WETFLAG Calculator | Paediatric Emergency Tool
When a child is acutely unwell, the hardest part is not remembering the acronym, it is getting safe weight-based values quickly without adding pressure to an already stressful situation.
This WETFLAG calculator instantly generates paediatric emergency values (Weight, Energy, Tube, Fluids, Lorazepam, Adrenaline, Glucose) using established UK formulas. It allows known weight overrides, dual tube sizing, and toggleable formula breakdowns.
WETFLAG Calculator
What Is a WETFLAG Calculator?
A WETFLAG calculator is a vital paediatric emergency tool used by clinicians, GP trainees, and emergency care staff in the UK. The acronym WETFLAG stands for Weight, Energy, Tube, Fluids, Lorazepam, Adrenaline, and Glucose. Our tool automates the standard APLS/EPALS formulas required during resuscitation, saving critical time and reducing the risk of cognitive overload and calculation errors.
How to Use This WETFLAG Calculator
- Step 1: Enter the patient's age. Use the dropdown to toggle between months and years for infants.
- Step 2: Select "Known weight" if you have a recent, accurate measurement. Otherwise, leave it as "Estimate from age".
- Step 3: Choose your fluid context. Select 20ml/kg for standard medical shock or 10ml/kg for trauma/cautious boluses.
- Step 4: Click "Calculate WETFLAG" for immediate, screen-friendly results. Use "Big Display Mode" if viewing from across the resuscitation bay.
What Each WETFLAG Result Means
Weight
All emergency interventions scale based on weight. If a known weight is unavailable, the calculator estimates it using standard formulas. In children under 1 year, weight increases rapidly, so inputting exact months provides a more accurate estimate.
Energy
Energy denotes the defibrillation shock strength in Joules (J). The standard dose is 4 Joules per kilogram. Always ensure you are familiar with your specific defibrillator model and pad sizes.
Tube (Endotracheal)
Calculates the Internal Diameter (ID) for cuffed and uncuffed tubes, as well as depth markers for oral and nasal placement. Modern UK practice increasingly favours cuffed tubes, even in younger children, to ensure reliable ventilation and protect the airway. Always prepare one size larger and smaller.
Fluids
Provides the total volume of crystalloid bolus. Medical resuscitation typically requires 20ml/kg. For trauma or conditions requiring caution (such as DKA or cardiac failure), the bolus is reduced to 10ml/kg to prevent complications.
Lorazepam
The standard first-line IV/IO medication for status epilepticus. The dose is strictly weight-based (0.1mg/kg), but you must be aware of local maximum dose caps (often 4mg).
Adrenaline
For cardiac arrest, 1:10,000 Adrenaline is used intravenously or intraosseously. The dose is 10 micrograms per kilogram, which translates to 0.1ml/kg of the 1:10,000 solution.
Glucose
Required for severe hypoglycaemia. Standard treatment in paediatric emergencies is a rapid infusion of 10% Glucose at 2ml/kg.
WETFLAG Formula Table
| Parameter | Standard UK Formula | Unit |
|---|---|---|
| Weight (< 12 months) | (0.5 × age in months) + 4 | kg |
| Weight (1 - 5 years) | (2 × age in years) + 8 | kg |
| Weight (6 - 12 years) | (3 × age in years) + 7 | kg |
| Energy | 4 × Weight | Joules |
| Tube (Cuffed) | (Age in years / 4) + 3.5 | mm ID |
| Tube (Uncuffed) | (Age in years / 4) + 4 | mm ID |
| Fluids (Medical) | 20 × Weight | ml |
| Lorazepam | 0.1 × Weight | mg |
| Adrenaline (1:10k) | 0.1 × Weight | ml |
| Glucose (10%) | 2 × Weight | ml |
Note: Some localities still teach the weight formula (Age + 4) × 2 for children over 1 year. The formulas above align with widely accepted contemporary UK guidance. Validate against your NHS Trust.
Common Mistakes to Avoid
- Ignoring Known Weight: Always use an actual recently recorded weight if available, as estimations can be highly inaccurate.
- Failing to Recalculate: If the patient's age or weight input is updated during preparation, you must recalculate all values immediately.
- Unit Confusion: Be incredibly careful not to mix up milligrams (mg) and millilitres (ml) or administer the wrong concentration of adrenaline (1:1,000 instead of 1:10,000).
- Overlooking Local Protocols: This tool does not override your local NHS Trust policies or specific consultant directives.
- Blind Trust in Formulas: Assuming one weight algorithm fits every biological variation perfectly is dangerous. Look at the child.
When You Should Use Extra Caution
Emergency calculators require clinical sense. Exercise heightened monitoring and caution in these scenarios:
- Infants under 12 months: Rapid physiological shifts occur in neonates and young infants.
- Extreme Body Habitus: Very small or obese children may require adjusted dosing strategies.
- Systemic Conditions: Trauma, Diabetic Ketoacidosis (DKA), and known congenital cardiac anomalies often require vastly different, highly constrained fluid management.