Unit 3 electrolytes

What two ways does chloride maintain electrical neutrality?

-Na+ is reabsorbed along with Cl- in proximal tubules -electrical neutrality is maintained through the chloride shift

What are the 3 primary routes of hypochloremia?

-GI -skin -urinary tract

What methods are used for measuring Chloride?

-ISEs -Amperometric-Coulometric titration Mercurimetric titration -colorimetry

What is total CO2 compromised of?

-bicarbonate ion -carbon dioxide -carbonic acid -dissolved carbon dioxide *total CO2 is indicative of HCO3 measurement

What are the three most common methods for measuring total serum Mg?

-calmagite -formazan dye -methylthymol blue

Describe Mg regulation

-controlled largely by kidneys -proximal convoluted tubule reabsorbs 25-30% -loop of henle reabsorbs 50-60% -about 6% of filtered Mg is excreted into urine per day

What can cause hypermagnesemia?

-decreased excretion -acute or chronic renal failure (GFR < 30 ml/ min) -hypoaldosteronism

What does metabolic acidosis do in HCO3 and CO2 levels?

-decreased pCO2 due to compensation by hypoventilation -decreased HCO3 as bicarbonate ions combine with hydrogen to produce CO2

What can hemolysis do to sodium levels in a specimen?

-doesn't cause a significant change in serum or plasma but Na levels can be decreased as a result of a dilution effect

What can interfere with potassium concentrations?

-drugs -increased intake -cellular redistribution -decreased renal excretion

What can interfere with K+ specimens?

-excessive fist clenching -hemolysis -prolonged tourniquet use -storing and collection (24 hour period and in heparin tubes)

How is chloride processed?

-filtered out by glomerulus and passively absorbed by the proximal tubules -excreted in urine and sweat

What are the methods for determining osmolality?

-freezing point -vapor pressure

Magnesium is an essential cofactor for?

-glycolysis -trans cellular ion transport -neuromuscular transmission -synthesis of carbohydrates, proteins, lipids, and nucleic acids -release of and response to certain hormones

What patients are commonly seen with hypomagnesium?

-hospitalized individuals in ICUs or those receiving diuretic therapy

What does metabolic alkalosis do to HCO3 and CO2 levels?

-increased CO2 concentration -increased pCO2 due to compensation by hypoventilation

What does parathyroid hormone do?

-increases renal absorption of Mg and enhances the absorption of Mg in the intestine *aldosterone and thyroxine have the opposite effect, increasing the renal excretion of Mg

What are suitable anticoagulants?

-lithium heparin -ammonium heparin -lithium oxalate

What does potassium regulate?

-neuromuscular excitability -contraction of the heart -intracellular fluid volume -H+ concentration

What patients are at risk for hypovolemia?

-older patients with diminished mental status -infants -unconscious patients

What are the four physical properties of a solution?

-osmotic pressure -vapor pressure -boiling point -freezing point

What does alkalemia do?

-promotes intracellular loss of hydrogen to minimize elevation of extra cellular fluid, both K+ and Na+ enter cells

Bicarbonate specimen

-serum or dry lithium plasma samples -anaerobic environment obtains most accurate results -if sample is left uncapped, CO2 escapes

Rate of diffusion May be altered by?

-size and charge of ion -nature of membrane -physiologic and hormonal processes

Describe water

-solvent for all processes in human body -transports nutrients to cells -removes waste products by way of urine -body's coolant

What three processes of sodium regulation are of primary importance?

-the intake of water -excretion of water -blood volume status

What can cause elevated levels of Mg?

-uremia/renal failure -ketoacidosis -lactic acidosis -hypernatremia -ethyl alchol or salicylate poisoning

What factors affect blood volume?

-volume receptors stimulate the release of AVP -GFR increases with volume expansion and decreases with volume depletion -urine osmolality decreased in diabetes insipidous

What causes acid base imbalance?

-vomiting -hypokaelemia -excessive alkali intake

What factors influence the distribution of potassium between cells and ECF?

-when K/Na ATPase pump is inhibited by conditions such as hypoxia, hypomagnesemia, or digoxin overdose -insulin -catecholamimes such as epinephrine

polydipsia

excessive thirst

intracellular fluid

fluid within cells

Hypernatremia

high sodium

Osmometer

instrument for measuring osmotic pressure

Hypomagnesemia

insufficient amount of magnesium in the extracellular fluid

Osmotic pressure

the external pressure that must be applied to stop osmosis

What are electrolytes?

Ions capable of carrying electric charges

Why is osmolality in plasma important?

It is the parameter to which the hypothalamus responds

What controls distributions of water in the various body fluid compartments?

Maintaining the concentration of electrolytes and proteins in the individual compartments

What is a bicarbonate ion?

Major component of the acid base buffering system in the blood and is the second most abundant anion in the ECF

What is chloride?

