Electrolyte Homeostasis Flashcards
explain the regulation and function of potassium in the body.
potassium is regulated by two major mechanisms: renal mechanisms that conserve or eliminate potassium and a transcellular buffer system that remove potassium and release it into the serum as needed.
renal: regulation of potassium elimination is controlled by secretion from the blood into the tubular filtrate. Potassium is filtered in the glomerulus, reabsorbed along with sodium and water in the proximal tubular and with sodium and chloride in the thick ascending loop of Henle and then secreted into the late distal and cortical collecting tubes for elimination into urine. Further, In the presence of aldosterone, Na is transported back to the blood and K+ is secreted in the tubular filtrate for elimination into urine.
ECF compartments: sodium potassium pump, exercise, acid-base disorders, insulin, and Beta-adrenergic antagonists.
potassium’s function is: Potassium is an essential mineral and electrolyte involved in heart function, muscle contraction, and water balance.
state the causes of hyperkalemia and hypokalemia
hyperkalemia:
excessive intake (oral, supplements, rapid infusion),
release from intracellular compartment (tissue trauma, burns, seizures, extreme exercise)
inadequate elimination by kidneys (renal failure, adrenal insufficiency–Addison disease, tx with potassium sparing diuretics, treatment with ACE inhibitors or ARBs)
hypokalemia: inadequate intake (diet deficient, inability to eat, potassium free parenteral solutions) excessive renal loss (diuretics therapy--not potassium sparing, diuretic phase of renal failure, increase mineralocorticoid levels, primary hyperaldosteronism, treatment with corticosteroid drugs) excessive gastrointestinal losses (vomiting, diarrhea, gi suction, draining gi fistula) transcompartmental shift (administration of beta-adrenergic antagonist, administration of insulin for tx of diabetic ketoacidosis, alkalosis--metabolic or respiratory)
should only have to know the basics, but parentheses just in case.
discuss the numerous functions of calcium in the body–where is it stored?
calcium is stored in the bones, and a small percentage is in the cells.
Calcium functions to:
Calcium makes up much of the structure of bones and teeth and allows normal bodily movement by keeping tissue rigid, strong, and flexible. The small ionized pool of calcium in the circulatory system, extracellular fluid, and various tissues mediates blood vessel contraction and dilation, muscle function, blood clotting, nerve transmission, and hormonal secretion.
what stimulates calcium storage? (reabsorption)
PVTPG
PTH (parathyroid hormone) vitamin D thiazide diuretics phosphate levels glucose and insulin levels
Perhaps Vicki Took Paul Golfing
what stimulates calcium release?
kidney excretion, muscle contraction, PTH acts on the bones to stimulate osteoclasts involved in bone reabsorption and the release of free calcium.
list several causes of hypocalcemia
impaired ability to mobilize calcium from bone (hypoparathyroidism, resistance to the actions of PTH, hypomagnesemia)
decreased intake or absorption (malabsorption, Vitamin D deficiency–failure to activate, liver disease, kidney disease, medications that impair the action of Vitamin D–phenytoin)
abnormal renal losses (renal failure and hyperphosphatemia)
increased protein binding or chelation (increased pH, increased fatty acids, rapid transfusion of citrated blood)
increased sequestration (acute pancreatitis)
relate the functions of potassium to the clinical signs of hyperkalemia and hypokalemia
**hypokalemia
relate the functions of potassium to the clinical signs of hyperkalemia and hypokalemia
water balance: impaired ability to concentrate urine (polyuria, polydipsia, urine with low osmolality and specific gravity), acid-base disorders (metabolic alkalosis)
heart function: cardiovascular manifestations (postural hypertension, increased sensitivity to digitalis toxicity, changes in electrocardiogram, and cardiac dysrhythmias)
other effects: neuromuscular manifestations: muscle flabbiness, weakness and fatigue, muscle cramps/tenderness, paresthesias, paralysis
CNS manifestations: confusion and depression
relate the functions of potassium to the clinical signs of hyperkalemia and hypokalemia
Potassium is an essential mineral and electrolyte involved in heart function, muscle contraction, and water balance.
hyperkalemia
water balance: lab values (above 5.0mEq/L) GI manifestations (nausea and vomiting, intestinal cramps, diarrhea)
muscle contraction: neuromuscular manifestations (paresthesias, weakness/dizziness, muscle cramps)
heart function: cardiovascular manifestations (changes in electrocardiogram, risk of cardiac arrest with severe excess.)
describe the physiologic effects of hypocalcemia and hypercalcemia
hypocalcemia: Neuromuscular manifestations: serum calcium below 8.5 mg/dL paresthesias, especially numbness and tingling skeletal muscle cramps abdominal spasms and cramps hyperactive reflexes carpopedal spasm tetany laryngeal spasm positive chovostek and trousseau signs
Cardiovascular manifestations:
hypotension
signs of cardiac insufficiency
failure to respond to drugs that act by calcium-mediated mechanisms
prolongation of QT interval predisposes to ventricular dysrhythmias
skeletal manifestations (chronic deficiency) osteomalacia bone pain, deformities, fracture
describe the physiologic effects of hypercalcemia
hypercalcemia:
labs: calcium level above 10.5 mg/dL
impaired ability to concentrate urine and exposure of kidney to increased concentration of calcium (polyuria, polydipsia, flank pain, signs of acute and chronic renal insufficiency)
gastrointestinal manifestations (anorexia, nausea, vomiting, cramping)
Neuromuscular manifestations (muscle weakness and atrophy, ataxia–loss of muscle tone)
Skeletal manifestations (osteopenia, osteoporosis)
CNS manifestations (lethargy, personality and behavior changes, stupor and coma)
Cardiovascular manifestations (hypertension, shortening of the QT interval, atrioventricular black on electrocardiogram)
