What Happens When Kidneys Stop Working Flashcards
What happens when kidneys stop working
Loss excretatory function - accumulation of waste products
Loss homeostatic function - electrolyte function, acid base, volume control
Loss endocrine - loss erythropoietin production, failure of 1 alpha hydroxylase vit D
Abnormality of glucose homeostasis - decrease gluconeogenesis
Ways to assess kidney function
Urea Creatinine Creatinine clearance Inulin clearance Radionuclide studies
Why is inulin clearance not useful
Complicated and invasive but is the best test, used in labs only
What are the cons of creatinine clearance test for kidney function
Affected by muscle mass, race, age
Vary way to much from person to person
What are the cons of urea conc test for kidney function
Urea up if urine output down
Up if urea production increase eg GI bleed
Urea down if liver failure
Urea up if catabolic bc on steroids
Urea level vary too much between situations
What is eGFR
Estimated GFR using equation and creatinine and patient factors eg age and race
What are the pros and cons of radionuclide clearance test for kidney function
Radionuclide version of inulin clearance
EDTA clearance
Reliable but expensive
Used by oncologists when planning chemo regimes
Symptoms of renal failure?
Extreme lethargy
Weakness
Anorexia
Clinical volume depleted leading to severe hypotension
What is tested and shown in order to diagnose renal failure?
Elevated plasma urea and creatinine
What complicates renal failure?
Hypekalaemia
Hyponatraemia
Metabolic acidosis
Anaemia
What causes lethargy and anorexia?
FAILURE OF EXCRETION causes nitrogenous waste, hormones, peptides and other middle sized molecules to build up to build up
FAILURE OF HOMEOSTASIS, acidosis, hyponatraemia, volume depletion (low bp)
FAILURE OF ENDOCRINE FUNCTION, anaemia
What causes a salt and water imbalance in renal failure? What does that lead to?
Tendency to retain sodium leading to hypertension, oedema, pulmonary oedema, volume depletion (low bp)
When can salt and water loss be seen in renal failure patients?
If they have tubulointerstitial disorders in which the concentrating mechanisms have been damaged
What causes acidosis in renal failure patients?
Decreased excretion of H+ ions and by retention of acid bases
What effect can acidosis have on renal failure patients?
It is buffered by H+ ions passing into cells in exchange for K+ ions therefore aggravates tendency to hyperkalaemia, increases CO2 loss through lungs - kussmahls respiration, exacerbates anorexia and increases muscle catabolism
What causes hyperkalaemia in renal failure patients?
Failure of distal tubule to secrete potassium
What exacerbates hyperkalaemia in renal failure patients?
Acidosis - causing shift of K+ from intracellular to extracellular space
What can hyperkalaemia cause in renal failure patients?
Cardiac arrhythmias (loss of p waves and bradycardia) and arrest, affect neural and muscular activity
What are clinical features of hyperkalaemia dependent on?
Chronicity of the hyperkalaemia
Why can severe hyperkalaemia sometimes lead to heart block?
Increase plasma K+ can lead to membrane depolarisation, which can be large enough that a portion of Na channels inactivate so can’t contribute to AP upstroke leading to less conduction and excitability
How can severe hyperkalaemia lead to bradycardia?
Depolarisation due to increased plasma K+ can lead to reduced SA nodal cell upstroke leading to less firing rate
What does a lower erythropoietin production in renal failure lead to?
Anaemia
What does low 1-25 Vit D levels result in in the long and short term?
Poor intestinal calcium absorption
Short term = hypocalcaemia
Long term = hyperparathyroidism
What is a major predictor of end stage renal failure?
CKD - chronic kidney disease
What is a major outcome for patients with CDK?
Cardiovascular disease
How is a renal failure patient initially managed?
Intravenous normal saline to correct fluid depletion
Intravenous sodium bicarbonate to correct acidosis
Intravenous insulin and dextrose to lower plasma potassium by driving back in cells
Transfer to CX for dialysis
Traditional ways to assess GFR?
Urea Creatinine Creatinine clearance Inulin clearance Radionuclide studies
How to estimate GFR => serum creatinine?
- modification of diet in renal disease MDRD
2. CKD epidemiological collaboration CKD-EPI - better estimate true DFR at >45mL/min
How is renal failure managed long term?
Haemodialysis for 4 hrs 3x a week
Low K+ diet and fluid restriction
Erythropoietin injections to correct anaemia
1,25VitD supplements to prevent hyperparathyroid bone disease
What is osmotic diuresis
the increase of urination rate caused by the presence of certain substances in the small tubes of the kidneys. The excretion occurs when substances such as glucose enter the kidney tubules and cannot be reabsorbed (due to a pathological state or the normal nature of the substance)
