APACHE II Calculator

The APACHE II (Acute Physiology and Chronic Health Evaluation II) score ranges from 0 to 71 and is compiled from three major categories: acute physiological measurements, age, and previous chronic health status. The core calculation sums individual points assigned to deviations from normal physiological ranges across parameters such as temperature, mean arterial pressure, heart rate, respiratory rate, oxygenation, arterial pH, serum sodium, potassium, creatinine, hematocrit, white blood cell count, and the Glasgow Coma Scale. Additional points are added for advanced age and specific acute surgical or chronic organ failure conditions. Mathematically, the final result is expressed as: Result = Acute Physiology Score + Age Points + Chronic Health Points.

Consider a 65-year-old patient admitted to the ICU following emergency abdominal surgery. Their clinical parameters include a temperature of 38.5°C (1 point), a mean arterial pressure of 85 mmHg (0 points), a heart rate of 115 bpm (3 points), a respiratory rate of 24 breaths per minute (2 points), and an arterial pH of 7.32 (2 points). Furthermore, their Glasgow Coma Scale is 13 (yielding 15 - 13 = 2 points), serum sodium is 138 mEq/L (0 points), potassium is 4.2 mEq/L (0 points), and creatinine is elevated at 1.8 mg/dL without acute renal failure (2 points). Factoring in age (65 years adds 3 points), white blood cell count of 14,000 (2 points), hematocrit of 38% (1 point), and acute surgery status (5 points), the cumulative APACHE II score totals 23 points, indicating a high level of physiological derangement and elevated predicted mortality.

When gathering data for the APACHE II score, always use the worst physiological values recorded during the first 24 hours of ICU admission to ensure accurate risk stratification. Avoid scoring measurements that are temporarily altered by acute interventions before baseline stabilization. Always verify whether chronic organ insufficiency is documented in the medical record, as this heavily weights the chronic health component of the final score.