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Week 4

Potassium, Calcium & Magnesium Homeostasis and Imbalances

QuestionAnswer
What is an ion? Charged molecule
What is the chemical symbol for potassium? K+
What is the chemical symbol for calcium? Ca++
What is the chemical symbol for magnesium? Mg++
What are the principles of electrolyte homeostasis and imbalances? (4) 1. Intake and absorption 2. Distribution 3. Excretion 4. Loss through abnormal routes
To maintain homeostasis, ___ + ____ must equal ____ + ____ Intake, absorption; excretion, loss
Which electrolyte imbalances are “floppy”? Hyperkalemia, hypokalemia, hypercalce,ia, hypermagnesemia
Which electrolyte imbalances are “twitchy”? Hypocalcemia, hypomagnesemia
Potassium ions are necessary for normal function of all cells, especially ___ and ____ cells Neurons, muscle cells
The ratio of potassium inside/outside of the cell determines its ____ potential. RMP: resting membrane potential
Most of the potassium ions in the body are _____ the cells Inside
The sodium-potassium pump used ____ to maintain cell homeostasis ATP
Normal muscle cells have a very small electrical charge across their membranes, called the ______. Resting membrane potential
If potassium ratio is altered, _______ will be different and muscle can have abnormal function. Resting membrane potential
Potassium imbalances can affect... Function of skeletal muscle, smooth muscle and/or heart muscle
The word ‘potassium’ comes from the word ____ Potash, meaning plant residue
How do we take in potassium? Through diet, or potassium-containing medication
What foods contain potassium? Fruits- bananas, oranges, raisins, cantaloupe, apricots. Vegetables- Asparagus, bok choy, broccoli, carrots, celery. Other- nuts, molasses, sunflower seeds
What mechanism pumps K+ ions into cell to keep intracellular K+ level high? Sodium-potassium pump
What causes K+ to move from plasma into cells? Alkalosis, insulin, and beta-adrenergic stimulation
What causes K+ to move from cells into plasma? Acidosis due to mineral acids (caused by bicarbonate loss in diarrhea)
Potassium is normally excreted in... Urine, feces, sweat
More potassium is excreted than normal in ____ Diarrhea
Potassium excretion by the kidneys is ____ dependent Flow dependent
Flow-dependent excretion of K+ in kidneys means... The larger the urine volume, the more potassium is excreted
What hormones increase potassium excretion in the urine? Aldosterone, glucocorticoid hormones (cortisol)
Aldosterone pulls in ___ from the urine, and pushes ___ out
Potassium may be lost through abnormal routes via.... emesis, drainage from tubes inserted into the GI tract (nasogastric tubes), or other losses of body fluids
What is hypokalemia? Serum potassium concentration that is below normal (< 3.5 mEq/L). Plasma deficit of K+, whole body K+ may be decreased, normal, or increased
With hypokalemia, whole body potassium levels may be... Decreased, normal or increased
What are the 4 general risk factors for hypokalemia? 1. Decreased K+ intake 2. Shift of K+ from plasma into cells 3. Increased K+ secretion 4. Loss of K+ through abnormal route
What are risk factors for decreased potassium intake? Anorexia; unusual weigh-loss diets that do not contain K+; NPO orders; prolonged IV therapy without K+
What are risk factors that shift K+ from plasma into cells? Alkalosis; hypersecretion of insulin (response to TPN- total parenteral nutrition); insulin overdose; excessive beta-adrenergic stimulation (epinephrine, albuterol); hypothermia
