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

Question 1

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

Answer 1

Question 2

Effects of severe hyperkalemia

Answer 2

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

Question 3

Normal Plasma [K+]

Answer 3

3.5 to 5.0 mEq/L

Question 4

Effects of severe hypokalemia

Answer 4

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

Question 5

Where is the largest amount of potassium?

Answer 5

intracellular fluid

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

Question 6

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

Answer 6

Insulin

Aldosterone

a-adrenergic

Alkalosis

Question 7

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

Answer 7

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

Question 8

Renal tubular sites of potassoim reabsorption and secretion

Answer 8

Question 9

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

Answer 9

Intercalated; principal

Question 10

Which factors increase K+ secretion?

Answer 10

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

NOTE: Acidosis leads to decrease in K+ secretion.

Question 11

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

Answer 11

Question 12

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

Answer 12

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

Question 13

Effects of diuretics to cause potassium depletion

Answer 13

Question 14

Effect of increased sodium intake on potassium excretion

Answer 14

Question 15

___________ (acidosis/alkalosis) decreases cell K+.

Answer 15

Acidosis

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

Question 16

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

Answer 16

Question 17

Causes of hyperkalemia

Answer 17

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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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

Question 20

Causes of hypokalemia

Answer 20

• 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

Question 21

Compensatory responses to decreased plasma ionized calcium

Answer 21

Question 22

Proximal tubular calcium

Answer 22

Question 23

Hormones that affect plasma Ca++ levels

Answer 23

• Calcitriol
• Calcitonin
• PTH

Question 24

Hierarchy of Responses to Disturbanches of Body Fluid Regulation

Answer 24

Question 25

Causes of AKI

Answer 25

Question 26

How can ischemia lead to decreased GFR?

Answer 26

Question 27

Mechanism of action of ADH in distal and collecting tubules

Answer 27

Question 28

Chronic lithium treatment in bipolar patients results in nephrogenic \_\_\_\_\_\_\_\_\_\_.

Answer 28

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

Question 29

How does lithium affect ADH response?

Answer 29

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).

Question 30

Symptoms of lithium toxicity

Answer 30

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

Question 31

How do you distinguish between central and nephrogenic diabetes insipidus?

Answer 31

**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