Fluids and electrolytes in surgical patients

Question 1

What are the causes of fluid loss in surgical patients

Answer 1

Excess insensible loss
Exudate in peritoneal cavity
GIT
Plasma
Blood

Question 2

Explain the 2 types of diuresis

Answer 2

Watewr diuresis:
- Water in excess
- ADH secretion is suppressed

Osmotic diuresis
- When more solute is presented to the tubules than can be absorbed

Question 3

Explain the different disturbances of TBW

Answer 3

Water depletion: Usually associated with sodium

Water intoxication: Usually due to impaired renal excretion, cardiac failure, liver disease, hypoalbuminaemia

Question 4

Explain the different electrolyte disturbances

Answer 4

Sodium: Major cation in the ECF, almost all absorbed from GIT

Potassium: Main intracellular cation

Magnesium

Phosphate

Calcium

Question 5

Explain sodium electrolyte disturbances

Answer 5

Regulated by Kidneys through the Renin-angiotensin -aldosterone system

Hypernatraemia: usually due to poor fluid intake
- if dehydrated: oral intake or free water via NGT

Hyponatraemia: usually due to fluid overload
- Water restriction, correct Na slowly

Question 6

Which factors affect serum potassium

Answer 6

Aldosterone - increases excretion distal tubule

Insulin: Promotes entry into cells

Acid base balance:
- Acidosis: increased serum K, Alkalosis opposite

Hydration: Dehydration - K lost from cells

Catabolic states: K lost from cells

Question 7

Explain the ECG findings for hyper/hypokalaemia

Answer 7

Hyperkalaemia:
- Peaked T-waves
- Often occurs with renal failure

Hypokalaemia
- T waves dissapear
- Can also occur with diarrhoea

Question 8

Explain causes of hyper and hypo magnesaemia

Answer 8

Hyper:
- Renal failure
- Magnesium containing products

Hypo:
- Massive diuresis
- Chronic TPN
- ETOH abuse

Question 9

Explain hyper and hypophosphataemia

Answer 9

Hyper:
Most often due to renal failure

Hypo:
Most often associated with refeeding syndrome

Question 10

Calcium

Answer 10

Read Slide 28 in this lecture