L34: Dehydration

what three things have the most influence on osmolarity?

1. sodium

2. glucose

3. urea

MCQ: what dehydration type is consistent with a decrease in total body sodium?

hypotonic dehydration

MCQ: what dehydration type is consistent with total body sodium within reference interval?

isotonic

hypertonic dehydration

from restricted water acess; water loss is greater than Na+ loss

isotonic dehydration

water loss = Na+ loss

what electrolyte imbalance will result from hypertonic dehydration?

hypernatremia

what electrolyte imbalance will result from hypotonic dehydration?

hyponatremia

hypotonic dehydration

Na+ loss is greater than water loss

what will happen to chloride concentration if Na+ concentration increases?

chloride will increase

what will happen to chloride concentration if HCO3- concentration DECREASES?

chloride will increase

pathogenesis of hypernatremia

1. decreased water intake

2. increased “pure” water loss via kidneys

3. water vapor loss in lungs

4. increased water loss over Na+ loss

what USG value will we expect if an animal that has had restricted water access is hypernatremic?

>1.030 (dogs) or 1.040 (cats)

what leads to increased “pure” water loss via kidneys leading to hypernatremia?

1. central diabetes insipidus (lack of ADH)

2. renal diabetes insipidus (defective response to ADH)

what USG value do we expect for central diabetes insipidus or renal diabetes insipidus?

below 1.007

what lead to water vapor loss in the lungs?

fever or panting

in cases of hypernatremia, what causes an increased water loss over sodium loss?

1. osmotic diuresis

2. osmotic diarrhea

what is the USG value for osmotic diuresis?

greater than 1.020

what are causes for osmotic diarrhea?

1. paint ball toxicity

2. grain overload

renal osmotic diuresis

increased urine volume due to osmotic molecules in the renal tubules, resulting in excess water loss in urine and increased NaCl in the blood

what can cause osmotic diuresis?

glucose from diabetes

MCQ: You perform a panel on a dehydrated dog. Your values are hypernatremia, hyperchoremia, normal glucose, increased osmolality and USG of 1.050. what best explains the changes in Na+ and Cl- concentration?

hypertonic dehydration due to decreased intake of water

MCQ: You perform a panel on a dehydrated dog. Your values are hypernatremia, hyperchloremia, normal glucose, increased osmolality, and a USG of 1.002. what best explains the changes in Na+ and Cl- concentrations?

hypertonic dehydration due to central diabetes insipidus (1.002 USG value)

dehydration state

Na+ loss > water loss

edematous states

water retention > Na+ retention

what are the clinical conditions of hypotonic dehydration?

1. intestinal loss

2. sweating (horses)

3. renal loss in certain diseases

what intestinal losses will lead to hypotonic dehydration?

1. diarrhea

2. intestinal sequestration (horses)

3. vomitting

how does diarrhea and sweating in horses lead to hypotonic dehydration?

1. increased loss of NaCl and water leads to dehydration and hypovolemia

2. animal stimulated to be thirsty and drink more water (RAAS)

3. ADH released and increases renal absorption of water

4. water dilutes electrolytes

MCQ: You have the following panel from a dehydrated dog with diarrhea. You observe: hyponatremia, hypochloremia, glucose WRI, low osmolality, and a USG value of 1.050. What is the best explanation of the changes in Na+ and Cl-?

hypotonic dehydration due to NaCl loss and dilution of water

what is the pathogenesis of hypotonic dehydration due to renal loss (focusing on aldosterone) ?

1. damage to kidney or hypoadrenocorticism decreases aldosterone production in collecting tubule

2. decreased renal conservation of sodium leading to decreased NaCl in body

what is the pathogenesis of hypotonic dehydration due to renal loss (focusing on cortisol)?

1. decreased cortisol production

2. inhibition of ADH release

3. increased ADH secretion

4. increased water retention

5. dilute remaining Na+

what leads to renal Na+ loss with anions?

1. diabetes mellitus

2. metabolic alkalosis

3. hypoxia

why does renal loss with anions lead to hyponatremia?

persistent loss of anions obligates loss of Na+ to maintain electroneutrality

how does the prolonged use of furosemide lead to hypotonic dehydration?

1. furosemide inhibits LOH and DT NaCl pumps

2. hypovolemia stimulates ADH and thirst

3. increased water retention dilutes electrolytes

4. Loss of sodium and water

what leads to 3rd spacing loss of Na+?

bladder rupture

how does cardiac/liver disease lead to an edematous state?

leads to increase in blood volume and fluid accumulation = water retention = hyponatremia and hypochloremia

You receive the following data on a dehydrated dog with cardiac failure: hyponatremia, hypochloremia, glucose and osmalility WRI, nad USG 1.030. What is the best explanation of the changes in Na+ and Cl-?

hyponatremic dehydration due to water retention being greater than Na+ and Cl- retention

what conditions lead to a net retention of isotonic fluid causing and edema or transudate (both Na+ and water increased)?

1. congestive heart failure

2. hepatic cirrohsis

3. nephrotic syndrome

what conditions lead to a new loss of isotonic fluids causing isotonic dehydration?

1. alimentary losses

2. sweat

3. renal losses

what is the pathogenesis of edmeatous normonatremic dehydration (increased net retention of isotonic fluids)?

1. decreased blood volume activates RAAS

2. increased reabsorption of NaCl

3. increased ADH = retention of water

4. isotonic fluid moves into ECF and peritoneal cavity

when can we get false hyponatremia and hypochloremia?

when the sample has lipids it will falsely decrease concentrations due to lipids displacing water in the sample

what can cause an increase in bicarbonate and decrease in chloride?

1. vomiting

2. sequestration in abomasum