Abstract
Altered mental status (AMS) is a syndrome posing substantial burden to patients in
the intensive care unit (ICU) in both prevalence and intensity. Unfortunately, ICU
patients are often diagnosed merely with syndromic labels, particularly the duo of
toxic–metabolic encephalopathy (TME) and delirium. Before applying a nonspecific diagnostic
label, every patient with AMS should be evaluated for specific, treatable diseases
affecting the central nervous system. This review offers a structured approach to
increase the probability of identifying specific causal etiologies of AMS in the critically
ill. We provide tips for bedside assessment in the challenging ICU environment and
review the role and yield of common neurodiagnostic procedures, including specialized
bedside modalities of diagnostic utility in unstable patients. We briefly review two
common etiologies of TME (uremic and septic encephalopathies), and then review a selection
of high-yield toxicologic, neurologic, and infectious causes of AMS in the ICU, with
an emphasis on those that require deliberate consideration as they elude routine screening.
The final section lays out an approach to the various etiologies of AMS in the critically
ill.
Keywords
intensive care unit - encephalopathy - sepsis - altered mental status - status epilepticus
- acute stroke - delirium - toxicology
