Disorders of Water and Sodium Regulation Flashcards
What are the two primary compartments of Total Body Water?
Intracellular fluid
Extracellular fluid
What % of our body is water?
60%
What is the percentage breakdown between ICF and ECF?
ICF = 67% TBW ECF = 33% TBW
What are the two types of fluids that are included in the ECF?
Interstitial fluid : Lymphatic fluid –> 3/4
Intravascular fluid: plasma –> 1/4
What is the major electrolyte in the ICF? What is the major electrolyte in the ECF?
Potassium –> ICF
Sodium –> ECF
Water balance is achieved through ________?
Hint: A chemistry concept
Osmolality
How do we calculate the osmolality of the ECF?
Osm = 2 [Na] + [Glucose]/18 + [BUN]/2.8
In times of increased osmolality, what does the body do, hormonally, to regulate this? Decreased osmolality?
Increased osmolality
- body secretes vasopressin
- body secretes aldosterone
Decreased osmolality
- shut off aldersterone and vasopressin
- body secretes atrial natiuretic peptide
Vasopressin
Aldosterone
Atrial natiuretic peptide
What do these hormones do?
Vasopressin - also called ADH prevents fluid loss (sent by HP and secreted in pituitary)
Aldosterone - released by the adrenal glands, regulates blood pressure by acting on distal tubule and collecting duct (sodium retention)
Atrial natiuretic peptide (ANP) - secreted by heart muscle cells to promote excretion of sodium and water via kidneys
What are some reasons why you would experience hypovolemia?
Poor fluid intake
GI losses: diarrhea, vomiting, bleeding
Renal losses: diuretic overuse
Insensible losses - fever, sweating (mostly evaporation)
What are some late signs of hypovolemia?
Orthostatic hypotension
Tachycardia
Confusion
What are lab indications that signal for orthostatic hypotension?
DBP decreases more than 10
SBP decreases more than 20
HR increases more than 10
What is a normal BUN:SCr ratio?
What is considered a low urine Na+ level?
What are some elevated plasma values during a hypovolemic state?
10:1
Na+ <20mEq
Elevated Na, hemoglobin, hematocrit
What is the treatment for hypovolemia? How do we go about finding the right amount?
Administer IV fluids
Calculate the deficit = TBW * [1 - (Nat)/(Nam)]
~~Nat is usually 140
Why do we use half normal saline in patients with a strong need for water?
To avoid potential hypernatriemia
Why does D5W or D10W follow normal TBW distribution (2/3 ICF, 1/3 ECF) and not NS nor half NS?
D5W and D10W is free of Na+ and will distribute normally
If patient is symptomatic, which compartment of TBW should be replenished?
ECF
What are the three types of hyponatremia?
Hypovolemic hyponatremia
Isovolemic hyponatremia
Hypervolemic hyponatremia
What does hypovolemic hyponatremia mean? What are its causes? What are the symptoms? Treatment?
Hypovolemic hyponatremia - sodium is lost way more than water
Causes: GI losses, inappropriate diuretic use, sweating
S/S: thirsty, tachycardia, decreased urine output
Treatment: IV NS or 1/2 NS
What does Isovolemic hyponatremia mean? What are its causes? What are the symptoms? Treatment?
Isovolemic hyponatremia - there is only water gain so it appears that sodium is getting low but it is within normal limits
Causes: Psychogenic H2O drinking, SIADH
S/S: Excessive H2O drinking, low urine output, high concentrated urine
Treatment: restrict water intake (<1 L/d)
What does Hypervolemic hyponatremia mean? What are its causes? What are the symptoms? Treatment?
Hypervolemic hyponatremia - excess of both water and sodium increase
Causes: CHF, cirrhosis
S/S: water weight gain, edema
Treatment: furosemide or vaptans for acute CHF
What is SIADH? What are some etiologies?
SIADH is excess ADH activity in the kidneys
- more retention of water -> hyponatremia
Etiologies:
- Lung cancer, pneumonia, head trauma
- Drug causes (3-C’s most common)
- chlorpropamide, cyclophosphamide, carbamazepine)
What is the treatment for acute SIADH? Chronic SIADH?
Explain what the MOA of each of the meds are
Acute - water restriction
Chronic - Demclocycline 600mg BID (inhibits ADH secretion)
- Vaptan (vasopressin receptor antagonists)
What is the recommended rate of Na+ correction? What is the maximum?
Recommended rate: 0.5-1 mEq/L/hr
Maximum rate: 12 mEq/L/hr
When would you administer “hot salt” and which line (central or peripheral) do you use to administer it? How much do you have to monitor the patient after administration?
Hot salt - 3% hypertonic saline
You would administer it in patients that have severe hyponatremia who are experiencing seizures. Central line should be used to avoid swelling
You need to closely monitor them
How do you calculate the change in serum Na+ with 1 liter of saline solution?
(Infusion Na - Serum Na)/(TBW + 1)
What does hypovolemic hypernatremia mean? What are its causes? What are the symptoms? Treatment?
Hypovolemic hypernatremia - loss of water faster than loss of sodium
Causes: fluid loss, diuretics, diarrhea
S/S: thirsty, tachycardia, lowered BP
Treatment: give D5W or 1/2 NS to fill fluid deficit
When replacing fluid, how should you do it?
Give 1/2 of deficit in 12 hours then give the last 1/2 over the next 24 hours
What does isovolemic hypernatremia mean? What are its causes? Treatment?
Isovolemic hypernatremia - it is called diabetes insipidus; water from ICF is lost (not ECF) while Na+ is near normal
Causes: (mainly respective to ADH sensitivity)
Nephrogenic - kidneys don’t respond to ADH
Central - lack of ADH secretion from pituitary gland
Drug induced - decreases kidney sensitivity to ADH (most commonly from lithium)
Treatment:
Nephrogenic - Thiazides to trick body
Central - Desmopressin (ADH analog)
- 3 -Cs
Drug induced - stop the drug
What does hypervolemic hypernatremia mean? What are its causes? What are the symptoms? Treatment?
Hypervolemic hypernatremia - more sodium gain than water
Causes: excessive Na+ intake
S/S: edema, SOB
Treatment: furosemide and D5W
