Ch. 11 Fluid & Electrolyte Imbalances (M.S.)

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Homeostasis:
- Proper functioning of all body systems; requires fluid and electrolyte balance
- Normal distribution of total body water in adults.
- ECF is typically your plasma; outside of the cell
- ICF: inside the cell
- Interstitial: between the cells
- Transcellular: CSF (everything else)
Filtration:
- Movement of fluid through cell or blood vessel membrane because of differences in water pressure (hydrostatic pressure)
- This is related to water volume pressing against confining walls
Hydrostatic Pressure:
- "Water-pushing pressure"
- Force that pushes water outward from a confined space through a membrane
- Amount of water in any body fluid space determines pressure
- Example: Blood pressure
Moving whole blood from the heart to capillaries where filtration occurs to exchange water, nutrients, and waste products between the blood and tissues
Clinical Significance: Edema
- Develops with changes in normal hydrostatic pressure differences
- Edema forms with changes in hydrostatic pressure differences between the capillary blood and the interstitial fluid, such as in patients with right-sided heart failure. In this condition, the volume of blood in the right side of the heart increases because the right ventricle is too weak to pump blood efficiently into the lung blood vessels. As blood backs up into the venous and capillary systems, the capillary hydrostatic pressure rises until it is higher than the hydrostatic pressure in the interstitial space. Then, excess filtration of fluids from the capillaries into the interstitial space occurs, forming visible edema.
Diffusion:
- Free movement of particles (solute) across permeable membrane from area of higher to lower concentration
- Important in transport of most electrolytes; other particles diffuse through cell membranes
-Sodium pumps: Usually ECF has ten times more sodium ions than in the ICF. This extreme difference is caused by cell membrane impermeability to sodium and by special "sodium pumps" that move any extra sodium present inside the cell out of the cell "uphill" against its concentration gradient and back into the ECF.
- Glucose cannot enter most cell membranes without help of insulin; When insulin is present, it binds to insulin receptors on cell membranes, which then makes the membranes much more permeable to glucose. As a result, glucose can cross the cell membrane down its concentration gradient until equilibrium of glucose concentration is achieved.
Osmosis:
- For osmosis to occur, a membrane must separate two fluid spaces and one space must have particles that cannot move through the membrane; the concentration equilibrium occurs by the movement of water molecules rather than the movement of solute particles.
Osmosis & Filtration:
- Act together at capillary membrane to maintain normal ECF and ICF volumes
Example of how osmosis helps maintain homeostasis:
- Thirst mechanism is example of how osmosis helps maintain homeostasis
- Feeling of thirst caused by activation of brain cells responding to changes in ECF osmolarity
- The cells in the thirst center shrink as water moves from the cells into the hypertonic ECF. The shrinking of these cells triggers a person's awareness of thirst and increases the urge to drink. Drinking replaces the amuount of water lost through sweating and dilutes the ECF osmolarity, restoring it to normal. The thirst mechanism is less sensitive in older adults, increasing their risk for dehydration.
Fluid Balance: Intake & Loss
- Closely linked to/affected by electrolyte concentrations
- Fluid intake: is regulated through the thirst drive. Fluid enters the body as liquids and as solid foods, which contain up to 85% water.
- Fluid loss: Minimum urine amount needed to excrete toxic waste products = 400 to 600 mL/day; if you have less than this then you will have toxic waste buildup
- Insensible water loss - Through skin, lungs, stool
- The kidney is the most important and the most sensitive water loss route because it is regulated and is adjustable.
- Water loss can also occur from salivation, drainage from fistulas and drains, and GI suction.
Aldosterone:
- Secreted by adrenal cortex when sodium level in ECF are decreased.
- Prevents water and sodium loss
- When aldosterone is released it acts on the kidney nephrons triggering them to reabsorb sodium and water from the urine back into the blood, This action increases blood osmolarity and blood volume. Aldosterone prevents excessive kidney excretion of sodium. It also helps prevent potassium levels from becoming too high.
Antidiuretic hormone:
- Released from posterior pituitary due to changes in osmolarity
- Retains water
- Acts directly on kidney tubules and collecting ducts, making them more permeable to water only. As a result, more water is reabsorbed by tubules in kidneys and returned to the blood, decreasing blood osmolarity by making it more dilute.
Natriuretic peptides:
- Hormones secreted by special cells that line the atria and ventricles of heart
- Secreted in response to increase in blood volume and blood pressure, which stretch the heart tissue.
