Electrolytes Flashcards
What happens when there’s a 1-2% increase in Na or a 10% decrease in blood volume?
osmoreceptors in the hypothalamus sense the change–> vasopressin secreted from posterior pituitary–> enhances H2O resorption in renal CDs
Na is a major determinant of intra or extracellular osmolality?
extra
incr in BP–> sensed by ______–> impulses to the ____ to inhibit ____ release and decrease ___ resorption in the distal nephron
incr in BP–> sensed by arterial and atrial baroreceptors–> impulses to the hypothalamus to inhibit vasopressin release and decrease Na resorption in the distal nephron
What happens when there is a decrease in BP to stimulate an increase in resorbed water in the kidneys?
decr in BP–> sensed by juxtaglomerular cells–> activate RAAS by secreting renin–> renin cleaves angiotensinogen to angiotensin I–> angiotensin I converted to angiotensinogen II by ACE–> angiotensinogen triggers release of aldosterone from the adrenals, secretion of vasopressin, and stimulates thirst
What are the actions of angiotensinogen II?
triggers release of aldosterone from the adrenals, secretion of vasopressin, and stimulates thirst
T or F: All hyperNa animals are hyperosmolar
T
What is the normal ECF osmolality?
300 mOsm/kg
What are effective osmoles?
osmoles that contribute to tonicity
What are examples of effective osmoles?
glucose, EG, propylene glycol
T or F: BUN is a strong effective osmole
F- BUN is an osmole but doesn’t cornice to tonicity b/c can freely diffuse across membranes
What is an example of a hypertonic rumens where BUN actually contributes to hypertonicity and is an effective osmole?
urea toxicosis
T or F: Hypoosmolar pts always have hypoNa.
T
T or F: HypoNa pts always are hypoosmolar.
F (if concurrent hyperglycemia)
What are 3 scenarios where you may have hyponatremia without a decrease in osmolality?
- Pseudohyponatremia when indirect potentiometry and flame photometry are used and Na is measured in plasma and not just plasma H2O
- Marked hyperlipemia or hyperproteinemia displaces the plasma H2O
- Translocational hypoNa: concurrent hyperosmolality from some other substance (glucose, EG, mannitol, etc)
HypoNa in a normovol patient indicates…
increased total body Na
HypoNa in a dehydrated patient indicates…
Na and H2O are being lost together but Na loss is > H20; indicates severe total body Na deficit
HypoNa in a pt with ascites or edema indicates…
H2O is accumulating faster than Na can increase; tuna is normal to increased
HyperNa in a dehydrated pt indicates…
H2O loss w/o Na loss, tbNa is normal and ECF volume is decreased
HyperNa in a normovol pt indicates…
increase in tuna (usually excess salt w/o access to water)
What are 3 mechanisms of hypoNa?
- excess water diluting out Na
- endogenous shifts
- losing Na in excess of H2O
What are 3 causes of renal Na loss leading to hypovolemic hypoNa?
- proximal tubule dysfx–> less Na resorption
- Addisons
- osmotic diuresis (DM)
What are 3 main causes of non-renal Na loss leading to hypovolemic hypoNa?
- GI (diarrhea or vomiting)
- 3rd spacing (ruptured bladder, peritonitis, chylothorax)
- cutaneous (sweating in horses)
What are 4 causes of excessive water intake causing euvolemic hypoNa?
- PD
- SIADH
- Antidiuretics
- hypotonic fluid admin
What are 4 causes of volume overload leading to hypervolemic hypoNa?
- CHF
- Liver disease
- nephrotic syndrome
- advanced (oliguric/anuric) renal failure
What are 5 reasons for low Na:K?
- addisons
- renal/urinary tract disease
- GI dz/parasitism
- body cavity effusions
- repeated chylothorax drainage
Chloride is an anion or cation?
anion
Chloride is primarily in the ECF or ICF?
