L13: Fluid, Electrolytes, and Acid-Base Balance Flashcards
what are the characteristics of body fluids that affect cell function(4)?
1) volume (amount)
2) osmolarity (concentration)
3) electrolyte concentration (composition)
4) pH (degree of acidity)
how much total body water is in intracellular fluid (ICF) in adults?
about 2/3
how much total body water is in extracellular fluid (ECF) in adults?
about 1/3
what are the two major divisions of extracellular fluid?
1) intravascular fluid (liquid part of blood-plasma)
2) interstitial fluid (between cells and the outside of blood vessels
what is the minor division of extracellular fluid?
transcellular fluid (cerebrospinal fluid, pleural, peritoneal, and synovial fluids)
fluid that contains a large number of dissolved particles is _________ than the same fluid that contains only a few particles
more concentrated
what is the osmolarity of a fluid?
a measure of the number of particles per kg of water
Can sodium cross easily through cell membranes?
it can but not easily
what sets the tonicity of a fluid?
presence of particles that can not cross easily across cell membranes
what is tonicity?
the effective concentration of a fluid. A measure of how a solution affects the volume and pressure of a cell’s fluid
what is an isotonic fluid?
having equal osmotic pressure or concentration of water and solutes.
e.g. blood
what is a hypertonic solution?
a solution with a higher concentration of solutes than another solution, or than the inside of a cell. Water moves out of the cell into the hypertonic solution, causing the cell to shrink or shrivel
a solution that is more concentrated than blood
what is a hypotonic solution?
a solution that has a lower concentration of solute compared to the cell.
a solution that is more dilute than blood
what is fluid homeostasis?
the dynamic interplay of three processes:
1) fluid intake and absorption
2) fluid distribution
3) fluid output
what is fluid intake?
drinking and eating
what is fluid distribution?
the movement of fluid among its various compartments and between the intracellular and extracellular compartments
how does fluid distribution between intracellular and extracellular compartments occur?
by osmosis
how does fluid distribution between vascular and interstitial portions of the ECF occur?
by filtration
what are examples of fluid output?
urine and sweat
to maintain homeostasis, intake and output have to be…
equal to each other
how much is the average fluid intake via eating and drinking?
2300mL for healthy adults
describe thirst(2)
1) the conscious desire for water, regulates fluid intake when plasma osmolarity increases
2) thirst-control mechanism is located in the hypothalamus
what are osmoreceptors?
receptors that continuously monitor plasma osmolarity. when it increases, they cause thirst by stimulating neurons in the hypothalamus
osmoreceptors-mediated thirst
baroreceptor-mediated thirst
Changes in arterial blood pressure, sensed by arterial baroreceptors, influence drinking behavior. Decreases in ABP stimulate fluid intake, an effect that appears to be mediated entirely via arterial baroreceptor-evoked renin secretion with the resulting increase in blood levels of angiotensin II acting on the brain to stimulate drinking
Angiotensin II- and III-mediated thirst
refers to the physiological mechanism where the hormones angiotensin II and, to a lesser extent, angiotensin III, directly stimulate the sensation of thirst by acting on specific receptors in the brain, primarily within the subfornical organ (SFO), leading to an increased urge to drink water when the body detects low blood volume or dehydration
what is angiotensin II’s role in the thirst response?
binds to the hypothalmus in the brain, stimulating thirst
describe the relationship between hormones and the kidneys when it comes to fluid output
the kidneys respond to some hormones that influence urine production
which hormones influence urine production in the kidneys(3)?
1) antidiuretic hormone (ADH)
2) renin-angiotensin-aldosterone mechanism
3) atrial natriuretic peptides (ANPs)
what are the avenues of fluid output(4)?
1) kidneys
2) skin
3) lungs
4) GI tract
what is insensible fluid output?
fluid output that is not visible
1) skin (sweat)
2) lungs
what is sensible fluid output?
visible fluid output
1) kidneys
2) GI tract
how much fluid moves into the GI tract then returns to the ECF?
3 - 6 L
the average adults excretes how much fluid each day through feces?
100mL
what are S/Sx of clinical dehydration(2)?
1) ECV deficit
2) hypernatremia
what is another name for ADH?
vasopressin
- A patient is diaphoretic and has an oral temperature of 104° F. These are classic signs of:
A. ADH deficit.
B. extracellular fluid loss.
C. insensible water loss.
D. sensible water loss.
C
Fluid and Electrolytes for Nursing Students YouTube Videos
https://www.youtube.com/watch?v=7piicQkfauk
https://www.youtube.com/watch?v=Xdf7jutmSvg
what are normal sodium (Na+) lab values?
