Altered Mental Status: The Forgotten Four

by Bob Stuntz


Altered mental status is an all too familiar complaint to emergency physicians.  The differential is broad, and includes multiple life threatening diagnoses.  We of course think the worst: does the patient have a head bleed or a stroke?  Are they septic?  Have they ingested some life threatening drug or toxin?

All too often, we get caught up in the rush to get the patient to CT without thinking about a few common, easily diagnosed, and relatively easily fixed problems that require no radiation.  It is something we all do from time to time.  I have noted four diagnoses that I and my residents occasionally forget to look for, and wind up kicking ourselves over later.  Think about these early, and look for them routinely.  

1. Glucose: In my experience this is far and away the most commonly forgotten cause of AMS.  Glucose is the syphillis of AMS.  It can cause seizures, mimic strokes, and make a patient look like they are having an MI.  I have seen patients sent to CT for stroke and even intubated, only to later discover they have a low serum glucose.  Ask EMS for a fingerstick reading on all AMS patients.  If they did not check, you should.  Consider D for Dextrose along with disability in your ABC’s (and remember to ask for a chem stick on your oral boards!).  Treatment options range from oral glucose in the awake, to IV dextrose in those with contraindications to oral repletion (1-2 mg glucagon IM is an option if IV access is not immediately available).  What you give depends on age:

Adults: 1 mL/kg D50

Kids: 2 mL/kg of D 25

Infant/newborn: 5 mL/kg D10 

2. Hypoxia: You would think this is a simple one, but it does get missed.  A patient is not themselves at home, and a family member brings them in.  In the heat of the moment, no one tells the triage nurse they are oxygen dependent and ran out of their home O2 the day before.   This one is as simple as sticking a pulse ox on and administering supplemental O2.  

3. Hypercarbia: Seen frequently in COPD, and thus usually in an older, sicker population, we often forget to look for hypercarbia as we look for other causes of AMS.  This is as simple as getting a screening VBG or iSTAT (an iSTAT gets you your glucose as well).  As I described in a previous post, a venous pCO2 < 45 mmHg is nearly 100% sensitive in the evaluation of hypercarbia.  Remember, however, that it does not correlate well to an absolute number.  The interpretation: Normal pH and pCO2 < 45 mmHg on your VBG, and you are clear.  If the patient is acidotic or has an elevated pCO2, get an ABG to get a true evaluation and ventilate them (invasively or non invasively as indicated).  

4. Hepatic encephalopathy: You would think this would be easy: Your patient is yellow, or has a history of liver disease.  But again, patients prone to hepatic encephalopathy tend to be overall sickly, and I see extensive workups to rule out ICH, sepsis, or other causes of AMS, but lack a simple ammonia.  Do not forget to check that ammonia if the patient has any risk factors for  hepatic encephalopathy.  Treatment involves initiation of lactulose and further investigation as to the root cause.  

Three of these can be checked and treatment initiated within 5 minutes of arrival (apply a pulse ox and get an iSTAT to check a sugar and screen for hypercarbia).  While you always want to fully work up your patients with AMS, do not miss these oft forgotten, easily identified and fixed causes of AMS.