Renal FUNDAMENTALS SEM 3
osmolality - correct answer ratio of plasma solutes and plasma water, plasma solutes mostly
are Na+
osmolarity vs osmolality - correct answer mOsm/L vs mOsm/kg
tonicity - correct answer effective plasma osmolality, ie effect on volume of a cell related to
osmolality, taking into consideration the ability of a solute to cross the cell membrane -- can
have iso-osmolality without isotonicity
hypervolemia - correct answer excess of total body Na+ and water --> expansion of
extracellular compartment
hypovolemia / volume depletion - correct answer decreased intravascular volume from loss of
salt and water or decrease in blood volume
dehydration - correct answer reduction of total body of water to below normal without
proportional Na+ and K+ reduction leads to rise in plasma Na+
maintenance fluid - correct answer given to replace ongoing loss of water sometimes with
electrolytes out in urine, sweat, stool, respiration
replacement fluid - correct answer given to correct deficits of water sometimes with
electrolytes lost in urine, sweat, stool, hemorrhage, third space sequestration
hyponatremia - correct answer serum sodium concentration caused by excess water relative to
sodium, Na+ <135 mEq/L
What is the most common electrolyte abnormality in hospitalized patients? - correct answer
hyponatremia
Chronic hyponatremia vs acute hyponatremia? - correct answer ≥48 hrs vs <48 hrs
Acute decrease in external osmolality causes brain cells to ___________ - correct answer swell
mild hyponatremia (130-134 mEq/L) - correct answer attention deficit, gait disturbances,
fatigue, slight subtle neurocognitive deficits
moderate hyponatremia (120-129 mEq/L) - correct answer nausea, confusion, lethargy,
headache, vomiting
severe hyponatremia (<120 mEq/L) - correct answer delirium, impaired consciousness, seizures
What happens to brain cells over time with hyponatremia? - correct answer They extrude
electrolytes and organic osmolytes in response to acute swelling
,hypovolemic hyponatremia - correct answer true volume depletion
hypervolemic hyponatremia - correct answer increased total body (plasma + extracellular
volume), but volume sensors sense low intravascular volume
major causes of hyponatremia - hypovolemia - correct answer vomiting, diarrhea, diuretics
major causes of hyponatremia - hypervolemia - correct answer heart failure, liver disease with
cirrhosis
major causes of hyponatremia - euvolemia - correct answer syndrome of inappropriate ADH
secretion (SIADH), thiazide diuretics
common causes of SIADH - correct answer SSRIs, pulmonary infections, CNS pathology, nausea,
pain, stress commonly after surgery
Thiazide induced hyponatremia tends to occur in what patient population group? - correct
answer Older females with low muscle mass
Evaluate urine osmolality step 1 - correct answer <100 mOsmol/kg is low and appropriate, if
>150, is high and insufficiently dilute
Evaluate urine sodium levels step 2 - correct answer <15 meq/L is low, seen in true or effective
volume depletion like HF, cirrhosis, if >40 meq/L, is not low, seen with diuretics, advanced
kidney disease, euvolemia causes like SIADH
How to treat hyponatremia? - correct answer if true hypovolemia only cause, give isotonic fluid
alone, otherwise, implement water restriction +/- salt tablets, if symptomatic or severe give
hypertonic saline
How to treat chronic hyponatremia? - correct answer goal to change 4-6 mEq/L over 24 hrs, do
not exceed 8 mEq/L because if you increase the sodium too fast ECF becomes hypertonic and
the water will rush out of the brain cells too quickly
osmotic demyelination syndrome - correct answer neurological manifestation associated with
overly rapid correction of hyponatremia, clinical manifestations typically are delayed 2-6 days
Clinical presentation of osmotic demyelination syndrome - correct answer
paraparesis/quadriparesis, seizures, lethargy, confusion, disorientation, obtundation, coma,
dysarthria, dysphagia, behavioral disturbances, movement disorders
risk factors for osmotic demyelination syndrome - correct answer chronic hyponatremia <110
mEq/L, alcoholism, hepatic failure, liver transplant, K+ depletion, malnutrition,
If patient has osteoporosis or falls or hip fractures, what differential diagnosis can you
consider? - correct answer Hyponatremia, especially with older patients, associated with bone
fractures
, hypernatremia - correct answer Na+ >145 mEq/L. water deficit relative to body Na+ and K+
common causes of hypernatremia - correct answer excess water or hypotonic fluid loss
