When should I calculate SAPS II?

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.

What "worst value" means?

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.

Should I use SAPS II or APACHE II?

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.

Can SAPS II predict individual patient outcomes?

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.

Why does GCS score so many points?

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).

Does SAPS II need updating?

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.

SAPS II — Simplified Acute Physiology Score Calculator

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.

⚠️ Medical Disclaimer: SAPS II is a severity-of-illness score for ICU populations. It estimates group mortality risk, not individual patient outcomes. Never use severity scores to withdraw or withhold care from individual patients.

Demographics

Age (years)

Admission Type

Vital Signs (worst in first 24h)

Heart Rate (bpm)

Systolic BP (mmHg)

Temperature (°C)

Labs (worst in first 24h)

BUN (mg/dL)

WBC (×10³/µL)

Potassium (mEq/L)

Sodium (mEq/L)

Bicarbonate (mEq/L)

Bilirubin (mg/dL)

GCS (3–15)

Respiratory

On Ventilator / CPAP?

PaO₂/FiO₂ RatioOnly scored if ventilated

Urine Output (mL/24h)

Chronic Disease

Metastatic Cancer?

Hematologic Malignancy?

AIDS?

SAPS II Score

Sum of all weighted components

Predicted Mortality

4.7%

Hospital mortality estimate

Risk Level

Low

Based on predicted mortality

SAPS II: 22 — 4.7% predicted mortality

Score Breakdown

Variable	Value	Points
Age	65 years	12
Heart Rate	90 bpm	0
Systolic BP	100 mmHg	0
Temperature	38.2°C	0
PaO₂/FiO₂	Not ventilated	0
Urine (24h)	800 mL	4
BUN	25 mg/dL	0
WBC	12 ×10³/µL	0
Potassium	4.2 mEq/L	0
Sodium	138 mEq/L	0
Bicarbonate	22 mEq/L	0
Bilirubin	1.2 mg/dL	0
GCS	15	0
Chronic Disease	Meta:0, Heme:0, AIDS:0	0
Admission Type	medical	6
Total SAPS II Score		22

Planning notes, formulas, and examples

About the SAPS II — Simplified Acute Physiology Score Calculator

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.

When This Page Helps

SAPS II is most useful when the first ICU day needs to be translated into a standardized severity estimate rather than a narrative impression. This calculator keeps the admission context, physiology, and chronic-risk factors in one place so the total score can support benchmarking, case-mix review, and mortality-model interpretation without losing the variable-by-variable breakdown.

How to Use the Inputs

Record the worst (most abnormal) value for each physiological variable during the first 24 hours of ICU admission.
Enter demographics: age and type of ICU admission (medical, scheduled surgical, unscheduled surgical).
Enter worst vital signs: heart rate, systolic BP, and temperature.
Enter worst lab values: BUN, WBC, potassium, sodium, bicarbonate, bilirubin.
Enter GCS (lowest score), ventilation status with P/F ratio, and 24-hour urine output.
Indicate chronic conditions (metastatic cancer, hematologic malignancy, AIDS).
Review the total SAPS II score, predicted mortality, and point-by-point breakdown.

Formula used

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)

Example Calculation

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.

Tips & Best Practices

Use the worst value in 24 hours, not the first or most recent — this is critical for score accuracy.
For non-ventilated patients, PaO₂/FiO₂ is scored as 0 points, not estimated.
GCS should be assessed before sedation if possible, or use the pre-sedation GCS.
Urine output is the 24-hour total — adjust for the collection period if admission is less than 24 hours.
Compare your ICU's observed/predicted mortality ratio (SMR) over time — SMR < 1.0 indicates better-than-predicted outcomes.

Use the First 24 Hours Consistently

SAPS II is built around the worst values recorded during the first ICU day, not the admission snapshot and not a rolling daily score. That makes data collection discipline important: the value used for each variable should reflect the most physiologically abnormal point in that opening window.

Group-Level Prognosis, Not Individual Destiny

The mortality estimate is helpful for comparing groups of similar patients, benchmarking ICU outcomes, and describing illness severity in research. It is much less useful as a standalone prediction for one patient at the bedside, where trajectory, response to treatment, and diagnosis-specific factors often matter more than the modeled percentage.

Common Sources of Drift

The score is easiest to distort when clinicians mix first values with worst values, estimate unmeasured variables, or ignore how sedation and ventilation affect GCS and oxygenation. A careful variable-by-variable review matters more than the arithmetic, because the logistic formula only works as well as the underlying data entry.

Sources & Methodology

Last updated: March 28, 2026

Methodology

This calculator sums the 17 published SAPS II variables using the worst values recorded during the first 24 hours of ICU admission, then applies the original logistic equation to convert the total score into a modeled hospital-mortality estimate. The page keeps the point breakdown visible so the score can be reviewed variable by variable instead of treated as a black box.

The mortality percentage is best understood as a group-level model output. It is useful for benchmarking and case-mix review, but it should not be used as a stand-alone prognosis for one patient.

Sources

A new Simplified Acute Physiology Score (SAPS II) based on a European/North American multicenter study (PubMed / JAMA) — Original SAPS II derivation and validation paper.
Predictive Performance of the Simplified Acute Physiology Score (SAPS) II and the Initial Sequential Organ Failure Assessment (SOFA) Score in Acutely Ill Intensive Care Patients (PubMed / Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine) — Modern validation and calibration context for SAPS II.

Frequently Asked Questions

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.