Regulation of K+, Ca2+, P Balance and Diueretics Flashcards
Normal potassium intake, distribution, and output from the body.
Effects of severe hyperkalemia
- Partial depolarization of cell membranes
- Cardiac toxicity, ventricular fibrillation or asystole
Normal Plasma [K+]
3.5 to 5.0 mEq/L
Effects of severe hypokalemia
- Hyperpolarization of cell membranes
- Fatique, muscle weakness
- Hypoventilation
- Delayed ventricular repolarization
Where is the largest amount of potassium?
intracellular fluid
NOTE: At the cellular level, the N/K pump regulates intracellular K concentration compared to extracellular
Which factors cause a migration of K+ from the extracellular compartment to the intracellular compartment?
Insulin
Aldosterone
a-adrenergic
Alkalosis
Which factors cause a migration of K+ from the intracellular compartment to the extracellular compartment?
- Cell lysis
- Strenous exercise
- B-blockade
- Acidosis
- Diabetes (insulin deficiency)
- Addison’s Disease (Aldosterone deficiency)
- ECF osmolality
Renal tubular sites of potassoim reabsorption and secretion
Potassium is reabsobed by ________ cells and secreted by ________ cells.
Intercalated; principal
Which factors increase K+ secretion?
- Increase in extracellular K+ concentration
- Aldosterone
- Sodium delivery
- Alkalosis
NOTE: Acidosis leads to decrease in K+ secretion.
Effect of changes in K+ intake on plasma K+ after blocking aldosterone system
What effect does collecting tubule flow rate have on K+ secretion?
A rise in distal tubular flow rate, as occurs with volume expansion, high sodium intake, or treatment with some diuretics, stimulates potassium secretion
Effects of diuretics to cause potassium depletion
Effect of increased sodium intake on potassium excretion
___________ (acidosis/alkalosis) decreases cell K+.
Acidosis
- Acidosis reduces the activity of the Na-K- ATPase pump
- Acidosis reduces # of K channels
____________ (acidosis/alkalosis) increases cell K+ and increases K excretion.
Causes of hyperkalemia
- Renal failure
- Decreased distal nephron flow
- Decreased aldosterone or decreased effect of aldosterone
- Metabolic acidos
- Diabetes
Which factors tend to cause hyperkalemia, with regards to diabetes?
- Decreased insulin (type 1)
- Insulin resistance (type 2)
- Acidosis
- Dehydration (increased plasma osmolarity)
- low GFR
Which factors tend to cause hypOkalemia, with regards to diabetes?
- Osmotic diuresis (high distal tubular flow)
- Administration of insulin
- Rehydration
Causes of hypokalemia
- 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
Compensatory responses to decreased plasma ionized calcium
Proximal tubular calcium
Hormones that affect plasma Ca++ levels
- Calcitriol
- Calcitonin
- PTH
Hierarchy of Responses to Disturbanches of Body Fluid Regulation
Causes of AKI
How can ischemia lead to decreased GFR?
Mechanism of action of ADH in distal and collecting tubules
Chronic lithium treatment in bipolar patients results in nephrogenic __________.
Diabetes insipidus
NOTE: This is in contrast to central/neurogenic diabetes insipidus, which is caused by insufficient levels of antidiuretic hormone
How does lithium affect ADH response?
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).
Symptoms of lithium toxicity
- Volume depletion
- Hypotension
- Orthostasis
- Tachycardia
- Dry mouth
- Altered mental status
- Other anti-psychotics
- Haloperidol
- Hypotension and polyuria
- Decrease ADH levels
- Haloperidol
How do you distinguish between central and nephrogenic diabetes insipidus?
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
