Fluids

Question 1

What determines water balance in the body?

Answer 1

1. Intake - dietary
2. Output - obligatory losses (skin, lungs), controlled losses (kidneys, gut, ADH)
3. Redistribution

Question 2

What does ADH do?

Answer 2

Acts on the renal collecting duct to insert aquaporins to make them more permeable to water, more concentrated urine.

Question 3

What stimulates ADH secretion?

Answer 3

1. Increase in plasma osmolality
2. Decrease in plasma volume (overrises change in osmolality)
3. Pain, nausea, drugs (post-operative hyponatraemia)
4. Lung and CNS lesions

Question 4

What inhibits ADH secretion?

Answer 4

1. Decrease in plasma osmolality
2. Increase in plasma volume
3. Alcohol

Question 5

How can you assess fluid balance in history and examination?

Answer 5

1. History - fluid intake/output, vomiting/diarrhoea, PMHx, DHx.
2. Examination - lying/standing BP, fluid balance, drug chart, pulse, JVP, CRT, mucous membranes, ascites, auscultate lung bases, skin turgor, oedema.

Question 6

What would you find on examination of a dehydrated individual?

Answer 6

1. Tachycardia, slow CRT
2. Diminished skin turgor
3. Dry mucous membranes
4. Low urine output

Question 7

What would you find in the bloods of a dehydrated individual?

Answer 7

1. Disproportionate rise in urea relative to rise in creatinine.
2. Rise in albumin
3. Raised haematocrit

Question 8

What would you find on examination of an overloaded individual?

Answer 8

1. Raised JVP
2. Pitting oedema
3. Tachypnoea
4. Bibasal crepitations
5. Pulmonary oedema on CXR

Question 9

Which two tests assist in diagnosing a fluid balance issue?

Answer 9

Urinary sodium and osmolality levels

Question 10

How is serum osmolality calculated and what is the normal range?

Answer 10

1. 2Na + urea + glucose

2. 275-295

Question 11

What would the urinary sodium and urine:serum osmolality show if there was water loss?

Answer 11

1. > 20mmol/L

2. <1

Question 12

What would the urinary sodium and urine:serum osmolality show if there was water conservation?

Answer 12

1. <20mmol/L

2. >1

Question 13

What are the standard maintenance fluids?

Answer 13

1. 0.9% saline over 8 hours

2. Two consecutive 5% dextrose + 20mmol KCL over 8 hours

Question 14

What should you not use dextrose for?

Answer 14

Fluid resus

Question 15

Which fluid is good for hyperosmotic coma?

Answer 15

Dextrose as it is basically water and they are water deplete.