Cam Icu Calculator
Screen for delirium in ICU patients using the Confusion Assessment Method for ICU. Enter values for instant results with step-by-step formulas.
Calculator
Adjust values & calculateThe RASS must be -3 or higher to assess for delirium.
Is there an acute change from mental status baseline? OR Has the mental status fluctuated (RASS or GCS varied) in the past 24 hours?
Read SAVEAHAART letters - squeeze hand on A only. More than 2 errors out of 10 = inattention present.
Current RASS is 0. Feature 3 is NEGATIVE (RASS is 0).
Ask 4 yes/no questions + 1 command. Combined more than 1 error = disorganized thinking.
Formula
Delirium is present when both Feature 1 (acute onset or fluctuating course) AND Feature 2 (inattention) are present, PLUS either Feature 3 (altered level of consciousness, RASS not 0) OR Feature 4 (disorganized thinking). If RASS is -4 or -5, the patient is too sedated to assess.
Last reviewed: January 2026
Worked Examples
Example 1: Positive CAM-ICU in Postoperative Patient
Example 2: Negative CAM-ICU in Sedated Patient
Background & Theory
The Cam-Icu Calculator applies the following established principles and formulas. Health and medicine calculators are grounded in validated physiological measurement methods established through decades of clinical research. Body Mass Index, or BMI, is calculated by dividing weight in kilograms by height in meters squared (kg/m²), a formula originating from Adolphe Quetelet's 19th-century statistical work and later codified by the WHO into standard classifications: underweight below 18.5, normal weight 18.5 to 24.9, overweight 25 to 29.9, and obese at 30 and above. Basal Metabolic Rate quantifies the minimum energy required to sustain life at rest. The Mifflin-St Jeor equation, published in 1990 and widely regarded as the most accurate for most adults, calculates BMR as (10 × weight in kg) + (6.25 × height in cm) − (5 × age) ± sex adjustment. The older Harris-Benedict equations, revised in 1984 by Roza and Shizgal, remain in common use. Total Daily Energy Expenditure is derived by multiplying BMR by a physical activity factor ranging from 1.2 for sedentary individuals to 1.9 for extremely active ones, following the methodology validated by doubly labeled water studies. Body fat percentage can be estimated without laboratory equipment using the U.S. Navy circumference method, which uses neck, waist, and hip measurements, or via BMI-derived equations adjusted for age and sex. The Jackson-Pollock skinfold method offers higher precision with calipers. Blood pressure classification, according to the American College of Cardiology and the 2017 ACC/AHA guidelines, defines normal as below 120/80 mmHg, elevated as 120 to 129 systolic, and hypertension stage 1 as 130 to 139 systolic or 80 to 89 diastolic. Target heart rate zones for aerobic exercise are derived from maximum heart rate estimates, most commonly using the formula 220 minus age in years, with moderate-intensity training typically defined as 50 to 70 percent of maximum heart rate and vigorous intensity at 70 to 85 percent, consistent with CDC and American Heart Association guidelines. These thresholds guide safe and effective cardiovascular conditioning.
History
The history behind the Cam-Icu Calculator traces back through the following developments. The history of health measurement stretches back to ancient Greece, where Hippocrates around 400 BCE laid the foundation for observational medicine by systematically recording patient symptoms, diet, and environment. His humoral theory, though scientifically superseded, established the principle that the body operates as an interconnected system subject to measurable imbalance. The transformation toward modern medicine accelerated in the 19th century. Louis Pasteur and Robert Koch developed germ theory in the 1860s and 1870s, identifying microorganisms as disease agents and enabling targeted interventions. Florence Nightingale, working during the Crimean War in the 1850s, introduced statistical analysis to nursing practice, demonstrating through data visualization that sanitation reduced mortality. Her work is foundational to evidence-based health measurement. The discovery of vitamins in the early 20th century, beginning with Casimir Funk's coinage of the term in 1912 and culminating in the isolation of vitamins A through K, created the field of nutritional science and gave rise to dietary reference intake frameworks. The World Health Organization, founded in 1948, subsequently established global standards for health metrics, disease classification through the International Classification of Diseases, and recommended daily allowances. The BMI as a clinical screening tool gained traction in the 1970s through Ancel Keys' large-scale epidemiological work, which validated Quetelet's index as a population-level obesity indicator. Through the 1980s and 1990s, the Framingham Heart Study produced landmark data linking cholesterol, blood pressure, and lifestyle factors to cardiovascular disease risk, directly shaping the numeric thresholds still used in health calculators. The evidence-based medicine movement, formalized by Gordon Guyatt and colleagues at McMaster University in the early 1990s, demanded that all health recommendations derive from systematically graded clinical evidence. The digital health era beginning in the 2000s brought these formulas to consumer devices, wearable sensors, and smartphone applications, expanding access to health self-monitoring on a global scale and enabling population-level data collection that continues to refine clinical reference ranges.
