Fluid-electrolyte physio Flashcards
what is formula for fluid balance
input-output
what is main predictor of water volume in ECF
Na, as water follows Na
what happens when add isotonic solution to body
adds ECF volume and ICF stays the same
4 consequences of dec. ECF vol
- low plamsa vol
- low blood volume
- low CO
- low BP
major consequence to high ECF volume
pulmonary edema
how does added isotonic solution dist in ECF
1:3 plasma to ISF
how does ISF volume change when change plasma vol? (2)
via changes in both hydrostatic and plasma oncotic pressure
what happens in hypoalbumenemia
ECF vol stays the same, but movement from plasma to ISF
how does body sense Na and ECF balance
via changes in effective arterial volume
what is effective arterial volume
volume of blood in arterial tress that is effectively perfusing tissues
what are sensors of effective arterial volume
baroreceptors (sense stretch)
where are baroreceptors located
- central arteries
- renal afferet art.
- cardiac atria and vents
4 possible responses to baroreceptors
- SNS
- RAAS system
- ADH
- atrial naturetic peptide - to lower
3 main functions of angiotensin 2
- art. contstriction
- renal Na absorption, both direct and via adlosterone
- increased thirst and ADH
3 effects of Ang2 induced eff arteriole constriction
- incr glom cap pressure
- changes in peritubular cap. factors
- net effect of wasted out, but Na kept in
3 pathologies of chronic RAAS activity
- atheriosclerois
- cardiac remodelling
- renal scarring post-injury
what is typical Na intake in a day
150mmol
what is neg Na balance
intake less than output
5 places Na can be lost
- skin - sweat and burn oozes
- GI - diarrhea or vomiting
- kidneys
- 3rd space
- bleeding
3 causes of too much Na from kidneys
- diuretics (that inhib Na absrob)
- glucose diuresis - after diabted mellitus
- renal tubular disease
what are 3rd space losses
fluid that is not in intravasuclr or interstitum - major surg, crush injury
2 renal responses to hypovolemia
- hypotension and renal vasoconstrict. - lower GFR
2. incr. renal Na absorb (Ang, SNS)
manifestations of Na loss
- fatigue
- hypotension - may only be postural
- tachy
- cold sweaty skin (SNS activ)
- low urine
- circ. shock
treatment of volume depletion
- treat underlying cause
2. give fluids - isotonic
what is pos. Na balance
intake more than excrete
what happens when increase Na intake
- will increase Na in ECF (more volume)
2. eventually get Na excretion to equal, but never lose the ECF vol
how is high ECF vol sensed
baroreceptors
3 ways body tries to fix ECF vol increase
- lower Na reabsorb (Ang2, aldo, SNS)
- release naturetic peptide
- pressure naturesis
2 potential problems with Na excretions
- primary renal prob - failure, nephrotic synd
2. failure in signalling - heart failure, cirrosis
what happens in renal falure
low GFR - can’t get out Na
3 mechanisms in nephrotic syndrome
- protenuria>hypoalbumenemia>edema
- protenuria>activation of eNaC>more Na reabsorbtion
- proteinuria>hypoalbumenemia>increase LDL production>hypercholesterolemia
what is effect of heart failure
- low CO
2. leads to Na retention to react to low arterial volume, because volume is all in veins
how does cirrosis affect Na balance
- scar liver
- portal hypertenion > blood pools in vessels
- low effective art. volume
how much edema is detectable
3L
2 main effects of Na high
- hypertension
2. edema (esp. pulmonary)
treatment of high Na balnce (3)
- reduce intake
- increase Na out
- treat underlying issue
site of action and mech of acetazolamide
site: PCT
mech: carbonic anhydrase inhib
site of action and mech of furosamide
site: ALOH
mech: inhibs Nak2Cl
site of action and mech of hydrochlorothiazide and metazone
site: DCT
mech: inhib NaCl transporter
site of action and mech of spironolactone
site: CCD
mech: aldosterone antagonist
site of action and mech of amiloride
site: CCD
mech: Na channel blocker
4 places drugs can work on the RAAS
- renin inhibitor
- ACE inhib
- aldosterone antagonist
- angiotensin receptor blocker
4 clinical uses of RAAS antagonists
- hypertension
- CHfailure
- renal disease
- after MI
