Paediatric Anesthesia Guide: Physiology, Drugs & Airway (Free PDF)
Figure 1: Paediatric Anesthesia Overview.
Introduction: Tiny Humans, Big Differences
Paediatric anesthesia is one of the most high-stakes areas of our practice. The margin for error is small because children desaturate faster, have higher metabolic rates, and have anatomical differences that make airway management challenging.
Before you anesthetize a child, you must memorize the differences between them and adults. Let's break it down system by system.
1. Key Physiological Differences (Adult vs. Child)
You cannot treat a neonate like a 70kg man. Their physiology dictates how we manage their airway and hemodynamics.
Figure 2: Key Physiological Differences.
System Breakdown
- Airway: The pediatric airway is narrower, more anterior, and the tongue is relatively large. This puts them at high risk for obstruction and difficult intubation.
- Respiratory: Children have a higher Respiratory Rate (RR) and higher O2 consumption.
Result: They desaturate VERY fast during apnea. You have seconds, not minutes. - Cardiovascular: Cardiac Output (CO) in kids is Rate-Dependent. They have a fixed stroke volume.
Clinical Pearl: Bradycardia is the enemy! If HR drops, CO drops instantly. - Thermoregulation: They have a large surface area-to-mass ratio and less subcutaneous fat. They are prone to rapid hypothermia.
2. Paediatric Airway & Equipment Sizing
Choosing the right tube size is not a guess—it is a formula. Using a tube that is too large causes edema (croup); too small causes a leak.
Figure 3: Airway Equipment & ETT Formulas.
| Equipment | Sizing/Rule | Notes |
|---|---|---|
| Endotracheal Tube (Uncuffed) | (Age / 4) + 4 | Used for younger children to prevent subglottic stenosis. |
| Endotracheal Tube (Cuffed) | (Age / 4) + 3.5 | Modern Microcuff tubes are safe even for infants. |
| Laryngoscope Blade | Miller (Straight) | Preferred for infants to lift the floppy epiglottis directly. |
| Guedel Airway | Corner of mouth to Angle of Jaw | Essential to relieve obstruction from the large tongue. |
3. Common Medications & Dosing
Safety First: ALWAYS calculate and double-check your weight-based doses before induction. There is no "standard ampoule" in paeds.
Figure 4: Weight-Based Drug Dosing.
- Premedication: Midazolam (Oral 0.5 mg/kg) is excellent for separation anxiety. Give it 20 mins pre-op.
- Induction:
- Propofol: 2.5 - 3.5 mg/kg (Kids need a higher dose per kg than adults!).
- Sevoflurane: The gold standard for inhalational induction (Mask Induction).
- Muscle Relaxants:
- Atracurium: 0.5 mg/kg.
- Rocuronium: 0.6 - 1.2 mg/kg for RSI.
- Reversal: Neostigmine (0.05 mg/kg) + Glycopyrrolate (0.01 mg/kg) to prevent bradycardia.
4. Fluid Management & Emergencies
Managing fluids in children requires the classic Holliday-Segar Rule (4-2-1 Rule).
Figure 5: The 4-2-1 Fluid Rule & Laryngospasm.
The 4-2-1 Rule for Maintenance Fluid
- First 10kg: 4 ml/kg/hr
- Next 10kg (11-20kg): + 2 ml/kg/hr
- Each kg > 20kg: + 1 ml/kg/hr
Example: A 25kg child needs (40 + 20 + 5) = 65 ml/hr.
Signs: Stridor, tracheal tug, desaturation.
Treatment: 100% O2, CPAP (Jaw Thrust), Propofol, and if that fails -> Succinylcholine.
Conclusion
Paediatric anesthesia requires precision. You must know your equipment sizes, fluid rates, and emergency drugs by heart. Preparation is the key to safety.
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Disclaimer: This article is for educational purposes only. Always check specific pediatric guidelines.
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