Fluid and Electrolyte Disturbance (Na, K) Flashcards
What are the major EC and IC molecules?
Extracellular:
- Na+
- Cl-
Intracellular:
- Proteins
- K+
What is the overarching causes of extracellular edema?
- Increased capillary hydrostatic pressure
- decreased plasma proteins
- increase capillary permeability
- Blocked lymph return
What are the common causes of increased capillary hydrostatic pressure?
- Excess kidney retention of salt and water
- high venous pressure
- decreased arteriolar resistance
What causes decreased plasma proteins (leading to extracellular edema)?
- Loss of protein in urine (nephrotic syndrome)
- loss of protein from skin (burns, wounds)
- failure to produce proteins (liver disease, malnutrition)
What causes blockage of lymph return?
- Infections (filarial, nematodes)
- Cancer
What factors work to prevent extracellular edema?
- Interstitium has low compliance (doesn’t expand easily)
- lymphatic flow can increase 10-50 fold
- protein wash out happens quickly in interstitium making retaining water in the interstitium harder
What are the two main causes of intracellular edema?
- depression of metabolic systems of tissues
- lack of adequate nutrition to the cells
too little EC Na+ or too much water are other factors
What in the body measures sodium content?
stretch receptors that sense effective vascular volume
What are two clinical causes that lead to hypoosmolality and cellular swelling?
- SIADH - impaired ability to excrete water
- Minearalocorticoid deficiency - impaired ability to keep Na+
Differentiate a -natremia problem from a -volemia problem
- natremia
- Concerned with Na+ concentration, but the problem is how much water is present
- volemia
- problem with Na+ content
Delivery of solute to the juxtaglomerular apparatus is sense by the ________ __________
Macula densa
What are the three sodium transporters found in the proximal tubule on the apical membrane (between the cell and lumen)?
- Na+/H+ exchanger
- Na+ w/: aa, organic solute, or glucose cotransporter
- Cl-/anion exchange
what are the major regulatory hormones of the proximal tubule?
- Angiotensin II
- Epinephrine
- Norepinephrine
What are the major regulatory hormones of the late distal tubule and collecting duct?
- Aldosterone
- Atrial Natriuretic Peptide
Explain what happens in response to an increase in effective circulating volume
Decrease in Sympathetic input:
- Increase GFR
- increase ANP (heart)
- decrease ADH (brain)
- Less: Renin, angiotensin II, aldosterone
Describe why your body might have a lowered effective circulating volume, but have a high total body sodium?
in CHF the brain sense it’s not getting enough blood so it stimulates retention of sodium. However, the problem lies in the mechanical inability of the heart not the volume within the vasculature.
Other Conditions:
- cirrhosis (extrarenal cause)
- severe nephrotic syndrome (renal cause)
What is Conn syndrome?
same thing as primary hyperaldosteronism
Define the values associated with hypernatremia and hyponatremia
Hypernatremia: plasma [Na+] > 145 mEq/L
Hyponatremia: plasma [Na+] < 135 mEq/L
Again, because we’re talking about concentration this is a water problem, concentration heavily determined by water volume present
What’s normal blood osmolality?
285 - 295 mOsm/kg
Quick formula: 2 x [Na+]plasma
What is the two major stimulators for ADH release from the posterior pituitary?
- High plasma osmolality
- Lowered blood volume/pressure
Increased thirst is correlated with…
- increased osmolarity
- decreased BV/BP
- increased angiotensin II
- dryness of mouth
What kind of hyponatremia is caused by SIADH?
euvolemic hyponatremia
What are the hyponatremic symptoms
Stupor/coma
Anorexia, nausea, vomiting
Lethargy
Tendon reflexes decreased
Limp muscles (weakness)
Orthostatic hypotension
Seizures/headache
Stomach cramping
How would you treat a patient with moderate symptoms of hyponatremia Such as nausea, confusion, disorientation, and altered mental status?
level 2
- Vaptans (aquaretics) or hypertonic NaCl
- Fluid restriction
How would you treat a patient with severe symptoms of hyponatremia such as vomiting, seizures, obtundation, respiratory distress, and coma?
Level 3
- Hypertonic NaCl
- Fluid restriction or vaptan (aquaretic)
What must you be cautious when correcting chronic hyponatremia?
Too rapid of a correction of hyponatremia can result in osmotic demyelination syndrome (locked-in syndrome)
Classic tumor producing vasopressin ectopically causing SIADH?
Oat-cell carcinoma
Where is hypernatremia commonly seen?
- nursing home neglect
- traveling in the desert w/o enough water (southwest US)
- individuals living at home alone who fall
What are causes of hypervolemic hypernatremia?
- Primary hyperaldosteronism
- cushing syndrome
What are the symptoms of hypernatremia?
Twitching, tremors, hyperreflexia
Restlessness, irritable, confusion (due to brain cell shrinkage)
Intense thirst, dry mouth, decreased urine output
Pulmonary and peripheral edema
What things cause potassium to enter a cell?
- Insulin
- aldosterone deficiency
- alkalosis
- β2-agonist (Epi)
What is the major stimulus for aldosterone secretion?
hyperkalemia
What is a major cause of hyperkalemia?
pseudohyperkalemia due to lysed RBCs while taking a blood sample
What are the signs and symptoms associated with hypokalemia?
Neuromuscular (most prominent manifestation)
- Skeletal muscle weakness
- smooth muscle weakness (ileus, constipation)
Cardiovascular
- Ventricular arrhythmias
- hypotension
- cardiac arrest
Renal (impaired concentrating ability)
- Polyuria and nocturia
Metabolic —> hyperglycemia
What are the main causes of metabolic alkalosis due to hypokalemia?
- Vomiting
- bartter syndrome (pt has a normal BP)
- hyperaldosteronism (pt has high BP)
- mineralcorticoid excess (pt has high BP) - licorice
What are the main signs/symptoms of Hyperkalemia?
Cardiac:
- Tall T waves
- Bradycardia
Neuromuscular:
- Numberless, weakness
- flaccid paralysis
What are medications that can cause hyperkalemia?
ACEI and ARBs
How do we treat Hyperkalemia?
- IV calcium (counteracts cardiac symptoms)
redistribute K+ into cells:
- Insulin and glucose (best)
- albuerol (also works)
Facilitate K+ elimination:
- K+ losing diuretic
- dialysis
- cation exchange resin
what parameters define hypokalemia and hyperkalemia?
Hypokalemia: < 3.5 mEq/L
Hyperkalemia: > 5.5 mEq/L
