What is the Confusion Assessment Method (CAM)?
The Confusion Assessment Method (CAM) is a widely-used, standardized tool for the clinical diagnosis of delirium. Developed to help non-psychiatrists identify delirium quickly at the bedside, the original CAM was validated against a gold standard of a psychiatric interview. It is typically applied to older adult patients in general medical wards, nursing homes, and emergency departments, where a patient is able to communicate verbally.
The CAM algorithm requires the presence of an acute onset or fluctuating course of mental status changes and inattention, plus either disorganized thinking or an altered level of consciousness. The assessment is structured to be brief, taking around five minutes to complete. While a formal cognitive test, like a brief mental status exam, is typically required for accurate scoring, the CAM's strength lies in its ability to be incorporated into routine assessments.
What is the CAM for the Intensive Care Unit (CAM-ICU)?
The CAM for the Intensive Care Unit (CAM-ICU) was developed as a specialized adaptation of the CAM specifically for critically ill patients. The most significant feature of the CAM-ICU is its ability to diagnose delirium in patients who are non-verbal, which is crucial in the ICU where many patients are sedated or mechanically ventilated. This adaptation retains the four cardinal features of the original CAM but utilizes non-verbal methods for assessment.
Unlike the standard CAM, which relies on verbal questions and responses, the CAM-ICU uses a different approach. The assessment begins with a check of the patient's level of consciousness, often using a validated sedation scale. If the patient is responsive enough for a focused assessment, the clinician then proceeds to check for the four key features using methods that do not require speech. For example, inattention is tested using a visual task, such as asking the patient to squeeze the clinician's hand when they see a specific letter presented on a card. This makes it a rapid and highly feasible tool for the demanding ICU environment.
Comparison Table: CAM vs. CAM-ICU
| Feature | Confusion Assessment Method (CAM) | CAM for the Intensive Care Unit (CAM-ICU) |
|---|---|---|
| Target Population | Non-ICU patients, typically older adults in general medicine wards, nursing homes, or emergency departments. | Critically ill patients in the Intensive Care Unit (ICU), including those who are mechanically ventilated or non-verbal. |
| Communication Needs | Requires verbal communication from the patient to complete the assessment, including formal cognitive testing. | Designed to be used with non-verbal patients. Uses visual or motor cues, like hand squeezes, instead of verbal responses. |
| Assessment Method | Based on observations made during formal cognitive testing, with reliance on verbal responses. | Follows a staged protocol, starting with level of consciousness and using non-verbal tasks for the core features. |
| Administration Time | Approximately 5 minutes to complete. | Rapid administration, often taking less than 1 minute for a skilled user. |
| Key Features Assessed | Four Features: (1) Acute onset or fluctuating course, (2) Inattention, (3) Disorganized thinking, and (4) Altered level of consciousness. | Four Features: (1) Acute onset or fluctuating course, (2) Inattention, (3) Altered level of consciousness, and (4) Disorganized thinking (features assessed non-verbally). |
| Use Case | Routine delirium screening in non-critical care settings. | Standard-of-care delirium monitoring in the ICU, often performed once per shift. |
| Sensitivity & Specificity | High sensitivity (86-100%) and specificity (90-95%) reported in various studies compared to psychiatric assessment. | High sensitivity (93-100%) and specificity (89-100%) reported in ICU populations compared to reference standard diagnosis. |
Why The Need for Different Tools?
The development of the CAM-ICU highlights the significant differences in patient populations and clinical contexts. In non-ICU settings, many patients with suspected cognitive issues are still able to communicate. The original CAM, with its reliance on brief cognitive testing and verbal interaction, is perfectly suited for this group. It allows for a nuanced, yet efficient, bedside assessment.
However, in the ICU, many patients are not awake enough or are otherwise unable to communicate verbally due to mechanical ventilation, sedation, or their critical condition. Using the standard CAM in this population would be impossible and lead to missed diagnoses. Critically ill patients are also at a higher risk for delirium, which is independently associated with worse outcomes, including increased mortality and prolonged hospital stays. Early detection is critical for managing this condition. The CAM-ICU addresses this by providing a reliable tool that can be used on these vulnerable patients, ensuring they receive appropriate monitoring and care.
Adaptations and Impact
Several adaptations of the CAM have been developed over the years, each tailored to a specific patient population or setting. The CAM-ICU is arguably one of the most impactful of these, having been validated and translated into multiple languages for global use. Its ease of use, with minimal training required for administration, has made it a cornerstone of ICU best practices. The integration of the CAM-ICU into care bundles, such as the ABCDEF bundle (Awakening and Breathing Coordination, Delirium monitoring, and Early mobility), further emphasizes its importance in modern critical care.
Considerations for Use
While both tools are highly valuable, it is crucial to use the correct version for the specific patient population. Using the standard CAM in a non-verbal, ventilated ICU patient is inappropriate, and relying on informal bedside assessment is not accurate. Clinicians must be trained on the specific protocol for the tool they are using to ensure consistent and reliable results. Regularly monitoring for delirium, especially in at-risk ICU patients, is standard practice, with CAM-ICU assessments often conducted once per shift.
Conclusion
In summary, the Confusion Assessment Method (CAM) and the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) are both reliable tools for diagnosing delirium, but they are designed for two distinct patient populations. The original CAM is for verbally responsive, non-critically ill patients, while the CAM-ICU is an essential adaptation for critically ill, often non-verbal, patients in the ICU. The core diagnostic features remain the same, but the assessment methodology and communication requirements are tailored to the specific clinical environment. By understanding this key difference between CAM and CAM-ICU, clinicians can ensure they are using the appropriate tool for accurate delirium assessment, leading to better patient outcomes. For more detailed information on critical care guidelines, consult resources such as the Society of Critical Care Medicine's website.