common with young children, elderly in long term care facilities, critically ill, renal issues
(diuretics, osmotic diuresis), GI (diarrhea, vomiting), skin (sweating, burns), excess hypertonic
fluids (IV, TPN), decreased thirst, acute hypernatremia is uncommon
symptoms of hypernatremia - correct answer thirst, weakness, confusion, diminished
consciousness, seizures, coma, tachycardia, dry mucous membranes, poor tissue turgor,
oliguria, polyuria, urinalysis, urine osmolality, urine Na often <20
potassium importance - correct answer 2nd most abundant cation in body, controls cell resting
potential, essential for impulse transmission and muscle contraction etc,
What is the major route of K+ elimination? - correct answer kidneys, mostly out via urine,
controlled by aldosterone activity on principal cells of renal cortical collecting duct, controlled
by distal delivery of Na+ and water
hypokalemia - correct answer serum potassium <3.5 mEq/L
common causes of hypokalemia - correct answer increased losses (vomiting, diarrhea, diuretics,
hyperaldosteronism), inadequate intake, redistribution into cells (like elevated extracellular pH,
meds) insulin
signs and symptoms of hypokalemia - correct answer fatigue, weakness, decreased muscle
tone, cardiac arrhythmias, eKG will have U waves after the T wave, look at V4-V6
Check the urine potassium-- if potassium isn't being wasted in the urine what range would this
fall in? - correct answer 20-30 mEq/L
hypokalemia treatment - correct answer If mild (2.5-3.5) oral replacement, if severe (<2.5) IV
replacement, must also replace magnesium if low or pt will remain hypokalemic
hyperkalemia - correct answer serum K+ >5.2 mEq/L, risk inversely proportional to eGFR,
prevalent in CKD
major risk factors of hyperkalemia - correct answer CKD stage III and beyond; ability to maintain
K+ balance preserved until >50% kidney function lost; diabetes mellitus, HF, agents blocking
RAAS
pseudohyperkalemia - correct answer K+ movement out of cells during or after blood drawn,
will high serum K+, normal plasma K+, see hemolysis, high platelet count (thrombocytosis),
occurs if fist clenching too much or too tight tourniquet
reverse pseudohyperkalemia - correct answer plasma K+ > serum K+, high white blood cell
count, occurs in chronic lymphocytic leukemia from fragility of luekocytes
osmolality - correct answer ratio of plasma solutes and plasma water, plasma solutes mostly
are Na+
osmolarity vs osmolality - correct answer mOsm/L vs mOsm/kg
tonicity - correct answer effective plasma osmolality, ie effect on volume of a cell related to
osmolality, taking into consideration the ability of a solute to cross the cell membrane -- can
have iso-osmolality without isotonicity
hypervolemia - correct answer excess of total body Na+ and water --> expansion of
extracellular compartment
hypovolemia / volume depletion - correct answer decreased intravascular volume from loss of
salt and water or decrease in blood volume
dehydration - correct answer reduction of total body of water to below normal without
proportional Na+ and K+ reduction leads to rise in plasma Na+
maintenance fluid - correct answer given to replace ongoing loss of water sometimes with
electrolytes out in urine, sweat, stool, respiration
replacement fluid - correct answer given to correct deficits of water sometimes with
electrolytes lost in urine, sweat, stool, hemorrhage, third space sequestration
hyponatremia - correct answer serum sodium concentration caused by excess water relative to
sodium, Na+ <135 mEq/L
What is the most common electrolyte abnormality in hospitalized patients? - correct answer
hyponatremia
Chronic hyponatremia vs acute hyponatremia? - correct answer ≥48 hrs vs <48 hrs
Acute decrease in external osmolality causes brain cells to ___________ - correct answer swell
mild hyponatremia (130-134 mEq/L) - correct answer attention deficit, gait disturbances,
fatigue, slight subtle neurocognitive deficits
moderate hyponatremia (120-129 mEq/L) - correct answer nausea, confusion, lethargy,
headache, vomiting
severe hyponatremia (<120 mEq/L) - correct answer delirium, impaired consciousness, seizures
What happens to brain cells over time with hyponatremia? - correct answer They extrude
electrolytes and organic osmolytes in response to acute swelling
,hypovolemic hyponatremia - correct answer true volume depletion
hypervolemic hyponatremia - correct answer increased total body (plasma + extracellular
volume), but volume sensors sense low intravascular volume
major causes of hyponatremia - hypovolemia - correct answer vomiting, diarrhea, diuretics
