πΆ SNAP-II Score Calculator
Neonatal acute physiology, scored.
For informational purposes only, not medical advice. Consult a healthcare professional.
The Score for Neonatal Acute Physiology II condenses newborn illness severity into six variables scored 0 to 115 from the first 12 hours in the NICU. Developed by Richardson and colleagues, it predicts mortality and benchmarks units: scores under 20 carry low risk while scores above 40 carry very high risk, with the curve steepening fast in between. Neonatologists use it for research stratification and quality comparison, not for bedside triage of individual babies. This calculator reproduces it for education and reference.
How to Use This Calculator
Select the worst value in the first 12 hours for each of the six SNAP-II variables. The score totals automatically with severity bands.
Use the worst value for each variable in the first 12 hours after NICU admission, per the original method.
Work through all six selects: blood pressure, temperature, oxygenation, pH, seizures, urine output.
Read the total out of 115. Higher means more severe physiologic derangement and higher mortality risk.
How the Math Works
Points per variable: mean blood pressure 30+ scores 0, 20 to 29 scores 9, under 20 scores 19; lowest temperature 96F+ scores 0, 95 to 95.9 scores 8, under 95 scores 15; PaO2/FiO2 2.5+ scores 0, 1.0 to 2.49 scores 5, 0.3 to 0.99 scores 16, under 0.3 scores 28; pH 7.20+ scores 0, 7.10 to 7.19 scores 7, under 7.10 scores 16; multiple seizures add 19; urine output 1.0+ scores 0, 0.1 to 0.9 scores 5, under 0.1 scores 18. Severity bands used in practice: under 20 lower, 20 to 39 moderate, 40 and above high. Mortality rises steeply past 40 in the validation cohorts.
Worked Example
A newborn totaling 24 points lands in the Moderate severity band the calculator reports. That means real physiologic derangement, sicker than the low-risk group but below the steep part of the mortality curve past 40. In a unit benchmarking report, this baby contributes to the moderate-severity stratum; at the bedside, the team treats the physiology, not the points.
Reading Your Result
Under 20 describes relatively stable NICU physiology with low predicted mortality. The 20 to 39 band is moderate severity where close monitoring and active management are the norm. At 40 and above, mortality risk is high and the score often parallels decisions about escalation and family counseling. The score was built for populations: applying it to one baby overstates its precision, and clinical course regularly defies the number in both directions.
| SNAP-II | Severity | Context |
|---|---|---|
| Under 20 | Lower | Relatively stable |
| 20-39 | Moderate | Active management |
| 40+ | High | High mortality risk |
Limitations
SNAP-II predicts for groups, not individuals, and must never drive withdrawal or triage decisions for a specific baby. It uses first-12-hour worst values, so later deterioration is invisible to it. Calibration varies across eras and populations. It excludes some conditions and was validated in NICU admissions, not delivery-room resuscitations.
Related Calculators
Related tools: pediatric blood volume calculator pediatric GFR calculator oxygenation index calculator.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is SNAP-II?
Score for Neonatal Acute Physiology II: six physiologic variables from the first 12 NICU hours, weighted 0 to 115 points, predicting neonatal mortality. Developed by Richardson et al. for severity stratification and unit benchmarking. Higher scores mean sicker babies.
What are the six SNAP-II variables?
Lowest mean blood pressure, lowest temperature, worst PaO2/FiO2 ratio, lowest pH, multiple seizures, and lowest urine output. Each reflects a failing system; together they summarize whole-baby physiology.
What SNAP-II score is bad?
Under 20 is lower risk, 20 to 39 moderate, 40 and above high risk with steeply rising mortality. There is no single bad number; the curve climbs continuously. Context of gestational age and diagnosis matters enormously.
How is SNAP-II different from CRIB?
Both are neonatal severity scores. CRIB uses birth weight, gestation, and early variables and is simpler; SNAP-II uses 12-hour physiology and is more detailed. Units pick one for consistent benchmarking.
Can SNAP-II predict an individual baby outcome?
Not reliably. It was validated for populations and unit comparison. Individual babies routinely beat or belie their scores, which is why it must never guide withdrawal decisions. Treat the baby, use the score for the system.
Why 12 hours of worst values?
To standardize severity measurement across babies admitted at different times and states. The worst-value convention captures the depth of derangement regardless of when in the window it occurred.
Does gestational age affect SNAP-II?
Profoundly in real life, though the score itself does not include it: a 24-weeker and a term baby with the same score have different outlooks. Scores are interpreted within gestational-age strata.
What is SNAPPE-II?
SNAP-II plus perinatal extension: adds birth weight, small-for-gestational-age status, and Apgar score. It predicts slightly better by including the baby starting point alongside the physiology.
How do NICUs use severity scores?
For benchmarking outcomes between units, risk-adjusting research, and quality improvement. Comparing raw mortality without severity adjustment punishes units that take the sickest babies.
Should parents be told the score?
The concepts behind it, yes: how sick the baby is and what the team is watching. The raw number adds little for families and risks false precision. Honest plain-language counseling beats reciting points.