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MD4001 Physiology > Fluid and electrolyte balance > Flashcards

Fluid and electrolyte balance Flashcards

1
Q

what are the major fluid compartments of the body

A

plasma, interstitial fluid, intracellular

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2
Q

what is the normal volume of plasma

A

3L

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3
Q

what is the normal volume of interstitial fluid

A

11L

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4
Q

what is the normal volume in intracellular fluid

A

28L

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5
Q

what is the intracellular concentration of potassium

A

150 mM

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6
Q

what is the normal plasma conc of potassium

A

4.5 mM

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7
Q

what is the normal plasma conc of Na

A

130 mM

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8
Q

what are the major gains of water to the body

A

food and water, and food oxidation

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9
Q

what are the major losses of water from the body

A

urine, faeces, sweat, insensible loss

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10
Q

what is insensible water loss

A

transepidermal diffusion
evaporation from the respiratory tract

these losses are solute free and can’t be controlled or prevented
causes heat loss

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11
Q

what sensors monitor body fluid

A

hypothalamic osmoreceptors
low pressure baroreceptors in the right atria
high pressure sensors in the carotid sinus

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12
Q

what ion is the key driver of total plasma volume

A

sodium

if sodium drops then the volume will fall (due to osmolality being tightly controlled)

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13
Q

how can sodium be controlled

A

kidneys/ urine output

controlled indirectly via volume sensors

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14
Q

how is the amount of sodium reabsorbed changed

A

rate of flow, aldosterone, ANP

change in GFR

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15
Q

if blood osmolality changes how does the volume change

A

increases

also increase in ADH

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16
Q

what happens when there is an increase in volume

A

detected by baroreceptors
decrease in renin and aldosterone
increase in ANP
decrease sodium and water retention

17
Q

how is potassium lost from the body

A

mostly urine (little is lost in sweat and faeces unlike with sodium)

so controlled by the kidney

18
Q

describe the control of potassium in the kidneys

A

potassium is freely filtered
reabsorbed again in the PCT
controlled secretion at the DCT
secretion is linked to Na reabsorption

intracellular potassium acts as a reservoir in order to regulate change

19
Q

what is the effect of aldosterone on the DCT

A

increases activity of the basolateral sodium pump
increases the number of sodium pumps
increases the number of sodium and potassium channels in the apical membrane
this causes increases reabsorption of sodium and increased secretion of potassium

20
Q

what is Conn’s syndrome

A

hyperaldosteronism leading to hypertension from increased fluid volume and hypokalaemia

21
Q

what is 5% dextrose solution

A

an IV fluid
effectively just adding water as the glucose is metabolised

distributes into all body compartments

22
Q

what is isotonic saline

A

0.9% NaCl

23
Q

what is plasmalyte

A

an IV fluid which closely mimics normal plasma, so does not enter cells

24
Q

what are the features of 4.5% albumin (colloid)

A

supplied in 0.9% NaCl
tends to stay in plasma
blood product

25
Q

what is hydrolysed gelatin (colloid)

A

supplied in 0.9% NaCl
stays in plasma
protein is metabolised over time

26
Q

what questions should you ask before prescribing fluid

A

what volume is my patient starting from
does my patient need IV fluid

Am I prescribing maintenance fluid, replacement fluid or resuscitation fluid

what volume and what type of fluid

27
Q

what are the features of DKA

A 
dehydration 
tachycardia
hypotension
reduced consciousness
Kussmaul's respiration 
acetone on breath 
abdominal pain 
vomiting
28
Q

what causes dehydration in DKA

A

hyperglycaemia
vomiting
kaussmaul resp
reduced intake due to reduced consciousness

29
Q

what fluid would you give an adult with DKA

A

1L 0.9% saline over one hour

30
Q

what IV insulin would you give someone with DKA

A

infusion of 6 units in one hour

31
Q

why is potassium important in DKA

A

there may be raised or possibly lowered potassium

insulin pushes potassium into cells and so must be monitored

32
Q

how should you treat someone with DKA and very low potassium

A

hold insulin until potassium has normalised

33
Q

how should you treat someone with DKA and normal potassium

A

give 20-30 mmol/L/hour of potassium

if potassium is raised it should still be checked every 2 hours

34
Q

what ion channel is important for maintaining the concentrations in the intracellular fluid

A

Na- K atp-ase

MD4001 Physiology (19 decks)

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