what are the 3 big “pools” of fluid in the body?
intracellular fluid, interstitial fluid, and the plasma
what are the four ways the body naturally loses water?
feces, urine, sweat, lungs
what does aldosterone respond to, and what does it cause?
low blood pressure triggers the RAAS system to release aldosterone which causes renal sodium and water retention to increase blood pressure again
what causes ADH release and what does it do?
increase in extracellular osmolarity causes ADH release, which increases thirst and increased water retention
what are the 3 broad ways in which body water can change?
- increase in TBW: excess fluid intake or excessive fluid therapy, maybe inappropriate ADH release
- decrease in TBW: decrease fluid intake, increase fluid losses (diarrhea or vomiting, sweating, etc)
- redistribution: from ICF to ECF, increase in hydrostatic pressure or decreased oncotic pressure (think edema), shock, or 3rd space loss
what are some things we use in clinic to assess total body water?
clinical signs!!! Hct, TP, USG
____ is the most important osmotically effective solute in the ECF
sodium
____ is interpreted in conjugation with patient’s hydration status
sodium
what are the 3 types of dehydration in relation to Na+?
- hypernatremic/hypertonic dehydration: mainly losing water
- normonatremic or isotonic dehydration: equal loss of water and Na+
- hyponatremic or hypotonic dehydration: mainly losing electrolytes
what are three ways in which you get can a decrease in total body H2O?
- water deprivation/inadequate water intake
- pure water loss (panting, hyperventilation, diabetes insipidus)
- water loss moreso than Na loss, osmotic diuresis
what are two ways you can get an increased total body Na+?
- iatrogenic: giving sodium containing IV fluids
- increased sodium intake without concurrent water intake, salt poisoning
what is the most common rason for a hyponatremia?
- excessive loss with continued water intake:::
- GI loss (vomitting, diarrhea, sequestration)
- renal loss (addisons, prolonged diuresis)
- cutaneous loss (sweating)
- third space loss (pleural or peritoneal effusion)
what are two other less common reasons for hyponatremia?
- excessive H2O like with edematous disorders like CHF
- shifting of water from ICF to ECF like with hyperglycemia and a change in osmostic gradient
what are some reasons for a hyperchloremia?
- similar causes to hypernatremia
- hyperchloremic metabolic acidosis (normal anion gap, alimentary loss of bicarb or renal loss of bicarb)
what is pseudohyperchloremia?
when you give KBr and the machine mistakes Br for Cl so it’s essentially a “fake” hyperchloremia
what are some causes for hypochloremia?
- similar causes to hyponatremia
- hypochloremic metabolic alkalosis (loss or sequestration of Hcl like vomitting, displaced abomasum, GI obstruction, bicarb increases to compensate and maintain eletroneutrality)
is most of K in ICF or ECF?
ICF
potassium is regulated via what hormone?
aldosterone, promotes renal K excretion
translocation of K+ into cells from ECF to ICF depends on
insulin and catecholamines (like epinepherine)
what is pesudohyerkalemia?
when there is a thrombocytosis and the sample is left out for a long time and the K from the platelets leak into the serum, creating a hyperkalemia that isn’t “true”. OR it can be a breed thing where the RBCs have K that undergo hemolysis and leaks into the plasma as well.
what is the most common cause for hyperkalemia?
- decreased renal excretion (renal failure, UT obstruction, addisons disease)
- rare, but giving potassium rich fluid
what are some less common reasons for hyperkalemia?
- shifting from ICF to ECF with tissue necrosis (rhabdo in horses) or diabetes mellitus
what are some causes for a hypokalemia?
decreased total body potassium like with anorexia, increased renal excretion, GI loss, or cutaneous loss
the principle regulators of acid base balance are whom????
lungs and kidneys