Major extracellular anion involved in maintaining osmolality, blood volume, and electrical neutrality

What do the active transport systems do?

Na/K ATPase ions pumps that are present on cell membranes to facilitate transport in and out of the cell preventing equilibrium

How does osmolality and volume correlate with each other?

Osmolality (NA) is regulated by changes in water (volume) balance, and volume is regulated by changes in sodium balance

What is the major intracellular cation In the body?

Potassium

Hypovolemia

decreased blood volume

Hypochloremia

deficiency of chloride in the blood plasma

Hypokalemia

deficient potassium in the blood

Hyponatremia

deficient sodium in the blood

Anion gap

The difference between the sum of the commonly measured actions and the sum of the commonly measured anions

What is magnesium?

The fourth most abundant cation in the body and second most abundant intracellular ion -53% found in bone, 46% found in muscle and other organs, less than 1% in serum -present in serum, about one third is bound to protein (primarily albumin)

What is the formulate for osmolality?

(1.86 x Na) + (GLU / 18) + (BUN / 2.8) + 9

Where is sodium reabsorbed?

-60-75% is reabsorbed In proximal tubule and the rest is I'm the loop of Henle and distal tubule

What is the anion gap reference range?

10-20 mmol/L

What are dangerous levels for magnesium to be at?

5.0 mmol/ L

How does osmolality work with AVP production?

A 1-2% increase in osmolality causes a fourfold increase in the circulating concentration of AVP, and a 1-2% decrease in osmolality shuts off AVP production

Hypermagnesemia

A serum/plasma magnesium concentration above the upper limit of the reference range

Hyperkalemia

A serum/plasma potassium concentration above the upper limit of the reference range

What gives us the sensation of thirst? What stimulates it?

AVP (arginine vasopressin hormone) called antidiuretic hormone (ADH) is stimulates by the hypothalamus in response to an increase osmolality

How are electrons classified?

Anions: negative charged ions that move toward anode Cation: positive charged ions that move toward cathode

What serum level of hypomagnesemia are not asymptomatic?

Below .5 mmol/L

Extra cellular fluid

Body fluids outside the cell

Why is Mg deficiency bad?

Can impair PTH secretion and target tissue (bone) resistance to PTH, resulting in secondary hypocalcemia

What can happen if sodium levels are below 125 mmol/l?

Causes neuropsychiatric symptoms due to H20 moving into cells, swelling CNS cells -muscular weakness -headache -lethargy -Aaxia

Electrolyte

Charged low molecular mass molecules present in plasma and cytosol

What is the anion gap?

Difference between unmeasured anions (Cl- + HCO3-) and unmeasured cations (Na+ + K+)

How is the concentration of ions maintained?

Energy consuming active transport and by diffusion or passive transport

Intracellular fluid vs extra cellular fluid

ICF accounts for two thirds of total body water ECF accounts for one third of total body water

What are the two types of ISE measurements?

Indirect method: a diluted sample is used to interact with ISE membrane Direct method: an undiluted sample (more accurate)

Excessive sweating stimulates what?

Release of aldosterone which adds on the sweat glands to conserve Na+ and Cl-

What does the renin-angiotensin-aldosterone system do?

Responds to a decreased blood volume -renin is secreted by granular cells In response to decreased blood flow -angiotensin 2 causes vasoconstriction, increasing BP, and secretion of aldosterone which increased Renal retention of sodium and water

Why might serum have more potassium?

The coagulation process releases potassium from platelets

What is osmolality measured in? What are the major electrolytes?

Serum or urine; sodium, chloride, and bicarbonate

Hypercholremia

Serum/plasma concentration of chloride above the upper limits of the reference range

What is the major cation in extracellular fluid?

Sodium

What is the most abundant cation in extracellular fluid?

Sodium

Pilocarpine iontophoresis

Sweat test for CF

Osmolality/Osmolarity

The concentration of solutes per kilogram of solvent

Active transport

The passage of ions or molecules across a cell membrane by an energy-consuming process.

Diffusion

The passive movement of ions across a membrane depending on the size and charge of the ion being transported and on the nature of the membrane through which it is passing

Where is AVP produced?

The posterior pituitary gland; acts on the kidneys by increasing the reabsorption of water in collecting ducts

Where is potassium reabsorbed?

The proximal tubules

Hypervolemia

abnormal increase in the volume of blood plasma in the body

ion-selective electrode

an electrode sensitive to the concentration of a particular ion in solution

How is total carbon dioxide measured in the clinical laboratory?

—acidification of a serum or plasma sample -enzymatic alkalinization and indirect measurement of total bicarbonate -in indirect ISE, an acid reagent is used to convert all the forms of C02 to CO2 gas which is measured by a pCO2 gas electrode -indirect enzyme method alkalinizes the sample to convert all forms of CO2 and carbonic acid to HCO3