Electrolytes Exam 3
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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)