9: Electrolytes Flashcards

1
Q

How do you work out osmolality?

A

2 (Na + K) + glucose + BUN

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2
Q

What causes the osmolal gap?

A

Unmeasured solutes

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3
Q

What is the usual osmolal gap?

A

10mOsm/kg

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4
Q

Which electrolyte has the highest conc in the ECF?

A

Na as freely permeates

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5
Q

What % of body weight is circulating blood volume?

A

6-8%

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6
Q

What % of blood is venous and what % is arterial?

A

70% venous, 30% arterial

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7
Q

WHich volumes must be maintained during hypovolaemia?

A

ICF and circulating volume

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8
Q

Which two pressures affect Na and protein distribution?

A

Osmotic and oncotic

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9
Q

WHich receptor does ADH act on to cause vasoconstriction?

A

V1

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10
Q

How does the V1 receptor cause vasoconstriction?

A

Increasing intracellular Ca

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11
Q

Which receptor does ADH act on to cause antidiuretic effect?

A

V2

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12
Q

What % of water does ADH allow resorption of?

A

90% rather than 80%

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13
Q

What is a primary cause of nephrogenic diabetes insipidus?

A

Congenital receptor problem

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14
Q

What is a secondary cause of nephrogenic diabetes insipidus?

A

Hypercalcaemia or endotoxins

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15
Q

What are some examples of things that cause receptor interference in nephrogenic DI?

A

Toxins e.g. E Coli, drugs e.g. GCs, metabolic e.g. hypoK, hyperCa, tubular injury/loss e.g. pyelonephritis

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16
Q

Which breed can inherit Fanconi syndrome?

A

Basenjis

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17
Q

What can cause acquired Fanconi syndrome?

A

Gentamycin and ethylene glycol

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18
Q

WHat are clinical signs of Fanconi syndrome?

A

PUPD, weight loss, poor coat, weakness, dehydration

19
Q

How does Fanconi syndrome affect urine?

A

Glucosuria and aminoaciduria and phosphaturia

20
Q

What does Fanconi syndrome cause impaired absorption of?

A

Na, K, HCO3,

21
Q

What does Fanconi syndrome cause hypo- of?

A

Hypophosphataemia

22
Q

How does congestive heart failure cause a viscious circle?

A

Reduced renal perfusion activates RAS, so high ADH and angiotensin II, so cardiac remodelling and fibrosis so volume overload and condition worsens

23
Q

What happens if ECF tonicity is too high?

A

Brain cells produce idiogenic osmoles to maintain intracellular osmolality

24
Q

What happens if you correct hyperNa too quickly?

A

Osmotic brain swelling

25
Q

How quickly should you correct hyperNa?

A

0.5mEq/l/hr

26
Q

What are the three aims of treatment of hyperK?

A

Shift K to ICF, promote K excretion, stabilise APs

27
Q

How do you treat hyperK?

A

IV fluids, soluble insulin and glucose

28
Q

What are the signs for hypo vs hyper Na?

A

Similar

29
Q

Where is K absorbed to most?

A

Proximal GI tract

30
Q

Where is K excreted?

A

Kidneys

31
Q

What will happen to K in acidosis?

A

Exits cell into serum

32
Q

What happens to K following insulin and in alkalosis?

A

Exits serum into cell

33
Q

What are three causes of hypoK?

A

Reduced intake, transcellular distribution, increased excretion

34
Q

What are some causes of increased K excretion?

A

V/D, renal, diuresis, hypoaldosteronism, renal tubular acidosis

35
Q

What are the clinical signs of hypo K?

A

Lethargy, weakness, inappetance, dysrhythmias (brady/tachy), central ventroflexion in cats

36
Q

How do you treat mild hypoK?

A

Supplement diet

37
Q

How do you treat severe hypoK?

A

IV KCl, but mix thoroughly

38
Q

What are the signs of hyperK?

A

Weakness, nausea/vomiting and bradydysrhthymias

39
Q

How common is increased intake as a cause of hyperK?

A

Uncommon

40
Q

What can cause altered K distribution leading to hyperK?

A

Acidosis, tissue damage

41
Q

What can cause decreased K excretion leading to hyperK?

A

CKD, ARF or Addisons

42
Q

WHich medications can cause hyperK?

A

K sparing, ACE inhibitor

43
Q

Why do LUT obstructions cause hyperK?

A

Damage epithelium so can’t excrete Na/K