Diuretics and Renal Replacement Therapy Flashcards
What is a diuretic?
A substance/drug that promotes diuresis
Increased renal excretion
What percentage is the normal fractional excretion of Na+?
Less than or equal to 1%
Aldosterone increases the expression of which channels/transporters?
Na/K/ATPase
ENaC
K+ channels
How do loop diuretics work and give an example?
Act on the loop of Henle
Block NKCC2 cotransporter
Eg. Furosemide
How do thiazides work and give an example?
Act on early DCT
Block NaCl cotransporter
Eg. Metolazone
How do K+ sparing diuretics work and give an example?
Act on late DCT and CD
Block ENaC channels
Eg. Amiloride
How do aldosterone antagonists work and give an example?
Eg. Spironolactone
Competitive inhibition of aldosterone on principle cells in late DT and CD
How does mannitol work?
Use small molecules to increase osmolarity of filtrate
Increased water excretion (decreased water reabsorption)
How are carbonic anhydrase inhibitors used as a diuretic?
Prevents uptake of bicarbonate as it cannot from water and CO2 to enter the cells
However can lead to metabolic acidosis due to all the bicarbonate in the urine
How do loop diuretics affect magnesium and calcium?
Magnesium and calcium reabsorption rely on the gradient of the thick ascending limb LOH
Therefore loop diuretics inhibit their reabsorption
Increased loss of calcium and magnesium
Can cause hypocalcaemia and hypomagnesiumia
Why are loop diuretics chosen to help heart failure failure and acute pulmonary oedema?
They are very potent diuretics
What can we use loop diuretics to treat?
Heart failure Pulmonary oedema Nephrotic syndrome Renal failure Liver cirrhosis Hypercalcaemia
Why are thiazides good diuretics for the elderly?
Blocking Na+ reabsorption increases the Ca2+ reabsorption
Good for the elderly who are prone to osteoporosis
Why are thiazides ineffective in renal failure?
Less potent as only 5% sodium reabsorption inhibited
What are thiazides widely used for and why?
Hypertension
Decreased effective circulating volume and cause vasodilation
What is the potential problem when using thiazides?
Hypokalaemia
Why are K+ sparing diuretics often a bad choice?
Mild diuretics therefore cannot cope with large volume increases
Can produce severe hyperkalaemia esp if used in conjunction with ACEi, K+ supplements or in pts with renal failure
What is the preferred drug to treat ascites and oedema in cirrhosis?
Spironolactone
Which diuretics are often used in conjunction for heart failure?
Spironolactone
Loop diuretics
Why do we have to be careful when using diuretics?
Decreased circulatory volume and reduce perfusion pressure to the kidneys
This can activate RAAS
Causes water retention (counter productive)
Describe nephrotic syndrome
Increase in glomerular BM permeability to proteins
Proteinuria
Low plasma albumin - decreased oncotic pressure - oedema
What is ascites?
Free fluid in the peritoneal cavity
Describe hepatic encephalopathy
Reversible syndrome of impaired brain function
Occurs in cirrhosis with advanced liver failure
Causes confusion and comas
Signs - constructional apraxia (cannot draw a 5 pointed star) and flapping tremors
Includes elevated ammonia levels in blood
Hypokalaemia can cause this
Name some adverse effects of diuretics
Potassium abnormalities Decreased blood volume - postural hypotension, dehydration Increased uric acid levels - gout Glucose intolerance Raised LDLs Erectile dysfunction (thiazides) Gynaecomastia (spironolactone)
How can alcohol affect blood volume levels?
Inhibits ADH release
How does coffee affect the kidney?
Increases GFR
Decreased Na+ reabsorption
Increased loss of Na+ and water
Diuresis
Define end stage renal failure (ESRF)
When death is likely without renal replacement therapy
eGFR < 15 ml/min
Give some symptoms/signs of ESRF
Tiredness - overwhelming fatigue physically and mentally Difficulty sleeping Difficulty concentrating Volume overload - oedema, SoB Nausea/vomiting/reduced appetite Restless legs/cramps Pruritus (itchy) Sexual dysfunction/reduced fertility Increased infections
What percentage of patients with CKD are hypertensive?
