Electrolytes 1 Flashcards
What labs need to be ordered separately?
Magnesium & Phosphate
- Total body water is __% of total body weight.
- Intracellular Fluid Compartment (ICF) is ___ of body water
- Extracellular Fluid Compartment (ECF) is ___ of body water.
- TBW: 60%
- ICF: 2/3
- ECF: 1/3
- Total body water for infants is ___% of total body weight.
- Total body water for elderly is ___% of total body weight.
- 80%
- 45%
Does a lean or an obese individual have a higher percentage of total body water?
Lean = 60%
Obese = 30%
TIE : 60/40/20
- Total body fluid = 60% total body weight
- Intracellular = 40% of total body weight
- Extracellular = 20% of total body weight
Definition:
- Total solute concentration in a fluid compartment
- What 3 solutes determine the calculated value of the ECF?
- Which solute is most important?
Osmolality
- Sodium (most important)
- Glucose
- Urea
- Normal range for Osmolality is 280-295mOsm/kg
- Symptoms occur if >____ mmOsm/kg
>320
What are 4 other “osmotically active” substances that aren’t included in the calculated osmolality?
- Mannitol (& other proteins)
- Ethanol
- Methanol
- Ethylene glycol (antifreeze)
- A normal osmolal gap is <__
- A high osmolal gap is >___
- 10
- 10
Definition:
- the ability of the combined effect of all of the solutes to generate an osmotic driving force that causes water movement from one compartment to another
Tonicity
- To increase ECF tonicity, a solute must be confined to the _____ (unable to cross from ECF to ICF).
- ____ easily crosses cell membranes and therefore distributes evenly throughout total body water (so it contributes to ____, but NOT ____)
- ECF compartment
- Urea (contributes to osmolality, but NOT tonicity)
- The reason why we care about tonicity is because it affects ____
- Decreased ___, leads to decreased tonicity of ECF, which causes a shift of water from ECF to ICF, which leads to _________.
- the size of cells
- Na / cells swelling w/ extra water (including brain cells)
- The total amount of ___ in the ECF is the major determinant of the size of ECFV (extracellular fluid volume)
Na
- Increased Na & increased ECFV
Hypervolemia
- Decreased Na & Decreased ECFV
Hypovolemia
Serum ___ is the principle cation in the ___ where 90-95% of total body __ is located.
Na / sodium
Serum ___ (lab value) primarily refers to the amount of water relative to __ in the ECF.
(NOT the total body __ amount)
Na
- Abnormal serum Na is a sign of ______.
- If Na is high, water is ___. (relative)
- If Na is low, water is ____. (relative)
- A disorder of water regulation
- too little
- too much
With any sodium disorder, it is REALLY important to determine _____.
the patient’s volume status
Clinical volume status is proportional to the size of ____.
the ECFV (extracellular fluid volume)
5 causes of Hypovolemia
- GI losses (bleed, NG suction, V/D)
-
Renal losses
- (diuretics cause salt & water loss)
- (diabetes insipidus causes water loss)
- Skin losses (sweat, burns)
-
Sequestration w/o loss
- intestinal obstruction, pancreatitis, rhabdomyolysis
- Hemorrhage/bleeding
Signs of what?
- CNS depression
- Weakness / muscle cramps
- Decreased BP / postural hypotension
- Dizziness
- Increased pulse / postural pulse increase
Hypovolemia
What are the top 2 causes of Hypervolemia?
Liver disease & Heart failure
The following are causes of what?
- Acute/Chronic renal failure
- Nephrotic syndrome
- Primary hyperaldosteronism
- Cushing’s syndrome
- Pregnancy
Hypervolemia
Clinical Features of what?
- Edema
- SOB
- Orthopnea
- Paroxysmal nocturnal dyspnea (PND)
- Jugular venous distension
- Hepatojugular reflux
- Crackles on pulmonary exam
Hypervolemia
Water retention is influenced by what 2 things?
