride shift helps maintain correct balance of
anions in ECF and ICF
 Kidneys are main regulators of blood HCO3
-
Can form and release HCO3
- when low or excrete excess

48. Bicarbonate
48
CO2 + H2O H2CO3 H+ + HCO3-
 tCO2 includes many components:
Majority of plasma CO2 exists in the form of
bicarbonate
 Bicarbonate maintains electrical neutrality along with K
in the cell (intracellularly)
 It is the most important buffer of the blood.
 Major metabolic component to balance pH

49. Clinical Significance of
Bicarbonate Ion Levels
49
Excess Blood bicarbonate
Metabolic alkalosis
Compensation for respiratory
acidosis
Decreased Blood bicarbonate
Metabolic acidosis
Compensation for respiratory
alkalosis

50. Electrolytes Methods of Analysis
50
 Ion selective Electrodes: Na, K, Cl
and HCO3-
 Flame Emission Photometry: Na
and K
 Colorimetry: Cl and HCO3-
 Minor Electrolyte Methods:
Colorimetric
Atomic Absorption Spectroscopy

51. Ion Selective Electrodes
51
 Only free/unbound ion is measured by
ISE
 Significant for measuring Ca & Mg b/c
about 33% to 50% of Ca is ionized
 Ion selective electrodes are covered by a
unique material that is more selective
for one ion than other ions.
 When the ion comes in contact with the
electrode, there is potential difference
 Lipemia interferes with indirect method

52. Method of Na Analysis Ion
Selective Electrode (ISE)
52
made of a lithium aluminum
silicate or other composite
silicon dioxide glass
compound
selective for Na+
Not selective K+ or H+

53. Method of K Analysis
53
The ISE for K typically contains a
selective membrane containing
valinomycin
binds well with K+
does not bind well
with Na+ or H+

54. Method of Cl Analysis
54
Ion Selective Electrode (ISE)
made of a Cl salt compound
selective for Cl-
Not selective other anions

55. Method of Na and K Analysis
using Flame emission photometry
55
 Sample is mixed with internal standard.
 Solution is aspirated into a flame.
 Ions are excited with the addition of the
thermal energy and emit radiant
energy.
 Photodetector detects the unique emitted
wavelengths of light specific to the Na+
and K+
 Concentration of Na+ or K+ in mmol/L is

56. 56

57. Methods for Cl Analysis
57
Spectrophotometric methods
Hg(SCN)2 + 2Cl- HgCl2 +2SCN-
3SCN- + Fe3+ Fe(SCN)3
(colored
ferricthiocyanate)
 The final chromogen is measured
photometrically at 480 nm
 mercuric thiocyanate, mercuric chloride,
thiocyanate; Ferric ions, reddish

58. Method of Bicarbonate Analysis
Photometric method:
• HCO + urea --(urea amidolyase) NH
3 4
+
.
NH4
+ + NADPH –(glutamate dehydrogenase) NADP + H
+ +
• Decrease in Abs is measured at 340 nm
62
58

59. Specimen for Cl Analysis
59
Serum or heparinized plasma
Mild hemolysis is accepted
Urine
CSF
Sweat

60. Specimens for Na and K
60
 Venous Serum
 Heparinized plasma
 Effect of Hemolysis
No error for Na but causes false elevation of
K
 Avoid lipemic sera
 Separate serum or plasma quickly from
cells
 CSF for Na but not K

61. Specimens for Bicarbonate
61
Serum
Arterial
Venous
Heparinized whole blood
Arterial

62. Sources of Error for Na and K
Analysis
62
Hemolysis
Failure to quickly separate
plasma/serum from cells
Anticoagulants other than heparin
Prolonged use of tourniquet
Lipemia
Errors of analysis
Not calibrated

63. Sources of Error in Cl
Analysis
63
Specimen errors are associated with:
 Anticoagulants other than heparin
Analysis errors:
 In ISE Br- ions may interfere in Cl- electrodes
 Protein coating on the electrode
 In spectrophotometric method, poor
calibration or in accurate instrument
operation

64. Sources of Error for Bicarbonate
Analysis
64
 Specimen errors due to:
Wrong anticoagulant
Failing to keep the specimen stoppered
Not fresh
Hemolysis
 Analytic errors due to:
Protein contamination of membrane in ISE
Poorly calibrated analyzers
 Reporting errors due to:
Using wrong reference ranges with type of specimen
(whole blood versus plasma)