136-145mEq/L
what are normal potassium (K+) lab values?
3.5-5.0 mEq/L
what are normal chloride (Cl-) lab values?
98-106 mEq/L
what are normal total CO2 lab values?
22-30 mEq/L
what are normal bicarbonate (HCO3) lab values?
arterial: 21-28 mEq/L
venous: 24-30 mEq/L
what are normal total calcium (Ca2+) lab values?
9-10.5 mg/dL
what are normal **ionized calcium (Ca2+) lab values?
4.5-5.6 mg/d
what are normal magnesium (Mg2+) lab values?
1.3-2.1 mEq/L
what are normal phosphate lab values?
3.0-4.5 mEq/L
what are normal anion gap lab values?
6+/-4 mEq/L
what are the different types of ECF imbalances(2)?
1) volume
2) osmolarity
what are the types of osmolarity imbalances?
1) hypertonic (hypernatremia, water deficit)
2) hypotonic (hyponatremia, water excess)
what is clinical dehydration?
ECV deficit and hypernatremia combined
Acid-base balance & blood Gas Interpretation You tube video
https://www.youtube.com/watch?v=kh62SRovgrI
what are ABGs measure?
1) paCO2 (partial pressure of carbon dioxide)
2) HCO3 (concentration of the base bicarbonate)
3) PaO2 (partial pressure of oxygen)
4) SaO2 (oxygen saturation)
5) pH (acid/base)
describe PaCO2
partial pressure of carbon dioxide - a measure of how well the lungs are excreting CO2 produced by the cells
describe HCO3
bicarbonate - a measure of how well the kidneys are excreting metabolic acids
describe PaO2
partial pressure of oxygen - a measure of how well gas exchange is occurring the the alveoli
describe SaO2
oxygen saturation - percentage of hemoglobin that is carrying as much oxygen as possible
describe what deviations in normal PaCO2 readings mean
increased levels - indicates CO2 accumulation in the blood (more carbonic acid) caused by hypoventilation
decreased levels - indicate excessive CO2 excretion (less carbonic acid) through hyperventilation
describe what deviations in normal HCO3 readings mean
increased levels - indicates blood has too few metabolic acids
decreased levels - indicates that the blood has too many metabolic acids
describe what deviations in PaO2 readings mean
values below normal - indicates poor oxygenation of the blood
what is SaO2 influenced by?
pH, PaCO2, and body temperature
what is base excess?
observed buffering capacity minus the normal buffering capacity. its a measure of how well the blood buffers are managing metabolic acids
what are normal PaCO2 lab values?
35-45 mmHg
what are normal HCO3 lab values?
21-28 mEq/L
what are normal PaO2 lab values?
80-100 mmHg
what are normal SaO2 lab values?
95-100%
what are normal base excess lab values?
-2 - +2 mEq/L
describe what deviations in normal base excess readings mean
values below -2 mEq/L - indicate excessive metabolic acids
values above +2 mEq/L - indicate excessive amounts of bicarbonate (acid production)
What’s is normal blood pH
7.35 - 7.45
Values below 7.35 indicate abnormally acid; above 7.45 they indicate abnormally alkaline.
what is respiratory acidosis?
the lungs are unable to excrete enough CO2
what is respiratory alkalosis?
the lungs excrete too much carbonic acid
what is metabolic acidosis?
occurs from an increase of metabolic acid or a decrease in base (HCO3-)
what is metabolic alkalosis?
occurs from a direct increase of base (HCO3-) or a decrease in metabolic acid
what are some things that cause respiratory acidosis(3)?
1) COPD
2) respiratory failure
3) drug overdose
what are some things that cause respiratory alkalosis(4)?
1) hypoxemia
2) acute pain
3) anxiety
4) sobbing
what are some things that cause metabolic acidosis(3)?
1) ketoacidosis
2) circulatory shock
3) end stage renal disease
what are some things that cause metabolic alkalosis(3)?
1) excessive sodium bicarbonate
2) excessive vomiting
3) hypokalemia
infants and young children are at risk for which fluid, electrolyte, and acid-base imbalances and why?
ECV deficit and hypernatremia because body water loss is proportionally greater per kg of weight than older children and adults
An infant’s proportion of total body water (________% total body weight) is greater than that of children or adults.
