Paediatric prescribing Flashcards
How are neonates and young children different?
larger surface area and volume of distribution (relative to weight), different hepatic metabolism and poorer oral absorption and renal excretion of drugs
Why should aspirin not be given to children under the age of 16?
Because of risk of Reyes syndrome
How is GI motility different in children?
- Gastric emptying times are variable but generally slower
- Most drugs are absorbed in the small intestine and thus slowed gastric emptying results in variable oral absorption in infacts
How does intraluminal pH differ in children?
Just after birth, the gut intraluminal pH is above 4, increasing the absorption of acid-labile drugs (normally broken down by stomach acid) and so lower doses can be used.
Higher doses are needed of weakly acidic drugs such as phenobarbital.
The pH of gastric secretions approaches adult values (pH 1-2 ) by the age of three years.
How to calculate weight in neonates?
weigh them (in kilograms). Babies should be naked, and older children should have their shoes and outerwear removed and ideally weighed in their underwear. Babies may have a recent weight recorded in their parent held ‘red book’.
How to estimate Childs weight?
(Age + 4) x 2
However the Advanced Paediatric Life Support (APLS) course has recognised that the following formulas, which are more complicated to remember, are more accurate and therefore these are likely to be used in acute paediatric emergencies:
0 to 12 months = (0.5 x age in months) + 4
1 to 5 years = (2 x age in years) + 8
6 to 12 years = (3 x age in years) + 7
Alternatively you can use the Broselow tape, which does not rely on knowing the child’s age or memorising a formula. This is a tape that is laid under the child and will allow an estimation of the weight depending on the length of the child. The tape is usually divided into coloured ‘zones’ as seen in the diagram.
How to calculate maintenance fluid over 24 hr?
100 ml/kg for the first 10 kg.
50 ml/kg for the next 10 kg.
20 ml/kg for every remaining kg (for a child weighing over 20 kg).
Note: total fluid maintenance requirements in 24 hours are unlikely to exceed 2500 ml in men and 2000 ml in woman.
Dividing the total by 24 gives the hourly rate. Remember to reduce fluids by approximately a third (i.e. to between 50-80% of routine maintenance needs) if there is a risk of inappropriate ADH secretion.
What is usual maintenance of fluids in pads?
The usual routine maintenance fluids in paediatrics are:
An isotonic crystalloid that contains between 131-154 mmol/litre of sodium (e.g. sodium chloride 0.9%).
Remember to also consider electrolyte requirements (e.g. potassium) and measure glucose and electrolytes every 24 hours whilst on intravenous fluids.
What is the neonate guideline for fluids?
Day 1 of life: 50-60 ml/kg over 24 hours. Day 2: 70-80 ml/kg over 24 hours. Day 3: 80-100 ml/kg over 24 hours. Day 4: 100-120 ml/kg over 24 hours. Day 5-28: 120-150 ml/kg over 24 hours.
Maintenance additives such as sodium and potassium should be added according to electrolyte levels, clinical condition and the presence of other fluids (e.g. Total Parenteral Nutrition (TPN)). As a guide requirements are usually around:
Sodium at 2‒6 mmol/kg/day.
Potassium at 1‒3 mmol/kg/day.
What is parental rehydration?
Assess clinical response regularly.
If the patient is in shock, give a 20 ml/kg bolus of sodium chloride 0.9% and then give 100 ml/kg in addition to maintenance fluids.
It is normal practice to replace fluids over 24 hours, unless there is hypernatraemia present, in which case this should be provided more slowly (over 48 hours).
