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Brigham Young University
Clinical Laboratory Science
Clinical Laboratory Science Mmbio 423
Electrolytes Part 2
Electrolytes Part 2
Clinical Laboratory Science Mmbio 423
Brigham Young University
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Clinical Laboratory Chemistry
How does this result in artificial hyperkalemia?
Platelets release potassium during clotting.
How does hemolysis result in artificial hyperkalemia?
Potassium is mostly intracellular. During hemolysis, the RBC release intracellular contents so the potassium level increases.
What is important to remember about Clarissa Chloride?
The Chloride Shift
What is the normal range of chloride?
Is chloride a cation or anion?
Is chloride located in the ICF or ECF?
Is chloride a major or minor anion of the ECF?
Major anion of the ECF
What are the functions of Chloride?
Water distribution, osmotic pressure, anion-cation balance
What is important to remember about the Chloride Shift?
It is the exchange of chloride for bicarbonate. Bicarbonate out=chloride in. This process maintains the H2O distribution.
Where is chloride almost completely absorbed?
In the GI tract.
Where is chloride filtered?
In the glomerulus.
What percentage of chloride is reabsorbed in tubules?
Is this reabsorption passive or active?
What does this passive reabsorption depend upon?
The active reabsorption of sodium.
What are the causes of hypochloremia?
Prolonged vomiting, prolonged sweating, or deficient tubular reabsorption.
What affect does hypochloremia have upon bicarbonate?
Bicarbonate increases to compensate.
Does this result in acidosis or alkalosis?
Alkalosis due to increased bicarb.
What are the causes of hyperchloremia?
Dehydration, congestive heart failure, or renal tubular acidosis.
How does congestive heart failure cause hyperchloremia?
Decreased renal blood flow.
What is the normal range for Chloride in CSF?
CSF Chloride is decreased in what disease state?
Why is CSF Chloride decreased in this disease state?
Chloride is decreased because protein in increased.
What is the normal range for Chloride in sweat?
What is the normal range for sweat chloride in cystic fibrosis?
How much higher is the range for sweat chloride in cystic fibrosis when compared to the normal sweat chloride range?
What are the two methods of sweat collection?
Iontophoresis and ion specific electrodes
What is Iontophoresis?
It is the application of current by electrodes on the forearm. Pilocarpine induces sweating and the sweat accumulates in gauze squares.
What is the ion specific electrodes method for collecting sweat?
It is the local heating of skin. The sweat collection is preformed by placing guaze on the skin and covering it with parafilm.
What is the chemical formula for bicarbonate?
What is the normal range for HCO3-?
Is HCO3- the largest anion of the extracellular fluid?
No, it is the 2nd.
What is the function of HCO3- ?
Bicarbonate buffer system, transporting CO2 from tissues
What occurs when HCO3- is decreased?
What occurs when HCO3- is increased?
What are the HCO3- levels approximately equal to in the body?
What organ regulates HCO3- levels?
How often is urine Na+ measured?
When do we measure urine Na+?
It is measured if a patient is having problems with fluid balance.
What is the effect of ADH release?
Reduced urine volume and increased urine osmolality
In what condition do we see increased urine K+?
Why does acidosis increase urine K+?
In acidosis, K+ shifts out of the cells which results in more getting excreted in the urine.
When do we care about Na+ and K+ urinary excretion?
When a patient is having problems with water and/or electrolyte metabolism
What is the usual ratio of Na+ to K+ in the urine?
What can cause the Na+ to K+ ratio to reverse itself?
Increased aldosterone excretion
What is the normal urine Na+ range?
40-220 mmol/ 24hr
What is the normal urine K+ range?
25-150 mmol/ 24hr
What is the Na+ to K+ ratio in hyperaldosterone?
1 :2 - 1 :40
What is the Na+ to K+ ratio in hypoaldosterone?
What is the Anion Gap?