65. Interpretation of Serum Na and K
Levels
Test Unit Ref. Range
Na mmol/L 135-145
K mmol/L 3.3-4.9
Use reference ranges specific to the region or country.
 Compare the patient results to the reference ranges
to determine if increase or decrease in Na or K are
observed. 43
65

66. Interpretation of Cl Results
• Cl Reference Ranges:
Serum in
adult
infant
98-107
98-113
mmol/L
Urine in
adult
infant
child
110-250
2-10
15-40
mmol /24 hr
CSF in
adult
infant
118-132
110-130
mmol/L
Sweat 5-35 mmol/L 54
66

67. Interpretation of Bicarbonate
Levels
Specimen HCO3- Unit
Serum, Venous 22-29 mmol/L
Serum, Arterial 21-28 mmol/L
Whole blood,
Arterial 22-26 mmol/L
Reference Ranges:
66
67

68. Reporting and Documentation
68
 To avoid post-analytic errors,
 Report the patient result with :
 right name and result
 Include reference ranges
 Timely manner
 QC and patient results should be
documented in logbook and retained in
lab

69. Anion Gap
69
 Electrolytes exist in a balance to
provide electrolyte neutrality.
 Sum of anions, including chloride,
bicarbonate and ionized proteins =
sums of cations, including sodium and
potassium

70. Clinical Significance Anion Gap
70
 In many types of metabolic acidosis,
anion gap is increased (> 20 ) due to
deficit of bicarbonate ions and
presence of organic acids, such as
acetoacetic acid, lactate, salicylate,
formate or glycolate.
 ↑ sodium relative to ↓ bicarbonate will
also increase anion gap.

71. Gap
71
Decreased anion gap may be due
to:
↓ Na and or ↑ Cl and HCO3-
A decreased anion gap may be
found with:
Rare electrolye imbalance
More commonly, decreased anion
gap is an indication of technical

72. Calculation of Anion Gap
72
 Anion gap is a calculation of the
difference between anions and
cations in blood.
 represents chemical anions other than
those used in the formulas, chloride
and bicarbonate, that might be
present in blood.
 used to estimate acid-base and
electrolyte disturbances.

73. Calculation of Anion Gap
73
 The most commonly used formula
is
 (Na + K) -(Cl +CO2) with reference
range of: 10-20 mmol/L
 The formula (Na ) -(Cl+CO2) can be
used but is generally being
replaced by the formula that
includes potassium.

74. Interpretation of Results
Electrolyte Analysis
74
 In order to classify electrolyte
abnormalities, compare results to
the reference ranges and consider
critically high or low levels.
 Critical values indicate life-
threatening situation due to the
electrolyte abnormality. They are
typically established at each
institution.

75. Electrolyte Analysis
•
Critical
Values for
Electrolytes
Na
mmol/
L
K
mmol/ mmo/
L
Cl
L
HCO3
-
mmol/
L
>160 >6.2 > 120 > 40
< 120 < 2.8 < 80 <10
74
75

76. Interpretation of Serum
Electrolyte Levels
Test Unit Ref. Range
Na mmol/L 135-145
K mmol/L 3.3-4.9
Cl mmol/L 98-108
HCO3
-
mmol/L 22-28
Anion Gap none 10-20
75
76

77. Review Questions
77
 What are the patient sample
collection and handling processes
for electrolyte analysis.
 What is the effect of hemolysis on
Na and K results?

78. Review Questions
78
What are main causes of the
following:
Hyponatremia
Hypernatremia
Hypokalemia
hyperkalemia

79. 79
Calcium Analysis

80. Calcium Ca2+
80
 Most abundant mineral in body
 98% of calcium in adults in skeleton and
teeth
 In body fluids mainly an extracellular
cation
 Contributes to hardness of teeth and
bones
 Plays important roles in blood clotting,
neurotransmitter release, muscle tone,
and excitability of nervous and muscle
tissue

81. Calcium Ca2+
81
 Regulated by parathyroid hormone
Stimulates osteoclasts to release calcium from bone –
resorption
Also enhances reabsorption from glomerular filtrate
Increases production of calcitrol to increase absorption for
GI tract
 Calcitonin lowers blood calcium levels
 99% in bones, 1% in serum and soft
tissue
 (measured by serum Ca++)
 Works with phosphorus to form bones
and teeth