- Sodium reabsorption is inhibited, glomerular filtration is increased, urine output is increased as a result
- The outcome is decreased circulating blood volume and decreased blood osmolarity.
Significance of Fluid Balance: Renin-Angiotensin II Pathway
- Blood (plasma) volume and intracellular fluid most important to keep in balance
- Kidneys are major regulator of water and sodium balance; maintain blood and perfusion pressure to all tissues/organs
- When the kidneys sense a low parameter, they secrete renin that sets into motion a group of hormonal and blood vessel responses to ensure that blood pressure is raised back up to normal.
- Renin-angiotensin II pathway is greatly stimulated with shock, or when stress response is stimulated
- The most critical fluid balance to prevent death is maintaining blood volume at a sufficient level for blood pressure to remain high enough to ensure adequate perfusion ad gas exchange of all organs and tissues. Balance of both water and electrolytes is needed for this very vital function.
The Renin-Angiotensin-Aldosterone System:
- Kidneys say we have a perfusion issue first and renin is secreted.
- Renin helps angiotensinogen to form angiotensin I (which is relatively weak and has little action)
- This is then acted on by ACE which converts angiotensin I into its most active form, angiotensin II
- Angiotensin II is the power house and causes vasoconstriction; increases BP.
- Lastly, angiotensin II causes the adrenal glands to secrete aldosterone, which helps the kidneys reabsorb water and sodium preventing them from being excreted in the urine; this allows blood pressure and blood volume to increase due to returning the water and sodium to the blood.
ACE Inhibitors:
- Disrupt renin-angiotensin II pathway by reducing amount of ACE produced
- With less angiotensin II, less vasoconstriction and reduced peripheral resistance, less aldosterone production, and greater excretion of water and sodium in urine
- By locking angiotensin II receptors, blood pressure lowers
- Patients with hypertension often take ACE-inhibitor medications
- ACE inhibitors causes cough because it activates bradykinins which causes inflammation and a cough
Dehydration: Collaborative Care
- Fluid intake/retention does not meet body's fluid needs; results in fluid volume deficit
Manifestations:
- Cardiovascular: increased heart rate, decreased blood and pulse pressure
- Respiratory: increased respiratory rate
- Skin: dry, itchy skin; poor skin turgor; asses color and moisture
- Neurologic: mental status delayed; confusion is common; you may also see low-grade fever, which causes even more fluid loss the higher the fever rises
- Renal: decreased urine output; urine is a dark amber and has a strong odor
Interventions for Dehydration:
• Management of dehydration aims to prevent injury, prevent further fluid losses, and increase fluid compartment volumes to normal ranges.
• Main strategies include assuring patient safety, fluid replacement, and drug therapy.
• Ensure access to adequate fluids for patients who are unable to talk or who have limited mobility.
• Older adults are at high risk for dehydration because they have less total body water than younger adults. They also may take drugs such as diuretics, antihypertensives, and laxatives that increase fluid excretion.
Fluid Overload: Collaborative Care
- Overhydrated
Manifestations:
- Cardiac: increased BP, bounding pulse, decreased pulse pressure, weight gain, JVD
- Respiratory: crackles from fluid in the lungs, increased rate, shallow respirations, SOB
Skin: Edema in the feet and ankles, skin pale and cool to touch
- Neuromuscular: altered LOC, headache, visual disturbances, skeletal muscle weakness, paresthesias
- GI changes: enlarged liver, increased motility (urine output)
Interventions for Fluid Overload:
• Interventions for patients with fluid overload ensure patient safety, restore normal fluid balance, provide supportive care until the imbalance is resolved, and prevent future fluid overload.
• Use a pump or controller to deliver intravenous fluids to patients with fluid overload.
Sodium Normal Levels:
135-145 mmol/L
Sodium:
"Where sodium goes, water follows" - the ECF sodium level determines whether water is retained, excreted, or moved from one fluid space to another.
