APACHE II Calculator

If you’re responsible for managing critically ill patients in the intensive care unit, the APACHE II calculator is your indispensable partner for hospital mortality prediction. By providing you with a comprehensive apache ii score, this tool instantly translates a patient’s initial physiologic disturbance and chronic health conditions into real, actionable numbers—information that can guide early prognostication, resource triage, and clinical discussions. Imagine facing a complex ICU admission: this calculator clarifies risk, enabling data-driven decisions amidst uncertainty.

Understanding the APACHE II Calculator: Assessment and Application

How the APACHE II Calculator Works at ICU Admission

The APACHE II score—short for the Acute Physiology and Chronic Health Evaluation II—was introduced as a severity of disease scoring tool to facilitate risk assessment of the most severely ill patients. It is widely recognized as one of the most robust clinical prediction tools used in intensive care for estimating unit mortality. The score integrates 14 factors: a combination of acute clinical measurements, age, and previous health conditions, which together predict outcomes in the hospital setting with proven accuracy. This approach is not intended to influence the medical management of patients but serves as a reliable mortality prediction tool based on data captured during the first hours after patient admission to the intensive care unit. This online calculator for the acute physiology and chronic health evaluation (APACHE II) supports practitioners in evaluating critically ill patients. This tool is a widely used disease classification system for ICU patients.

Variables initially recorded during the patient’s admission are essential, as the APACHE II score should be calculated at the beginning of the ICU admission—ideally with the worst values recorded during the initial 24 hours in the intensive unit—in order to help determine the patient’s mortality risk. Notably, this calculation is not sequential and not intended to influence the medical management or show improvement or effect of interventions. This scoring method is one of the key physiological scoring systems in current practice and helps estimate icu mortality.

Key Variables: APACHE II Calculator, Physiological and Chronic Health Factors in the Scoring System

The APACHE II scoring system incorporates a wide range of clinical and health-related indicators to estimate the severity of disease. The patient’s clinical measurements are complemented by factors such as age, preexisting medical problems, and history of being immunosuppressed. Each parameter reflects residue from major organ systems, including lung, cardiovascular, renal, and liver function, as well as neurological status:

• Temperature (°C)
• Mean arterial pressure (mmHg)
• Heart rate (beats/minute)
• Respiratory rate (breaths/minute)
• Oxygenation: PaO₂ or A-aDO₂ (mmHg)
• Arterial pH or serum bicarbonate (HCO₃-), when pH unavailable
• Serum sodium (mmol/L)
• Serum potassium (mmol/L)
• Serum creatinine level (mg/dL), adjusted for acute kidney injury
• Hematocrit (%)
• WBC count (10³/μL)
• Glasgow Coma Score (GCS)
• Age (years)
• Severe organ insufficiency or immunosuppressed status

These variables are used to calculate the apache ii score, with scores assigned according to the deviation from normal laboratory values. The higher the cumulative score (minimum 0, maximum 71), the greater the patient’s assessed risk of death during their icu stay and subsequent hospital course. The scoring is based on 14 factors gathered during patient signs assessment, and is especially useful in acute disease stratification and guiding early conversation around expected prognosis. This scoring model is a reliable disease classification system for acute and chronic disease states.

Clinical Application: ICU Mortality Estimates and Limitations

This tool estimates ICU mortality and supports early risk stratification at the time of intensive monitoring unit entry. The score’s reliability is supported by validation studies, where it consistently demonstrates that an increasing value is associated with an increasing risk of death in the clinical setting. Although the score provides accurate statistical estimates, it is not calculated sequentially and is not meant to show improvement or effect of interventions. As such, it is not intended to influence clinical approaches nor replace clinical judgment and individualized diagnosis or management planning. It can help predict hospital mortality but is not meant to replace clinical judgment. The worst values recorded during the initial 24 hours in the monitoring unit are crucial for calculation and stratification.