A mathematical formula for the difference between the measured anions and cations in the serum
What is the Anion Gap formula? (With K+)
( Na+ + K+ ) - ( Cl- + HCO3- ) = 9-18 mmol/L
What is the Anion Gap formula? (Without K+)
( Na+ ) - ( Cl- + HCO3- ) = 5-14 mmol/L
Why do we not have to include K+ in the Anion Gap formula?
K+ value is doesnt have to be included because it is mostly intracellular and may move in or out of the cell quickly
What do we need to assume when using the Anion Gap?
We need to assume that all unmeasured ions are within normal range.
What can the Anion Gap results do?
Alert the physician to look for unsuspected causes of an abnormality
If the Anion Gap is out of range, what do we do next?
Repeat the measurements
What are the usual causes for a Gap being out of range?
1) Laboratory error, 2) the sample was drawn from an arm with IV solution, 3) sample was hemolyzed
How is the iron distributed in your body?
75% is involved in metabolism & 25% is present in storage forms.
What 3 things are iron involved in metabolism?
hemoglobin, myoglobin, cytochromes
What 2 things enhance the absorpotion of iron?
vitamin c & pH
What thing blocks the absorption of iron?
food with phosphates and other similar things
Where is iron absorbed?
in the mucosal cells of the intestine
What is the first protein that irion binds to when it is absorbed?
What form is iron in when it binds to apoferritin?
What protein does iron bind to in the plasma?
What are normal levels of iron in the plasma?
What is the normal total iron binding capacity?
What 4 things lead to decreased iron?
dietary insufficiency, malabsorption, blood loss, increased iron requirements
What is the leading cause of iron deficiency blood loss in females?
What is the leading cause of iron deficiency blood loss in males?
What is a common cause of increased iron requirements?
What 4 things lead to increased iron?
increased RBC destruction, decreased iron use, increased iron release from body stores, increased iron absorption
What is the main cause of increased iron absorption?
a genetic disease that makes your mucose cells absorb too much
What 3 things cause decreased TIBC?
transferrin deficiency, protein loss, increased catabolism
What 2 things increase TIBC?
increased transferrin production and oral contraceptives
What is the main cause of increased transferrin production?
What is the mechanism of increased TIBC with oral contraceptives?
they stimulate the liver to make more transferrin
What are the 4 steps in measuring iron?
1. splitting iron from its protein complex by exposure to acid 2. separation of iron and protein 3. reduction of 3+ to 2+ 4. reaction of iron with chromagen
What are the 3 kinds of acid that can be used to split iron from the protein?
HCl, H2SO4, TCA
What 3 things can we use to separate iron and protein?
protein precipitation, leaving protein in solution if it doesn't interfere, and dialysis
What 4 things can we use to reduce ferric iron to ferrous iron?
ascorbic acid, hydrazine, thioglycolic acid, hydroxylamine
What chromagens can we react iron with?
bathophanantroline, diphenylphanthroline, ferrozine, TPTZ
What are the 3 steps to measure TIBC?
1. saturate transferrin with excess iron 2. removal of excess unbound iron 3. perform conventional iron determination of supernatant
What 2 things can we use to saturate transferrin with iron?
ferric ammonium citrate or ferric chloride
What 2 methods can we use to remove the excess unbound iron?
ion exchange resin (amberlite resin sponge) & iron absorbant (MgCO3)
What are the 3 precautions we need to take when measuring iron?
1. avoid hemolysis 2. beware of diurnal variation 3. watch for contamination
Why do we need to avoid hemolysis?
because iron can be falsely elevated if we are measuring released hemoglobin from RBCs
What is diurnal variation?
iron levels change through out the course of the day. If we are measuring iron, the samples need to be taken at the same time everyday.
What is osmometry?
measuring particles in a solution
What are colligative properties?
properties that depend on the number of particles in a solution
What are some examples of colligative properties?
freezing point, vapour pressure, osmotic pressure, boiling point
What happens to freezing point as the number of particles in solution increases?
