Electrolytes Flashcards
Plasma [Na+]
Major extracellular fluid (ECF) ion
Actively eliminated from cells via sodium pump
Major influence on osmolality
T/F Osmoreceptors that secrete ALDOSTERONE indirectly influence serum Na+ concentration
False: its ADH
Renal tubular absorption of Na is regulated via
Aldosterone
T/F Na is absorbed through the GI
true: intestinal absorption
what 3 things effect plasma volume of Na
Urine, gastrointestinal tract (GIT), sweat (horses)
Sodium balance – 2 related & interdependent systems:
osmoregulation & volume regulation
osmoreceptors in hypothalamus
sense increased osmolality & secrete ADH
stretch receptors
sense volume changes
How does ADH regulate Na
Responds to:
- ↑ osmolality
- ↓↓↓ plasma volume
Acts on collecting ducts; maximizes water reabsorption
what is the main regulator of Na balance
Renin-angiotensin-aldosterone system (Na resorbed in distal tubule)
aldosterone is secreted in response to
- Angiotensin
- Hyperkalemia
- ACTH
aldosterone
conserves Na+
Secretes K+
causes of hyponatremia
loss of Na+ (GIT, renal, cutaneous)
Shifts (diabetes)
↑ extracellular H2O (CHF)
↓ intake (herbivores)
most common cause of hyponatremia
hypovolemia
causes of hypovolemia
GIT: vomiting, diarrhea, saliva
Renal loss:
- Hypoadrenocorticism (Addison’s): ↓ aldosterone
- Ketonuria
- Prolonged diuresis
Cutaneous: sweating, burns
3rd space: sequestration of fluid
examples of 3rd space syndromes (causing hyponatremia)
Peritonitis
Ascites
Uroabdomen
Chylothorax
GI sequestration
This effectively “dilutes” plasma Na+
2 causes of osmotic shifts (causing hyponatrmia)
hyperglycemia
mannitol administration
2 causes of increased extracellular water leading to hyponatremia
primary polydipsia (psychogenic water drinking)
excessive administration of Na+ poor IVF
consequences of hyponatremia if other osmotically active substances are NOT increased
hypoosmolality
cellular edema (cellular overhydration)
what is hypernatremia usually due to
dehydration
- inadequate water intake
- pure water loss (panting, fever, diabetes insipidus)
hypernatremia is less commonly due to
excessive Na+ intake or retention
Chloride
Major extracellular fluid (ECF) anion
Important in transport of electrolytes and water
Anion involved in acid base metabolism
who is chloride’s BFF
Na
if changes in Cl- and Na+ are proportional:
consider differentials that pertain to abnormalities in Na+ (Cl- is following Na+)
if the changes in Cl- are greater than Na+
consider acid-base abnormalities
how is chloride regulated
Controlled by electrochemical gradients
Corresponds to the active transport of sodium
what interferes with Cl transport
furosemide
GI enterotoxins
T/F Cl is usually regulated secondary to Na
true: usually parallels [Na]
T/F All causes of ↓Na+ are causes of ↓Cl-
true
most common cause of Cl- loss being greater than Na+ loss
hypochloremia metabolic alkalosis
- severe vomiting
- abomasal disorders, high GI obstructions
what can selective chloride loss lead to
Hypochloremic metabolic alkalosis +/- Paradoxical aciduria
when should selective chloride loss be suspected
corrected Cl- is below the reference interval
what 2 things does paradoxical aciduria require
volume depletion
chloride depletion
mechanism of paradoxical aciduria
Kidney:
• Resorbs Na+ to correct dehydration
• Resorbs HCO3- instead of Cl- (electoneutrality)
Result: exacerbated alkalosis (more HCO3-)
causes of hyperchloremia
Generally parallels increases with Na+
Hyperchloremic metabolic acidosis
− GIT loss of HCO3-
Alkalemia / HCO3- excess
functions of potassium
Major intracellular (IC) cation- IC osmotic pressure and fluid volume
Resting cell membrane potential
Carbohydrate metabolism
Electron transport
clinical signs of abnormal serum K+
cardiac dysfunction
skeletal muscle dysfunction
regulation of potassium
adequate intake
renal excretion
sweat
GI loss
causes of hyperkalemia
Failure of renal Excretion: most common
Redistribution
↑ intake: Parenteral administration of K+
examples of redistribution leading to hyperkalemia
- Inorganic acidosis
- Insulin deficiency
- Muscle trauma: rhabdomyolysis, seizures
- Massive hemolysis
hyperkalemia: examples of failure of renal excretion
Oliguria/ Anuria
Urethral obstruction
Ruptured urinary bladder
Hypoadrenocorticism (Addison’s): ↓ aldosterone
Drugs that decrease K+ excretion
• “Potassium Sparing Diuretics”
T/F redistribution is a major mechanism of hyperkalemia
true
T/F H+ & K+ balance maintains electroneutrality between ICF and ECF
true
pseudohyperkalemia
Generally in vitro, not in vivo
Marked thrombocytosis: leakage of intracellular K+
Hemolysis: K+ released from RBCs
EDTA CONTAMINATION!!
hypokalemia
Usually indicates marked depletion of cellular K+
causes of hypokalemia
Decreased intake or low K+ IV fluids
Loss
- Alimentary: vomiting, diarrhea, abomasal disorders
- Renal
- Horse sweat
Redistribution
- Alkalemia
- INSULIN injection (or glucose bolus)
consequences of hypokalemia
- Weakness
- Neurologic signs
- EKG abnormalities
potassium in diarrhea
loss of bicarb and K+
- leads to an acidosis
- H+ entersinto the cells and K+ leaves cells
- may mask total body K+ deficit
T/F With diarrhea, potassium supplementation may be indicated despite normal serum K+
true