Frequently Asked Questions
Sources & References
- 1Ely EW et al. Evaluation of delirium in critically ill patients: validation of the Confusion Assessment Method for the ICU (CAM-ICU). Critical Care Medicine, 2001
- 2ICU Delirium and Cognitive Impairment Study Group - CAM-ICU Training Manual
- 3Devlin JW et al. PADIS Guidelines. Critical Care Medicine, 2018
Formula
CAM-ICU Positive = Feature 1 + Feature 2 + (Feature 3 OR Feature 4)
Delirium is present when both Feature 1 (acute onset or fluctuating course) AND Feature 2 (inattention) are present, PLUS either Feature 3 (altered level of consciousness, RASS not 0) OR Feature 4 (disorganized thinking). If RASS is -4 or -5, the patient is too sedated to assess.
Worked Examples
Example 1: Positive CAM-ICU in Postoperative Patient
Problem: A 70-year-old post-cardiac surgery patient, RASS -1, was previously alert and oriented but has been intermittently confused over the past 12 hours. On the letter attention test (SAVEAHAART), the patient makes 4 errors. The patient answers yes when asked if a stone floats on water.
Solution: RASS: -1 (Drowsy) - assessable for delirium\nFeature 1 (Acute onset/fluctuation): POSITIVE - was oriented, now intermittently confused\nFeature 2 (Inattention): POSITIVE - 4 errors on ASE (>2 errors)\nFeature 3 (Altered LOC): POSITIVE - RASS -1 (not zero)\nFeature 4 (Disorganized thinking): POSITIVE - incorrect answer\nCAM-ICU = Feature 1 + Feature 2 + Feature 3 = POSITIVE
Result: CAM-ICU: POSITIVE - Delirium Present | Subtype: Hypoactive (RASS -1)
Example 2: Negative CAM-ICU in Sedated Patient
Problem: A 55-year-old mechanically ventilated patient on propofol, RASS 0 (alert and calm during awakening trial). No change from baseline mental status. On the letter attention test, the patient makes 1 error. The patient correctly answers all orientation questions.
Solution: RASS: 0 (Alert and Calm) - assessable for delirium\nFeature 1 (Acute onset/fluctuation): NEGATIVE - no change from baseline\nBecause Feature 1 is negative, CAM-ICU is NEGATIVE\n(Features 2-4 do not need to be positive if Feature 1 is negative)
Result: CAM-ICU: NEGATIVE - No Delirium Detected
Frequently Asked Questions
What is the CAM-ICU and what does it screen for?
The Confusion Assessment Method for the ICU (CAM-ICU) is a validated bedside screening tool designed to detect delirium in critically ill patients, including those who are mechanically ventilated and unable to speak. Developed by Dr. Wes Ely and colleagues at Vanderbilt University in 2001, it adapts the original Confusion Assessment Method for use in the ICU setting. The CAM-ICU assesses four features: acute onset or fluctuating mental status, inattention, altered level of consciousness, and disorganized thinking. Delirium is diagnosed when Features 1 and 2 are present along with either Feature 3 or Feature 4. The tool has a sensitivity of 93 to 100 percent and specificity of 89 to 100 percent for detecting delirium when performed by trained nurses, making it highly accurate for bedside screening.
How do you assess Feature 1 of the CAM-ICU?
