#33 - disorders of sodium homeostasis Flashcards
What are the 3 main determinants of “Effective Arterial blood volume” (EABV)
- intravascular volume
- peripheral vascular resistance
- cardiac output
EABV =
Effective Arterial blood volume
how long does it take for the body to adjust to a diuretic and have equal inputs/outputs of Na??
about 3 days. on the 4th day, it is normal, Na intake = Na excretion.
The body increases other
mechanisms (angiotensin, aldosterone,
sympathetic drive) to compensate and
maintain balance
Person is maintained on a constant sodium intake of 100 mmol / day. What is their urinary sodium excretion 7 days after starting a diuretic?
Equal to 100 mmol/day.
a total body sodium deficit leads to what?
-depletion of extracellular volume (most sodium is outside cells)
this is associated with hypovolemia / low EABV
hypovolemia ==
low plasma volume
T/F - total body sodium excess can be associated with low or high EABV
true.
High EABV = primary hyperaldosteronism
low EABV = CHF/ cirrhosis.
total body sodium excess leads to
expansion of the extracellular volume
T/F CHF is the 2nd most common cause of hospital admissions
False. It is the 4th most common cause of hospital admissions
T/F CHF is a disorder of sodium balance.
True. Baroreceptors detect low volume and order the kidney to pick up extra sodium through angiotensin/ aldosterone. This causes the symptoms of fluid overload.
How does the bodies response to dehydration (ie constriction of the efferent arteriole) affect the post-glomerular capillary fluid?
- decreased pressure
- increased protein concentration.
This enhances salt and water reabsorption from the proximal tubule.
3 most common etiologies for total body sodium deficit
- GI sodium losses (diarrhea, vomiting)
- Renal sodium losses (diuretics, osmotic diuresis)
Cutaneous sodium losses (sweating, burns)
total body sodium deficit symptoms
fatigue thirst muscle cramps dizziness syncope
Most important diagnostic test for sodium deficit
Clinical exam!!
clinical exam signs of sodium deficit/ low volume
- low BP
- tachycardia
- orthostatic tachycardia AND hypotension (MEASURE BOTH!!)
- decreased jugular venous pressure (can’t see neck veins when patient is lying flat)
- decreased skin turgor
Define orthostatic tachycardia and hypotension. (These should both be present in volume depletion!!)
- pulse rises >20
- BP: systolic BP drops >20mmHg
if orthostatic hypotension is observed, without rise in pulse, what is the differential?
- autonomic insufficiency
- drugs (eg beta blockers) that block sympathetic tone
lab tests for total body sodium deficit
- serum BUN:Creatinine >20:1
- rise in hematocrit
lab tests for total body sodium deficit due to renal sodium loss
urinary sodium >20
FEna>1%
(kidney not compensating with increased Na uptake appropriately)
lab tests for total body sodium deficit due to extra-renal sodium losses
urinary sodium
Treatment approach to total body sodium deficit (hypovolemia)
1-treat the underlying etology
2-give ISOTONIC saline to replace deficit
3-monitor symptoms/labas/physical exam to monitor response
disorder of sodium excess - hypertension, no edema
primary hyperaldosteronism
total body sodium excess - edema formation - what conditions cause it?
Secondary sodium retension - CHF, cirrhosis, nephrotic syndrome
Primary sodium retention-renal failure
Case: man w/ CHF comes in w/ pulmonary and extremity edema. Why is his urinary sodium
it is due to activation of the sympathetic and renin - angiotensin-aldosterone systems, leading to avid renal sodium retention
