Quiz 1: Electrolytes Flashcards
Serum vs Plasma
Serum: there is no additive in the tube so the blood will clot (red top collection tube)
Plasma: Various additives are present (indicated by cap colors), they prevent the blood from clotting by removing clotting factors.
4 Major Fluid Components Of The Body
Interstitital fluid (solution that bathes and surrounds the cells of multicellular animals, found in “interstitial spaces”)
Plasma or serum (Plasma is a very small amount of total water volume, most of the physiology of water exchange occurs intracellularly.)
Erythrocytes
Intracellular fluid
Modes For Water Intake And Loss By The Body
Hypothalamus action regulates Osmolality by stimulating thirst and releasing ADH (anti-diuretic hormone)
Renin-angiotensin-aldosterone system
Natriuretic peptides
Intracellular And Extracellular Electrolyte Compositions
Intracellular: Potassium (cation), Phosphates & proteins (anion and buffer)
Extracellular: Sodium (cation), Chloride (anion), Bicarbonate HCO3- (buffer)
Main Functions Of The Major Electrolytes
Sodium & Potassium/Chloride & Bicarbonate
• Maintain water volume and osmotic pressure
• Buffer pH
• Nerve synaptic transmission
• Cofactor for enzymes
• Help to solubilize proteins
• Membrane potential of cells
What is the cause of edema?
Excess of interstitial fluid, Locally, due to inflammation, hypersensitivity, venous blockage. General Edema due to cardiac, renal or pulmonary failure
Anion gap Calculation
Anion Gap = [Na+] – [Cl-] + [HCO3-]
What is Osmolality, why is it measured?
Osmolality is the total concentration of particles in a solution; dependent on the kind of particle, not the number of particles in the solution.
What are the 2 methods of osmolality measurement?
Freezing point depression:
1 osmol of solute lowers freezing point of water by 1.86C (mOsm/kg)
Vapor pressure depression: when solute is added to solvent, the vapor press of solvent in equilibrium with the liquid phase is decreased.
What is calculation for Osmolal Gap and how is it useful?
OG = measured serum osmolality − calculated osmolality
Calculated osmolality = 2 x [Na mmol/L] + [glucose mmol/L]/18 + BUN/2.8
In healthy individuals, Calculated equals Measured osmolality
Abnormal is > 10; indicating there exists an abnormal concentration of unmeasured substances.
What is the cause of Colloidal Osmotic Pressure (Oncotic Pressure)?
• A measurement of the osmolal pressure contributed by crystalloids or ions.
• Colloid Osmotic Pressure
Useful in determining pulmonary edema
Chronic Obstructive Pulmonary (COP) measurements can correlate with xrays
Hypothalamus action and what inactivates it
Vasopressin (ADH) from the hypothalamus stimulates renal reabsorption of water. (Ineffective ADH is due to diabetes insipidus)
Renin-angiotensin-aldosterone system
Regulates the body sodium and water content, arterial blood pressure and potassium balance.
Natriuretic peptides
Compounds that have a reciprocal effect to the Renin- angiotensin-aldosterone system.
Anion Gap Evaluations Show
Blood: May indicate a lab error or unmeasured ions in unusual concentrations. (always +, - indicates lab error)
Urine: significant in acid-base disorders; negative may indicate excess NH4+, positive may mean acidosis with the retention of bicarbonate and release of other anions
Indication of Elevated Anion Gap Values
Increase: anions will increase (ethanol, Ketones, Lactic Acid), cations will decrease (Mg, Ca)
Decrease: anions decrease (albumin), increased cations (Mg, Ca, Lithium); this could be caused by Hemodilution
Hypernatermia
High Sodium
Excessive retention of Sodium or insufficient water due to loss or edema
• Hyperaldosteronism due to adrenal or pituitary tumors or hyperplasia (Cushings syndrome)
• Diabetes insipidus (lack of effective ADH),
• Excessive salt ingestions or infusion.
• Response to insulin therapy,
• Dehydration, diarrheas, renal disorders
Hyponateremia
Low Sodium • Cancer chemotherapy • Metabolic (Diabetic) acidosis • Prolonged diarrhea • Deficient renal tubular reabsorption • Adrenal cortical insufficiency (lack of aldosterone synthesis as in Addison’s disease) • Excess antidiurectic hormone (ADH) secretion • Water intoxication
Potassium Transport
Difference between the concentrations of potassium in compartments is the result of the active transport of potassium into the cells in exchange for sodium.
Insulin, aldosterone & alkalosis enhance potassium transport into the cell
Decrease potassium intracellular transport or enhance leakage can be due to acidosis, alpha- adrenergic stimulation and tissue hypoxia
Potassium Intake and Output
Intake: diet
Output: GI tract, Skin, Kidneys (urine)
Hypokalemia
Low Potassium
• After insulin injections
• extracellular to intracellular K+ shift
• diuretic therapy w/o potassium replacement, laxative abuse, fasting, profuse sweating
• hyperaldosteronism (Cushing syndrome) as sodium is being retained by the kidney and K is lost instead
• Alkalosis as cells are exporting H as a response and K is being retained
• Licorice ingesting, Fanconi’s Syndrome (tubular acidosis)
Hyperkalemia
Intra to extracellular shift due to: tissue injury (burns), (Diabetic) acidosis, (Intravascular) hemolysis, low renal excretions (low GFR as in SLE, aldosterone deficiency (Addison’s), insulin deficiency, drug effects)
Chloride Intake, Output, and Transport
• Major anion in the extracellular space.
