Topic 7: Fluid Balance and Renal Failure

Question 1

What is the typical total fluid volume of the intracellular and extracellular fluid volume?

Answer 1

ICF = 25L/ 40% weight
ECF = 15L / 20% weight
- IF = 12L / 80% ECF
- Plasma = 3L / 20% ECF

Question 2

How does ADH regulate water balance?

Answer 2

Anti-Diuretic Hormone

Increased osmolarity + Na+ in plasma stimulates osmoreceptors in hypothalamus; releasing ADH and targets kidney ducts. This increases water reabsorption and decreases osmolarity.

Decreased plasma volume + BP inhibit baroreceptors in atrium which also stimulate ADH

Question 3

How does Angiotensin regulate water balance?

Answer 3

Stimulated by increased ECF and decreased plasma (causes dry mouth) which increased angiotensin II, and the stimulates hypothalamic thirst center. Water absorbs into GI tract and ECF onsmolaity decreased and plasma volume increases

Question 4

What are the 4 hormones which regulate water balance?

Answer 4

ADH
Angiotensin
Aldosterone
ANP

Question 5

How does ANP regulate water balance?

Answer 5

Atrial Natiuretic Peptide

Stimulated by increased blood volume and atrial strech, releasing ANP. Effects hypothalamus inhibiting vasopressin; the kidneys increase GFR and decrease renin; adrenal cortex inhibits aldosterone and BP. Leads to increased NaCl and H20 excretion

Question 6

Whats the difference between ADH, angiotension, aldosterone vs ANP

Answer 6

ADH, angiotensin and aldosterone all increase water absorption to prevent dehydration

ANP causes water excretion

Question 7

Link water/ electrolyte balance to resitng BP

Answer 7

Increased water, increases BP and dehydration decreases blood pressure. ADH, angiotensin & aldosterone use osmoreceptors to detect water levels in body and activate neurosecretary cells in hypothalamus to icnrease blood solutes. Vasopressin travel sot pituitary gland. ADH acts in kindyes increasing permiability of distal tubules; increasing absorption.

Question 8

What happens when youre thirsty?

Answer 8

Increased water intake and reabsorption decreases the concentratin of solutes in blood; causing negative feedback and stops ADH production

Question 9

What are 3 disorders of water balance hypovolaemia (dehydration)

Answer 9

isotonic
hypertonic
hypotonic

Question 10

Define isotonic

Answer 10

no change in ICF volume, caused by vomiting, diarrhoea

loss of water with preserved normal effective osmolarity of body fluids

Question 11

Define hypertonic

Answer 11

decrease in ECF & ICF volume, caused by low fuilds, DM,

Imbalance of water and salt - high salt due to water loss

Question 12

Define hypotonic

Answer 12

decrease in ECF and increase in ICF volume
Caused by low salt, vomiting, addisons disease
Loss of electrolytes

Question 13

Define hypervolaemia (hyperdyration)

Answer 13

the body holds onto water. sodium concentration in blood is abnormally low

Caused by renal or heart failure

Signs: oedema, increased skin turgor

Question 14

Define edema:

Answer 14

swelling causes by excess fluid in body tissues

Decreased movement of water into the lymphatic vessels

Question 15

Summarise the regulation of sodium concentration by the kidneys: renal PROCESS for sodium?

Answer 15

when blood volume or sodium concentration become too high, sensors in heart, blood vessels and kidneys detect the increase, which the kidneys increase sodium excretion returing blood volume to normal

Question 16

How many mmoles are in ECF, reabsorbed and filterd, and urine by kidneys each day

Answer 16

ECF 2450 mmole
Reabsorbed 25,400 mmole/day
Filtered 25,500 mmole/day
Urine 100 mmole/day

Question 17

Summarise the regulation of sodium concentration by kidneys: renal REGULATION of sodium?

Answer 17

65% of sodium in filtration is reabsorbed in the proximal tubules. 25% is reclained in loop of Henle, 10% is dependant on aldosterone release in combination of secreted potassium

Water follows sodium if tubule permeability has been increased with ADH

*******
Increased K or decreased Na+ concentration in blood plasma and Renin-angiotension mechanism
- stimulate
Adrenal cortex
- releases
Aldosterone
- targets
Kidney tubule
- effects
Increased NA reabsorption and K secretion
- restores
Homeostatic plasma levels of NA and K

Question 18

What is the renal process for Potassium?

Answer 18

K balance = excretion of the amount of potassium in urine equal to that ingested minus amount lost in faeces, sweat.
K is freely filtratable at the glomerulus and undergoes both reabsorption and secretion, the latter occuring at the collecting ducts
When body K is increased, aldosterone secretion is stimulated and this stimulates K excretion

Question 19

What is the renal regulation of potassium?

Answer 19

K dominates ICF
K is freely filtratable at the glomerulus, and undergoes reabsorption and secretion
Regulation is through aldosterone at the DCT and CD in combination with NA
Vital to maintain accurate K levels in plasma - low/high leads to effects on excitable tissues (heart, muscles)

Question 20

Summarise the regulation of Calcium in kidneys

Answer 20

Hypocalcemia stimulates parathyroid glands to release PTH

Goes into the blood streamand kidneys. Kidneys PTH activate osteoclastics and calcium and bicarbonate released into blood. PTH increases calcium reabsorption in kidney tubules, PTH promotes kidneys activation of vitamin D, which increases calcium absoprtion from food

Rising calcium in blood inbits PTH release

Question 21

What is not supposed to be in urine?

Answer 21

Glucose - glycosuria
Proteins - proteinuria
Ketone bodies - ketonuria
Hemoglobin - hemoglobinuria

Question 22

What solutes are found in urine tests?

Answer 22

95% water, 5% solutes

Nitrogenous wastes: urea, uric acid, creatine
Normal solutes: Na, K, PO4, Ca, Mg, HCO3

Question 23

What does BUN stand for?

Answer 23

Blood Urea Nitrogen

Question 24

What is GFR?

Answer 24

Glomerular Filration

Where substances in blood plasma pass from glomerulus into Bowans Capsule, after passing afferent arteriole about 20% of the plasma flowing through glomeruli is filtered

Question 25

What are two methods for estimation of GFR?

Answer 25

EFPF - effective renal plasma flow
measured with PAH clearance

GFR - glomerular filtration rate
measured with inulin or creatinine clearance

Question 26

How do you calculate clearance of any substance when given urine flow and plasma concentration?

Answer 26

C = (U x V) / P

C = cleanance of substance S
U = urine concentration
V = urine flow volume 
P = plasma concentration

Question 27

What is acute renal failure?

Causes, treatment, outcomes

Answer 27

Causes: hypovolaemia, bladder obstruction

Assessment: clinical history, urine analysis, renal ultrasound

Signs: plasma: hyperkalaemia, hypocalcaemia

Management: BP control, infection, nutrition

Question 28

Define renal failure?

Answer 28

When the kidneys fail to remove metabolic end products from the blood and regulate the gluid, electrolyte and pH balance of teh extracellular fluids

Question 29

What are the most common causes of kindey disease?

Answer 29

DM

Hypertension

Question 30

What are the 5 clinical stages of CKD?

Answer 30

1. Damage with normal/increased GFR
2. Mild reduction of GFR
3. Moderate reduction of GFR
4. Severe reduction of GFR
5. Kidney Failure