Ch 26 Electrolytes Flashcards
electrolytes
- ions or molecules that have an electric charge
- carry an electric current
- Na+, K+, H+, HCO3-
osmolarity
concentration of molecules/ions per VOLUME of solution (mOsm/Liter)
osmolality
concentration of molecules/ions per WEIGHT of solution (mOsm/Kg)
milliequivalent per liter
mEq/L
number of electrical charges in one liter of body fluid
intracellular fluid = ICF
- 2/3 of body fluid
- K+, Mg2+, SO4^2-, HPO4^2-, H2PO4-, PO4^3-
extracellular fluid = ECF
- 1/3 of body fluid
- Na+, Cl-, Ca2+, HCO3-
who plays a primary role in distribution of water and total fluid content of the body?
Electrolytes
Fluid INTAKE is regulated primarily by hypothalamic thirst center. What stimulates it?
- dry mouth
- increased angiotensin II
- increased blood osmolarity picked up by central osmoreceptors in hypothalamus
- this increases fluid intake
regulation of water loss
- determined primarily by the kidney
- under regulation of many hormones; ADH, aldosterone, Angiotensin II, ANP
- minimum of 500 mL excreted/day to flush out urine solutes
Volume depletion(fluid deficiency) = hypovolemia
- same amount of water and electrolytes are lost without replacement
- fluid osmolality remains fairly normal
- occurs with; hemorrhage, surgical losses, severe GI loss, severe burns, hyposecretion of aldosterone, some diuretics
Dehydration(fluid deficiency)
- body loses more water than electrolytes
- fluid osmolality goes up
- causes; decreased ingestion of fluid, excessive sweating, heavy respirations, excessive urination(diabetes mellitus, ketonuria, some diuretics, alcohol intake, diabetes insipidus)
Volume excess(fluid overload)
- both water and electrolytes are retained = hypervolemia
- causes; too much aldosterone, too much cortisol, renal failure, excessive IV fluids, medication side effects, heart failure
Hypotonic hydration(fluid overload)
- more water than sodium is retained, or you lose water plus electrolytes but replace only with plain water
- ECF becomes hypotonic
- causes; drinking H2O to replace isotonic losses, SIADH, severe CHF or renal insufficiency, psychogenic polydipsia
Fluid sequestration
- fluid accumulates in a particular location
- causes; edema, internal hemorrhage, pleural effusion, ascites, vascular shock
sodium
MOST ABUNDANT cation in ECF
- normal: ~140 mEq/L
- hyponatremia: 145 mEq/L
- regulation: aldosterone, angiotensin II, ANP, estrogen, progesterone, epinephrine, norepinephrine
potassium
MOST ABUNDANT cation in ICF
- disorders can be life threatening
- necessary for NORMAL INSULIN SECRETION
- normal: ~3.5-5 mEq/L
- hypokalemia: 5.0 mEq/L
chloride
MOST ABUNDANT anion in ECF
- normal: ~100 mEq/L
- hypochloremia: 105 mEq/L
calcium
essential for normal muscle and neuron function and normal bone structure.
- regulated by PTH, and calcitriol
- normal: 4.5-5.2 mEq/L
- hypocalcemia: 5.2 mEq/L
magnesium
cofactor of enzymes, REQUIRED for normal membrane functions
What type of patients are at risk for electrolyte imbalance?
- those who depend on others for fluid/food (infants, elderly, comatose)
- post-operative patients
- people with large amounts of emesis/diarrhea
- those with severe burns & trauma
Causes of hyper-electrolyte conditions
- dehydration
- kidney failure
- sudden release of ion from tissues
- hormonal imbalances
- acid-base imbalances
- excessive intake
Causes of hypo-electrolyte conditions
- increased losses
- inadequate absorption/reabsorption
- increased utilization
- hormonal imbalances
- acid-base imbalances
- hypotonic hydration
- inadequate intake
Phosphate anions
Important anions in ICF
- HPO4, H2PO4, PO4
normal: 1.6-2.9 mEq/L