Feature 1 evaluates whether there has been an acute change in mental status from the patient baseline or any fluctuation in mental status over the past 24 hours. This assessment requires knowledge of the patient prior to their current illness, which may come from family members, prior medical records, or nursing assessments from previous shifts. Acute onset refers to a sudden change from the patient normal cognitive function, such as a previously alert patient becoming confused or agitated. Fluctuating course means the mental status has varied during the current illness, waxing and waning between normal and abnormal. This can be assessed by reviewing the RASS or GCS scores documented over the past 24 hours and identifying any significant variations. If either acute onset or fluctuating course is present, Feature 1 is scored as positive.
How is Feature 2 (Inattention) tested in the CAM-ICU?
Feature 2 assesses inattention using either the Attention Screening Examination (ASE) with letters or pictures. For the auditory ASE, the examiner reads a series of 10 letters (S-A-V-E-A-H-A-A-R-T) and asks the patient to squeeze their hand only when they hear the letter A. There are 4 target letters (A) and 6 non-target letters. Errors include both failing to squeeze on A and squeezing on non-A letters. If the patient makes more than 2 errors out of 10, Feature 2 is positive for inattention. For patients who cannot hear well, a visual ASE using picture recognition can be used instead, where patients are shown 5 pictures and then asked to identify which pictures are new from a mixed set. More than 2 errors on either test indicates clinically significant inattention consistent with delirium.
What are the subtypes of ICU delirium?
ICU delirium is classified into three subtypes based on the patient psychomotor activity level, which can be assessed using the RASS score in conjunction with the CAM-ICU. Hyperactive delirium (RASS +1 to +4) involves agitation, restlessness, and sometimes combativeness, and accounts for only about 1 to 2 percent of all ICU delirium cases. Hypoactive delirium (RASS -1 to -3) is characterized by decreased alertness, reduced motor activity, and withdrawal, and is the most common subtype accounting for approximately 44 to 64 percent of cases. Mixed delirium alternates between hyperactive and hypoactive phases and accounts for roughly 6 to 55 percent of cases depending on the study. Hypoactive delirium is often underdiagnosed because patients appear calm and cooperative, yet it carries the worst prognosis of all subtypes.
How often should CAM-ICU screening be performed?
The Society of Critical Care Medicine PADIS guidelines recommend screening for delirium at least once per nursing shift, which typically means every 8 to 12 hours. However, many high-performing ICUs screen more frequently, performing CAM-ICU assessments every 4 hours or even at every RASS assessment. More frequent screening increases the sensitivity for detecting delirium, particularly the hypoactive and mixed subtypes that may fluctuate throughout the day. The CAM-ICU should also be performed whenever there is a clinically significant change in mental status, after sedation interruptions or spontaneous awakening trials, and when family members report that the patient seems confused or different. Consistent screening with documented results helps track delirium duration, which is an important prognostic indicator since longer delirium duration is associated with worse cognitive outcomes at hospital discharge.
What are the risk factors for developing ICU delirium?
ICU delirium has numerous risk factors that are categorized as predisposing (baseline patient characteristics) and precipitating (ICU-specific factors). Major predisposing factors include advanced age over 65 years, pre-existing cognitive impairment or dementia, history of alcohol abuse, high severity of illness scores at admission, and vision or hearing impairment. Key precipitating factors include benzodiazepine use (the strongest modifiable medication risk factor), opioid administration, sleep deprivation, physical restraints, immobility, lack of natural light exposure, absence of familiar objects or family presence, and environmental factors like noise and frequent interruptions. Medical precipitants include sepsis, hypoxia, metabolic derangements, and major surgery. Understanding these risk factors enables implementation of preventive strategies through the ABCDEF bundle that targets modifiable risk factors.
References
- Ely EW et al. Evaluation of delirium in critically ill patients: validation of the Confusion Assessment Method for the ICU (CAM-ICU). Critical Care Medicine, 2001
- ICU Delirium and Cognitive Impairment Study Group - CAM-ICU Training Manual
- Devlin JW et al. PADIS Guidelines. Critical Care Medicine, 2018
Reviewed by Rahul Singh, Health & Wellness Specialist · Editorial policy