Renal CN Flashcards
Polyuria
>2.5 L urine/day Causes: - diabetes mellitus - diabetes insipidus - excess caffeine or alcohol - kidney disease - certain drugs such as diuretics - sickle cell anemia -excessive water intake
usually associated with polydipsia (increased thirst)
four mechanisms of cause:
- increased intake of fluids as in psychogenic causes, stress, and anxiety
- increased GFR as in hyperthyroidism, fever, hypermetabolic states
- increased output of solutes as occurs in DM, hyperthyroidism, use of diuretics (present more solute at the DCT)
- inability of kidney to reabsorb water in DCT as in CDI, NDI, drugs, and chronic renal failure
Oliguria
Output below the minimum volume (300-500 mL/day) Causes: -dehydration - blood loss - diarrhea - cardiogenic shock - kidney disease - enlarged prostate
Anuria
virtual absence of urine production (< 50 mL/day)
Causes:
- kidney failure
-obstruction: such as kidney stone or tumor
- enlarged prostate
Water diuresis
increased water excretion without corresponding increase in salt excretion
-primary cause: increased water intake, polydipsia, diabetes insipidus
Solute (osmotic) diuresis
increased water excretion with a concurrent increase in salt excretion
- Primary cause: significant increase in the salt present in the tubular fluid
- -> i.v. NaCl
- -> hyperglycemia
- -> high protein intake
- -> recovery from Acute Kidney Injury (AKI)
Edema
Causes
1. Alteration in capillary hemodynamics (altered Staling Forces with increased net filtration pressure)- fluid moves from vascular space into interstitium
- edema not palpable until ISV increased by 2.5-3.0 L. Normal plasma volume is 3L
- edema fluid is not derived only from plasma
- compensatory renal retention of Na+ and H2O to maintain plasma volume in response to under filling of vasculature must occur in this situation to cause edema
Ex: congestive heart failure
- Renal retention of dietary Na+ and H2O expansion of ECF volume
- inappropriate renal fluid retention
- usually results in elevated blood pressure, expanded plasma and ISV
- E.g. primary renal disease ( glomerulonephritis, nephrotic syndrome)
—non-pitting edema- swollen cells due to increased ICF volume
— pitting-edema - increased ISV
— edema often treated with diuretics
Dextrose 5% in water (D5W)
-Isotonic Uses: - fluid loss - dehydration -hypernatraemia
Gets into the intracellular space mostly then interstitial and lymphatic and least into the plasma volume
0.9% Sodium Chloride
Isotonic Uses - Shock - Hyponatraemia - blood transfusion - resuscitation - fluid challenges -DKA
Gets into the interstitial and laymphatic spaces mostly and plasma minorly
Lactated Ringer’s (Hartmanns)
Isotonic Uses - dehydration - burns - Lower GI fluid loss - Acute fluid loss - hypovolemia due to third spacing
Dehydration
- occurs due to decreased water intake, increased fluid loss, or both
- elderly people: impaired thirst sensation, chronic illness, fever and sickness are common reasons for decreased water intake
- increased fluid loss: from vomiting, diarrhea, diuresis and sweating
- working in hot water without replacement
- can either be hypernatremic or hyponatremic
Hyponatremic (hypotonic) Dehydration
- loss of sodium is greater than the loss of water in ECF
- serum sodium conc. In the ICF is greater than that of the ECF
- Water shifts from ECF to ICF to establish osmotic equilibrium causing cells to swell and hypovolemia
- Serum sodium and osmolality will be les than the normal range (130-135 mEq/L)
- increased ICF causes edema, brain cell swelling, irritability, depression, confusion, weakness, muscle crams, anorexia, nausea, and diarrhea
- pure sodium deficits cause hypotension, tachycardia, and decreased urine output
Hypernatremic (Hypertonic) Dehydration
- loss of water is greater than the loss of sodium in ECF
- serum sodium concentration in the ECF is greater than the ICF, water shifts from the ICF to the ECF
- serum osmolarity will exceed 300 mOsm/kg
- serum sodium will be more than 150 mEq/L
- causing intracellular dehydration including shrinkage of brain cells
- excess extracellular fluid causes edema and increased BP
- high Sodium level causes muscular weakness and hyperactive reflexes
- decreased ICF causes thirst, decreased urine output, confusion, and ultimately coma
Isosmotic volume contraction
- Acute fluid loss conditions like hemorrhage, diarrhea and vomiting
- diarrhea causes loss of isosmotic fluid from the GI tract
- decrease in ECF volume and no change in body osmolality and ICF volume
Hyperosmotic Volume Contraction
- Hypotonic fluid loss conditions like dehydration, diabetes insipidus, and alcoholism
- insensible water loss from ECF, solute is left behind and becomes concentrated
- decrease in ECF volume and ICF volume, but an increase in body osmolarity
Hyposmotic volume contraction
- ICF volume increases, ECF volume decreases, osmolarity decreases
- adrenal insufficiency due to loss of aldosterone leading to excessive loss of NaCl in urine
- transient response: ECF osmolarity decreases and fluid shifts to ICF until osmolarity equilibrates
