Fluid prescribing (children & adults) Flashcards
What is the normal urine output for a child <2 years old?
> 2ml/kg/h
What is the normal urine output for a child >2 years old?
> 1 ml/kg/h
What are the total daily fluid requirements for a child? (not neonates)
- 100 mL/kg/day for the 1st 10kg
- 50 mL/kg/day for the 2nd 10kg
- 20 mL/kg/day for the remainder of bodyweight
What electrolytes does a child also need and in how much(in mmol/kg/day)?
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)
What fluid type is usually prescribed for maintenance in children?
500 mL of 0.9% saline + 5% dextrose with 10 mmol KCl
Define mild dehydration in children.
- 50ml/kg deficit
- 5% body weight
What are the clinical features of mild dehydration?
- Slightly dry mucous membranes
- Increased thirst
- Decreased urine output
What is the management of mild dehydration in children?
- Oral/NG rehydration solution (1-1.5x maintenance) OR
- IV maintenance
Define moderate dehydration in children.
- 100ml/kg deficit
- 10% body weight
What are the clinical features of moderate dehydration?
- Dry mucous membranes
- Tachycardia
- Reduced urine output
- Loss of skin turgor
- Sunken eyes/fontanelles
What is the management of moderate dehydration in children?
- IV bolus OR
- NG fluids at 25ml/kg/h for first 4h; ORS
Define severe dehydration in children.
- 150ml/kg deficit
- 15% body weight
What are the clinical features of severe dehydration?
- Same as in moderate and:
- Pronounced tachycardia
- Weak pulse
- Hypotension
- Delayed cap refill
- Mottled skin/cyanosis
- Dyspnoea
What is the management of severe dehydration in children?
- IV fluid bolus (may require multiple boluses)
How much of a fluid bolus is appropriate to give to a child? And what solution do you give?
10-20 ml/kg of 0.9% saline
How much fluids should be given for an oral rehydration solution fluid challenge?
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
When is an oral rehydration solution fluid challenge indicated?
Mild-moderate gastroenteritis
How much water (ml/kg/day) does an adult require?
25-30 ml/kg/day
How much potassium, sodium, and chloride (mmol/kg/day) does an adult require?
1 mmol/kg/day
How much glucose (g/day) does an adult require?
50-100g/day
How should you adjust fluid prescribing for obese patients?
Adjust prescription according to their ideal body weight - patients rarely need >3L per day
In which groups should you consider prescribing less fluid (i.e., 20-25 ml/kg/day)?
- Elderly patients
- Patients with renal impairment or cardiac failure
- Malnourished patients at risk of refeeding syndrome
How do you choose the most appropriate maintenance fluid for an adult?
Calculate the patients daily requirements based on their weight and then choose fluids which match these requirements closest.
What is maximum rate at which potassium can be given at?
10 mmol/h (any more than this is very dangerous)
Describe the use of 5% dextrose, and its possible advantages and disadvantages.
- 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
Describe the use of dextrose-saline, and its possible advantages and disadvantages.
- 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
Describe the use of Hartmann’s solution, and its possible advantages and disadvantages.
- 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+
Describe the use of 0.9% saline, and its possible advantages and disadvantages.
- 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)
What is the approximate loss of electrolytes (mmol/L) through vomiting/NG tube loss?
Na+: 20-40 mmol/L
K+: 14 mmol/L
Cl-: 140 mmol/L
H+: 60-80 mmol/L
What is the approximate loss of electrolytes (mmol/L) through diarrhoea/excess colostomy loss?
Na+: 30-140 mmol/L
K+: 30-70 mmol/L
HCO3-: 20-80 mmol/L
What is the approximate loss of electrolytes (mmol/L) through jejunal loss (stoma/fisutla)?
Na+: 140 mmol/L
K+: 5 mmol/L
Cl-: 135 mmol/L
HCO3-: 8 mmol/L
What is the approximate loss of electrolytes (mmol/L) through high volume ileal loss (new stoma, high stoma, or fistula)?
Na+: 100-140 mmol/L
K+: 4-5 mmol/L
Cl-: 75-125 mmol/L
HCO3-: 0-30 mmol/L
What is the approximate loss of electrolytes (mmol/L) through lower volume ileal loss (established stoma or fistula)?
Na+: 50-100 mmol/L
K+: 4-5 mmol/L
Cl-: 25-75 mmol/L
HCO3-: 0-30 mmol/L
What is the approximate loss of electrolytes (mmol/L) through pancreatic drain or fistula loss?
Na+: 125-138 mmol/L
K+: 8 mmol/L
Cl-: 56 mmol/L
HCO3-: 85 mmol/L
What is the approximate loss of electrolytes (mmol/L) through biliary drainage loss?
Na+: 145 mmol/L
K+: 5 mmol/L
Cl-: 105 mmol/L
HCO3-: 30 mmol/L
How might fluid prescriptions be adjusted post-surgery?
- 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
How might fluid prescriptions be adjusted in sepsis?
- 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
How might fluid prescriptions be adjusted in heart failure?
- 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
How might fluid prescriptions be adjusted in liver disease?
- 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
How might fluid prescriptions be adjusted in AKI?
Be cautious with potassium because they are at risk of hyperkalaemia
How might fluid prescriptions be adjusted in severe CKD?
Avoid excess fluid, Na+, and K+ as the kidneys may not be able to excrete them
How might fluid prescriptions be adjusted in alcohol abuse/risk of refeeding syndrome?
- 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
How might fluid prescriptions be adjusted in brain haemorrhage/stroke?
- Avoid dextrose as this can cause osmotic haematoma swelling
- Dextrose destroys the brain if there’s a bleed
- Saline is best