major causes of hyponatremia - hypervolemia - correct answer heart failure, liver disease with
cirrhosis
major causes of hyponatremia - euvolemia - correct answer syndrome of inappropriate ADH
secretion (SIADH), thiazide diuretics
common causes of SIADH - correct answer SSRIs, pulmonary infections, CNS pathology, nausea,
pain, stress commonly after surgery
Thiazide induced hyponatremia tends to occur in what patient population group? - correct
answer Older females with low muscle mass
Evaluate urine osmolality step 1 - correct answer <100 mOsmol/kg is low and appropriate, if
>150, is high and insufficiently dilute
Evaluate urine sodium levels step 2 - correct answer <15 meq/L is low, seen in true or effective
volume depletion like HF, cirrhosis, if >40 meq/L, is not low, seen with diuretics, advanced
kidney disease, euvolemia causes like SIADH
How to treat hyponatremia? - correct answer if true hypovolemia only cause, give isotonic fluid
alone, otherwise, implement water restriction +/- salt tablets, if symptomatic or severe give
hypertonic saline
How to treat chronic hyponatremia? - correct answer goal to change 4-6 mEq/L over 24 hrs, do
not exceed 8 mEq/L because if you increase the sodium too fast ECF becomes hypertonic and
the water will rush out of the brain cells too quickly
osmotic demyelination syndrome - correct answer neurological manifestation associated with
overly rapid correction of hyponatremia, clinical manifestations typically are delayed 2-6 days
Clinical presentation of osmotic demyelination syndrome - correct answer
paraparesis/quadriparesis, seizures, lethargy, confusion, disorientation, obtundation, coma,
dysarthria, dysphagia, behavioral disturbances, movement disorders
risk factors for osmotic demyelination syndrome - correct answer chronic hyponatremia <110
mEq/L, alcoholism, hepatic failure, liver transplant, K+ depletion, malnutrition,
If patient has osteoporosis or falls or hip fractures, what differential diagnosis can you
consider? - correct answer Hyponatremia, especially with older patients, associated with bone
fractures
, hypernatremia - correct answer Na+ >145 mEq/L. water deficit relative to body Na+ and K+
common causes of hypernatremia - correct answer excess water or hypotonic fluid loss
common with young children, elderly in long term care facilities, critically ill, renal issues
(diuretics, osmotic diuresis), GI (diarrhea, vomiting), skin (sweating, burns), excess hypertonic
fluids (IV, TPN), decreased thirst, acute hypernatremia is uncommon
symptoms of hypernatremia - correct answer thirst, weakness, confusion, diminished
consciousness, seizures, coma, tachycardia, dry mucous membranes, poor tissue turgor,
oliguria, polyuria, urinalysis, urine osmolality, urine Na often <20
potassium importance - correct answer 2nd most abundant cation in body, controls cell resting
potential, essential for impulse transmission and muscle contraction etc,
What is the major route of K+ elimination? - correct answer kidneys, mostly out via urine,
controlled by aldosterone activity on principal cells of renal cortical collecting duct, controlled
by distal delivery of Na+ and water
hypokalemia - correct answer serum potassium <3.5 mEq/L
common causes of hypokalemia - correct answer increased losses (vomiting, diarrhea, diuretics,
hyperaldosteronism), inadequate intake, redistribution into cells (like elevated extracellular pH,
meds) insulin
signs and symptoms of hypokalemia - correct answer fatigue, weakness, decreased muscle
tone, cardiac arrhythmias, eKG will have U waves after the T wave, look at V4-V6
Check the urine potassium-- if potassium isn't being wasted in the urine what range would this
fall in? - correct answer 20-30 mEq/L
hypokalemia treatment - correct answer If mild (2.5-3.5) oral replacement, if severe (<2.5) IV
replacement, must also replace magnesium if low or pt will remain hypokalemic
hyperkalemia - correct answer serum K+ >5.2 mEq/L, risk inversely proportional to eGFR,
prevalent in CKD
major risk factors of hyperkalemia - correct answer CKD stage III and beyond; ability to maintain
K+ balance preserved until >50% kidney function lost; diabetes mellitus, HF, agents blocking
RAAS
pseudohyperkalemia - correct answer K+ movement out of cells during or after blood drawn,
will high serum K+, normal plasma K+, see hemolysis, high platelet count (thrombocytosis),
occurs if fist clenching too much or too tight tourniquet
reverse pseudohyperkalemia - correct answer plasma K+ > serum K+, high white blood cell
count, occurs in chronic lymphocytic leukemia from fragility of luekocytes