80-85%
If you have no ADH, how much urine could be produced a day?
30 L/day
Give some symptoms of uraemia
Reduced appetite
Nausea/vomiting
Pruritus
Why do lots of drugs require dose alteration with CKD?
Reduced metabolism and/or elimination of the drug
Drug sensitivity can be increased
What are the treatment options when the kidneys fail?
Haemodialysis
Peritoneal dialysis
Transplant
Conservative care
Describe haemodialysis
Artificial pump in system to keep at high enough pressure
Anti-coagulant added
Gets rid of waste products in blood over artificial membrane
Enters back into venous system
A fistula has to be created between an artery and vein
How often does haemodialysis have to be performed?
4 hours
3 times a week
What are the advantages and disadvantages of haemodialysis?
Advantages: less responsibility, days off treatment
Disadvantages: travel to hospital/waiting, ‘tied’ to your dialysis time, restrictor on travel, restrictions on fluid and food intake
Approximately how many tablets per day do people on haemodialysis have to take?
19
What are the contraindications for haemodialysis?
Failed vascular access
Heart failure
Coagulopathy
What are some complications of haemodialysis?
Lines: infection, thrombosis, venous stenosis
Thrombosis, bleeding, access failure - steal syndrome
CVS instability
Feel chronically unwell
Accumulate morbidities
Describe peritoneal dialysis
Waste products cross semi-permeable peritoneal membrane into the peritoneal cavity
Can do 4-5 bags throughout the day (30 min each)
Or can do overnight
What are the advantages and disadvantages to peritoneal dialysis?
Advantages: independence, less fluid/food restrictions, fairly easy to travel, renal function may be better preserved
Disadvantages: frequent daily exchanges, responsibility of own care
Approximately how many medications does a patient on peritoneal dialysis have to take per day?
10 tablets
SC EPO injection
What are the contraindications for peritoneal dialysis?
Failure of peritoneal membrane
Adhesions, previous abdo surgery, hernia, stoma
Patient or carer unable to connect/disconnect themselves
Obese/large muscle mass
How often do patients on peritoneal dialysis get peritonitis?
Once every 20 months on average
Give some complications of peritoneal dialysis
Peritonitis
Ultrafiltration failure
Leaks
Development of hernia
Describe home/nocturnal haemodialysis
Same as haemodialysis but at home and possibly overnight
Allows more dialysis hours so better clearance
Requires someone at home with you - as if it goes wrong you can bleed out v rapidly
What are the advantages of home haemodialysis?
Patient often feels better
Patient often needs fewer medications
Can pick your own schedule
Can do it overnight so doesn’t interfere
Does a transplant have a higher or lower mortality/morbidity than dialysis?
Lower
Better quality of life too
For how long is the peri-operative risk after transplant?
3 months
What are the peri-operative risks of kidney transplant?
Dampening of immune system:
Malignancy
Infection
Risk of diabetes and hypertension from meds (steroids)
What vessels do they connect renal transplants to?
Iliac vessels
What are the different types of transplant?
Live donor (related or unrelated)
Deceased after brain death (DBD)
Deceased after circulatory death (DCD)
Kidney transplants are matched according to …
Tissue match - blood type and HLA
Length of time on waiting list
Age
What is the average wait for a kidney from a deceased donor?
3 years
What is the average life of the transplanted kidney from a live related donor?
12 years
What is the average life of the transplanted kidney from a live unrelated donor?
11 years
What is the average life of a transplanted kidney form a DBD donor?
10 years
How many immunosuppressants are you generally on after a kidney transplant?
3
What are the problems with being on immunosuppressants after a kidney transplant?
LOTS of side effects
Including being nephrotoxic
Dialysis tends to prolong survival by how long?
2 years
What is the average life expectancy of people diagnosed with ESRD aged 25-29 years?
18 years from diagnosis
What is the greatest killer in dialysis patients?
Cardiac disease
What is the greatest killer in transplant patients?
Malignancy
What is your daily fluid allowance if you are anuric and on dialysis?
500 ml
What is your daily fluid allowance if you are on dialysis and pass urine?
500 ml plus the volume of urine that you pass