ECF
How can hyperCl be related to secretory acidoses?
when you lose bicarb, you retain Cl to stay electroneutral
What are 5 conditions that you might lose bicarb and have a resulting hyperCl?
- diarrhea
- saliva loss in cattle
- vomiting
- renal loss with proximal or distal tubular acidosis
- chronic respiratory alkalosis (there’s a decr in renal conservation of bicarb)
What can cause an artificial increase in chloride?
halides (bromide or iodide)
What is the corrected Cl formula?
Corr Cl= Normal Na/measured Na x measured Cl
K is primarily and intra or extracellular ion?
intra
Is K an anion or cation?
cation
Which species have normally high intracellular K?
Horses, pigs, primates
___-___% of K is excreted in the kidneys. Where is the rest excreted?
90-95%, 5-10% excreted in colon
What are the 3 major mechanisms of hyperK?
decreased renal excretion
shift from ICF to ECF
artifactual
What are the 3 major mechanisms of hypoK?
decreased intake
increased excretion/loss
shift from ECF-> ICF
What are 7 causes of decreased renal excretion as a cause of hypoK?
renal failure (anuric/oliguric in SA, polyuric in horses)
urethral obstruction
ruptured urinary bladder
ill bitches in late pregnancy
addisons
high doses of TMS
hypovolemia (3rd spacing, GI dz/whipworms)
What are 7 causes of intercellular shifts leading to hyperK?
Metabolic acidosis (nonunion gap) Insulin deficiency Cellular damage Hyperosmolality Secretory diarrhea HYPP Oleander tox
What are 6 causes of artifactual hyperK?
K leaks out after blood draw Blood clotting Hemolysis contamination of sample with EDTA delayed serum removal thrombocytosis
What are 5 renal causes of hypoK?
CRF Distal renal tubular acidosis postobstructive diuresis DKA diuretics
What are 3 major mechanisms of increased excretion/loss of K causing hypoK?
GI loss (vomiting/diarrhea) Renal Hyperaldosteronism
What are 5 causes of intercellular shifts leading to hypoK?
excess insulin
glucose infusion
met alkalosis
pain, sepsis, trauma (catecholamine indued)
admin of alkalinizing fluid in acidotic patient
What are the main ECF cations?
Na, K, Ca, Mg
What are the main ECF anions?
Cl, HCO3, plasma proteins, organic acid ions, phosphate, sulfate
What is the anion gap?
The difference between unmeasured anions (Na + K) and cations (Cl - HCO3) (more anions unmeasured than cations)
Ca, P, and Mg are higher in the intra or extra cellular fluid?
ICF
Calcitonin is made by _____.
thyroid parafollicular C cells
PTH is made by ____.
parathyroid gland chief cells
How does calcitonin decrease serum Ca and P?
inhibits bone and kidney resorption
What are PTH’s effects on Ca and P?
increases Ca (increases Ca resorption from bone and kidney) and decreases P (phosphaturic and decreases renal P resorption)
What is active Vit D’s effect on Ca and P?
increases both by increasing their absorption from the GI
______ is made in the liver and metabolized to calcidiol–> goes to ____ in response to PTH to become _____.
Cholecalciferol is made in the liver and metabolized to calcidiol–> goes to kidneys in response to PTH to become calcitriol (active Vit D).
iCa is ____% of total Ca.
50%
Typical patterns in primary hyperparathyroidism: PTHrp- PTH- Ca- P-
PTHrp- normal/decr
PTH- incr
Ca- incr
P- decr unless dehydrated
Typical patterns in hypercalcemia of malignancy: PTHrp- PTH- Ca- P-
PTHrp- incr
PTH- decr
Ca- incr
P- decr unless dehydrated
Typical pattern in primary hypoPTHism
Ca-
P-
PTH-
Ca- decr
P- incr
PTH- decr
What are 3 ways that diet can play a role in hypoCa?
malabsorptive disease
Vit D def
cantharidiasis
What 2 electrolyte abnormalities can lead to hypoCa? secondarily?
hypoMg
hyperK
What is the mechanism for hypoCa caused by hypoMg? What is an example of a condition that causes this?
hypoMg–> decr PTH secretion & actin–> decr Ca
Grass tetany
What are 2 diseases that can cause hypoCa secondary to hyperP?
renal failure
nutritional secondary hyperPTHism (excess P in diet or low Ca:P ratio)
P is excreted mainly through the ____ in SAs but not in cows– they excrete mainly in the ____.
