4. Control Of Body Fluid Volume

Question 1

What are pressure natriuresis and pressure diuresis

Answer 1

Increased sodium and water excretion

Question 2

Explain how congestive cardiac failure can cause pulmonary oedema

Answer 2

-CO doesnt perfuse kidney via renal artery sufficiently
-Na+ and water reatined as kidneys interpret hypovolaemia
-puts more strain on failing heart, excess fluid goes to lungs
-increases pulmonary venous pressure
-transudation from capillaries causes pulmonary oedema

Question 3

Management of pulmonary oedema caused by CCF

Answer 3

-diuretics
-ACE inhibitors
-nitrates
-vasodilators

Basically reduce fluid load and workload of heart

Question 4

How does hypovolaemic shock affect blood supply to organs?

Answer 4

-vasodilation in vital organs to maintain blood supply
-but kidneys arent included so acute tubular necrosis occurs

Question 5

What substance is secreted in kidneys during hypovolaemic shock to maintain blood presure?

Answer 5

Prostaglandins counteract excess vasoconstriction

Question 6

Treatment of hypovolaemic shock

Answer 6

Fluid replacement to restore ECf

Question 7

Hypertensive changes seen in kidneys:

Answer 7

-arteriosclerosis of renal arteries
-hyalinisation (glassy appearance of intima) of small vessels

Question 8

Renal causes of secondary hypertension

Answer 8

-renin release
-impaired sodium and water excretion
-renal artery stenosis= RAAS activation

Question 9

What does ADh cause via
-V1 receptor
-V2 receptor

Answer 9

V1: blood vessel vasoconstriction
V2: reduced water excretion

Question 10

Where does ADH introduce aquaporin channels?

Answer 10

In cell walls of collecting duct

Question 11

If circulating volume drops, is it more important to reestablish correct fluid volume, or osmolality of the fluid?

Answer 11

Volume

Question 12

Main compensation for water deficit

Answer 12

Drinking

Question 13

2 typed of diabetes insipidus and what they are

Answer 13

Central: imapired ADH synthesis or secretion by hypothalamus
Nephrogenic: acquired insensitivity’s of kidney to ADH

Question 14

Treatment of central diabetes insipidus

Answer 14

Desmopressin

Question 15

Symptoms of SIADH

Answer 15

-hyponatremia
-low plasma osmolality
-higher urine osmolality

Question 16

Limit for hypernatraemia

Answer 16

Plasma sodium conc over 146mmol/L

Question 17

Causes of hypernatraemia

Answer 17

-osmotic diuresis e.g. uncontrolled diabetes
-fluid loss without replacement e.g. sweating, burns
-diabetes’ insipidus
-incorrect IV fluid replacement
-primary aldosteronism

Question 18

Is hyponatraemia more common than hyper?

Answer 18

Yes

Question 19

Limit for hyponatraemia

Answer 19

Plasma conc of sodium less than 130mmol/L

Question 20

Causes of hyponatraemia

Answer 20

-diuretics
-water retention
-increased ADh
-diarrhoea and vomiting
-peritonitis
-burns
-heart failure
-kidney disease

Question 21

Normal serum osmolality

Answer 21

275x295 mosm/kg

Question 22

Calculated osmolarity

Answer 22

2Na+ glucose + urea +potassium

Question 23

Symptoms/signs of hypernatraemia

Answer 23

-increased BP
-ascites
-oedema
-bounding pulse
-SOB/cough

Question 24

Symptoms/signs of hyponatraemia

Answer 24

-cold clammy
-BO drop
-mucous membrane dry
-Weak pulse

Question 25

Treatment of hyponatraemia

Answer 25

Fluid restriction

-can give hypertonic saline and furosemide if needed

Question 26

Risk when correcting hyponatraemia too fast

Answer 26

Pontine demyelination: myelin sheath damaged as neurons swell

Question 27

Main vause of hypo and hypernatraemia

Answer 27

Change in fluid volume, NOT Na+ levels

Question 28

Go through 4.2.2 case studies

Answer 28

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