Paediatrics: Prescribing

As an FY1 it is likely that you will manage paediatric patients during their admission, often in other specialties like general surgery. Having a few prescribing skills under your belt will help you feel more confident in managing them in these cases. Ask the paediatric team or paediatric pharmacist to provide brief teaching on prescribing if you can.

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Prescribing

Prescribing in children and adults tends to be very similar, although there are a few key differences:

  • Weight. Almost every prescription is based on weight or age in children. So document these clearly on the drug chart. Occasionally body surface area (BSA) is needed to calculate a dose. There is a handy table in the BNF to help you estimate the BSA if you only know the weight.
  • Oral Suspension. Most children hate taking tablets, so prescribe the oral suspension equivalent of drugs.
  • Taste. Some medications just taste awful. Prednisolone for example is particularly bad. Discuss with seniors if alternatives could be used, i.e. Dexamethasone tastes much better than Prednisolone. This may just improve your patient’s adherence.

Ensure you have support from seniors or the paediatric team/nurses when you are prescribing. Due to the increased complexity, it can be easy to make a mistake! Have a look at some of the following which you might use in surgery:

  • Pain: paracetamol & ibuprofen
    • 2nd line: oral morphine
    • Intranasal fentanyl or Entonox for procedures
  • Vomiting: cyclizine or ondansetron
  • Constipation: paediatric movicol sachets

Fluids

When prescribing fluids for children, it is always important to ask the question ‘Is there an alternative to Intravenous Fluids?’. This may be an oral fluid challenge or even an NG tube. However, if a child is nil by mouth, IV fluids are often the only way to go. There are some differences to adult fluid prescribing but some of the principles still apply.

Local protocols and guidelines should be used in the first instance but for official advice, use the following

Maintenance Fluids

Here we give an example of how maintenance fluids might be calculated over a 24 hour period. Requirements are typically calculated on the patient’s weight:

  • 100ml/kg: For the first 10kg of weight
  • 50ml/kg: For the second 10kg of weight
  • 20ml/kg: For the remainder

The fluid most commonly used is 0.9% sodium chloride with 5% Dextrose. Bags are typically prescribed 500ml at a time. Electrolyte requirements in 24 hours might be:

  • Sodium: 2-4mmol/kg.
  • Potassium: 1-2mmol/kg.

So to show a worked example for a 25kg child would require:

  • 100ml/kg: For the first 10kg. 100 x 10= 1000ml.
  • 50ml/kg: For the second 10kg. 50 x 10= 500ml.
  • 20ml/kg: For the remainder. 20 x 5= 100ml.

Overall requirements 1600ml in 24 hours, which equals a rate of 66.7ml/hr. 
Therefore the prescription for the above would be: 500 ml 0.9% sodium chloride with 5% dextrose at a rate of 66.7ml/hr.

Replacement Fluids

Children may require extra fluids if they appear dehydrated. The amount depends on the level of dehydration. Here are some examples (but again refer to official guidelines & local protocols).

  • Mild (5%): Dry mucous membranes. Appears thirsty. Decreased urine output. Normal obs.
  • Moderate (10%): Mild tachycardia. Sunken eyes. Normal blood pressure.
  • Severe (15%): Marked tachycardia, hypotension, delayed capillary refill, mottled/cyanotic.

Formula: Replacement fluids = % dehydrated x weight x 10

Remember, this is in addition to the maintenance fluids. Replacement fluids for mild and moderate dehydration are normally given slowly over 24 or 48 hours.

Worked example:
If our 25kg child was 5% dehydrated, they would require: 5 x 25 x 10= 1250ml.
To replace this over 24 hours, you add the replacement volume to the maintenance volume.
1250 + 1600 = 2850 divided by 24 = 118.75ml/hr

Boluses

Those severely dehydrated or in shock may need fluid boluses. You should never be treating an unwell child by yourself so get urgent help. They may advise for a shocked child to be prescribed a 10-20 ml/kg 0.9% sodium chloride bolus. If your team is not available, the paediatricians will often provide advice and support in these situations.

Dr A Przystupa (FY3 Paediatrics: DGH in the East of England)

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