P is excreted mainly through the kidneys in SAs but not in cows– they excrete mainly in the GI.
What are the 3 main mechanisms of hyperP?
decreased excretion/GFR
increased load
redistribution from bone or ICF to ECF
What are 3 causes of decreased excretion of P causing hyperP?
CRF
dehydration
GI obstruction in cattle (can’t excrete like they normally do in GI)
What are 4 causes of increased P load causing hyperP?
high P diet
EG poisoning
hypervit D
phosphate enema
What are 3 causes of hyperP that are from redistribution from bone or ICF to ECF fluid?
osteolytic lesions cell injury (acute tumor lysis, acute myopathies) acidosis (decreases cell uptake of P)
What are 3 causes of hormonal imbalances leading to hypoP?
primary hyperPTHism
hypovit D
pariparturient hypoCa
What are 5 causes of hypoP due to increased renal excretion/decreased resorption?
defects in prox tubules (fanconis) diuresis DKA- diuresis and phosphate used as buffer for excreted acids CRF in horses hyperPTHism
What are 3 causes of hypoP due to decreased intestinal absorption?
prolonged anorexia or low P diet
vomiting, diarrhea, malabsorptive disease
hypovitD
What are 3 causes of hypoP due to redistribution of ECF to ICF?
insulin admin resp alkalosis (CO2 out of cell, P in) accelerated metabolism (P needed for cell fx)
Mg is mainly intra or extra cellular?
intra
What % of Mg is ionized/free?
70%
HypoMg can lead to decreases in what other 2 electrolytes?
K & Ca
What are 2 causes of hypoMg due to increased loss?
GI in SAs (malabsorption or diarrhea)
kidneys in SAs (diuresis & renal disease)
What are 2 major diseases in large animals that involve hypoMg?
grass tetany
milk tetany
What is the mechanism of grass tetany?
grass tetany–> eat lush pastures high in K & low in Mg–> high K blocks Mg absorption in rumen
Between non diluted/direct and diluted/indirect measurements of electrolytes, which is not affected by increases in the non-aqueous phase (by lipemia or hyperproteinemia)?
nondiluted/direct
Between non diluted/direct and diluted/indirect measurements of electrolytes, which is affected by increases in the non-aqueous phase (by lipemia or hyperproteinemia)?
diluted/indirect
Most chemistry analyzers use non diluted/direct or diluted/indirect to measure electrolytes?
diluted/indirect
What are the 4 major unmeasured anions in health?
albumin
phosphates
sulfates
small organic acids (lactic, BHB)
What are the 4 major unmeasured cations in health?
Ca
Mg
y-globs
some abx
What are 3 causes of decreased anion gap?
hemodilution, hypoalb, increase in some cations (Ca)
What is the SID formula?
SID= cations that dissociate at body pH - anions that dissociate at body pH
Increased SID indicates-
met alkalosis
Decreased SID indicates-
met acidosis
Why would producers feed an acidifying diet to pre parturient cows?
acidosis will cause more Ca to be in the ionized fraction– used to prevent milk fever
What is DCAD? How is it used? What is the formula?
Dietary cation anion difference
(Na + K) - (Cl - SO4)
Impt in choosing diet for preparturient cows– want a food with a DCAD
What 2 opposing forces determine pH during exercise?
lactic acidosis
hyperventilation and decreased pCO2 (alkalosis)
What electrolyte changes do horses usually get during exercise due to sweating?
mild-severe hypoK, hypoCl, usually mild hypoNa