82. 82
Participates in blood clotting Minor
electrolyte or mineral
 Obtained from our diet
 Found in ECF
Bound to protein or
Inactive ions in transit b/n storage
Active intracellular form
 Affects cardiac muscle contraction

83. Source of Calcium
83
 Calcium is a common mineral found
in bones, teeth, and plasma.
 50% plasma calcium is Ca++
 50% plasma calcium is bound to
albumin

84. Calcium
84
Intracellular Ca++
Muscle contraction
Metabolism
Hormone secretion
Hemostasis/ clotting
Enzyme activation
Extracellular Ca++
Electrolyte balance

85. Clinical Significance of
Calcium
85
 Hypercalcemia
Primary hyperparathyroidism
Cancers
Kidney stones
Sarcoidosis
 Hypocalcemia
Secondary hyperparathyroidism
Renal failure
GI loss

86. Methods of Calcium Analysis
86
General Principles of Total
Calcium
Spectrophotometric
Atomic Absorption spectroscopy
General Principles of Ionized
Calcium
Electrochemistry

87. Spectrophotometric Calcium
Analysis
87
 Total Calcium (ionized and protein
bound forms) + acid free
calcium
 Free Calcium + O-cresolphthalein
complexone
red chromagen
 Measured at 580 nm

88. Other methods: Calcium
Analysis
88
 Atomic Absorption Spectroscopy
 Reference Method
 Calcium mixed with buffer that frees
protein bound forms.
 Free calcium in sample is excited with
unique wavelength from hollow cathode
lamp (HCL) supplying radiant energy
 Absorption of light is proportional to
concentration

89. 89

90. Ionized Calcium Analysis
• Ion Selective Electrode:
• Electrode with PVC
/polyvinyl chloride/
membrane selective for
Ca
• Ag/ AgCl reference
electrode has constant
voltage potential
• potential in the
reference solution is
measured due to
presence of Ca++
90

91. Specimens for Calcium
• Serum
• Heparinized plasma
• Urine
– Random
– 24 hour urine
91

92. Results
92
Reference Ranges:
 Adult serum total calcium: 8.6-10.2
mg/dL
 Urine calcium: 50-150 mg / 24 hr
(dietary dependent)
 Adult plasma Ca++: 1.15 to 1.33 mmol/L
 Compare patient results with reference
ranges to interpret calcium results for
hyper- or hypocalcemia.

93. Sources of Error
93
 Wrong anticoagulant
 Hemolysis
 Lipemia
 Icterus
 Unpreserved urine
 Reagent deterioration
 Instrument temperature fluctuation
 Nonlinearity of reaction

94. Reporting and Documentation
94
• To avoid post-analytic errors,
• Report the patient result with :
o–Right name and result
o–Include reference ranges
o–Timely manner
QC and patient results should be
documented in logbook and
retained in lab

95. 95
Phosphorus and
Magnesium
Analysis

96. Introduction to Phosphorus
and Magnesium
96
 They are minerals similar to calcium
 Inorganic forms in bone, teeth
 Phosphates are intracellular anions
 Magnesium is intracellular cation

97. Source of Phosphorus and
Magnesium
97
 Derived from diet
 Found as inorganic forms in bones,
teeth
 Smaller amounts in intracellular or
 In plasma:
protein bound
ionized
 Regulated by kidneys and parathyroid
gland

98. Phosphate
98
 About 85% in adults present as calcium phosphate
salts in bone and teeth
 Remaining 15% ionized – HPO4
2- and PO4
3- are
important intracellular anions
Parathyroid hormone – stimulates resorption of bone by
osteoclasts releasing calcium and phosphate but inhibits
reabsorption of phosphate ions in kidneys
Calcitrol promotes absorption of phosphates and calcium
from GI tract

99. Magnesium
99
 In adults, about 54% of total body magnesium is part of
bone as magnesium salts
 Remaining 46% as Mg2+ in ICF (45%) or ECF (1%)
 Second most common intracellular cation
 Cofactor for certain enzymes and sodium-potassium
pump
 Essential for normal neuromuscular activity, synaptic
transmission, and myocardial function

100. Mg
100
Phosphorus/ phosphates
 pH buffering
 Electrolyte balance: intracellular anion
 Shifts internally with Insulin release
Magnesium
 Minor electrolyte: intracellular cation
 Enzyme activator or cofactor
 Minor role in blood hemostasis

101. Clinical Significance of
Phosphorus &magnesium
101
 Hyperphosphatemia: increased phosphate and other
forms of phosphorus in the blood plasma.
 Hypophosphatemia: decreased phosphate and other
forms of phosphorus in the blood plasma.
 Hypermagnesemia: increased magnesium in the
blood plasma.
 Hypormagnesemia: decreased magnesium in the
blood plasma.

