Fluid prescribing (children & adults)

Question 1

What is the normal urine output for a child <2 years old?

Answer 1

> 2ml/kg/h

Question 2

What is the normal urine output for a child >2 years old?

Answer 2

> 1 ml/kg/h

Question 3

What are the total daily fluid requirements for a child? (not neonates)

Answer 3

1. 100 mL/kg/day for the 1st 10kg
2. 50 mL/kg/day for the 2nd 10kg
3. 20 mL/kg/day for the remainder of bodyweight

Question 4

What electrolytes does a child also need and in how much(in mmol/kg/day)?

Answer 4

Sodium:
- 2-4 mmol/kg/day (based on a study involving obese American children with high-salt diets, so this is generally ignored)

Potassium:
- 1-2 mmol/kg/day (500ml bags come with 10 mmol KCl)

Question 5

What fluid type is usually prescribed for maintenance in children?

Answer 5

500 mL of 0.9% saline + 5% dextrose with 10 mmol KCl

Question 6

Define mild dehydration in children.

Answer 6

• 50ml/kg deficit

- 5% body weight

Question 7

What are the clinical features of mild dehydration?

Answer 7

• Slightly dry mucous membranes
• Increased thirst
• Decreased urine output

Question 8

What is the management of mild dehydration in children?

Answer 8

• Oral/NG rehydration solution (1-1.5x maintenance) OR

- IV maintenance

Question 9

Define moderate dehydration in children.

Answer 9

• 100ml/kg deficit

- 10% body weight

Question 10

What are the clinical features of moderate dehydration?

Answer 10

• Dry mucous membranes
• Tachycardia
• Reduced urine output
• Loss of skin turgor
• Sunken eyes/fontanelles

Question 11

What is the management of moderate dehydration in children?

Answer 11

• IV bolus OR

- NG fluids at 25ml/kg/h for first 4h; ORS

Question 12

Define severe dehydration in children.

Answer 12

• 150ml/kg deficit

- 15% body weight

Question 13

What are the clinical features of severe dehydration?

Answer 13

• Same as in moderate and:
• Pronounced tachycardia
• Weak pulse
• Hypotension
• Delayed cap refill
• Mottled skin/cyanosis
• Dyspnoea

Question 14

What is the management of severe dehydration in children?

Answer 14

• IV fluid bolus (may require multiple boluses)

Question 15

How much of a fluid bolus is appropriate to give to a child? And what solution do you give?

Answer 15

10-20 ml/kg of 0.9% saline

Question 16

How much fluids should be given for an oral rehydration solution fluid challenge?

Answer 16

1-2 mL/kg of ORS every 10 mins

20 ml/kg of oral fluid in 2 hours should be adequate, if not child may need admission

Question 17

When is an oral rehydration solution fluid challenge indicated?

Answer 17

Mild-moderate gastroenteritis

Question 18

How much water (ml/kg/day) does an adult require?

Answer 18

25-30 ml/kg/day

Question 19

How much potassium, sodium, and chloride (mmol/kg/day) does an adult require?

Answer 19

1 mmol/kg/day

Question 20

How much glucose (g/day) does an adult require?

Answer 20

50-100g/day

Question 21

How should you adjust fluid prescribing for obese patients?

Answer 21

Adjust prescription according to their ideal body weight - patients rarely need >3L per day

Question 22

In which groups should you consider prescribing less fluid (i.e., 20-25 ml/kg/day)?

Answer 22

• Elderly patients
• Patients with renal impairment or cardiac failure
• Malnourished patients at risk of refeeding syndrome

Question 23

How do you choose the most appropriate maintenance fluid for an adult?

Answer 23

Calculate the patients daily requirements based on their weight and then choose fluids which match these requirements closest.

Question 24

What is maximum rate at which potassium can be given at?

Answer 24

10 mmol/h (any more than this is very dangerous)

Question 25

Describe the use of 5% dextrose, and its possible advantages and disadvantages.

Answer 25

- Given instead of pure water - Glucose is present to maintain initial osmolality but is quickly used up - Used as part of maintenance fluid regimen, when water is required without electrolytes - Is of no use in treating hypovolaemia when it is not physiological and distributes widely across all fluid compartments - Administering too much, too quickly can cause hyponatraemia

Question 26

Describe the use of dextrose-saline, and its possible advantages and disadvantages.

Answer 26

- Good choice for maintenance fluids, when given alone at the correct maintenance rate it will provide approximately the correct sodium replacement requirement over 24h - The sodium content is much lower than that of plasma, therefore it is of no use in treating hypovolaemia - Administering too much, too quickly can cause hyponatraemia

Question 27

Describe the use of Hartmann's solution, and its possible advantages and disadvantages.