Worked Examples for APACHE II Calculation

Let’s walk through three illustrative cases to show how APACHE II at presentation functions as an early prognostic indicator of disease severity and acute and chronic disease burden. These cases demonstrate how the score is initially recorded during the patient’s admission and help determine the patient’s risk of death in various scenarios, especially for immunosuppressed patients:

• Patient 1: Severe sepsis with multi-organ involvement (high)
  1. Findings: Temperature 39°C; MAP 65 mmHg; HR 130; RR 34; PaO₂ 65 mmHg; arterial pH 7.15; sodium 125 mmol/L; potassium 5.8 mmol/L; creatinine 3.2 mg/dL (acute kidney injury, requires adjustment); hematocrit 24%; WBC 28,000; GCS 11; age 72; immunosuppressed with cirrhosis.
  2. Apply parameter weights (see table below): Each input value corresponds to a specific score (for example, serum creatinine above 3.5 mg/dL in acute kidney injury scores higher points; GCS of 11 gives 4 points; MAP < 70 mmHg, more points, etc.).
  3. Total score calculation: Values sum to approx. 38.
  4. Interpretation: High probability of fatal outcome (synonym for mortality), supports intensive monitoring and discussions regarding prognosis.
• Patient 2: Young trauma, mild derangements (moderate)
  1. Findings: Temperature 36.5°C; MAP 91 mmHg; HR 105; RR 22; PaO₂ 85 mmHg; pH 7.38; sodium 138 mmol/L; potassium 4.2 mmol/L; creatinine 1.2 mg/dL; hematocrit 35%; WBC 13,000; GCS 15; age 26; no preexisting issues.
  2. Apply scoring ranges: Most values within normal limits score zero; modest elevations/decreases (e.g., HR, WBC) assign minor points.
  3. Total score calculation: Example score is 7.
  4. Interpretation: Lower probability of fatal outcome; prognosis is favorable, though ongoing assessment is required.
• Patient 3: Elderly, comorbidities with acute pneumonia (variable score factors)
  1. Findings: Temperature 36°C; MAP 75 mmHg; HR 92; RR 28; PaO₂ 69 mmHg; pH 7.31; sodium 129 mmol/L; potassium 3.7 mmol/L; creatinine 2.0 mg/dL; hematocrit 28%; WBC 11,000; GCS 13; age 80; diabetes, congestive heart failure.
  2. Sum scoring components: Multiple mild to moderate derangements—each assigned points; age group and comorbidity history increase total.
  3. Total score calculation: Example score is 21.
  4. Interpretation: Moderate to high risk of fatal outcome; guides the care team to consider palliative options if appropriate.

Sample APACHE II Parameter Scoring Reference

Contributors, Related Tools & Source References for the Acute Physiology and Chronic Health Evaluation (APACHE II) Calculator

Meet the Development Team: Creator, Contributors, and Content Experts

• Project Lead: Dr. William A. Knaus, developer of the acute disease scoring model II and recognized authority in severity scoring models.
• Contributors: An interdisciplinary clinical and informatics team with expertise in intensive care medicine, medical severity scoring, patient monitoring, and outcomes evaluation.
• About the content: Evidence-based and regularly reviewed to maintain alignment with the latest research in intensive care and unit management.

Explore Similar ICU Calculators and Medical Management Tools

• Online calculator for the acute physiology and chronic health evaluation (APACHE II) – Similar interface, alternate risk calculation.
• Ranson Score – For distinguishing mild from severe pancreatitis; comparable with APACHE II.
• SOFA Score – Sequential Organ Failure Assessment, another estimation tool for ICU patients.
• Medscape APACHE II Calculator – Alternate access point for rapid reference during the unit stay.

Reference Materials & Further Reading on APACHE II Scoring and ICU Mortality

1. Knaus WA, Draper EA, Wagner DP, Zimmerman JE. "APACHE II: A severity of disease scoring system." Critical Care Medicine 1985;13(10):818-829. [Original validation study]
2. Friedman G, Silva E, Vincent J-L. "Prognostic value of a repeat assessment using the APACHE II system in critically ill patients." Critical Care Medicine 1995.
3. Bouch DC, Thompson JP. "Severity scoring models in the critically ill." Continuing Education in Anaesthesia Critical Care & Pain 2008;8(5):181-185.
4. For further reading, see [Society of Critical Care Medicine](https://www.sccm.org/Clinical-Resources/Guidelines/Guidelines/APACHE-II) guidelines and literature on methods that predict inpatient mortality.