Fluid Balance Flashcards
ICF
intracellular fluid, 2/3 of total body water (~60%)
ECF
extracellular fluid, 1/3 of total body water (~40%)
plasma volume
intravascular fluid, 1/4 of ECT (1/12 of total body water)
interstitial fluid
separated from plasma by capillary wall (3/12 of total body water)
ADH function
stimulates water conservation in nephron, secreted by hypothalamus to cause thirst and retain H2O.
third spacing
movement of ECT into space between skin and fascia, fluid is unavailable for use or exchange w/ intravascular fluid. different from acites; associated w/ burns and pancreatitis.
osmosis
net movement of water or other solvent to an area of higher solute concentration
osmolarity
concentration of a solution (number of particles/liter)
tonicity
relative concentration of two solutions, that determines the direction of diffusion
isotonic
two solutions separated by a membrane have the same concentration
hypertonic
solution that has a higher solute concentration than the solution on the opposite side of a membrane
hypotonic
solution that has a lower solute concentration than the solution on the opposite side of a membrane
what is the primary ion present in ECF?
Na+
what is the primary ion present in the ICF?
K+
what is the main determinant of osmolality in the body?
[Na+]
what 4 factors change in parallel to help maintain a somewhat constant volume in the body?
- ECF volume
- vascular volume
- arterial BP
- cardiac output
what factors regulate Na+?
- SNS (stretch receptors)
- renal (JG apparatus)
- CV control (ANP: atrial natriuretic peptide)
function of Na+
determines osmolality of ECF
what factors regulate K+?
- plasma [K]
- aldosterone
- nephron tubular flow rates
- distal nephron tubular [Na]
- acidosis/alkalosis
function of K+
critical for cell cycle, cell membrane exciteability
function of Ca2+
intracellular ion, 99% stored in bone, involved in cell cycle, membrane excitability, bone formation, coagulation
what factors regulate Ca2+?
regulated in the kidney, GI tract, and bone
- parathyroid hormone
- calcitriol (activated vit D)
- calcitonin
function of H+
very low concentration in body, determines pH
what factors regulate H+?
regulated by the kidneys and lungs
- intracellular pH
- aldosterone
- [K+]
function of bicarbonate
predominant buffer system in body
what structures help regulate bicarbonate?
regulated by kidneys and lungs
where is bicarbonate resorbed in the nephron?
very efficiently reabsorbed in the proximal tubule (not via direct absorption of HCO3-)
what factors regulate Cl-?
coupled w/ Na+absorption in the nephron, passively follows Na+ to keep electrolyte balance
function of phosphate
component in many organic molecules (ATP, DNA, RNA etc.); imporatnat urinary and bone buffer
what factors and structures regulate phosphate?
- PTH
- calcitriol (via GI tract)
- kidneys
4 .bone
what is the main challenge to diagnosing patients with fluid/electrolyte disorders?
symptoms are often very nonspecific
what happens to the cells if a patient is hyponatremic?
cells swell, this can be very dangerous for the brain
what is the treatment for a patient w/ hypervolumic hyponatremia?
diuretics, fluid restriction
what is the treatment for a patient w/ hypovolumic hyponatremia?
saline
what is the treatment for a patient w/ euvolumic hyponatremia?
fluid restriction, in some cases, saline plus loop diuretics
what happens to the cells if a patient is hypernatremic?
cells shrink, this can be very dangerous for the brain
what is the treatment for a patient w/ hyperkalemia?
- CaGluconate IV to stabilize cardiac arrhythmia
- shift K+ into cells (insulin/glucose, beta agonist-albuterol, bicarbonate)
- K+ excretion in urine (diuretics or dialysis if in renal failure)
- K+ excretion in stool (kayexelate)
what is the treatment for a patient w/ hypokalemia?
oral or IV K+
what is the treatment for a patient w/ hypocalcemia?
depends on severity and acuity, give Ca2+ IV for acute and symptomatic hypocalcemia
what are the clinical presentations of a patient w/ hypocalcemia?
tetany, muscle spasms/cramps, seizures, arrhythima, hypotension, bradycardia
what diagnostics tests would you use to diagnose hypocalcemia?
- Mg
- PTH
- Vit D
- Phos level
what are the clinical presentations of a patient w/ hypercalcemia?
“stones, groans, psychiatric overtones”
- HTN
- GI symptoms
- mental status changes
- polyuria
what diagnostic tests would you use to diagnose hypercalcemia?
- PTH
- Phos level
- vit D
what is the treatment for a patient w/ hypercalcemia?
- increase urinary excretion of Ca (loop diuretic/saline)
2. consider dialysis if in renal failure
what are the clinical presentations of a patient w/ hyponatremia?
fatigue, impaired concentration, anorexia, N/V, seizures, coma and death
what diagnostic tests would you use to diagnose hyponatremia?
- urine Na+
- serum osmolality
- urine osmolality
- Hx and physical
- basic chemistry
what are the clinical presentations of a patient w/ hypernatremia?
fatigue, thirst, impaired concentration, anorexia, N/V, seizures, coma and death
what diagnostic tests would you use to diagnose hypernatremia?
- urine osmolality
- serum osmolality
- urine Na+
what are the clinical presentations of a patient w/ hypokalemia?
paresthesias, muscle cramps, weakness, ileus, cardiac arrhythmia, abnormal EKG (flat T waves, ST depression)
what diagnostic tests would you use to diagnose hypokalemia?
- Hx and physical
- FeK
- chemistries
what are the clinical presentations of a patient w/ hyperkalemia?
paresthesias, muscle weakness, cardiac arrest, abnormal EKG (peaked T waves, PR prolongation, QRS widening)
what diagnostic tests would you use to diagnose hyperkalemia?
- Hx and physical
- chemistries
- urine K+ excretion
what are the clinical presentations of a patient w/ hypophosphatemia?
myalgials, weakness, rhabdomyolysis, MS changes
what are the clinical presentations of a patient w/ hyperphosphatemia?
hypocalceima, tetany, metastatic soft tissue calcificatnion and secondary hyperPTH
how would you treat a patient w/ hypophosphatemia?
repleting
what are the clinical presentations of a patient w/ hypomagnesemia?
myoclonus, neurologic symptoms, EKG abnormalities (flat T waves, prolonged PR/QT/QRS), hypocalcemia, and hypokalemia
what diagnostic tests would you use to diagnose hypomagnesemia?
- Hx and physical
2. full chemistry panel
what is the treatment for a patient w/ hypomagnesemia?
- oral for mild to moderal deficiency
2. IV magnesium for severe deficiency
