Chapter 31 Disorders of Fluid and Electrolyte Balance Flashcards
Which cellular compartment has a higher concentration of K+
intracellular compartment
which cellular compartment has a higher concentration of Na+
extracellular compartment
Does the extracellular or intracellular compartment have more of the TBW?
intracellular
What makes up extracellular fluid compartments?
interstitial space, tissues, fluid around organs, blood vessels
What is the composition of the ECF?
large amounts of Na, Cl, moderate amounts of bicarb, small amounts of K, Mg, Ca, and P
What is the composition of the ICF?
Large amounts of K, moderate amounts of Mg, small amounts of Na, Cl, bicarb, and P. Almost no Ca
Why would high amounts of Ca+ be dangerous in the ICF?
Because it can open ion channels and other pathways
What is an isotonic?
Where the concentrations are similar, causes the cell to neither shrink nor swell
What is a hypotonic?
Lower water concentration inside the cell – Causes water to diffuse into the cell = swelling
What is a hypertonic?
Lower water concentration outside the cell (dehydration) that causes the shift of fluids to outside the cell = shrinking
Which direction of concentration does water follow?
High concentrations to low concentrations
Where is the accumulation of fluid in edema?
in the ECF
Pitting edema is caused by swelling from …
fluid
non-pitting edema is caused by swelling from …
fluid and plasma proteins and other things
What are the physiologic mechanisms that contribute to the formation of edema?
increase in capillary filtration pressure, decrease in capillary colloid osmotic pressure, increase in capillary permeability, an obstruction to lymph flow
What is dependent edema?
edema due to gravity – think of in pregnant women where the fluid does not return as quickly and collects in the feet/ankles
What are the physiologic mechanisms assisting in regulating body water?
thirst, ADH, changes in EC osmolality and volume
How does thirst regulate water intake?
there are osmo receptors in the hypothalamus that tell us if the blood is getting thick then sends signals to the thirst center to get us to drink water
How does ADH regulate water intake?
allows water to be reabsorbed by the kidney tubules
What is the percentage of TBW for infants, young males and females, older males and females and obese people?
Infants: 75-80%
Young males: 60%
Young females: 50%
Older males: 50%
Older females: 40%
Obesity: 30-40%
A person requires how many mL of water for every 100 calories metabolized?
100 mL
What are insensible losses?
Water loss that you don’t feel you are losing – losing through every day processes that you aren’t really aware of
What are the main regulators of sodium?
the kidney
How does the kidney regulate sodium?
retains sodium when pressure is decreased and eliminates it when arterial pressure is increased, the RAAS system helps reabsorb sodium, and ANP is released when blood pressure is high and causes excretion of sodium (and water) to get the blood pressure down
What is a disorder of ADH expression?
Diabetes Insipidus
What is Diabetes Insipidus and how does it work?
There is a deficiency in ADH or a decreased response to ADH. Patients are unable to concentrate urine during periods of water restriction (like at night) and then excrete large volumes of urine
What is neurogenic diabetes insipidus?
defect in ADH synthesis or release – you are either unable to make it or unable to release it
What is nephrogenic diabetes insipidus?
kidneys do not respond to ADH
What are the disorders of sodium and water balance?
isotonic fluid volume deficit and excess, hyponatremia and hypernatremia
What is isotonic fluid volume deficit?
regular dehydration
What are the clinical manifestations of isotonic fluid volume deficit?
tachycardia, weak pulse, postural hypotension, headache, dry skin, dry mucous membranes
What is the treatment for isotonic fluid volume deficit?
giving isotonic solutions for rehydration - like Gatorade or Pedialyte
What is isotonic fluid volume excess?
fluid is being retained in the body - either by decreased sodium and water elimination due to impaired renal function, heart failure, liver failure, or corticosteroid excess
What are the clinical manifestations for isotonic fluid volume excess?
weight gain, edema, ascites
What is the treatment for isotonic fluid volume excess?
low sodium diet, use of diuretics
What is hyponatremia?
low levels of sodium in the blood, less than 135 mmol/L
What is the cause of hyponatremia?
diuretics (can cause too much sodium loss), diarrhea, vomiting, excessive water intake = water toxicity. Too low of sodium or too much water
How does hyponatremia affect the cells?
the decrease in ECF osmotic pressure so water moves into the cell via osmosis = swelling
what are the clinical manifestations of hyponatremia?
lethargy, headache, confusion, apprehension, seizures, coma
What is the treatment for hyponatremia?
address the underlying cause (like diarrhea or vomiting), restrict water intake, administer IV fluids
What is hypernatremia?
