Fluid & Electrolytes Flashcards
Extracellular fluid compatments
interstitial fluid
blood
lymph
Intracellular fluid compartment
cytosol
osmolality
solute concentration of fluid # of particles per kg of water
Fluid characteristics
volume
osmolality
Important electrolytes
sodium
potassium
magnesium
calcium
Primary site of calcium absorption
duodenum
Physiological processes regulating F/E
intake & absorption
distribution
output
Intake & absorption
process where fluids/electrolytes are physically brought into the body & enter the bloodstream
Distribution
process where fluid/electrolytes move between fluid comparments
Output
physical removal of F/E from the body
Na+ levels
135-145 meq/L
K+ levels
- 5-5.0 meq/L
* most K+ stored intracellularly
Factors stimulating thirst
Angiotensin II
Dry oral mucous membranes
Arterial baroreceptors (hypovolemia)
Fluid osmolality
Na+ fluid compartment
mainly located in the ECF
K+ fluid compartment
98% of total body potassium stored intracellularly
Ca++ compartment
bone
Mg++ compartment
cells & bones
Normal excretory routes
kidneys
lungs
skin
GI tract
Abnormal excretory routes
emesis
hemorrhage
drainage through tubes or fistulas
clinical interventions
3 Main causes of F/E imbalances
output > intake/absorption
intake/absorption > output
altered distribution
Major electrolytes in ECF
sodium
bicarbonate
chloride
Stimuli triggering thrist
osmoreceptors detecting change in serum osmolality
baroreceptors detecting change in effective circulating volume
ATII –> production of nonosmotic thirst
Factors decreasing GFR
SNS activation
Angiotensin II
Factors decreasing ADH rls
alcohol
Fluid compartments
ICF
ECF
Third space
Circulatory overload
caused by increase in blood volume
Causes of circulatory overlaod
increased Na+ retention
infusion of IV fluids
excessive blood transfusion
Effects of HF on F/E volume
decreased effective circulatory volume
decreased renal blood flow
compensatory Na+/H2O retention
Which organ metabolizes aldosterone
Liver
Liver Failure & F/E balance
decreased aldosterone metabolism
decreased effective circulating volume
decreased renal perfusion
Electrolyte definition
particles that dissociate into cations and anions in a solution
Cation
positive ion
Anion
negative ion
Acute onset hyponatremia
<48 hours
Osmotic demyelination syndrome
syndrome that occurs d/t rapid correction of hyponatremia in the brain
results in destruction of myelin of axons crossing the brainstem –> severe neurological injury & death
Types of Hyponatremia
Hypertonic hyponatremia
Hypovolemic hypotonic hyponatremia
Euvolemic hyponatremia
Hypervolemic hypotonic hyponatremia
3 types of dehydration
isotonic
hypertonic
hypotonic
Hypertonic dehydration
water loss exceeds sodium loss –> hypernatremia
causes water to move from ICF –> ECF shrinking cells
Hypotonic dehydration
sodium loss exceeds water loss –> hyponatremia
causes water to move from ECF –> ICF causing cells to swell
At risk populations for dehydration
older adults (diminished thirst response) neonates
Third space compartment
fluid compartment that is not considered ICF or ECF
non-functional (ex: joints, serous membranes)
increase in third space is considered abnormal and takes away fluid volume for normal physiologic processes
S/S of dehydration
early: thirst response decreased urine output , dark urine decreased sweating headache, fatigue dry mucous membranes decreased skin turgor
late: confusion headache, dizziness, light-headedness hypotension, tachycardia, tachypnea, fever muscle cramps (ischemic injury)
rare:
hypovolemic shock
seizure
unconsciousness, death
Causes of dehydration
medication (esp diuretics)
inadequate intake
excessive output (diarrhea, vomiting)
decreased blood colloid oncotic pressure (inadequate albumin production)
decreased blood osmolarity (hyponatremia)
Older Adult Risk Factors
decreased muscle mass (muscle holds water)
diminished thirst response
dysphagia/swallowing difficulties
inadequate food intake
increased output d/t chronic conditions (diabetes)
cognitive deficits
fear of incontinence
Dehydration treatment
increased oral intake IV fluids (rehydrate & replace lost electrolytes) treat underlying condition
Insensible water loss
water evaporation from skin (not consciously perceived)
increased with fever
Primary sources of water loss
sweating
urination
excretion
abnormal: vomiting, diarrhea, hemorrhage
Normal serum osmolality
285-295 mOsm/kg
Crystalloid
a solution with particles small enough to pass through cell membranes
ex: NaCl infusion
Colloids
a solution where the particles are too large to pass through the cell membrane
ex: albumin infusion
Risk of output > intake
increased osmolality (hypernatremia) fluid volume deficit (dehydration hypokalemia
Risk of intake > output
edema (dependent, pulmonary)
increase in the third space compartment
decreased osmolality (hyponatremia)
hyperkalemia
Osmotic Demyelination syndrome
rapid Na+ resuscitation can cause demyelination in the CNS
this is b/c neurons adapt to electrolyte imbalances by changing concentration of intracellular osmolytes to prevent fluid shift. this process takes time to correct which is why rapid infusion can damage neurons
Hypernatremia
> 145 mEq/L
occurs when water loss > intake
S/S of Hypernatremia
thirst neurologic symptoms d/t loss of water from brain cells confusion neuromuscular excitability seizures coma
Normal daily urine output
1-2 L
Osmotic pressure
amount of hydrostatic pressure needed to stop osmotic movement into an area. determined by solute concentration
Oncotic pressure
osmotic pressure exerted by proteins (albumin)
Osmotic diuresis
increase in urine output d/t increased excretion of solutes (draws water with it)
Serum osmolality solutes
sodium, BUN, glucose
Urine osmolality solutes
urea, creatinine, uric acid
Normal serum osmolality
275-300 mmol/L
Normal urine osmolality
250-900 mmol/L
Normal urine specific gravity
1.010-1.025
Urine Specific Gravity
a functional kidney test
measures kidney’s ability to reabsorb water –> concentrate water
decreased urine specific gravity –> decreased water reabsorption (increased risk of dehydration)
Normal BUN levels
3.6-7.2 mmol/L
Factors increasing BUN
decreased renal function GI bleeding dehydration increased protein intake fever sepsis
Factors decreasing BUN
end-stage liver disease
low-protein diet
starvation
fluid excess
Normal serum creatinine
60-130 mmol/L
used to indirectly measure GFR
Hematocrit
total volume percentage of RBC in whole blood
Normal hematocrit
men: 0.440-0.520
women: 0.397-0.470
Factors increasing hematocrit
dehydration
polycythemia
Factors decreasing hematocrit
anemia
overhydration
Hypotonic dehydration
loss of water with reduced osmolality of blood plasma
caused by excess loss of body fluids replaced with hypotonic fluids
causes a shift from the ECF –> ICF (cellular swelling)
Hypertonic dehydration
loss of water assoc with increased osmolality of body plasma
caused by excessive loss of body fluids (sweating, tachypnea, emesis)
causes a shift from ICF –> ECF (cellular dehydration)
Isotonic dehydration
solutes and water are lost in equal concentrations
causes a loss of blood plasma (hypovolemia) but does not cause a fluid shift between ICF & ECF
How rapidly should sodium be increased
1 mEq/L/kg
NICE Fluid Assessment
HR, BP, Cap refill, central venous pressure
peripheral edema
orthostatic hypotension
Normal BUN
3.6-7.2
Normal Creatinine
50-110
S/S of Circulatory overload
tachycardia, increased BP venous distension increased central venous pressure edema SOB, cough