Hyponatremia:
- <136
- Causes: excessive sweating, diuretics, wound drainage, decreased secretion of aldosterone, hyperlipidemia, kidney disease, nothing by mouth, low-salt diet, hyperglycemia, excessive ingestion of hypotonic fluids, psychogenic polydipsia, kidney failure, SIADH, heart failure
- Symptoms: increased confusion, muscle weakness (if this is present, immediately check respiratory effectiveness), deep tendon reflexes diminish, increased motility (causing nausea, diarrhea, and abdominal cramping), rapid/weal/thready pulse, decreased blood pressure, severe orthostatic hypotension
Hypernatremia:
- >145
- Causes: hyperaldosteronism, kidney failure, corticosteriods, Cushing's syndrome or disease, excessive oral sodium ingestion, excessive administration of sodium-containing IV fluids, nothing by mouth, increased rate of metabolism, fever, hyperventilation, infection, excessive diaphoresis, watery diarrhea, dehydration
- Symptoms: altered cerebral function, short attention span, easily agitated, confused, lethargic, drowsy, stuporous, comatose, muscle twitching and irregular muscle contractions, muscle weakness, deep tendon reflexes reduced or absent, decreased contractility, increased pulse rate, hypotension, JVD
Potassium Normal Levels:
3.5-5.0 mEq/L
Potassium:
- Some control over intracellular osmolarity and volume
- Regulate protein synthesis, glucose use and storage
- Lasix, which is a diuretic, can cause potassium to be excreted out through urine; CHECK POTASSIUM LEVELS BEFORE GIVING
Hypokalemia:
- <3.5
- Causes: inappropriate or excessive use of drugs (diuretics, digitalis, corticosteriods), increased secretion of aldosterone, Cushing's syndrome, diarrhea, vomiting, wound drainage, prolonged nasogastric suction, heat-induced excessive diaphoresis, kidney disease impairing reabsorption of potassium, nothing by mouth, alkalosis, total parenteral nutrition, IV therapy with potassium-poor solutions
- Symptoms: shallow respirations, skeletal muscle weakness, reduced deep tendon reflexes, may cause flaccid paralysis, weak and thready pulse, dysrhythmia, orthostatic (postural) hypotension, altered mental status, irritability, anxiety, lethargy, acute confusion, coma, decreased perstalsis, hypoactive bowel sounds, nausea, vomiting, constipation, abdominal distention
More info. about Potassium:
o Follow facility policy for cardiac monitoring in the presence of hypokalemia.
o Before infusing any IV solution containing potassium chloride, check and re-check the dilution of the drug in the IV solution container.
o Do not give intravenous potassium at a rate greater than 20 mEq/hr.
o Never give potassium supplements by the intramuscular, subcutaneous, or IV push routes.
o Use a pump or controller when giving intravenous potassium-containing solutions.
o Because potassium is a severe irritant to the vein, assess the IV site hourly, and ask the patient whether he or she feels burning or pain at the site.
o Immediately stop the infusion of potassium-containing solutions if infiltration or phlebitis is suspected.
o Oral potassium preparations have a strong, unpleasant taste and can cause nausea and vomiting. Give the drug during or after a meal and advise patients to not take it on an empty stomach at home.
Hyperkalemia:
- >5.0
- Causes: over ingestion of potassium-containg foods or medications (salt substitutes, potassium chloride, rapid infusion of potassium-containing IV solution, bolus IV potassium injections), transfusions of whole blood or packed cells, adrenal insufficiency, kidney failure, potassium-sparing diuretics, ACEIs, tissue damage, acidosis, hyperuricemia, uncontrolled diabetes mellitus
- Symptoms: bradycardia, hypotension, ECG changes, muscle twitch, tingling and burning sensations, numbness in hands/feet/mouth, muscle weakness and flaccid paralysis may occur, increased motility, diarrhea, hyperactive bowel sounds, frequent and watery bowel movements
Calcium Normal Levels:
9.0-10.5 mg/dL
Calcium:
- Absorption requires active form of vitamin D
- Stored in bones
- Parathyroid hormone: releases when more calcium is needed; helps the bone release more calcium
- Thyrocalcitonin: when we have too much this is released to cut back in calcium
- When calcium is up, phosphorus is down and vive versa
Hypocalcemia:
- <9.0
- Causes: inadequate oral intake of calcium, lactose intolerance, malabsorption syndromes (celiac sprue, Crohn's disease), inadequate intake of vitamin D, end-stage kidney disease, diarrhea, steatorrhea, wound drainage, alkalosis, hyperproteinemia, immobility, acute pancreatitis, removal or destruction of parathyroid glands