What happens to vapour pressure as the number of particles in solution increases?
What happens to osmotic pressure as the number of particles in solution increases?
What happens to boiling point as the number of particles in solution increases?
How far does the freezing point depress if we add 1 mol of a non electrolyte?
1.86 degrees C
What osmometry is 1 mol of a non electrolyte equal to?
How far does the freezing point depress if we add 1 mol of an electrolyte?
3.72 degrees C
What osmometry is 1 mol of an electrolyte?
What is the equation for the osmolal gap?
1.86 (Na) + (glu/18) + (BUN/2.8)
What is a normal osmolal gap?
What is a normal osmolality?
What does osmolal gap refer to?
the difference between the calculated osmolality and the measured osmolality
What value to we consider an increased osmolal gap?
What things can cause an increased gap?
pseudohyponatremia, low molecular weight substances and laboratory error
What 2 things cause pseudohyponatremia?
What are low molecular weight substances that can cause an increased osmolal gap?
ethanol, methanol, isopropanol, ethylene glycol, mannitol
What happens if you drink antifreeze?
you will have a very large osmolal gap
What do we usually use the osmolal gap for?
What other measure do we use for QA purposes?
Is increased or decreased anion gap more common?
What could cause increased anion gap?
Renal disease (retention of unmeasured anions), ketoacidosis, toxin ingestion (salicylate, methanol, ethylene glycol), lactic acidosis, ↓ unmeasured cations
What could cause decreased anion gap?
Hypoalbuminemia, underestimation of serum Na (lab error or lipemia, hyperglycemia), overestimation of Cl (lab error or bromism), increased cations (paraproteins, polyclonal gammopathy)
What disease could decrease anion gap by increasing cations?
How does hemolysis affect potassium levels?
What are three sodium-potassium methods of measurement?
Atomic Absorption (reference method), flame photometry, ion specific electrodes (ISE)
How does ISE work for sodium-potassium measurement?
It incorporates a neutral antibiotic (valinomycin) into its organic liquid membrane which has a greater affinity for K than for Na
How does ISE work for chloride measurement?
Uses quaternary ammonium salt anion-exchange material to make it more selective for Cl
What is the classic spectrophotometric Cl- method?
Schales & Schales
Describe the Schales & Schales spectrophotometric chloride method:
1. Specimen + Hg(NO3)2 ⇒ HgCl2 2. Diphenylcarbazone + excess Hg2+ ⇒ blue-violet color
Describe the Mercuric Thiocyanate spectrophotometric chloride method:
1. Specimen + mercuric thiocyanate ⇒ mercuric chloride and free thiocyanate 2. Thiocyanate + ferric ions ⇒ reddish-brown color
What is the name of the chloride titration method?
Coulometric or Amperometric method
What is the element used for titration in the chloride titration method?
What are the four routinely measured electrolytes?
Na, K, Cl, HCO3
What is the normal range for magnesium?
What are the functions of magnesium?
Enzyme activation and neuromuscular irritability
What can cause hypomagnesemia?
Malabsorption or severe diarrhea
What are the symptoms of a decreased magnesium?
Tetany and convulsions (in children mostly), neuromuscular hyperirritability
What can cause hypermagnesemia?
Uremia, dehydration, magnesium poisoning
What are the symptoms of an increased magnesium?
Muscle weakness, CNS depression, mental confusion
What is the name of the magnesium measurement method?
The Pierce method
Explain the Pierce method for measuring magnesium:
Sample + calmagite ⇒ pink complex or Sample + titan yellow ⇒ red complex
What is the purpose of measuring lithium?
To make sure it is in therapeutic range (psychiatric patients)
Is lithium normally present in serum?
As a drug, what is lithium used for?
To treat bipolar disorder
What is the therapeutic range for lithium?
What two things can be affected by exceeding the therapeutic range for lithium?
CNS and kidneys
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