Essential Clinical Math
OSCE Emergency & Paediatric Fluid Formulas
Step-by-step calculations and examiner scoring rubrics for high-stress paediatric fluid and resuscitation stations.
Fluids
Holliday-Segar Maintenance Fluid Rule (4-2-1 Rule)
First 10kg: 100ml/kg/day (4ml/kg/hr) | Next 10-20kg: +50ml/kg/day (+2ml/kg/hr) | Each kg > 20kg: +20ml/kg/day (+1ml/kg/hr)
OSCE Station Scenario: A 14kg child with gastroenteritis is admitted to the paediatric ward. Calculate 24-hour maintenance IV fluid requirements.
Examiner High-Yield Pearl: For 14kg: (10 × 100) + (4 × 50) = 1,000 + 200 = 1,200 ml/24 hours (~50 ml/hr). Remember to add potassium (KCl 20mmol/L) once the child has passed urine!
Resuscitation
Paediatric Emergency Fluid Bolus for Shock
10 to 20 ml/kg of 0.9% Normal Saline over 10-15 minutes (Use 10 ml/kg in diabetic ketoacidosis or suspected cardiogenic shock / trauma).
OSCE Station Scenario: A 10kg infant presents with tachycardia (180 bpm), capillary refill time 4 seconds, and cool extremities. Prescribe the emergency fluid bolus.
Examiner High-Yield Pearl: Bolus = 20ml/kg × 10kg = 200ml 0.9% Normal Saline STAT. Reassess ABCDE and reassess capillary refill and heart rate immediately post-infusion.
Burns
Parkland Burn Resuscitation Formula
Total Hartmann's in 24 hours = 4 ml × Body Weight (kg) × % Total Body Surface Area (TBSA) burned.
OSCE Station Scenario: A 70kg male sustains 25% deep partial-thickness flame burns. Calculate fluid requirements in the first 8 hours.
Examiner High-Yield Pearl: Total = 4 × 70 × 25 = 7,000 ml in 24 hours. EXACTLY HALF (3,500 ml) must be infused in the FIRST 8 hours from the TIME OF INJURY (not time of arrival!).
Paediatric Analgesia
Paediatric Weight-Based Analgesia Dosing
Oral Paracetamol: 15 mg/kg every 4–6 hours (max 60 mg/kg/day, max 4 doses). Oral Ibuprofen: 5–10 mg/kg every 6–8 hours (max 30 mg/kg/day with food).
OSCE Station Scenario: Prescribe oral paracetamol syrup (120mg/5ml) for a 12kg child presenting with painful acute otitis media.
Examiner High-Yield Pearl: Dose = 15mg × 12kg = 180mg. Using 120mg/5ml suspension: 180 / 120 × 5 = 7.5 ml orally every 4 to 6 hours as needed.