Session 7 - Part II Flashcards
What are the main classes of diuretics?
In use - Loop Diuretics
Thiazide Diuretics
K+ Sparing Diuretics
Aldosterone Antagonist
Not in use - Inhibitors of Carbonic Anhydrase
Osmotic Diuretics
When are diuretics used?
Conditions with ECF expansion & Oedema eg congestive heart failure and nephrotic syndrome. Cirrhosis of the liver Hypertension Hypercalcaemia Osmotic diuretics (Cerebral oedema only) Carbonic anhydrase inhibitors (Glucoma)
How does congestive heart failure cause oedema and ECF expansion?
Increased venous pressure
A drop in CO leads to RAAS activation
Leads to Na+ and water retention
How does Nephrotic syndrome cause oedema and ECF expansion?
Protein is lost in the urine
Low plasma albumin which causes low oncotic pressure
Causes oedema and reduced circulatory volume
RAAS is activated
Na and water retention occurs
How does liver cirrhosis cause oedema and ECF expansion?
Less albumin in produced in the liver so there is low plasma albumin and low oncotic pressure
Leads to oedema and reduced circulatory volume, activating RAAS leading to Na+ and water retention.
Also have portal hypertension and ascites which causes reduced circulatory volume and RAAS activation
Which diuretics may cause hypokalaemia?
Loop and Thiazide diuretics increase the loss of
potassium in the urine
Which diuretics may cause hyperkalaemia?
K+ sparing Diuretics & Aldosterone antagonists
reduce excretion of potassium in the urine
How can you reduce the effects of diuretics on K+?
Combination of Loop /thiazide diuretic with a
K+ sparing diuretic / Aldosterone antagonist can be used to minimise changes in potassium
Monitor electrolytes
What are some of the adverse effects of diuretics?
Hypovolaemia Hyponatraemia ↑ Uric acid levels in blood - can precipitate attack of Gout Metabolic effects - glucose intolerence - ↑LDL levels Thiazides – erectile dysfunction
What other substances have a diuretic effect?
Alcohol (Inhibits ADH release)
Coffee (↑GFR and ↓ tubular Na+ reabsorption)
Lithium (inhibit ADH action on Collecting ducts)
What diseases can cause polyurea?
Diabetes Mellitus (glucose in filtrate - osmotic diuresis) Psychogenic polydipsia (Increased intake of fluid) Diabetes Insipidus (cranial)- ↓ADH release from post pituitary → diuresis Diabetes Insipidus (nephrogenic) – Poor response of Collecting ducts to ADH → diuresis
What reabsorbs Na+ in the Proximal Convoluted Tubule?
Na/H antiporter
Na/Glucose Symporter
Na/Amino Acid Symporter
What reabsorbs Na+ in the Loop of Henle?
Na/K/2Cl symporter
What reabsorbs Na+ in the Early Distal Convoluted Tubule?
Na/Cl symporter
What reabsorbs Na+ in the Late Distal Convoluted Tubule & Collecting Duct?
ENaC (Epithelial Na+ channels)
