Calculate the SAPS II ICU severity score from 17 variables. Estimates hospital mortality risk for critically ill patients using the worst values in the first 24 hours of ICU admission.
The Simplified Acute Physiology Score II (SAPS II) is one of the most widely used severity-of-illness scoring systems in intensive care medicine. Developed by Le Gall and colleagues from a multinational database of 13,152 ICU patients, it estimates hospital mortality risk from 17 variables recorded during the first 24 hours of ICU admission.
SAPS II uses the worst (most abnormal) values of 12 physiological variables, plus age, admission type, and three chronic health conditions. The score ranges from 0 to 163, converted to predicted mortality via a logistic regression equation. It is used clinically for ICU benchmarking, case-mix adjustment in research, resource allocation planning, and quality improvement programs.
Unlike its predecessor (SAPS I) and competitor (APACHE II), SAPS II requires no chronic health point adjustments beyond three specific conditions (metastatic cancer, hematologic malignancy, AIDS) and can be calculated from routine laboratory and monitoring data available in any ICU. This makes it practical for real-time severity assessment across diverse healthcare settings worldwide.
SAPS II enables objective severity-of-illness assessment that standardizes communication between clinicians, supports quality benchmarking (observed vs predicted mortality), adjusts for case-mix in research studies, and helps ICU administrators understand patient acuity trends. Unlike subjective clinical impression, SAPS II provides reproducible, quantitative data for healthcare decision-making. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain.
SAPS II = Sum of points from 17 variables (age, HR, SBP, temp, GCS, PaO₂/FiO₂, urine output, BUN, WBC, K⁺, Na⁺, HCO₃⁻, bilirubin, admission type, chronic disease) logit = −7.7631 + 0.0737 × SAPS II + 0.9971 × ln(SAPS II + 1) Predicted mortality = e^logit / (1 + e^logit)
Result: SAPS II = 33, Predicted mortality = 13.5%
A 65-year-old medical admission with HR 90, SBP 100, normal labs except mild BUN elevation scores 33 on SAPS II. The logistic regression model converts this to 13.5% predicted hospital mortality. This moderate score suggests the patient is ill but has a favorable prognosis with appropriate ICU management.
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Most mistakes come from mixed standards, rounding too early, or misread labels. Recheck final values before use. ## Practical Notes
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Track units and conversion paths before applying the result. ## Practical Notes
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SAPS II is calculated once using the worst values from the first 24 hours of ICU admission. It is not designed for serial measurement (unlike SOFA or MODS). If daily risk assessment is needed, consider using SOFA score instead.
The most physiologically deranged value during the first 24 hours. For heart rate, this could be the highest or lowest, whichever scores more points. For temperature, the highest is used. The principle is to capture the maximum severity of illness.
Both are validated. SAPS II is simpler (17 vs 34+ variables) and requires no arterial blood gas in non-ventilated patients. APACHE II provides better discrimination in some surgical populations. Many ICUs calculate both. APACHE IV and SAPS 3 are newer alternatives.
No. SAPS II predicts mortality for groups of similar patients, not individuals. A predicted mortality of 40% does NOT mean an individual patient has a 40% chance of dying — it means that of 100 similar patients, about 40 would be expected to die. Never use severity scores for individual care decisions.
Neurological status is the strongest single predictor of ICU mortality. A GCS of 3–5 scores 26 points because it indicates severe brain injury, which carries high mortality from the brain injury itself and from its complications (aspiration, prolonged ventilation, immobility).
Yes. SAPS II was developed in 1993, and overall ICU mortality has improved. Many centers report observed mortality lower than SAPS II predictions (standardized mortality ratio < 1.0). SAPS 3 (2005) provides updated coefficients and custom calibration by geographic region.