- Symptoms: painful muscle spasms "Charley horses", sensations of tingling and numbness, HR may become slower or faster than normal with a weak/thready pulse, severe hypotension, increased peristaltic activity, painful abdominal cramping, diarrhea, bones are less dense/more brittle and fragile and may break easily, overall height loss
Hypercalcemia:
- >10.5
- Causes: excessive oral intake of calcium or vitamin D, kidney failure, use of thiazide diuretics, hyperparathyroidism, malignancy, hyperthyroidism, immobility, use of glucocorticoids, dehydration
- Symptoms: increased heart rate and blood pressure, slowed HR if severe, blood clots are more likely, assess for slowed or impaired blood flow, sever muscle weakness, decreased deep tendon reflexes, may be confused or lethargic, decreased peristalsis, constipation, anorexia, nausea, vomiting, abdominal distention and pain, hypoactive or absent bowel sounds
Phosphorus Normal Levels:
3.0-4.5 mg/dL
Phosphorus:
- Found in bones
- Activates vitamins and enzymes; assists in cell growth and metabolism; active in forming ATP for energy supplies
- Plasma levels of calcium and phosphorus exist in a balanced reciprocal relationship
Hypophosphatemia:
- <3.0
- Causes: malnutrition, starvation, use of aluminum hydroxide-based or magnesium-based antacids, hyperparathyroidism, hypercalcemia, kidney failure, malignancy, hyperglycemia, hyperalimentation, respiratory alkalosis, uncontrolled diabetes mellitus, alcohol abuse
- Symptoms: weak contractility, decreased SV, decreased CO, peripheral pulses are slow/hard to find/ and easy to block, can cause progressive but irreverisble cardiac muscle damage, weak skeletal muscles that may progress to acute muscle breakdown, can lead to respiratory failure, bone density is decreased (leads to bone fractures), irritability, may progress seizure activity followed by coma
Hyperphosphatemia:
- >4.5
- Causes: decreased kidney excretion resulting from kidney disease, tumor lysis syndrome, increased intake of phosphorus, hypoparathyroidism
Magnesium Normal Levels:
1.3 to 2.1 mg/dL
Magnesium:
- Critical for skeletal muscle contraction, carbohydrate metabolism, ATP formation, vitamin activation, cell growth
Hypomagnesemia:
- <1.3
- Causes: malnutrition, starvation, diarrhea, steatorrhea, celiac disease, Crohn's disease, drugs, citrate (blood products), ethanol ingestion
- Symptoms: hyperactive deep tendon reflexes, numbness and tingling, painful muscle contractions, may have tetany and seizures, positive Chvostek and Trousseau signs, reduced motility, anorexia, nausea, constipation, abdominal distention, a paralytic ileus may occur
Hypermagnesemia:
- >2.1
- Causes: increased magnesium intake (magnesium-containing antacids and laxatives, IV magnesium replacement), decreased kidney excretion of magnesium resulting from kidney disease
- Symptoms: bradycardia, peripheral vasodilation, hypotension, ECG changes, drowsy or lethargic, coma may occur if severe or prolonged, reduced or absent deep tendon reflexes, may have respiratory failure or death
Chloride Normal Levels:
98 to 106 mEq/L
Chloride:
- Imbalance occurs as a result of other electrolyte imbalances
- Treat underlying electrolyte imbalance or acid-base problem
Considerations for Older Adults:
- At risk for most electrolyte imbalances from age-related organ changes
- Have less total body water than younger adults; more at risk for fluid imbalances; more likely to be taking drugs affecting fluid or electrolyte balance
While monitoring a patient who has fluid overload, the nurse would be most concerned about which assessment finding?
Bounding pulse
Neck vein distention
Pitting edema in the feet
Presence of crackles in the lungs (Correct)
A patient has been having frequent liquid diarrhea for the last 24 hours. A stool sample was sent to the laboratory to confirm possible Clostridium difficile infection. The nurse should monitor the patient for which electrolyte imbalance?
Dehydration
Hypokalemia (Correct)
Hyponatremia
Hypocalcemia
- You lose a lot of potassium when you have diarrhea; you lose a lot of sodium when you vomit
A 25-year-old student has been taken to an urgent care clinic because of dehydration. She says she has had "the flu," with vomiting and diarrhea "all night" and has had very little to eat or drink. She says the GI symptoms have subsided, but she feels weak. The nurse expects which type of rehydration to occur?
IV fluid replacement
Oral rehydration therapy with tea
Oral rehydration therapy with water
Oral rehydration therapy with a solution containing glucose and electrolytes (Correct)
- Gatorade
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