Kidneys and Dialysis Flashcards
Nephron
functional unit of the kidneys
- Glomerulus: Filtration Membrane –> 1 000 000 per kidney
!!! Pressure in Glomerulus is kept constant! - local pressure regulation by changing the diameter
- 2 arteriole systems connected serially
Tasks of the kidney
- clearing blood from urea, watersoluble toxins and medicaments
actuator in:
- body fluid regulation
- regulation of pH
- blood pressure regulation
- blood formation
Autoregulation
- Perfusion stays constant –> independent of blood pressure changes
- keep pressure in Glomerulus constant
- renal blood perfusion constant for a wide range of arterial blood pressure values (80-200 mmHg)
Exchanger
- passive process –> they don’t consume energy
- countercurrent exchangers are more efficient than parallel flow exchange
- heat and matter exchange in body
Does the kidney operate as a countercurrent exchanger?
partly, it is doing more: Countercurrent exchange and Countercurrent Multiplication
Countercurrent Multiplication: builds up own concentration gradient against spatial gradient using active energy –> different to countercurrent exchange!!
–> automatic build-up of osmotic gradient
Chronic Kidney Failure
4 Stages:
1) visible hypertension
2) creatinine value: 2 - 8 mg/dl
3) maximal creatinine values: 8 mg/dl up to renal decompensation
4) creatinine values: 10 - 13 mg/dl
- -> need for dialysis or transplant
Therapy Option: Transplantation
pros & cons
- not in position of the healthy kidney
Advantages:
- continuous treatment
- fewer secondary diseases
- mobility
- freedom from time management
Disadvantages:
- rejection of organ
- immunosuppression
- lack of organ donations
Therapy Option: Peritoneal Dialysis
- peritoneum as a semipermeable membrane
- sac with fresh solution & sac with consumed solution
Therapy Option: Hemodialysis
- blood purification
- dialyzer: Countercurrent exchanger
- additional Ultrafiltration
- vascular access through arm
- 3x per week, 4-6 hours each –> great life restriction
- clearance, specifically for high molecular weight proteins is worse than in kidneys –> higher mortality
Ultrafiltration - Formula
UFR = L * A * (Pnet - Posm) L = hydraulic permeability of the membrane A = membrane area Pnet = transmembrane pressure Posm = osmotic pressure
Membrane Therapy - Hemodialysis
- classic procedure for chronic blood purification
- ultrafiltration: 1-2 l/h
- lower TMP
Membrane Therapy - Hemofiltration
compare to Hemodialysis
- when it needs to be faster
- UFR 3 l/h
- higher transmembrane pressure, lower flow rates –> protective for circulatory system
- hemofilters –> different pores: you can suck larger molecules out of blood
Membrane Therapy - Hemodiafiltration
- mixed concept –> common for chronic patients
- transmembrane pressure between Hemodialysis and Hemofiltration
- still works with dialysis
Hypotension
What may be an influencing factor?
life-threatining condition
- due to unadjusted ultrafiltration rate
- -> sudden, unpredictable drop of blood pressure
Body Compartments
Intracellular volume: 23l
Intestitial volume: 15l
Blood volume: 5l
goal: keep all compartments equally regulated (not reality!)
