13. Electrolytes and Fluid Balance

Start Studying!

Terms

undefined, object

copy deck

What is the normal body water distribution?: Intracellular = 66%

Extracellular = 33%
What primarily determines the body H2O distribution?: Osmotic pressure
What is Osmotic pressure?: The force that moves water between body compartments.
What type of ions contribute to the osmotic pressure?: Colloids and nondiffusible ions.
What is the normal Osmolality of the body?: 285-298 mOsm/kg
What instrument is used to measure body osmolality?: a Thermistor - to measure the vapor point of blood.
How can the body's osmolality be estimated instead of measuring with thermistor?: Calculate the Osmolal Gap
What's the osmolality gap calculation?: 1.86Na + Glu/18 + BUN/2.8 +9
What 5 things stimulate Aldosterone secretion?: -Decreased Blood volume
-Decreased SODIUM
-Increased POTASSIUM
-Stress
-Renin
What determines the H2O distribution between the vasculature and interstitium?: Starling's forces
What is the Starling equation in a nutshell?: NFP=K x (Forces Out - In)
What are forces out in a capillary?: Hydrostatic
What are forces in for a capillary?: Colloid osmotic
What force is higher in: -Arterioles? -Venules?: Arterioles: Hydrost. > osmotic
Venules: Osmotic > Hydrost.
When all is said and done, what force is greater for water movement?: Filtration > reabsorption; so water has to return via lymphatic system.
What's the anion gap?: The difference between the measured cations and anions.
What 4 conditions can cause an increased anion gap?: 1. Diabetic ketoacidosis
2. Decreased Calcium/Mg
3. Starvation
4. Toxins
What 3 things can cause a decreased anion gap? What's most common?: 1. Lab error - most common
2. Multiple myeloma
3. Increased Ca/Mg
List 5 roles of electrolytes:: 1. Maintain osmotic pressure
2. Maintain pH
3. Regulate muscle function
4. Participate in redox
5. Participate in enzyme catalysis
What is the major extracellular cation?: Sodium
Where is most Na reabsorbed?: in the proximal tubule
How would the following hormonal conditions affect Na? -Cushing's -Addison's: Addisons = Hyponatremia

Cushing's = Hypernatremia
What specimens are tested for Sodium levels?: -Serum/plasma
-Sweat
-Urine
-Feces
-GI fluids
Are sodium levels affected by hemolysis?: No
What is the major intracellular cation?: Potassium
What is the major controller of Na after reabsorption in the prox tubules?: Aldosterone
How does Aldosterone function?: To increase Na reabsorption and H2O also
What hormone counteracts Aldosterone?: Atrial Natiuretic Factor ANF
Where does ADH act on the kidney?: Collecting ducts
What 2 important Receptors affect sodium levels?: -Osmoreceptors
-Baroreceptors
What do osmoreceptors detect? Where are they located?: -increased osmolarity
-in hypothalamus
What happens when increased osmolarity is detected?: Stimulates the release of ADH to increase H2O reabsorption and thus decrease osmolarity
What do Baroreceptors detect? Where are they located?: Detect changes in blood pressure
-located in smooth muscle of vasculature
What results when baroreceptors detect increased blood pressure?: -Stimulates ADH release from brain
-ADH stimulates RAS to start
How does the RAS result in increased Na/H2o reabsorption?: Because renin is a stimlator of aldosterone release
What are 3 types of hyponatremia?: -Depletional
-Dilutional
-Hormonal
What type of pH is generally associated with hyponatremia?: Metabolic acidosis
Why does acidosis cause low Na?: Because of sodium wasting - have to excrete Na+ to reabsorb HCO3- and have the charges balance.
What causes a dilutional hyponatremia?: -Excessive water reabsorption
-Edema
-siADH
What is hormonal hyponatremia?: Addison's disease
How would increased ADH affect body sodium levels?: Increased ADH = too much H2O reabsorption, so dilutional hyponatremia.
How would decreased ADH affect body sodium levels?: Not enough H2O so hypernatremia
What type of Ca and K levels are usually seen with hypernatremia?: -Hypercalcemia
-Hypokalemia
What hormonal problem usually causes hypernatremia?: Cushings'
What is the general reason for most hypernatremia conditinos?: Disproportionate loss of water vs. sodium.
How do urine sodium levels change in: -Hypernatremia -Hyponatremia: Hypernatremia = hyponatruria

