Physiological Transition to Extrauterine Life
Key Cardiopulmonary Changes at Birth
- First Breath: CO₂ accumulation → central acidosis → stimulation of respiratory centre → first inspiration. Lung aeration dramatically reduces pulmonary vascular resistance (PVR) and increases pulmonary blood flow (5–6× increase).
- Surfactant Role: Reduces surface tension in alveoli, preventing collapse and supporting functional residual capacity (FRC).
- Circulatory Changes:
- Closure of foramen ovale, ductus arteriosus, and ductus venosus
- Systemic vascular resistance rises (loss of low-resistance placenta)
- Pulmonary blood flow increases dramatically
- Oxygenation: Pre-ductal SpO₂ rises gradually: ~60% at birth → >90% by 10 minutes.
Failure of Transition
If PVR remains high → Persistent Pulmonary Hypertension of the Newborn (PPHN) → right-to-left shunting → hypoxaemia and acidosis.
Definitions & Risks of Prematurity
| Term | Definition |
|---|---|
| Newborn | First minutes to hours after birth |
| Preterm | 24–<37 weeks gestation |
| Neonate | First 28 days of life |
| Infant | Neonatal period to 12 months |
Risks in Preterm Infants
- Surfactant deficiency → reduced lung compliance
- Weak respiratory muscles & immature airway reflexes
- Compliant chest wall that deforms easily
- Hypothermia (increased O₂ consumption)
- Higher risk of intraventricular haemorrhage, NEC, ROP
APGAR Scoring
| Sign | Score 2 | Score 1 | Score 0 |
|---|---|---|---|
| Appearance | Pink | Extremities blue | Pale/blue |
| Pulse | >100 bpm | <100 bpm | Absent |
| Grimace | Cries/pulls away | Grimace/weak cry | No response |
| Activity | Active movement | Flexed limbs | Limp |
| Respiration | Strong cry | Slow/irregular | Absent |
Interpretation: 7–10 normal • 4–6 moderate depression • 0–3 severe depression requiring resuscitation.
Neonatal Resuscitation Algorithm
Core Principles (ANZCOR 13.1–13.7)
- 85% of term babies breathe spontaneously within 10–30 seconds
- 10% respond to drying/stimulation
- 3% need PPV
- 2% need intubation
- 0.1% need CPR ± adrenaline
Stepwise Approach
- Warm, dry, stimulate (30 seconds)
- Assess tone, colour, HR, RR
- PPV if HR <100 or gasping/apnoea
- CPR (3:1 ratio) if HR <60 after effective ventilation
- Adrenaline if persistent bradycardia
Airway & Ventilation
Goals of ventilation: Clear lung liquid • Establish FRC • Enable gas exchange.
Start with room air. Target pre-ductal SpO₂: 60–70% at 1 min → >90% by 10 min.
Devices Comparison
| Device | Advantages | Limitations |
|---|---|---|
| T-piece | Consistent PIP/PEEP | Requires gas source |
| Self-inflating bag | No gas source needed | Inconsistent pressures |
Circulation & Pharmacological Interventions
CPR Technique
- 3:1 compression:ventilation ratio
- 90 compressions/min (120 if intubated)
- Two-thumb encircling technique
Medications (Rarely Needed)
| Drug | Dose | Indication |
|---|---|---|
| Adrenaline 1:10,000 | 10 mcg/kg IV/IO | HR <60 despite CPR |
| Compound Sodium Lactate | 10 mL/kg bolus | Volume expansion |
| Glucose 10% | 2 mL/kg | BGL <2.6 mmol/L |