Regulation of K+, Ca2+, P Balance and Diueretics Flashcards

1
Q

Normal potassium intake, distribution, and output from the body.

A
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2
Q

Effects of severe hyperkalemia

A
  • Partial depolarization of cell membranes
  • Cardiac toxicity, ventricular fibrillation or asystole
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3
Q

Normal Plasma [K+]

A

3.5 to 5.0 mEq/L

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4
Q

Effects of severe hypokalemia

A
  • Hyperpolarization of cell membranes
  • Fatique, muscle weakness
  • Hypoventilation
  • Delayed ventricular repolarization
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5
Q

Where is the largest amount of potassium?

A

intracellular fluid

NOTE: At the cellular level, the N/K pump regulates intracellular K concentration compared to extracellular

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6
Q

Which factors cause a migration of K+ from the extracellular compartment to the intracellular compartment?

A

Insulin

Aldosterone

a-adrenergic

Alkalosis

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7
Q

Which factors cause a migration of K+ from the intracellular compartment to the extracellular compartment?

A
  • Cell lysis
  • Strenous exercise
  • B-blockade
  • Acidosis
  • Diabetes (insulin deficiency)
  • Addison’s Disease (Aldosterone deficiency)
  • ECF osmolality
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8
Q

Renal tubular sites of potassoim reabsorption and secretion

A
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9
Q

Potassium is reabsobed by ________ cells and secreted by ________ cells.

A

Intercalated; principal

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10
Q

Which factors increase K+ secretion?

A
  • Increase in extracellular K+ concentration
  • Aldosterone
  • Sodium delivery
  • Alkalosis

NOTE: Acidosis leads to decrease in K+ secretion.

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11
Q

Effect of changes in K+ intake on plasma K+ after blocking aldosterone system

A
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12
Q

What effect does collecting tubule flow rate have on K+ secretion?

A

A rise in distal tubular flow rate, as occurs with volume expansion, high sodium intake, or treatment with some diuretics, stimulates potassium secretion

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13
Q

Effects of diuretics to cause potassium depletion

A
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14
Q

Effect of increased sodium intake on potassium excretion

A
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15
Q

___________ (acidosis/alkalosis) decreases cell K+.

A

Acidosis

  • Acidosis reduces the activity of the Na-K- ATPase pump
  • Acidosis reduces # of K channels
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16
Q

____________ (acidosis/alkalosis) increases cell K+ and increases K excretion.

A
17
Q

Causes of hyperkalemia

A
  • Renal failure
  • Decreased distal nephron flow
  • Decreased aldosterone or decreased effect of aldosterone
  • Metabolic acidos
  • Diabetes
18
Q

Which factors tend to cause hyperkalemia, with regards to diabetes?

A
  • Decreased insulin (type 1)
  • Insulin resistance (type 2)
  • Acidosis
  • Dehydration (increased plasma osmolarity)
  • low GFR
19
Q

Which factors tend to cause hypOkalemia, with regards to diabetes?

A
  • Osmotic diuresis (high distal tubular flow)
  • Administration of insulin
  • Rehydration
20
Q

Causes of hypokalemia

A
  • Very low intake of K
  • GI loss of K+ (diarrhea)
  • Metabolic alkalosis
  • Excess insulin
  • Increased distal tubular flow
    • Salt wasting nephropathies
    • Osmotic diuretics
    • Loop diuretics
  • Excess aldosterone or other mineralocorticoids
21
Q

Compensatory responses to decreased plasma ionized calcium

A
22
Q

Proximal tubular calcium

A
23
Q

Hormones that affect plasma Ca++ levels

A
  • Calcitriol
  • Calcitonin
  • PTH
24
Q

Hierarchy of Responses to Disturbanches of Body Fluid Regulation

A
25
Q

Causes of AKI

A
26
Q

How can ischemia lead to decreased GFR?

A
27
Q

Mechanism of action of ADH in distal and collecting tubules

A
28
Q

Chronic lithium treatment in bipolar patients results in nephrogenic __________.

A

Diabetes insipidus

NOTE: This is in contrast to central/neurogenic diabetes insipidus, which is caused by insufficient levels of antidiuretic hormone

29
Q

How does lithium affect ADH response?

A

Chronic lithium ingestion – appears to affect the tubules by entering the collecting tubule cells through sodium channels, accumulating and interfering with the normal response to ADH (ADH resistance).

30
Q

Symptoms of lithium toxicity

A
  • Volume depletion
    • Hypotension
    • Orthostasis
    • Tachycardia
    • Dry mouth
    • Altered mental status
  • Other anti-psychotics
    • Haloperidol
      • Hypotension and polyuria
    • Decrease ADH levels
31
Q

How do you distinguish between central and nephrogenic diabetes insipidus?

A

Vasopressin/Desmopressin Challenge

  • If central- Urine osmolality increase by about 50%
    • Due to a lack of ADH, which can be due to damage to the hypothalamus or pituatary gland or genetics
  • If nephrogenic- Urine osmolality increase less than 10 %
    • Occures when kidneys do not respond properly to vasopressin