renal system

Question 1

when are thiazides used to treat hypertension (more effective than ACEi but side effect of polyuria means less compliance)

Answer 1

first line treatment if >55 year old or afro-Caribbean (salt sensitive hypertensives); second/third line if <55

Question 2

why are thiazides used to treat hypertension compared to other diurectics

Answer 2

with all diuretics, they have an initial response of 4-6 weeks due to decreased plasma volume, but after this plasma volume restored (sensitive to tolerance); with chronic thiazides, they decrease TPR due to activation of eNOS in endothelium (vasodilation), Ca2+ channel antagonism (prevent forceful contraction) or cause K(Ca) channel opening in smooth muscle (hyperpolarise cells to prevent contraction)

Question 3

how are loop diuretics used to treat heart failure and oedema

Answer 3

in heart failure, reduced cardiac output (causing SNS and RAAS to turn on to preserve BP, but if long term cardiac remodelling exacerbates heart failure and causing congestion due to backlog of fluid increasing capillary bed pressure); loop diuretics decrease Na+ (by 30%) and water retention (acute reduction in congestion)

Question 4

why is chronic use of loop diuretics associated with resistance when used to treat heart failure and oedema

Answer 4

they activate RAAS as increase renin secretion

Question 5

what is used to combat chronic resistance of loop diuretics when used to treat heart failure and oedema

Answer 5

additional use of K+-sparing diuretics, which reduce Na+/K+ exchange later on in kidney, so greater effect of reducing Na+ and H2O retention, further preventing congestion