- Thirst
- ADH (antidiuretic hormone) (vasopressin)
Salt retention is influenced by what?
Renin-Angiotensin system
- Atrial Natriuretic Peptide
- Catecholamines
- Renal function (GFR), renal blood flow
ADH is produced by the _____, then transported to the _____, from which it is released into the bloodstream.
hypothalamus / posterior pituitary
Renin-Angiotensin Aldosterone System (RAAS)
- Aldosterone has what 2 actions?
- Increase renal sodium reabsorption (Na retention)
- Increase renal potassium secretion (K excretion)
(Keeps Na and gets rid of K)
- What is the most common electrolyte abnormality in hospitalized patients
- Can be acute or chronic
- Hyponatremia
Hyponatremia
- Most common in what age groups?
- Can be seen in associated with which 2 conditions?
- What should you always look up if pt has this?
- The faster the Na decreases, the _____.
- Very young / very old
- Pulmonary Disease or CNS disorders
- Baseline sodium
- more severe the sxs
What condition would have “neuro” or vague sxs?
- HA / dizziness
- N/V
- Lethargy
- Weakness
- Confusion
- Hypoventilation, respiratory arrest
- Seizures*******
- Coma
Hyponatremia
With treating hyponatremia, the goal is to prevent what 2 outcomes?
Seizures & Coma
What are the 5 types of Hyponatremia?
-
Causes:
- Pseudohyponatremia
- Redistributive hyponatremia
-
Determining volume status is important:
- Hypovolemic hyponatremia
- Hypervolemic hyponatremia
- Euvolemic hyponatremia
- Falsely low serum sodium
- Serum Na <135, but with NORMAL osmolality (isoosmolar)
- Occurs w/ what 2 conditions?
- It is a laboratory artifact
- If this is suspected, speak to lab about more specialized tests to confirm true sodium level….
Pseudohyponatremia
What is the most common cause of Redistributive Hyponatremia?
Hyperglycemia
What condition?
- Hyperosmolar state
- Caused by osmotically active solutes in extracellular space that draw H20 from cell diluting serum sodium concentration
- Increased glucose in ECF causes shift of water from ICF to ECF thus lowering serum Na
Redistributive Hyponatremia
“relative hyponatremia”
What are the 4 renal losses which lead to Hypovolemic Hyponatremia?
- Diuretics
- Osmotic diuresis
- Addison’s disease
- Hyperaldosteronism
3 causes of non-renal losses for Hypovolemic Hypnatremia
- External GI: V/D, NG suction, fistula
- Internal GI: pancreatitis, peritonitis
- Burns
Treatment of Hypovolemic Hyponatremia
- Replace fluid losses w/ isotonic fluid (normal saline)
- Treat underlying cause
3 causes of Hypervolemic Hyponatremia
- Hepatic cirrhosis
- CHF
- Renal failure
Treatment for Hypervolemic Hyponatremia
- Diuretics
- Dialysis
- Fluid restriction
4 causes of Euvolemic Hyponatremia
- SIADH (Syndrome of inappropriate antidiuretic hormone secretion)
- Psychogenic polydipsia (urine maximally dilute)
- Hypothyroidism
- Adrenal Insufficiency
Treatment for Euvolemic Hyponatremia
- Fluid restriction
- Treat underlying cause
What condition?
- Impairs free water excretion, but Na continues to be excreted normally
- Hallmark finding: Concentrated urine w/ low serum osmolality & euvolemia**
- Often occurs in hospital setting
- Associated w/ what? **
SIADH (Syndrome of inappropriate antidiuretic hormone secretion)
- Small cell lung cancer
How is SIADH diagnosed?
- Check urine (high osmolality)
- Check serum (low osmolality)
- Get CT / MRI of head to check for CNS disorder
- Get CXR to check for lung tumor/infection
- Review all pts meds
Treatment of SIADH
- Fluid restriction
- Tx of underlying pathology
-
If refractory case:
- Hypertonic saline
- Demeclocycline
- Urea
- Lithium
- Vaptan
