Chapter 3 electrolfgkjbkeuhfbjmhjbvyte.pptx

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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 terms of electronic components, reagents and endpoint detection

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. 3.1. Introduction to 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. Series of Events in Water 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-) Bicarbonate (HCO3-)

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).

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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

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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. ICF differs considerably from ECF 24 ECF most abundant cation is Na + , anion is Cl - ICF most abundant cation is K + , anion are proteins and phosphates (HPO 4 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. Disturbance of Acid Base Balance 33 Respiratory acidosis – abnormally high P CO2 in systemic arterial blood Inadequate exhalation of CO 2 Any condition that decreases movement of CO 2 out – emphysema, pulmonary edema, airway obstruction Kidneys can help raise blood pH Goal to increase exhalation of CO 2 – ventilation therapy

34. Disturbance of Acid Base 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 P CO2 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 HCO 3 - 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 HCO 3 - Can form and release HCO 3 - 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 determined.

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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 complex of ferricthiocyanate

58. Method of Bicarbonate Analysis Photometric method : • HCO + urea --(urea amidolyase)  NH 3 4 + . NH 4 + + 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 Urine sample with out preservative

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 an d 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. Clinical Significance Anion 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 problems.

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 HCO 3 - 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 HCO 3 - 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 Ca 2+ 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 Ca 2 + 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. Physiologic Functions of 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

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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. Interpretation of Calcium 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 : –Right name and result –Include reference ranges –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 PTH

98. Phosphate 98 About 85% in adults present as calcium phosphate salts in bone and teeth Remaining 15% ionized – HPO 4 2- and PO 4 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 Mg 2+ 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. Physiologic Functions of P and 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 O 24 . + 4 H O  2 pho s phomyolybdate 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 P )

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 – Fe 3+ • GI absorption requires – Fe 2+ – Gastric_juice converts dietary Fe 3+ 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. Other Methods for Iron 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 content (CtO2)-: % of oxyhemoglobin

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 blood.

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 S0 2 (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