Renal: Dialysis Flashcards
Name the two most common loop diurertics [2]
Furosemide & Bumetanide
At high doses, explain what AE loop diuretics can cause
Tinnitus & hearing loss:
- A similar NaCl2K transporter is found in the inner ear which regulates endolymph
Describe which pathology chronic loop diuretic use can lead to [2]
Gout: due to inhibition of uric acid secretion
Loop diuretics have the potential to effect drugs excreted by the kidneys.
Name and describe three examples [3]
Lithium: have reduced excretion, so have increased levels occur
Digoxin toxicity increased: due to diuretic associated hypokalaemia
Aminglycosides can become more nephrotoxic
What is important to note regarding furosemide prescription in patients with pulmonary oedma? [1]
bioavailbility (the proportion of furosemide absorbed from the gut) is reduced to gut wall oedema.
Manage by giving IV furosemide or bumetanide
Describe the MoA of loop diuretics [2]
Normal physiology:
- ATPase causes Na+ out of thick ascending limb into interstitium blood, and K+ into thick ascending limb
- NaKCl2 channel then pumps Na+ and K+ and Cl2 into thick ascending limb
- K+ pumped out otherside via ROMK into urine
Loop diuretic:
- Blocks NaKCl2 channel; preventing sodium and water reabsorption from urine into the thick ascending limb
Describe common AEs of loop diuretics [5]
hyponatremia
hypokalemia
hypochloremia
hypomagnesemia
kidney stones (due to calcuria)
metabolic alkalosis
Name two common thiazide like diuretics [2]
Bendroflumethiazide; hydrochlorothiazide; Indapamide
Describe the MoA of thiazide-like diuretics [1]
- Block Na/Cl channel from urine into DCT
- Blockage of the Na/Cl channel increases the flow of ions through the Na/Ca channel, resulting in increased calcium reabsorption into the interstitium in exchange for Na return to the DCT.
Describe common AEs of thiazide like diuretics [5]
Hypokalemia. Most widely recognized, the first adverse effect of thiazide diuretics is hypokalemia.
Hyponatremia. The MOA of thiazide diuretics is to decrease sodium reabsorption and therefore decreased fluid reabsorption; this directly causes decreased levels of circulating sodium.
Metabolic alkalosis. Patients on thiazide diuretics may experience a hypokalemic metabolic alkalosis due to the increase in aldosterone-mediated K and H ions excretion in the intercalated cells of the CT.
Hypercalcemia. By increasing calcium reabsorption from the luminal membrane into the interstitium in exchange for sodium, thiazides reduce urine calcium levels and increase blood calcium. However, if indicated, this effect of thiazide diuretics makes thiazides useful for nephrolithiasis and osteoporosis treatment. Decreased urinary calcium decreases stone development in the kidney, and increased blood calcium is beneficial for patients with osteoporosis and promotes bone health.
Hyperglycemia. Thiazide diuretics cause hypokalemia; at the level of the pancreatic B cells, this hypokalemia causes hyperpolarization of the B cell and decreases insulin secretion. Decreased K in the interstitium keeps the K channels open for an extended time, which causes the hyperpolarization of the cell. This hyperpolarization does not allow the voltage-gated calcium channels to open. When intracellular calcium does not increase through calcium influx via the voltage-gated calcium channels, exocytosis of insulin granules does not occur in the pancreatic B cells.
Hyperuricemia: increases risk of gout
What conditions are thiazides contraindicated in? [3]
Hypokalameia
Hyponatraemia
Gout
Thiazides effectiveness are reduced by which drug class? [1]
NSAIDs
Describe the two main types of dialysis [2]
Haemodialysis can be done at home or in-centre at a renal unit:
Peritoneal dialysis is a home-based treatment of which there are two types: CAPD and APD:
- Continuous ambulatory peritoneal dialysis
- Automated peritoneal dialysis
How can you prescribe a thiazide like diuretic but maintain normal K levels? [1]
Prescribe an ACE inhibitor alongside (as cause hyperkalaemia)
State the frequency of dialysis needed for haemodialysis and peritoneal dialysis [2]
haemodialysis means 4 treatment-free days a week, but the treatment sessions last longer and may need to visit hospital each time
home haemodialysis – you’ll usually need to have dialysis sessions more often than would in a clinic, but can choose a treatment plan that meets medical needs and fits around life
peritoneal dialysis can be done quite easily at home and can sometimes be done while sleeping, but it needs to be done every day
What is a therapeutic A/V fistula? [1]
An arteriovenous fistula is a surgical connection between an artery and a vein.
The blood from the artery goes straight into the vein, which then becomes bigger and firmer. This means that it is possible to put two needles into the enlarged vein so that blood can be taken out of the body, sent through the dialysis machine and then returned through the second needle.
Describe how haemodialysis occurs [5]
Blood is taken out of the body, passed through the dialysis machine, and pumped back into the body.
The blood passes along a series of semipermeable membranes inside the dialysis machine.
Solutes filter out of the blood, across the membrane and into a fluid called dialysate.
The concentration gradient between the blood and the dialysate fluid causes water and solutes to diffuse out of the blood and across the membrane.
Anticoagulation with citrate or heparin is necessary to prevent blood clotting in the machine and during the process.
What is the structure called that surrounds a tunneled catheter? [1]
A Dacron cuff surrounds the catheter. The cuff promotes healing and adhesion of tissue, making the catheter more permanent and providing a barrier to infection.
Name 4 AV fistula features to examine in an OSCE
Skin integrity
Aneurysms
Palpable thrill (a fine vibration felt over the anastomosis)
A “machinery murmur” on auscultation over the fistula
Describe exactly how a tunnelled catheter is put into place [3]
Inserted into the subclavian or jugular vein with a tip in the superior vena cava or right atrium.
It has two lumens, one for blood exiting the body (usually red) and one for blood entering the body (usually blue).
They can stay long-term and be used for regular haemodialysis.
What is the structure called that surrounds a tunnel catheter? [1] Why is this device used? [1]
A Dacron cuff surrounds the catheter.
The cuff promotes healing and adhesion of tissue, making the catheter more permanent and providing a barrier to infection.
Describe how an AV fistula works for dialysis [3]
An AV fistula is an artificial connection between an artery and a vein. It bypasses the capillary system and allows blood to flow under high pressure from the artery directly into the vein.
This provides a permanent, large, easy-access blood vessel with high-pressure arterial blood flow.
Creating an A-V fistula requires a surgical operation and a maturation period of 4-16 weeks before it can be used.
Which three locations can an AV fistula be placed in? [3]
Radiocephalic fistula at the wrist (radial artery to cephalic vein)
Brachiocephalic fistula at the antecubital fossa (brachial artery to cephalic vein)
Brachiobasilic fistula at the upper arm (less common and a more complex operation)
What is STEAL syndrome of an AV fistula? [2]
Inadequate blood flow to the limb distal to the fistula.
The AV fistula “steals” blood from the rest of the limb.
Blood is diverted away from the part of the limb it was supposed to supply, leading to ischaemia. Instead, it flows through the fistula and into the venous system.
Describe the process of peritoneal dialysis [3]
Peritoneal dialysis uses the peritoneal membrane to filter the blood.
A special dialysis solution containing dextrose is added to the peritoneal cavity.
Ultrafiltration occurs from the blood, across the peritoneal membrane, into the dialysis solution. The dialysis solution is replaced, taking away the waste products that have filtered out of the blood.
