Flashcards in Session 9 Deck (28):
Describe the role of carbonic anhydrase inhibitors.
Cause sodium carbonate diuresis, excretion of sodium, potassium and phosphate. Acts at the PCT. Affects reabsorption of sodium.
Describe the role of osmotic diuretics.
Increase osmotic gradient systemically. Can causes excessive water loss and cause hypernatraemia.
Describe the role of loop diuretics.
Affect the descending, thick limb of the loop of henle, used in oedematous states. Inhibits NaCl reabsorption, hence excretion of calcium and magnesium. Can cause hypokalaemia.
Describe the role of thiazides.
Inhibit NaCl reabsorption, promoting calcium reabsorption.
Describe the role of potassium sparing diuretics.
Act on the ENac channel in the late DCT and CD. Have no effect on potassium.
Describe the role of aldosterone antagonists.
Inhibit action of aldosterone on mineralocorticoid receptors, hence affecting NaKATPase and ENaC protein synthesis. Inhibits sodium retention.
Describe the role of ADH antagonists.
Reduces concentrating ability of urine in collecting ducts.
Give two ADRs of diuretics.
Anaphylaxis, hypovolaemia, electrolyte disturbance, metabolic abnormalities, hyperkalaemia, erectile dysfunction etc.
Give two major indications of diuretics.
Heart failure, hypertension, decompensated liver disease.
Give two examples of drugs causing renal complications.
ACE-inhibitors, aminoglycosides, penicillins, metformin and NDAIDs.
What can renovascular disease cause?
Renal artery stenosis, reducing renal function.
How do you manage hyperkalaemia?
Identify and remove the cause.
Absent P waves, prolonged QRS and tall T-waves.
Calcium gluconate, insulin, sodium bicarbonate and salbutamol.
How is an increase in blood pressure managed physiologically?
Downregulation of RAAS and reduced vasoconstriction. Causing decreased peripheral resistance. PNS is also upregulated, causing decreased cardiac output and a reduced BP.
Give three complications of high blood pressure.
-Increased arterial thickening
-Smooth muscle cell hypertrophy
-Loss of arterial compliance
-Target organ damage
Three pieces of lifestyle advice for high blood pressure.
Maintain normal weight, reduce salt intake, limit alcohol, eat lots of fruit and veg, reduce fat intake, stop smoking.
How do ACE-inhibitors work to lower blood pressure?
E.g. Ramipril. Inhibit ACE activity, preventing generation of angiotensin 2. Causes arteriolar vasodilation and prevents bradykinin breakdown. Reduced sodium and water reabsorption.
How do angiotensin receptor blockers work to lower blood pressure?
E.g. Losartan. Bind to AT1 receptors and inhibit vasoconstriction and aldosterone stimulation.
How do calcium channel blockers work to lower blood pressure?
Bind to subunit of L-type calcium channels, reducing calcium entry. They vasodilate peripheral, coronary and pulmonary arteries.
What are the three groups of calcium channel blockers?
1) Dihydropyridines, e.g. Amlodipine
2) Benzothiazepines, e.g. Diltiazem
3) Phenylalkylamines, e.g. Verapamil.
How does verapamil work?
Depresses SA node and slows AV conduction. Impedes calcium transport across the myocardial and vascular smooth muscle membrane. Peripheral vasodilatation and reduced preload and myocardial contractility.
How do thiazide diuretics work to lower blood pressure?
E.g. bendroflumethiazide. Reduces distal tubular sodium reabsorption by acting on the NaCl symporter in the DCT.
Give three secondary causes of hypertension.
Cushing's syndrome, thyroid disease, hyperparathyroidism, renovascular hypertension, diabetic renal disease, coartation of the aorta, OCP, pregnancy.
How would you treat an hypertensive emergency?
IV sodium nitroprusside. This acts as nitric oxide, causing vasodilation and rapidly reduces BP.
What is heart failure?
When the cardiac output is insufficiently adequate to perfuse the tissues, despite normal filling of the heart.
What are the main symptoms of heart failure?
Fatigue, breathlessness and exercise intolerance.
How would you treat heart failure?
-Start with an ACE-inhibitor to reduce load on the heart
-Add a diuretic to reduce circulating volume
-Add digoxin to increase force of contraction
-Add a beta-blocker
Give two side-effects of ACE-inhibitors and beta-blockers.
ACE-inhibitors: dry cough, light headedness, fatigue, upset stomach, oedema.
Beta-blockers: depression, fatigue, light headedness and memory loss.