Score for Neonatal Acute Physiology-II (SNAP-II)

A SNAP-II of 9 places the infant in the intermediate-high risk category, corresponding to approximately 10–15% mortality risk. This does not mean the infant will necessarily die; rather, it indicates substantial acute illness and increased risk compared to infants with lower scores. Clinically, this suggests the need for aggressive supportive care, close monitoring, and prognostic discussion with parents about realistic outcomes including the possibility of death or severe morbidity.

SNAP-II was developed specifically for VLBW (<1500 g) infants and is not validated in term infants. While the physiological variables are measured in all neonates, the prediction model and published mortality thresholds are not applicable to term populations. Use disease-specific severity scales or alternate risk stratification for term infants (e.g., PIM-3 for pediatric ICU patients, or condition-specific scores for meconium aspiration, sepsis, etc.).

The original SNAP-II is calculated once at 12 hours post-admission. Clinically, physiological status changes substantially in the first days of life, and an infant improving may have markedly lower scores on day 3. Some research groups have extended SNAP to later time points (SNAP-PE at 24–48 hours), but the standard SNAP-II is not intended for serial recalculation. Instead, clinicians use SNAP-II as a baseline risk assessment and integrate subsequent clinical changes into ongoing prognostic updates.

SNAP-II and CRIB are complementary but distinct. SNAP-II uses six physiological variables measured in the first 12 hours and predicts mortality in VLBW infants. CRIB incorporates birth weight, gestational age, gender, and Apgar score at admission and was originally designed for UK populations; different prediction models and thresholds apply. In practice, some NICUs calculate both scores; SNAP-II focuses on acute physiology whereas CRIB emphasizes demographic and delivery factors.