6. Fluid and Hemodynamics Flashcards
What is generally the major determinant of osmolality?
Sodium (you can basically double Na + 10) - glucose sometimes but in general it’s mostly sodium
Which osmole freely moves from ECF to ICF?
Urea
Do sodium and glucose move freely from ECF to ICF?
No - limited to the ECF component
What happens to the brain in hypo vs. hypernatremia?
Mental status changes (hyponatremia - swelling of cells, hypernatremia - shrinking of cells)
Why is there essentially no glucose, fructose, or galactose in cells?
Gets metabolized instantly
What happens to serum sodium when you have hyperglycemia?
Hyponatremia because water leaves cells - dilution effect
When we lose isotonic fluid, where does it come from?
ECF
When do we get isotonic loss of fluid?
Hemorrhage, diarrhea
When do we get isotonic gain of fluid?
Too much saline
What is it called when we lose more salt than water?
Loss of hypertonic solution (e.g. when we use diuretics)
What is the most common cause of gaining pure water without salt?
SIADH
What cancer has SIADH as a paraneoplastic syndrome?
Small cell lung cancer
What is the treatment of choice for SIADH?
Free water restriction because you’re constantly absorbing pure water
When ADH is present do you concentrate or dilute your urine?
Concentrate
Serum sodium < 120 - be suspicious of?
SIADH
What diabetic medications produce SIADH?
Oral sulfonylureas
What compartment is all the total body sodium in?
ECF
What clinical sign always accompanies increase in total body sodium?
Pitting edema (because of the increase in sodium in interstitial fluid)
What do you call it when we lose pure water?
Diabetes insipidus
What should you give an infant with diarrhea?
Hypotonic salt solution because they have hypotonic diarrhea
Sodium has to be combined with what to be absorbed in the GI for oral replacement?
Glucose because of cotransport
What is the tonicity of sweat?
Hypotonic salt solution
What is the sympathetic response to hypovolemia (decreased cardiac output)?
Catecholamines!
- Venoconstriction - increase return to the right side of the heart
- Increase HR and contractility
- Upregulate RAA axis - increase aldosterone to reabsorb salt and water
Where are the receptors that sense blood flow in the kidney?
JGA in afferent arteriole
What do you give in hypovolemic shock if you don’t have blood?
ISOTONIC saline - you need to keep the fluid in ECF (normal saline is basically plasma without the protein)
What is the tonicity of the fluid you absorb in the PCT?
Roughly isotonic
What is the tonicity of the fluid you absorb via aldosterone?
Roughly isotonic
What is the tonicity of the fluid you absorb via ADH?
Pure water (hypotonic)
What does ANP do?
Gets rid of salt - only released in volume overloaded states (when right or left atria are dilated)
What is the ADH level in central diabetes insipidus?
Low
What does skin turgor tell you?
Total body sodium (normal if skin snaps back)
What’s your nonpharmacologic treatment for any pitting edema state?
Restrict salt and water
