How this calculator works
Fifteen weighted items produce a total from 0 to 163. Use the worst value in the first 24 hours for heart rate, systolic pressure, urine output and the laboratory values, and the highest temperature. The PaO2/FiO2 points apply only while the patient is ventilated or on CPAP; otherwise that item scores zero. Convert serum urea in mmol/L to BUN in mg/dL by multiplying by 2.8 before applying the urea bands. The logistic equation then returns a predicted hospital mortality for the original European and North American cohort. It is a cohort estimate, not an individual prognosis. The result is an estimate for information only and is not medical advice.
Formula
SAPS II = the sum of the fifteen item points. Logit = -7.7631 + 0.0737 x score + 0.9971 x ln(score + 1). Predicted mortality = exp(logit) / (1 + exp(logit)).
Worked example
A 65-year-old with heart rate 130, systolic pressure 90 mmHg, temperature 38 C, ventilation with PaO2/FiO2 150, urine 0.8 L/day, BUN 30 mg/dL, white cells 15 x 10^9/L, potassium 4.0 mmol/L, sodium 140 mmol/L, bicarbonate 20 mEq/L, bilirubin 5 mg/dL, Glasgow Coma Scale 12, no chronic disease and a medical admission scores 55. The equation gives a predicted hospital mortality of about 57.5%.
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Frequently asked questions
Does the PaO2/FiO2 item apply without ventilation?
No. The published table scores that item only for a ventilated patient or one on CPAP. Without either, it contributes zero.
Should I enter BUN or urea?
Either. Select the unit you have. Serum urea in mmol/L is multiplied by 2.8 to give BUN in mg/dL before the bands are applied.
Is the predicted mortality valid for my patient?
It comes from a 1990s multicentre cohort and is a group estimate. Calibration differs by country, case mix and era, so it should not be presented as an individual probability.
Can the score be calculated from a total alone?
No. The item breakdown is needed, and the mortality equation uses the total only after every item has been scored.