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Clinical Pathology - Exam 2 > Lab Evaluation of Electrolytes and Fluids > Flashcards

Lab Evaluation of Electrolytes and Fluids Flashcards

1
Q

What is measured osmolality?

A

Measured osmolality is looking at the measurement of solute by freezing and/or vapor-point eval

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2
Q

What are the formulas for calculated osmolality?

A

Serum - 2[Na+] + (gluc/18) + (urea/2.8) = normally 299.4osm

Plasma - 1.86[Na+ + K+] + gluc + urea = normally 290-310 in dogs and 308-335 in cats

urine - equates closely with USG; normally 50-2800 in dogs and 50-3000 in cats

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3
Q

What is the difference btwn measured and calculated osmolality?

A

Osmolar Gap

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4
Q

What does an increase in the Osmolar Gap mean?

A

Increased osmolar gap = presence of exogenous solutes or pseudohyponatremia

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5
Q

How is osmolality of extracellular fluid regulated?

A

by adjusting water balance

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6
Q

How is the volume of extracellular fluid regulated?

A

by changes in [Na+]

-influenced by changes in vascular pressure

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7
Q

What are the clinical signs associated with water imbalance?

A

changes in skin turgor, CRT and changes in body weight

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8
Q

What are the biochemical signs associated with water imbalance?

A

an increase in PCV and plasma protein and/or BUN = dehydration

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9
Q

What does Aldosterone cause? When is it secreted?

A

an increase in Na+ (and H2O) and Cl- reabsorption and increased K+ excretion through distal tubules

Aldosterone is secreted in response to angiotensin, ACTH and hyperkalemia

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10
Q

What are the 3 types of dehydration?

A

hypertonic
isotonic
hypotonic

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11
Q

hypertonic dehydration means…

A

water loss > electrolyte loss
Increased serum Na and Cl
water is moved from ICF to ECF to maintain volume

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12
Q

isotonic dehydration means…

A

water loss = electrolyte loss
serum Na and Cl don’t change
no water shift btwn ICF and ECF - - there will be a decreased in ECF vol.

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13
Q

hypotonic dehydration means…

A

water loss

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14
Q

What electrolytes are we concerned with in our Labs?

A

Na
Cl
K

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15
Q

Most abnormalities in serum [Na+] are due to abnormalities in….

A

water

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16
Q

What can cause hyponatremia?

A

excess Na loss: V, D, renal loss, sweating, severe burns

increased extracellular water:
-osmotic shift from ICF to ECF - - hyperglycemia or mannitol admin.
-hypervolemia – decr. Na –> impaired H2O excretion –> fluid retention –> dilute Na
-syndrome of inappropriate ADH secretion (SIADH):
excess ADH despite lack of normal stimuli and normal renal function - - neoplasia and CNS/pulmonary disease

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17
Q

What is 3rd space syndrome?

A

extracellular Na/K equilibrates in sequestered fluids

  • hyponatremia
  • hypokalemia
18
Q

What are CS’s of hypernatremia?

A

neurologic, lethargy, depression, altered mentation, V, seizures

19
Q

How does the CNS adapt to hypernatremia in chronic hyperosmolar states?

A

producing idiogenic osmoles….

20
Q

What happens when the CNS correct the hypernatremia faster than the idiogenic osmoses can be cleared?

A

cellular swelling leading to cerebral edema, convulsions and death

21
Q

What causes hypernatremia?

A

inadequate water intake - primary hypodypsia due to defective ADH osmoregulation

excess water loss/deficit - diabetes insidious, panting, fever, urinary loss, osmotic diuresis, and GI shift of water

excess Na intake/retention - Increased ADH

22
Q

What is the function of Cl-?

A

transport of important electrolytes in water, crosses membranes by active transport, and acts as a conjugate anion in acid-base metabolism

23
Q

What are the CS’s associtated w/ hypochloremia?

A

neuro signs probably due to metabolic alkalosis and decreased ionized Ca2+

24
Q

What causes hypochloremia?

A

Cl- loss = Na+ loss –> same causes of hyponatremia

Cl-loss > Na+ loss

  • decreased Cl- = increased HCO3- = metabolic alkalosis
  • loss/sequestration of Cl- (cattle)
  • aggressive diuretics like thiazides
25
Q

What causes hyperchloremia?

A

Cl- increase = Na+ increase –> same causes of hypernatremia

Cl- increase > Na+ increase
-increased Cl- = decreased HCO3- = metabolic acidosis

26
Q

What is pseudohyperchloremia due to?

A

treatment with KBr –> Bromide competes with Cl-

27
Q

Hypochloremia is associated with…

A

metabolic alkalosis ***

REMEMBER THIS!

28
Q

How do you calculate correct Cl-?

A

Corrected Cl- = (Normal Na+/Measured Na+) x Measured Cl-

Changes in Cl- that are not related to water changes = acid-base abnormality

29
Q

What are the functions of K+?

A

resting cell membrane potential

30
Q

Who controls the excretion of K+ by the renal tubules?

A

Aldosterone

31
Q

If you have a decrease in Aldosterone, what is going to happen?

A

K+ retention and Increased Na+ (and therefore H2O) loss

32
Q

Hypokalemia is one of the most common electrolyte imbalances. What are the CS’s of hypokalemia?

A

muscular weakness, cardiac arrythmia, lethargy, anorexia, ileus, nausea, V

33
Q

What are the causes of hypokalemia?

A

Redistribution - seen in increased extracellular HCO3- (alkalosis); maintains electroneutrality btwn ICF and ECF

excessive K+ loss - V, D, 3rd space syndromes, renal loss, etc.

low K+ in IV fluid administration

34
Q

What are the causes of hyperkalemia?

A

redistribution - seen w/ loss of EC HCO3- (acidosis); maintains electroneutrality btwn ICF and ECF

decreased renal excretion - addison’s disease; renal failure, urinary tract obstruction, ruptured bladder

High K+ in IV fluids

35
Q

What is pseudohyperkalemia?

A

occurs in vitro (NOT IN VIVO) –> once blood hits the tube, see marked leakage of IC K+ and hemolysis

36
Q

What happens to cause Addison’s disease?

A

Decrease in Aldosterone –> K+ retention and increased Na+/H2O loss

Na:K Ratio =

37
Q

What is Equine Hyperkalemic Periodic Paralysis?

A

genetic mutation of skeletal ms. Na/K channel genes of quarter horses that causes periodic attacks of ms. fasciculation, weakness, and recumbency

38
Q

A normal fractional excretion of electrolytes indicates…

A

a non-renal cause for electrolyte loss

39
Q

What is Anion-Gap and how is it helpful?

A

a lab calculation of the difference btwn the anions and cations in serum
helps determine the cause of metabolic acidosis

40
Q

What is the most measured anion?

A

lactate

41
Q

If there is pure loss of bicarbonate = Secretional metabolic acidosis…what happens to the Anion-Gap?

A

a DECREASE in Anion-Gap

42
Q

Additional acid = Titrational metabolic acidosis…what happens to the Anion-Gap?

A

an INCREASE in Anion-Gap

Clinical Pathology - Exam 2 (7 decks)

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