What does insulin do to K+ in the plasma? Moves K+ into cells
What are risk factors for increased K+ excretion? medications that cause increased K+ excretion in urine); increased effect of aldosterone (hyperaldosteronism, CHF, cirrhosis); hypomagnesemia; black licorice; diarrhea, laxative overuse, colon cleansing/irrigation
What causes loss of K+ through abnormal routes? Emesis, nasogastric suction, intestinal decompression
What are some clinical signs of hypokalemia? Abdominal distention, decreased bowel sounds, constipation, paralytic ileus (GI not moving); polyuria; orthostatic hypotension; flaccid skeletal muscle weakness; flaccid paralysis; cardiac dysrhythmias; quadriceps weakness
Cardiac dysrhythmias can be caused by Both hypokalemia and hyperkalemia
Quadricep weakness is a sign of ____ Hypokalemia
Why is hypokalemia a “floppy” disorder? Hyperpolarization makes it harder to reach action potential (more negative)
What are important teachings for a patient with hypokalemia? Safe weight loss diet, bowel management to prevent diarrhea from laxative overuse. need for increased K+ intake to offset loss in diarrhea; K+ rich foods
What is hyperkalemia? Serum potassium concentration that is above normal (>5.0 mEq/L). Indicates a plsma excess of K+
In hyperkalemia , the whole body K+ level may be... Increased, normal or decreaed
What are the 3 general risk factors fro hyperkalemia? Increased K+ intake, shift of K+ from cells to plasma, decreased K+ excretion
What are risk factors for increased K+ intake? Oral intake is rarely a problem unless combined with decreased urine output. Too much/rapid KCl; insufficient mixing of KCl in IV bag; stored blood (K+ leaks out of cells into plasma in old blood); large does of penicillin G
When is use of stored blood an issue? When using large amounts ≥ 8 unitsl blood older than 3 days
What risk factors shift K+ from cells into plasma? Acidosis due to mineral acids (loss of bicarbonate in diarrhea); crushing injury or massive cell death; insulin deficiency
What risk factors cause decreased K+ excretion? Mediations, oliguric renal disease, severe hypovolemia , decreased aldosterone effect
How does severe hypovolemia cause decreased K+ excretion? Decreased ECV causes decreased kidney perfusion, producing less urine and excreting less K+
What are some clinical signs of hyperkalemia? Intestinal cramping and diarrhea; flaccid skeletal muscle weakness; flaccid paralysis; cardiac dysrhythmias
Which electrolyte imbalance causes most potentially dangerous dysrhythmias? Hyperkalemia
What are some important teachings for patients with hyperkalemia? Stop K+ containing preparations (KCl based salt substitutes), if urine volume decreases; reduce intake of K+ rich foods)
What normal ranges for serum calcium? 9-11 mg%; 4.5-5.5 mEq/L
Lab reports measure ____ calcium Total calcium
True or false: ionized calcium can be measured with low/high total calcium. True
What is the physiologically active form of calcium? Free, ionized calcium
Are calcium ions bound to albumin physiologically active? No. Physiologically inactive while bound
Are calcium ions bound to small organic anions like citrate physiologically active? No.
Plasma calcium and plasma ____ vary inversely Plasma phosphate
What decreases the amount of physiologically available Ca++? Alkalosis. Bicarbonate binds to Ca++
Which hormone regulates plasma Ca++ concentration? Parathyroid hormone (PTH)
What does PTH do? Increases plasma Ca++: takes it from bones and improves absorption of vitamin D needed for Ca++ absorption.
