Primary surfactant deficiency in preterm infants leads to high alveolar surface tension, microatelectasis, non-compliant lungs, V/Q mismatch, and severe respiratory distress.
Key Physiological Equations & Formulas
- Law of Laplace for Alveolar Surface Tension: $$P = \frac{2 \gamma}{r}$$ Surfactant dramatically lowers surface tension ($\gamma$), preventing small alveoli from collapsing into larger ones during exhalation.
Practical Clinical Pearls & Bedside Rules
- European Consensus Guidelines on RDS: Early non-invasive CPAP is standard first-line management; administer early rescue surfactant if FiO2 requirement exceeds 0.30 on CPAP 6 cmH2O.
- Natural vs Synthetic Surfactants: Porcine (Poractant alfa, 200 mg/kg) and Bovine (Beractant, 100 mg/kg) surfactant preparations provide rapid surface tension reduction and clinical stabilization.
Initial Settings & Clinical Titration Protocol
| Parameter | Recommended Initial Setting | Titration Goal / Safety Threshold |
|---|---|---|
| Initial Surfactant Dose (Poractant) | 200 mg/kg (2.5 mL/kg) | Provides faster oxygenation improvement than 100 mg/kg. |
| CPAP Pressure | 6-8 cmH2O | Prevents alveolar collapse and improves endogenous surfactant conservation. |
Bedside Troubleshooting & Red Flags
Warning
Surfactant Failure: If FiO2 remains >0.40 or acidosis worsens after surfactant, evaluate for congenital pneumonia, pulmonary hypoplasia, pneumothorax, or large PDA.
Key Takeaways & Summary
- Always evaluate patient synchrony and physiological response before changing ventilator parameters.
- Maintain lung-protective strategies to minimize driving pressure ($\Delta P$) and mechanical power.
- Continuously reassess liberation and extubation readiness on daily morning rounds.