Answer 27

- This is the most physiological fluid and so is very good for replacing plasma loss (e.g. GI losses or during surgery) - Not v good for maintenance fluids as 3L of Hartmann's solution over 24h would 3x too much Na+ and not enough K+

Question 28

Describe the use of 0.9% saline, and its possible advantages and disadvantages.

Answer 28

- More physiological than dextrose as it contains NaCl - Not as physiological as Hartmann's solution because it contains a greater concentration than plasma - Too much chloride can cause a hyperchloraemic metabolic acidosis - Can cause renal afferent arteriole vasoconstriction (increases risk of AKI)

Question 29

What is the approximate loss of electrolytes (mmol/L) through vomiting/NG tube loss?

Answer 29

Na+: 20-40 mmol/L K+: 14 mmol/L Cl-: 140 mmol/L H+: 60-80 mmol/L

Question 30

What is the approximate loss of electrolytes (mmol/L) through diarrhoea/excess colostomy loss?

Answer 30

Na+: 30-140 mmol/L K+: 30-70 mmol/L HCO3-: 20-80 mmol/L

Question 31

What is the approximate loss of electrolytes (mmol/L) through jejunal loss (stoma/fisutla)?

Answer 31

Na+: 140 mmol/L K+: 5 mmol/L Cl-: 135 mmol/L HCO3-: 8 mmol/L

Question 32

What is the approximate loss of electrolytes (mmol/L) through high volume ileal loss (new stoma, high stoma, or fistula)?

Answer 32

Na+: 100-140 mmol/L K+: 4-5 mmol/L Cl-: 75-125 mmol/L HCO3-: 0-30 mmol/L

Question 33

What is the approximate loss of electrolytes (mmol/L) through lower volume ileal loss (established stoma or fistula)?

Answer 33

Na+: 50-100 mmol/L K+: 4-5 mmol/L Cl-: 25-75 mmol/L HCO3-: 0-30 mmol/L

Question 34

What is the approximate loss of electrolytes (mmol/L) through pancreatic drain or fistula loss?

Answer 34

Na+: 125-138 mmol/L K+: 8 mmol/L Cl-: 56 mmol/L HCO3-: 85 mmol/L

Question 35

What is the approximate loss of electrolytes (mmol/L) through biliary drainage loss?

Answer 35

Na+: 145 mmol/L K+: 5 mmol/L Cl-: 105 mmol/L HCO3-: 30 mmol/L

Question 36

How might fluid prescriptions be adjusted post-surgery?

Answer 36

- K+ stores are mostly intracellular and serum levels can increase due to cell lysis during surgery - If K+ is >4.5 mmol/L post-operatively, omit from the fluid prescription for 24h - If K+ is normal/low, you can given some (e.g. 40 mmol in 24h) - 0.9% saline tends to be avoided as surgery triggers RAAS which causes Na+ and fluid retention and reduced urine output - Dextrose-saline is preferred for maintenance

Question 37

How might fluid prescriptions be adjusted in sepsis?

Answer 37

- Sepsis causes intravascular depletion due to plasma loss through leaky capillaries and vasodilation - Replace fluid with Hartmann's/plasmalyte or 0.9% saline, but avoid too much chloride if large quantities of fluid are required - Monitor response carefully

Question 38

How might fluid prescriptions be adjusted in heart failure?

Answer 38

- These patients are prone to fluid overload and pulmonary oedema - They many run normally hypotensive - If overload develops, start fluid restriction, furosemide, low sodium diet, and record daily weights

Question 39

How might fluid prescriptions be adjusted in liver disease?

Answer 39

- Excess Na+ may worsen ascites - Human albumin solution is a good alternative volume expander (e.g. 100mL 20% HAS) - Too much dextrose can also be problematic as it can worsen hyponatraemia

Question 40

How might fluid prescriptions be adjusted in AKI?

Answer 40

Be cautious with potassium because they are at risk of hyperkalaemia

Question 41

How might fluid prescriptions be adjusted in severe CKD?

Answer 41

Avoid excess fluid, Na+, and K+ as the kidneys may not be able to excrete them

Question 42

How might fluid prescriptions be adjusted in alcohol abuse/risk of refeeding syndrome?

Answer 42

- Avoid dextrose where possible because it can precipitate refeeding syndrome - If you need to give dextrose, give Pabrinex first because dextrose can precipitate Korsakoff syndrome

Question 43

How might fluid prescriptions be adjusted in brain haemorrhage/stroke?

Answer 43

- Avoid dextrose as this can cause osmotic haematoma swelling - Dextrose destroys the brain if there's a bleed - Saline is best