Body Fluid & Electrolytes

Question 0

ECF

Answer 0

1/3
14L
Plasma= 3.5L of this
More Na than K

Question 1

ICF

Answer 1

2/3
28L
More K than Na

Question 2

ADH

Answer 2

Released from Posterior pituitary 
Role: H20 preservation 
Binds to V2 rec in CD
Opens aquaporin channels 
Thirsty

Question 3

RAAS

Answer 3

Preserves BP & renal perfusion

Question 4

Types of fluid loss

Answer 4

Reference fluid here is plasma

Isotonic fluid loss- no change in plasma Na
Hypertonic fl- dec in p Na
Hypotonic fl- more common- diahhrea & sweating- inc in p Na

Question 5

Lab investigations in Na & H20 disorders

Answer 5

Plasma/serum Na
P/s osmolality 
P glucose 
Serum urea & creatinine
Urine osmolality & Na 
Urine vol 
Serum cortisol 
Serum TFTs

Question 6

Clinical features of hypokalaemia

Answer 6

Often asymptotic

Neuromuscular- muscle weakness/cramps/paralysis
Constipation
Paralytic ileus

Cardiac- ECG changes, arythmias, potentiates digoxin toxicity

Inc urine output & thirst

Question 7

ECG changes in hypokalaemia

Answer 7

Flat T waves
ST depression
Prominent U
Prolonged QT interval

Question 8

Causes of hypokalaemia

Answer 8

Dec intake
Transcellular K shift
Inc excretion (kidney or GI tract)

Question 9

Causes of Transcellular K shift causing hypokalaemia

Answer 9

Alkalosis
Insulin
B adrenergic agonists
Refeeding syndrome 
In vitro
Hypokalaemic periodic paralysis

Question 10

Causes of increased excretion of K

Answer 10

Renal loss: diuretics, excess diuresis, nephrotoxic drugs, hypomagnesaemia

Mineralocorticoid excess: Conn’s, Cushing’s, secondary hyperaldoseronism

Extra renal loss: D & V, ileostomy

Question 11

Hypokalaemia investigations

Answer 11

U&E
Mg
HCO3-