102. Methods of Phosphate and
Magnesium Analysis
102
 Photometric
Ammonia molybdate method
Spectrophotometric Dye-binding
Atomic Absorption spectroscopy

103. Principles of Phosphate Analysis
Ammonium molybdate
• P + (NH ) M
4 6 7 O24
.+ 4 H O 
2
phosphomyolybdate
complex
UV light absorption
Absorbs 600 nm
103

104. Magnesium Analysis
104
 Spectrophotometric: Metallochromic
method
 Mg + Calmagite colored
complex
 Absorbance
measured 540 nm

105. Magnesium Analysis
105
Atomic Absorption Spectroscopy
 Reference Method
 Magnesium in sample is excited with
unique wavelength from hollow cathode
lamp supplying radiant energy
 Absorption of light is proportional to
concentration

106. Specimens
106
 Serum (P and Mg)
 Urine (magnesium)

107. Sources of Error
107
 Hemolysis (P and Mg are intracellular)
 Anticoagulated
EDTA, citrate, heparin falsely decrease for
P
EDTA, citrate and some heparin interferes
for Mg
 Not fresh or exposed to heat
 Icterus
 Lipemia
 Detergent in glassware or water (contains

108. Interpretation of Phosphorus and
Magnesium Results
108
Phosphorus Reference Ranges:
 Adult: 2.5-4.5 mg/dL
Magnesium Reference Ranges:
 Adult serum: 1.6-2.6 mg/dL
 Urine: 3.0-5.0 mmol/24 hr
 Compare patient results with reference ranges to
determine if any results are outside of normal limits.

109. Iron Analysis
109

110. Terminology
110
 Ferric: Iron in 3+ valence
 Ferrous: Iron in 2+ valence
 Transferrin: beta globulin that transports Fe3+
 Ferritin: storage form of iron in liver, etc.

111. Introduction to Iron
111
 Part of the hemoglobin molecule
(heme)
 Transports O2 in hemoglobin
 Oxidative role
•Iron in the hemoglobin molecule
transports oxygen to the cells where it
participates in oxidative mechanisms.

112. Source of Iron
• Diet provides
– Fe3+
• GI absorption requires
– Fe2+
– Gastric_juice
converts dietary
Fe3+
to Fe 2+
112

113. Physiologic Control of Iron
113
Stored in liver, spleen, bone
marrow
Ferritin/ apoferritin protein
Heme synthesis in bone marrow
Circulates bound to transferrin
(transport globulin)

114. Clinical Significance of Iron
(total)
114
 Decreased serum iron :
Iron deficiency anemia
Anemia of chronic diseases
Liver disease
Pernicious anemia
Malignancies
 Increased serum iron:
Hemosiderosis
Hemachromatosus

115. Clinical Significance of Iron
Binding Capacity
115
 Iron Deficiency Anemia associated
with:
–Decreased % iron saturation
 Anemia of chronic Disease
associated with:
–Decreased Iron Binding
Capacity
–Decreased total iron

116. Methods of Total Iron Analysis
116
 General Principles
–Spectrophotometric Dye-binding
–Atomic Absorption spectroscopy

117. Analysis
117
Atomic Absorption Spectroscopy
 Reference Method
 Iron is mixed with buffer to release
from transferrin. Free iron in sample is
excited with unique radiant energy
from a hollow cathode lamp
 Absorption of light is proportional to
concentration

118. Specimens
118
 Non-hemolyzed serum
 Fasting
 Morning specimen is best

119. Sources of Error
119
 Anticoagulants remove iron
 Hemolysis
 Poorly maintained or calibrated
instrument
 Poor technique in pipetting or decanting
steps.

