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Flashcards in Kidney pathophysiology Deck (22):
1

Diuretics definition and purpose

Drugs that increase urine flow
Mainly given to cause loss of water and salts

2

Main clinical uses of diuretics

Cardiac failure
Oedema
Hypertension
Liver disease and some types of kidney disease
Overdose or poisoning to help excretion
Abuse- eating disorders patients to lose weight

3

Body fluid compartments (at least 70% of body = water)

Extracellular fluid (30% of body)
5% in plasma
20% in interstitial fluid (bathes the cells)
5% as transcellular fluid (between cells)
Intracellular fluid (40% of body)

4

Ion content of extracellular fluid

Cations:
Na+ 135
K+ 3.5
Ca++ 4.0
Anions:
Cl- 100
HCO3- 28

5

Ion content of intracellular fluid

Cations:
K+ 160
Na+ 10
Ca++ 1.0
Anions:
HPO4- 100
Protein 65

6

Characteristics of ideal diuretic

Removes sodium and other electrolytes in proportion to conc in ECF
Once oedema is eliminated there should be no further electrolyte loss
May be necessary to continue diuretic to prevent recurrence of oedema

7

Interrelated regulation of body fluid composition and volume

Internal osmotic pressure- mainly via ADH
Internal volume- mainly via aldosterone

8

Osmotic regulation

Increase in osmotic pressure in blood e.g. after sweating
Blood goes to hypothalamus (osmo-receptors)
Travels down nerve tract to
Posterior pituitary- increases ADH, increases permeability of distal tubule, increases water resorption

9

Volume regulation

Reduction is vascular volume leads to a decrease in renal blood flow
Leads to the renin-angiotensin cascade, releasing aldosterone from the adrenal cortex
Causes sodium and water retension leading to oedema

10

Oedema is caused by

An alteration of the balance between volume of fluid in blood capillaries and tissue spaces

11

Cardiac oedema

Two components (Starling)- backward failure theory and forward failure theory

12

Backward failure theory

Right side of heart fails, unable to clear returning blood
Increase in venous pressure causes increase in transudation of fluid into interstitial spaces
Decreases plasma volume
Leads to renin-angiotensin cascade and the renal retention of sodium and water

13

Forward failure theory

Failure of cardiac left side leads to back pressure in the pulmonary artery
Causes pulmonary oedema and reduction in respiratory function

14

Hepatic oedema

Caused/ aggravated by cirrhosis of the liver
Metabolism of aldosterone is impaired
Increased sodium retention
Causes excess fluid in peritoneum
Increased intra-abdominal pressure
Increased venous pressure in lower limbs

15

Nephrotic oedema

More prevalent in childhood and young adults
Inflammation and increased glomerular permeability to plasma proteins which are lost in urine
Causes reduced colloid oncotic pressure
Discourages water osmosis into plasma

16

Nephrotic oedema treatment

Protein diet
Diuretics
Glucocorticoids

17

Nutritional oedema

Similar to nephrotic oedema
Cause: lack of protein in diet
Lowers colloid oncotic pressure
Discourages water osmosis into plasma
Reduced plasma volume and aldosterone secretion
Oedema

18

Hormonal oedema

Occurs during pregnancy and menstrual cycle
Caused by progesterone secretion
Also phasic changes in posterior pituitary hormones (ADH, oxytocin)
Treatment of severe cases with diuretics

19

Postural oedema

May occur during pregnancy
Expansion of tissue in abdomen causes restricted venous return from lower body
Increased venous pressure and transudation

20

Angioneurotic oedema

Allergic type reaction
Histamine released from mast cells
Syndrome of swelling in the deep skin layers
Treat with antihistamines

21

Localised oedema

Cause: increased capillary permeability to plasma proteins and fluids
Localised skin oedema, weal and flare
Caused by histamine release
Treat with antihistamines

22

Altitude oedema

Heart pumps more blood to lungs
Causes pulmonary pooling to get more oxygen from rarified air
Fluid leaks into extracelular spaces in lungs
Can be fatal