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Medical Systems > Kidneys and Dialysis > Flashcards

Kidneys and Dialysis Flashcards

1
Q

Nephron

A

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
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2
Q

Tasks of the kidney

A
  • clearing blood from urea, watersoluble toxins and medicaments

actuator in:

  • body fluid regulation
  • regulation of pH
  • blood pressure regulation
  • blood formation
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3
Q

Autoregulation

A
  • 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)
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4
Q

Exchanger

A
  • passive process –> they don’t consume energy
  • countercurrent exchangers are more efficient than parallel flow exchange
  • heat and matter exchange in body
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5
Q

Does the kidney operate as a countercurrent exchanger?

A

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

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6
Q

Chronic Kidney Failure

A

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

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7
Q

Therapy Option: Transplantation

pros & cons

A
  • 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
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8
Q

Therapy Option: Peritoneal Dialysis

A
  • peritoneum as a semipermeable membrane

- sac with fresh solution & sac with consumed solution

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9
Q

Therapy Option: Hemodialysis

A
  • 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
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10
Q

Ultrafiltration - Formula

A 
UFR = L * A * (Pnet - Posm)
L = hydraulic permeability of the membrane
A = membrane area
Pnet = transmembrane pressure
Posm = osmotic pressure
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11
Q

Membrane Therapy - Hemodialysis

A
  • classic procedure for chronic blood purification
  • ultrafiltration: 1-2 l/h
  • lower TMP
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12
Q

Membrane Therapy - Hemofiltration

compare to Hemodialysis

A
  • 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
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13
Q

Membrane Therapy - Hemodiafiltration

A
  • mixed concept –> common for chronic patients
  • transmembrane pressure between Hemodialysis and Hemofiltration
  • still works with dialysis
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14
Q

Hypotension

What may be an influencing factor?

A

life-threatining condition

  • due to unadjusted ultrafiltration rate
  • -> sudden, unpredictable drop of blood pressure
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15
Q

Body Compartments

A

Intracellular volume: 23l
Intestitial volume: 15l
Blood volume: 5l

goal: keep all compartments equally regulated (not reality!)

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16
Q

Future: Closed-Loop Control

What are the effects of Body Core Temperature on

  • Cardiac Output
  • Blood pressure compensation
  • total peripheral resistance
A
  • use active control over selected parameters
    e. g. body core temperature

increasing body temperature:

  • -> total peripheral resistance decreases
  • -> cardiac output increases
  • -> insufficient blood pressure compensation
17
Q

What kind of pressure is required for ultrafiltration?

A

phyiscal negative pressure

18
Q

By which differential equation can the static behavior of an exchanger be described?

A

1st order ordinary differential equation

19
Q

Anti Diuretic Hormone (ADH)

A
  • recovers water from the collecting tube

–> regulates level of water and electrolytes in the body

20
Q

How does NaCl reach the ascending region of the loop of Henle?

A

NaCl is actively pumped

21
Q

Ultrafiltration

  • important variables
  • what does solvent drag mean?
A

important variables:

  • hydrostatic pressure gradient
  • osmotic pressure gradient
  • Solvent drag: extraction of fluid and particles simultaneously due to a pressure gradient
22
Q

Lowflux vs. Highflux Dialyzers

A

low flux –> smaller diameter of pores
high flux –> higher diameter of pores

UFR = 3000 ml/h

–> high flux membranes need lower TMP to reach the same rate of UFR!

23
Q

Does a Dialyzer exchange heat?

A

Yes, very efficient heat exchanger

  • idea: moderate cooling of patient to stabilize heat blood pressure

Medical Systems (11 decks)

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