Flashcards in Diarrhea: water balance & electrolyte abnormalities Deck (76):
Total body water usually is equal to what percentage of body weight?
What percentage of body weight is composed of intracellular fluid?
- ICF: 40%
- ECF: 20%
What percentage of body weight is composed of interstitial fluid?
What percentage of body weight is composed of plasma?
What are electrolytes?
Charged particles in aqueous solution.
Which electrolytes have a positive charge?
Which electrolytes have a negative charge?
When is there electrical neutrality?
When cations = anions
What are the 3 major electrolytes of ECF?
What are the 4 major electrolytes of ICF?
The water volume in each fluid compartment is primarily controlled by the major solutes and driven by what force?
What is osmolality determined by?
The number of particles in solution.
What are 6 small solutes that are present in high concentrations which compose about 95% of total osmolality?
T/F: Larger molecules contribute majorly to osmolality.
False - they contribute minimally.
Do effective osmoles diffuse across membranes?
What to effective osmoles generate?
Osmotic pressure which causes water to shift across the membrane.
What reflects the tonicity of a solution?
ECF = what?
Serum Na+ concentration
How can osmolality be regulated?
By adjusting H2O balance.
What percentage of change can osmolality be influenced by?
What are 2 things that can result from osmolality change?
- ADH release
What is volume regulated by?
Adjusting Na+ concentration
What is volume influenced by?
Changes in vascular pressure.
What are 2 results that can be seen with volume change?
- Activation of Renin-Angiotensin-Aldosterone system (RAAS)
- ADH will also be released for hypovolemia
What are changes in osmolality detected by?
Osmoreceptors in the hypothalamus.
What do changes in osmolality stimulate?
What is the result?
- Pituitary release of vasopressin/ADH
- H2O resorption from renal tubules
Changes in volume are detected by what?
Baroreceptors in the kidney and heart.
Changes in volume trigger what?
Which causes what?
- Trigger the RAAS to release aldosterone.
- Kidneys resorb Na+ and H2O follows.
What are 2 things ADH is secreted in response to?
- Increased osmolality
- Marked decrease in plasma volume
What effect does ADH have on the collecting ducts?
Maximizes H2O resorption
Aldosterone is secreted in response to what 3 things?
What effect does aldosterone have on the distal renal tubules?
Na+ resorption which is exchanged for K+ or H+.
Dehydration is caused by what 2 imbalances?
- Low body water
- High plasma osmolality
Dehydration can lead to what 2 clinical signs?
- Increased thirst
- Decreased water excretion leading to concentrate urine
Overhydration can be seen with what 2 imbalances?
- Excess body water
- Low plasma osmolality
Overhydration can lead to what clinical sign?
Increased renal water excretion which leads to dilute urine.
What are 3 things to evaluate on a physical exam to evaluate water balance?
- Skin turgor
- Body weight
What is skin turgor?
Interstitial tissue consistency
What does CRT assess?
Peripheral vascular blood flow.
What can body weight reflect?
Total body water
What is the best way to monitor hydration?
What are 2 things examined in biochemical analysis?
T/F: PCV and TP should move proportionally.
T/F: PCV and TP always reflect mild changes.
False - may not reflect mild changes.
PCV and TP can also be affected by what?
Blood loss or protein loss
T/F: Na+ and Cl- should move proportionally.
What can Na+ and Cl- balance also be affected by?
Na+/Cl- consumption and loss.
What are 3 other things that can be evaluated with biochemical analysis?
- Urine Specific gravity
When H2O loss is greater than electrolyte loss, the solution is what?
When H2O loss is equal to electrolyte loss, the solution is?
When H2O loss is less than electrolyte loss, the solution is what?
What are 2 possible causes of hypertonic dehydration?
- Osmotic diarrhea (lactuose)
What are 5 examples of maldigestion/malabsorption?
- Johne's disease
- Proximal enteritis
- Eosinophilic enteritis
With hypertonic dehydration, which way does water move to maintain volume?
From ICF to ECF
What happens to PCV and TP with hypertonic dehydration?
They both increase.
What happens to serum Na+ and Cl- with hypertonic dehydration?
They both increase.
What are 2 possible causes of isotonic dehydration?
- Some diarrheas
- Some renal diseases
What happens to ECF volume with isotonic dehydration?
With isotonic dehydration, what happens to osmolality and osmotic pressure?
Is there a shift between ICF and ECF with isotonic dehydration?
What happens with PCV and TP with isotonic dehydration?
What happens with serum NA+ and Cl- with isotonic dehydration?
They do not change.
What is the most common type of diarrhea seen clinically?
What are 3 causes of hypotonic diarrhea?
- Secretory diarrhea (calf scours)
- 3rd space loss (displaced abomasum)
What happens to water with hypotonic dehydration?
It shifts from vasculature to cells.
Hypotonic dehydration can lead to what 2 conditions?
- Volume depletion
- Cerebral edema
Since osmoreceptors are not stimulated with hypotonic dehydration, what happens to ADH?
ADH is not released.
What happens to PCV and TP with hypotonic dehydration?
They both increase.
What 3 things affect plasma volume in reference to sodium?
- GI tract
What are 2 systems that regulate sodium?
- Osmoreceptors in hypothalamus sense increases osmolality and secrete ADH
- Baroreceptors (stretch receptors) sense volume changes and activate the RAAS
What follow Na+?
What percentage of water intake is oral?
What percentage of water is excreted by the kidneys?
What is something that influences water output?
What percentage of water output is excreted in the GI tract?