Electrolytes Exam 3 Flashcards
What are the functions of electrolytes
Volume and osmotic regulation, maintain pH, regulation of heart muscles, redox reaction, cofactors in enzyme activation, blood coagulation
Extracellular anions and cations
Na+ and Cl-
Intracellular anions and cations
K+ and Po4-
What electrolyte is a major osmotic substance in osmolality and is its regulator?
Na+ is responsible for almost half of osmotic strength.
Intake of water in relationship to plasma osmolality, and response to thirst.
Excretion of water in relationship to blood volume and osmolality (release of ADH)
True or False: The main function of antidiuretic hormone is to increase the reabsorption of sodium and increase the secretion of potassium.
False, ADH wants to ensure the patient is properly hydrated, and reabsorption of sodium makes person dehydrated.
1-2% increase of osmolality causes 4x increase increase of
ADH
Excess intake of water
lowers plasma osmolality; ADH and thirst are suppressed hyposmolality
Absence of ADH will
increase urine production
In a water deficit
ADH and thirst is activated
ADH is released from
Anterior Pituitary to increase water absorption
Osmolality is defined as
total solute concentration per kg of water (w/w)
which electrolytes are main contributors to osmolality?
sodium, chloride, bicarbonate
Increase in osmolality
decreases freezing point temperature and vapor pressure in determining osmolality
What are some osmotically active substances?
ethanol, methanol, ethylene glycol, isopropanol, lactate or B-hydroxybutyrate
How much water is in the body and how is it distributed intracellularly and extracellulary?
Water is 40-75% of total body
67% is intracellular fluid
33% is extracellular fluid
Active transport
Requires energy
Intracellular K+ and plasma Na+ require energy from the breakdown of ATP by ATPase-dependent ion pumps.
Diffusion
Passive movement
Depends on size, charge of ion, and nature of membrane through which its passing
Rate of diffusion may be altered by
Physiological and hormonal processes
Kidneys conserve or excrete sodium depending on
aldosterone; including Sodium reabsorption and potassium excretion
Hyponatremia can be caused by
Increased Na loss (hypoadrenalism)
water imbalance (excess water intake)
Increased water retention (dilutional)
What happens if Hypernatremia is not corrected by oral or intravenous infusion of fluids?
Cerebral edema and death can be induced
What are the causes of hypernatremia?
Excess water loss (diabetes insipidus)
Decreased water intake or retention
Increased Na intake or retention (hyperaldosteronism) (sodium bicarbonate excess)
What is the most common test method used for electrolytes?
Ion Selective Electrode, transport of a specific ion from high concentration to a low concentration, through a selective binding within a membrane that creates a potential difference.
Pseudohyponatremia
Can occur when Na+ is measured using indirect ISE methods only
Increase of plasma water displacement where ion levels are falsely decreased (sample is diluted)
Falsely decreased ionic activity causes
Na+ within vitro hemolysis (Na+ released from RBCs)
Proximal tubules
reabsorb nearly all the K+
Aldosterone causes
additional K+ to be secreted in the urine in exchange of sodium in distal tubule and collecting ducts.
No renal threshold
K+ uptake from the extracellular fluid into the cells is important in
normalizing an acute rise in the plasma, K+ concentrations due to an increase intake
NaK ATPase pump can be inhibited by
Hypoxia
Hypomagnesemia
Digoxin overdose
Insulin promotes
acute entry of K ions into skeletal muscle and liver; by increasing NaK ATPase activity
Catecholamines (epinephrine)
promote cellular entry of K+
Propranolol
impairs cellular entry of K+
Forearm exercise during venipuncture can cause
erroneously high plasma K+ concentration
Hypokalemia can be a result of
GI loss
Urinary loss (Cushings syndrome, hyperaldosternonism)
Cellular shift (alkalosis- increased aldosterone)
Insulin overdose
When patients have an underlying disorder of renal insufficiency, diabetes mellitus, or metabolic acidosis they are most likely going to have
Hyperkalemia
True or False? blood is drawn into a vacutainer tube and allowed to clot. If the serum is not separated from the cells, the serum potassium will tend to decrease and the serum sodium will tend to increase.
False; K will increase and Na will decrease
How is chloride quantitated and what ions are used for it to bound to?
Amperometric- coulometric titration
Silver ions are used for it to be bound to
When maintaining electroneutrality, The amount of Na+ reabsorbed is
limited to the amount of Cl- present in the proximal tubules
Bicarb which helps maintain balance of cell comes from
carbon dioxide that was generated by cell metabolism that forms carbonic acid and splits into H+ and bicarbonate
Bicarbonate diffuses into the plasma while Cl- diffuses into
RBC to maintain balance of cell, creating inverse relationship.
Sweat chloride can be clinically presented as
Chronic obstructive pulmonary disease
Pancreatic insufficiency
Swear chloride is caused by
a defect in the cystic fibrosis transmembrane conductance regulator protein (CTFR)- more than 1500 mutations identified
CFTR usually regulates
electrolytes transport across epithelial membranes
Pilocarpine
is a cholinergic drug used to induce sweat in the positive electrode in the Gibson Cooke Qpit method
The negative electrode in the Gibson Cooke Qpit method has
NaCl
What is the ratio of bicarbonate to dissolved CO2?
bicarbonate to co2 is 20:1
What electrolyte is a major component in the buffering system in the blood?
Bicarbonate
Increased bicabonate can be seen in
Metabolic Alkalosis
Decreased bicarbonate can be seen in
renal failure and respiratory alkalosis
Overall regulation of Magnesium is controlled largely by
Kidney
The only acceptable coagulant for calcium is
Heparin
Ionized calcium is proportional to
amplitude of heart contraction, decreased concentration impairs myocardial function
Lactate is a by product of
Anaerobic metabolism
Which electrolyte is useful for metabolic monitoring of critically ill patients?
Lactate
Which of the following electrolytes would be increased in the serum if the sample was hemolyzed?
Potassium
Bicarb
Phosphate
Anion gap is
the difference between unmeasured anions and cations