Hyponatremia = hypernatruria
So back to this.. what is the major INTRACELLUAR cation?: Potassium
How is K kept inside cells?: By the Na/K pump - ATPase
What affects body potassium levels (hormone)?: Aldosterone
How doe aldosterone regulate K?: Increased Aldosterone causes increased K excretion
How does the body respond to hypokalemia?: -Weakness
-Tachycardia (slowed heartrate)
-EKG changes
-Paralysis
How does the body respond to hyperkalemia?: -Weak, numb, tingly
-Respiratory weakness
-Bradychardia
What hormonal disorder causes hypokalemia?: Cushing's
What hormonal disorder causes hyperkalemia?: Addison's
What are 3 causes of hypokalemia?: 1. Decreased dietary intake
2. Increased loss of K-rich fluids
3. Redistribution from extra to intracellular fluid
What are 2 things that make K go from extracellular fluid to intracellular?: 1. Insulin therapy
2. Alkalosis (decreased H+ buffering by Hgb so more room for K+)
What are 3 causes of hyperkalemia?: 1. IV infusion
2. Redistribute from intra-> extracellular fluid
3. Decreased excretion
What would make K go from intracellular to ECF?: Acidosis - need space inside the cells to buffer extra H+
What hormonal disorder would cause decreased K excretion?: Addison's
What is the body potassium in: -Hyperkaluria? -Hypokaluria?: Hyperkaluria = hypokalemia

Hypokaluria = hyperkalemia
What 4 preanalytical variables falsely increase potassium measurement?: 1. Clenching in phlebotomy
2. Clotting (don't use serum)
3. Hemolysis
4. Delay in centrifugn
What are 2 methods used to measure sodium and potassium?: 1. Flame emission spec
2. ISE
What membrane is used for Na?: Glass
What membrane is used for K?: Valinomycin - ion-exchange
What is the principle of ISE measurement?: Potentiometric - a change in potential as the ions interact with the membrane
What error can occur in ISE? What causes it?: Electrolyte exclusion effect - caused by other electrolytes in the fluid being measured.
How can you avoid EEE?: By using the direct ISE method where there is no dilution. (Indirect uses high ionic strength diluent)
What is the major extracellular anion?: Chloride
How is chloride reabsorbed in the kidneys?: Passively AND via active pumps
What are 3 causes of hypochloremia?: 1. Salt losing nephritis
2. Prolonged vomiting
3. Alkalosis
Why does alkalosis cause hypochloremia?: Because there is base excess, so to counter the negative charge more chloride ions are lost.
What 3 conditions are associated with hyperchloremia?: 1. Dehydration
2. Acute renal failure
3. Metabolic acidosis
What 3 methods are used for Cl measurement?: 1. Mercurimetric titration
2. Spectrophotometric
3. Coulometric - Amperometric
What type of electrode is used in coulometric measurement of Cl?: Silver chloride.
What is the principle of amperometric measurement for Cl?: -The electrode generates Cl ions which bind with pt. Cl -> Cl2
-Free Ag ions shut down the system.
What is the other major anion measured in electrolyte measurements?: Bicarbonate - HCO3-
What specimens are analyzed for HCO3 measurement?: Serum or plasma
What special care needs to be taken for CO2 measurement?: Anaerobic conditions
What are 3 methods for tCO2 measurement?: 1. Continuous flow
2. pCO2 electrode
3. Enzymatic
What is the principle of the continuous flow method?: 1. Acid buffer converts all CO2 to gas
2. Gas diffuses across membrane
3. pH buffer changes and detected with an indicator
How does the pCO2 electrode work?: As CO2 gas is detected in WB, the pH changes; rate of change is measured.
What enzymatic method is used for CO2 measurement?: 2 step method; phosphoenolpyruvate produces oxaloacetate; then measure
oxaloacetate + NADH by detecting NADH decrease
What wavelength is NADH detected at?: 340

Start Studying!

Deck Info

Number of cards 83