APACHE II

Overview

APACHE II uses 17 variables measured within the first 24 hours of ICU admission to estimate in-hospital mortality. Scores range from 0 to 71; higher scores indicate greater severity of illness.

The score is the sum of three components: Acute Physiology Score (APS), Age Points, and Chronic Health Points.

Score Components

Component	Variables	Max Points
Acute Physiology Score (APS)	12 physiological variables	60
Age Points	Age in years	6
Chronic Health Points	Severe organ insufficiency / immunocompromise	5

Physiological Variables (APS)

Variable	Normal Range
Temperature (rectal, °C)	36–38.4
Mean arterial pressure (mmHg)	70–109
Heart rate (bpm)	70–109
Respiratory rate (/min)	12–24
Oxygenation (AaDO₂ or PaO₂)	FiO₂ dependent
Arterial pH	7.33–7.49
Serum sodium (mmol/L)	130–149
Serum potassium (mmol/L)	3.5–5.4
Serum creatinine (mg/dL)	0.6–1.4
Haematocrit (%)	30–45.9
White blood cells (×10³/µL)	3–14.9
Glasgow Coma Scale	15 = 0 points

Mortality Prediction

APACHE II Score	Predicted Hospital Mortality
0–4	~4 %
5–9	~8 %
10–14	~15 %
15–19	~25 %
20–24	~40 %
25–29	~55 %
30–34	~75 %
≥ 35	> 80 %

Reference

Knaus WA, Draper EA, Wagner DP, Zimmerman JE. APACHE II: a severity of disease classification system. Crit Care Med. 1985;13(10):818–829.