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ICU patients commonly exhibit altered mental status(AMS), which may be due to any of several factors. For those who do not have head injury, below are the most common etiologies of AMS:
-Stroke/hemorrhage, post cardiac arrest, encephalitis, seizure, hypo/hyperthermia
-Drug or ETOH withdrawl, thiamine deficiency, water intoxication, toxins
-Hyperthyroid (apathetic), hypothyroid
-Medications, line sepsis
-Decreased pO2, increased pCO2, ARDS, pneumonia
-Heart failure, hyper/hypotension
-Hepatic failure, biliary sepsis
-Hyper/hypoglycemia, pancreatitis
-Adrenal insufficiency
-Renal failure, urosepsis, post-dialysis electrolyte imbalance (Na, Ca, PO4)
-Fat embolism
Ischemic stroke has been shown to be the most frequent cause of AMS on admission to the ICU, and septic encephalopathy the most commmon cause of AMS developing after admission to the ICU.
References
Bleck TP, Smith MC, Pierre-Louis SJ, et al. Neurologic complications of critical medical illnesses. Crit Care Med 1993;21:98-103.