High levels of sodium over 145 mmol/L
What causes hypernatremia?
sodium gain or water loss (dehydration)
How does hypernatremia affect the cells?
water leaves the cell to go into the ECF = shrinking
What are the clinical manifestations of hypernatremia?
decreased urine output, dry mucous membranes, headache, agitation, seizures, coma
What is the treatment for hypernatremia?
Oral rehydration therapy (ORT) that contains sodium
What is the intracellular concentrations of potassium?
140-150 mmol/L
what is the extracellular concentration of potassium?
3.5-5 mmol/L
How is plasma potassium regulated?
renal mechanisms that either conserve or get rid of plasma potassium, and the transcellular shift between the ICF and ECF
What is hypokalemia?
low potassium levels in the ECF, less than 3.5 mmol/L
What causes hypokalemia?
inadequate intake of K, excessive GI, renal and skin loss of K (think about the gastric suctioning putting people at risk for hypokalemia) or the redistribution of K between the ICF and ECF (too much is going into the cell and not enough staying out)
What is the treatment for hypokalemia?
oral potassium, eating foods rich in potassium, IV potassium (cautiously to avoid hyperkalemia and cardiac dysfunction)
What are the clinical manifestations of hypokalemia?
muscle cramps, pain, weakness, fatigue, paralysis, constipation, resp failure
What is hyperkalemia?
high potassium levels in the ECF above 5.0 mmol/L
What causes hyperkalemia?
decreased renal elimination of potassium, rapid administration of potassium, movement of K from ICF to ECF
What are the clinical manifestations of hyperkalemia?
abdominal pain, diarrhea, nausea, vomiting, chest pain, heart palpitations, arrhythmia, muscle weakness
What is the treatment for hyperkalemia?
diuretics to excrete excess potassium, potassium binders to attach excess potassium to stool and then have it be eliminated, Insulin to move potassium into blood cells, dialysis, give calcium which antagonizes the potassium, sodium bicarbonate to move K to the ICF,
How would you diagnose a potassium disorder?
physical exam - muscle weakness
Plasma potassium levels
ECG - potassium causes hyperpolarization of the membrane (causes low p wave, widening of QRS, and elevated T wave)
For every 2 _____ inside the cell there are 3 _____ outside the cell
2 potassium inside
3 sodium outside
What are the 3 things that help maintain calcium equilibrium?
Vitamin D, Calcitonin, Parathyroid Hormone
How does vitamin D maintain calcium equilibrium?
increases the absorption of calcium and phosphate from the intestine to sustain normal plasma levels
How does Calcitonin maintain the calcium equilibrium?
it tells osteoblasts to take calcium out of circulation and deposit it into the bones
How does Parathyroid Hormone maintain the calcium equilibrium?
increases plasma levels by increasing absorption from the kidneys and resorption from the bone
What is hypocalcemia?
Low levels of calcium
What causes hypocalcemia?
impaired ability to mobilize calcium stores from the bone, loss of calcium from kidneys (can happen in kidney disease) increased protein binding
What are the clinical manifestations of hypocalcemia?
increased neuromuscular excitability, hypotension, lowering of the strength of the heart contractions, muscle cramps, dry scaly skin, confusion, memory problems, muscle aches, muscle spasms, arrhythmias…
What is the treatment for hypocalcemia?
IV calcium solution or oral calcium supplement
What is hypercalcemia?
too much calcium
What are the causes of hypercalcemia?
increased bone resorption of calcium, excessive vitamin D and calcium absorption, decreased elimination of calcium with use of thiazide diuretics and lithium therapy
What are the clinical manifestations of hypercalcemia?
muscle weakness, increases cardiac contractility, arrhythmias…
What is the treatment for hypercalcemia?
increase urinary excretion and decrease bone resorption