Intake parallels sodium intake
Output occurs via GI, skin and kidney.
• Cl is passively distributed across the cell membrane (caused by the electrical potential difference across the cell. The inside of the cell is negative compared to the outside, Cl- outside the cell will be higher)
Sweat Chloride testing for Cystic Fibrosis
When excessive Cl concentrations are obtained by iontophoresis using pilocarpine to induce sweating.
Sweat composition of chloride is about 40mEq/L. The concentration of both Cl and Na in sweat is decreased by aldosterone.
Chloride Depletion
Metabolic alkalosis is caused when Cl depletion is due to loss of gastric fluid, can be associated with bicarbonate retention caused during renal compensation for chronic respiratory acidosis from diabetes or chronic pyelonephritis. Can also be due to prolonged vomiting and Aldosterone deficiency.
Chloride Interaction with Acid/Base System
• One of the two major extracellular anions (Cl- and HCO3-)
• Bicarbonate is consumed by reaction with H+ produced in metabolic acidosis.
If there were no anions produced with H+, Cl- is needed to replace the consumed bicarbonate to maintain electrical neutrality.
The increase in Cl- is caused by the reabsorption of greater proportion of Na+ with Cl- than with HCO3- in the tubules of the kidney
Diarrhea causes excessive Bicarb. loss, Renal tubular acidosis and adrenalcortical malfunction cause hightened Cl- levels
Bicarbonate ion (HCO3-) in acid /base balance
Bicarbonate is consumed by reaction with H+ produced in metabolic acidosis.
Henderson-Hasselbalch Equation
pH = pK’+ log [HCO3-]/[H2CO3]
pK’ of pCO2 is 6.1
H2CO3 = cdCO2 = PCO2 x alpha Alpha= 0.03 mmol/L per mm Hg
What regulates osmolality and how does it do this?
The Hypothalamus regulates osmolality by stimulating thirst and stimulating the Posterior Pituitary to secrete ADH (causing renal reabsorbtion of water)
What are the main electrolytes measured with Blood Gases?
Sodium, Potassium, Chloride, and total Carbon Dioxide
Chloride levels change proportionally to what cation?
Sodium
What controls serum levels of Calcium?
Parathyroid Hormone, Vitamin D, and Calcitonin
Parathyroid Hormone production is regulated by…?
As free Calcium levels rise, the production of PTH falls
What organs does Parathyroid Hormone act on, and what actions does it cause there?
Bone and Kidneys
Bone: activates osteoclasts to break down bone and release calcium
Kidneys: increases renal tubular reabsorbtion of calcium and stimulates hydroxylation of Vit D to active form
Where is Calcitonin produced and what are its functions?
Parafollicular cells in the Thyroid, it inhibits Vit D and Parathyroid Hormone activity to decrease serum Calcium
The pH of plasma comes from what 2 processes?
The partial pressure of Carbon Dioxide (regulated by lungs), and the concentration of Bicarbonate (regulated by kidneys)
Carbon Dioxide is regulated by ?
Bicarbonate is regulated by ?
Lungs
Kidneys
Sodium, Percentage of reabsorption
Major cation of extracellular fluid, 85% of which is reabsorbed in kidney tubules
Found via ISEs
Potassium, Testing Method
Major cation of intracellular fluid (23x higher in cells than in plasma) any damage to the cells during specimen processing will alter the results
Found using ISEs with Valinomycin membrane
Chloride Functions, Testing Methods
Major anion of extracellular fluid that maintains hydration, osmotic pressure, and anion-cation balance
Generally follows Sodium so when one is down the other will be too and vice versa
Found by ISE, Coulometric titration (using Silver to combine with Cl-), and Colorimetry (using Hg(SCN)2
CO2
CO2 + HCO3 + H2CO3 = Total CO2
Reflects Bicarbonate concentration, usually found through ISE that measures the pH change due to CO2
Anion Gap (Measurement and Calculation)
Reflects differences between unmeasured cations (K, Ca, Mg) and anions (Albumin, Sulfate, Phosphate)
Calculation: [(Na) + (K)] - [(Cl) + (HCO3)] or
(Na) - [(Cl) + (HCO3)]
Magnesium, Regulation, Function, Testing Methods
Found in similar proportions to Ca, with free portion biologically active
Excretion/reabsorption regulated by PTH
Ca channel blocking agent that is high in renal failure and low in cardiac disorders, Diabetes mellitus, and people on Diuretics
Found by Colormetric method - Calmagite, Formazen, or Methyl Thymol Blue
Calcium Percentages found in blood
50% free/ionized (biologically active), 40% bound to protein, 10% bound to ions
Calcium levels and Regulation
Low levels cause muscle spasms (tetany)
Regulated by PTH, Vit D, and Calcitonin