120. Interpretation of Iron Results
Reference Ranges
Iron: Adult male: 65-170 ug/dL
Adult female 50-170 ug/dL
Compare patient results with reference ranges
to determine if any results are outside of
normal limits. Use country-specific
reference ranges
120

121. Reporting and Documentation
121
 To avoid post-analytic errors,
 Report the patient result with :
–Right name and result
–Include reference ranges
–Timely manner
 QC and patient results should be
documented in logbook and retained
in lab

122. Blood Gas Analysis
122

123. Introduction
123
Arterial blood gases (ABGs), the
most frequently requested critical
tests, used to monitor and evaluate
–Respiratory function i.e ability to
supply oxygen into the blood and to
remove carbon dioxide from the blood
–Hb transport of oxygen
–Available oxygen to tissues

124. Terminology
124
 Partial pressure of Oxygen (PO2):
dissolved oxygen gas in the blood
 Partial pressure of Carbon dioxide
(PCO2): dissolved carbon dioxide in the
blood
 pH: potential of H+ concentration
 Bicarbonate (HCO3-): part of major
buffer system; salt form of carbon
dioxide
 Oxygen Saturation (SO2) and Oxygen

125. Blood Gas Analysis
125
1. Partial pressure of Oxygen (PO2)-
indicates how well the oxygen is able to
diffuse from the alveolar membrane into
the blood.
2. Partial pressure of Carbon dioxide
(PCO2)- indicates how well the CO2 is
able to move out with the exhaled air.
3. pH- it is the measure of hydrogen ion
concentration [H+] in blood which
indicates the acid and base nature of

126. Blood Gas Analysis
126
4. Bicarbonate (HCO3-)-It is the most
important buffer of the blood
5. Oxygen Saturation (SO2) and
Oxygen content (CtO2)- provide
information about the amount of oxygen
(dissolved and bind with Hb) in the
blood

127. Oxygen in Blood
127
 Total O2 content (ctO2) = sum of
oxyhemoglobin (O2Hb) and of dissolved
O2 (cdO2). i.e. ctO2 = O2Hb + cdO2.
 PO2 normally 90mmHg.
 Hypoxemia (lowPO2) results in O2
starvation of tissues.
 Decreased Hb in g/dL in anemic hypoxia.

128. Factors affecting Oxygen binding
to Hb
128
 Association or dissociation of O2 with Hb depends
on:
PO2, and
Affinity of Hb for O2 .
 Affinity of Hb for O2 depends on:
1. Temperature
2. pH
3. pCO2
4. Hemoglobinopathies

129. Oxygen –Hb Dissociation Curve
20 40 60 80 100
pO mmHg
2
1.0
0.8
0.6
0.4
0.2
S02
(Hgb) S0 =Hb 0 satur-
2 2
ation
p0 =partial pres-
2
sure of oxygen
129

130. Details of the Oxygen –Hb
Dissociation Curve
130
 Increase in [H+], PCO2 and Temp. decrease the
affinity of Hb for O2; curve shifts to the right.
 Patient oxygenation status is determined by the
pO2 result
 pO2 < 60mm Hg are considered as hypoxia
 pO2 decreases normally with age.

131. Analysis of Blood Gases
131
 General Principles
The analyzer is designed to
measure pH, pCO2, pO2 and
calculate HCO3- simultaneously.

132. Blood Gas Analysis: pH
• Glass electrode selective for
H+
• Ag/AgCl Reference
electrode
• KCl salt bridge
• potential proportional to
pH
132

133. Blood Gas Analysis: pCO2
• Gas selective
membrane
• pH change is measured
• Versus reference
electrode
133

134. Blood Gas Analysis: pO2
• pO2 permeable
membrane
• Platinum cathode
• Anode detecting
electrons
134

135. Blood Gas Specimens
135
 Heparinized whole blood, arterial
 Heparinized whole blood, capillary
 Specimens are collected without air
bubbles and sealed
 Analyzed quickly or placed in ice
during longer transportation times

136. Sources of Error
• Wrong anticoagulant or no anticoagulant
• Venous instead of Arterial (adult)
• Not preserved well
– Opened
– Warm
– Not fresh
136

137. Quality Control
137
 A normal & abnormal quality control
samples should be analyzed along with
patient samples, using Westgard or
other quality control rules for
acceptance or rejection of the
analytical run.
–Assayed known samples
–Commercially manufactured
 Validate patient results
 Detects analytical errors.

138. Reporting and Documentation
138
 To avoid post-analytic errors,
 Report the patient result with :
–Right name and result
–Include reference ranges
–Timely manner
 QC and patient results should be
documented in logbook and retained
in lab

139. Summary of Blood Gas
Analysis
139
This lesson emphasized on:
• Source and Clinical Significance of
Blood Gases (pH, pCO2 and pO2)
 Methods of Analysis, Specimen,
Interpretation compared to
reference ranges
 Quality Control, Sources of Error,
and Documentation and Reporting