70% to 80%
what is involved with a nursing history related to fluid, electrolyte, and acid-base balance?
age - very young and old at risk
environment - excessively hot?
dietary intake - fluids, salts, foods rich in potassium, calcium, and magnesium
lifestyle - alcohol intake history
medications - OTC, Herbals, Prescriptions
what age group frequently responds to illnesses with fevers of higher temps and longer duration?
children 2-12YO
what kind of water loss does fever increase the rate of?
insensible water loss
describe adolescent fluid balance
1) increased metabolism and increased water production due to rapid growth changes
2) fluctuations in fluid balance greater in adolescent girls due to hormonal changes associated with the menstrual cycle
what can excessive sweating lead to?
without replacement of salt and water it can lead to:
1) EVC deficit
2) hypernatremia
3) clinical dehydration
starvation diets and those with high fat and no carbs can lead to…
metabolic acidosis
what can chronic alcohol consumption do to your electrolytes?
it can cause hypomagnesemia due to excessive renal magnesium excretion
what items are looked at in medical history related to fluid, electrolyte, and acid-base balance(4)?
1) recent surgery (physiological stress)
2) GI output
3) acute illness or trauma
4) chronic illness
what type of acute illness can be related to fluid, electrolyte, and acid-base balance(4)?
1) respiratory disorders
2) burns
3) trauma
4) GI issues
5) acute oliguric renal disease
what kinds of chronic illness can be related to fluid, electrolyte, and acid-base balance?
1) cancer
2) heart failure
3) oliguric renal disease
what can happen to a patient’s ECV between the second to fifth postop day?
increased aldosterone, glucocorticoids, and ADH can cause increased ECV
head injuries typically alters antidiuretic hormone ADH secretion. what does that do to someone?
scenario #1 - can cause diabetes insipidus (ADH deficit) which causes excessive dilute urine output which leads to hypernatremia
scenario #2 - can cause excessive release of ADH which causes retention of of urine and hyponatremia
what occurs to a patient’s fluid and electrolyte balance when they experience hemorrhage(2)?
- ECV deficit and blood loss
- severe trauma such as crush injuries can cause hyperkalemia due to cell destruction causing the release of K+ into the blood
what can cancer do to fluid and electrolyte balance(3)?
1) hypercalcemia
2) metabolic and endocrine abnormalities
3) at risk for fluid and electrolyte imbalances due to side effects of chemotherapy, biological response modifiers, or radiation
what happens to fluid and electrolyte balance in chronic heart failure?
1) diminished CO activates RAAS
2) aldosterone action on the kidneys causes excessive ECV and hypokalemia
3) diuretics used to treat HF increases risk of hypokalemia
what is oliguria?
reduced unrination
what does chronic nephritis do to urination?
causes sudden onset of oliguria
what does chronic kidney disease do to urination?
leads to chronic oliguria
what does oliguric renal disease(5 S/Sx)?
prevents normal excretion of fluid, electrolytes, and metabolic acids, resulting in:
1) excess ECV
2) hyperkalemia
3) hypermagnesemia
4) hyperphosphatemia
5) metabolic acidosis
each kg (2.2 lb) lost or gained overnight is equal to how much fluid?
1L of fluid retained or lost
intake includes:
all liquids eaten, drunk, received through IV
output includes:
urine, diarrhea, vomit, gastric suction, wound drainage
how should you weight a patient when assessing for fluid retention or loss?
use same scale every day at the same time (preferably in morning) after pt voids
A senior student nurse delegates the task of intake and output to a new nursing assistant. The student will verify that the nursing assistant understands the task of I&O when the nursing assistant states,
A. “I will record the amount of all voided urine.”
B. “I will not count liquid stools as output.”
C. “I will not record a café mocha as intake.”
D. “I will notate perspiration and record it as a small or large amount.”
A
can I&O be delegated to NAPs?
after they are stable, yes
what are health promotion activities associated with fluid and electrolyte balance?
- Fluid replacement education
- Teach patients with chronic conditions about risk factors and signs and symptoms of imbalances.
what are some interventions related to electrolyte imbalances?
1) support prescribed medical therapies
2) aim to reverse existing acid-base imbalance
3) provide patient safety
what are interventions related to acid-base imbalances
regular arterial blood gas analysis
what are some restorative care implementations related to fluid and electrolyte balance(3)?
1) Home IV therapy
2) Nutrition support
3) medication safety
