Water balance, diabetes Insipidus and hyponatraemia

Question 1

What is Diabetes Insipidus now called?

Answer 1

Arginine vasopressin deficiency - AVP Deficiency

Arginine vasopressin resistance - AVP Resistance

Question 2

What hormones are stored in the posterior pituitary?

Answer 2

Vasopressin and oxytocin

Question 3

Where are vasopressin and oxytocin made?

Answer 3

Paraventricular nucleus and Supraoptic nucleus

Question 4

True or false: Vasopressin has a long half life

Answer 4

False, it’s short, 5-10 mins

Question 5

ADH bind to _-_____ coupled 7 transmembrane domain receptors

Answer 5

G-protein

Question 6

Release of vasopressin is controlled by what in day to day?

Answer 6

Osmoreceptors in hypothalamus

Question 7

Release of vasopressin is controlled by what in emergencies?

Answer 7

Baroreceptors in brainstem and great vessels

Question 8

ingestion of water leads to ____ in plasma osmolality

Answer 8

drop

Question 9

drop in plasma osmolality results in _____ cellular hydration

Answer 9

increased

Question 10

Decreased vasopressin secretion causes _____ urine water excretion by kidney

Answer 10

increased

Question 11

The vasopressin loop is sensitive to small changes in p____ o____

Answer 11

plasma osmolality

Question 12

vasopressin binds to __ receptors on the renal collecting duct principle cells

Answer 12

V2

Question 13

Osmolality

Answer 13

Concentration in plasma per kilo

Question 14

Symptoms of AVP deficiency and resistance

Answer 14

Polyuria
Polydypsia
No glycosuria

Question 15

Diagnosis of AVP deficiency and resistance

Answer 15

Measure urine volume - unlikely if urine volume <3l/day
Check renal function and serum calcium, biochemistry

Question 16

Management of AVP deficiency

Answer 16

Treat any underlying condition

Desmopressin - high activity at V2 receptor. Can be tablets, nasal spray or injection.

Question 17

What can you measure to help diagnose Diabetes insipidus

Answer 17

Copeptin

Question 18

Management of AVP resistance

Answer 18

Avoid precipitating drugs
Congenital, free access to water, very high dose desmopressin

Question 19

Hyponatraemia is most often caused by excess water rather than…

Answer 19

salt loss

Question 20

Definition of hyponatraemia

Answer 20

serum sodium < 135 mmol/l

Question 21

What is normal serum sodium levels

Answer 21

135-144 mmol

Question 22

Symptoms of hyponatraemia

Answer 22

Headache
Irritability
Nausea/vomiting
Mental slowing
Unstable gait / falls
Confusion / Delirium
disorientation
Stupor / coma
Convulsions
Respiratory arrest

Question 23

What is biochemical classification of mild hyponatraemia?

Answer 23

130-135 mmol/l

Question 24

What is biochemical classification of moderate hyponatraemia?

Answer 24

125-129 mmol/l

Question 25

What is biochemical classification of severe hyponatraemia?

Answer 25

<125 mmol/l

Question 26

True or false: start hypotonic fluids in hyponatraemic patients

Answer 26

False - stop these

Question 27

What tests to do for hyponatraemia

Answer 27

Plasma and urine osmolality urinary Na+ Glucose TFT's Assessment of Cortisol Assessment of underlying causes eg chest imaging

Question 28

SIADH

Answer 28

Syndrome of Inappropriate Antidiuretic hormone Common cause of hyponatraemia Too much AVP, low osmolality, plasma sodium is low, urine is inappropriately concentrated, water retention, increase GFR

Question 29

SIAD management

Answer 29

Fluid restriction Diagnose and treat underlying condition Sometimes demeclocycline / vaptan

Question 30

The brain undergoes _____ adaptation in response to gradual-onset hyponatraemia

Answer 30

volume

Question 30

Management of acute sever symptomatic hyponatraemia

Answer 30

IV 150ml of 3% saline over 20 mins Check serum Na+ Repeat twice until 5 mmol/l increase Na+ Stop hypertonic saline. Na+ 6 hourly for 1st 24 hours