Where is calcium absorbed? Duodenum (more acidic)
What is hypocalcemia? Plasma deficit of Ca++l serum levels may not reflect body stores
What are the 4 general risk factors for hypocalcemia? Decreases Ca++ intake or absorption; decreased physiological availability of Ca++; Increased Ca++ excretion; loss of Ca++ by abnormal route
What risk factors cause decreased Ca++ intake or absorption? Chronic malnutrition or poor calcium intake, vitamin D deficiency (lack of sunlight); antacid overuse (non-calcium); chronic diarrhea (includes laxative overuse); steatorrhea
Why does antacid overuse cause decreased calcium absorption? Because the bicarbonate in antacids makes GI less acidic
What is steatorrhea? Floating fats in stools (such as in pancreatitis) bind and excrete Ca++
What risk factors cause decreased physiological availability of Ca++? Massive transfusion with citrated blood; hypoparathyroidism (that includes removal of parathyroid glands); alkalosis (decreased acidity); overuse of phosphate-containing laxatives and enemas
What are clinical signs of hypocalcemia? Positive Chvostek sign, positive Trousseau sign; muscle twitching, cramping; carpopedal spasm, tetany; laryngospasm; seizures, cardiac dysrhythmias
Why is hypocalcemia a twtitchy disorder? Depolarization makes it easier to reach action potential
What are important teachings patients with hypocalcemia? Bowel management to prevent laxative overuse; calcium rich foods; alternate Ca++ sources for those who do not eat dairy; need or increased Ca++ for those with chronic diarrhea or malabsorption
What are some calcium rich foods? Milk, dairy products; almonds, cream of wheat and farina cereal; chocolate, canned fish (with bones); oranges; oysters, tofu, dark leafy greens, corn tortillas
What is hypercalcemia? excessive plasma Ca++
What are some general risk factors of hypercalcemia? Increased Ca++ intake/absorption; shift of Ca++ from bones to plasma; decreased Ca++ excretion
What risk factors cause shift of Ca++ from bones to plasma? prolonged immobilization, cancers, bone tumors, hyperparathyroidism, ectopic release of parathyroid- hormone related peptide
Is hypercalcemia floppy or twitchy ? floppy
What are some clinical signs of hypercalcemia? Anorexia, constipation, nausea and emesis, muscle weakness, fatigue, confusion and lethargy, personality and mood changes; polyuria
What are important teachings for a patient with hypercalcemia? Avoid massive vitamin D supplementation; need for adequate hydration to prevent renal damage with hypercalcemia
What are normal ranges for serum magnesium? 1.5-2.5 mEq/L
What are parts of total body magnesium? Ionized magnesium (physiologically active form), Mg++ bound to albumin (physiologically inactive); Mg++ bound to small organic anions like citrate (physiologically inactive)
Magnesium is absorbed primarily from the ____ Terminal ileum
What is hypomagnesemia? Plasma Mg++ deficit
More Mg++ mean less ____ Ach
Hypomagnesemia means less magnesium, more Ach released from motor nerve Twitchy
What are the general risk factors for hypomagnesemia? Decreased Mg++ intake or absorption; decreased physiologically availability of Mg++; increased Mg++ excretion; loss of Mg++ by abnormal route
What risk factors cause decreased Mg++ intake? Malabsorption syndromes, chronic diarrhea, steatorrhea, chronic malnutrition, chronic alcoholism, ileal resection
What risk factors cause increased Mg++ excretion? Diuretic therapy, diabetic ketoacidosis, hyperaldosteronism, chronic alcoholism, steatorrhea
What risk factors cause loss of Mg++ through abnormal route? Acute pancreatitis
What are some clinical signs of hypomagnesemia? Insomnia, hyperreflexia, positive Chvostek sign, positive Trousseau sign, skeletal muscle cramps, twitching, tremors, tetany, nystagmus, seizures, extreme confusion, cardiac dysrhythmias
Is hypomagnesemia floppy or twitchy? Twitchy. Less Mg++ mean MORE ACH
What are important teachings for a patient with hypomagnesemia? Information about alcoholism treatment, if applicable. Mg++ rich foods
What foods are rich in Mg++ Dark chocolate, nuts, dark green vegetables, legumes
What is hypermagnesemia? Plasma Mg++ excess
What are the general risk factors for hypermagnesemia? Increased Mg++ absorption, decreased Mg++ excretion
What risk factors cause increased Mg++ absorption? Excessive use of Mg++ (antacids)
What risk factors cause decreased Mg++ excretion? oliguric renal disease, adrenal insufficiency
What are some clinical signs of hypermagnesemia? Hypotension, drowsiness, lethargy, weak or absent deep tendon reflexes, flaccid muscle paralysis, respiratory depression, cardiac dysrhythmias
What are some important teachings for a patient who has hypermagnesemia? Replace chronic Mg++ laxative use with alternative methods of bowel management for older adults; avoid Mg++ containing antacids and laxatives if urine volume decreases
Which electrolyte imbalances cause cardiac dysrhythmias? All except hypercalcemia
Created by: kangaloo