5. All of the above

The differential diagnosis for an altered mental status is quite large. A popular mnemonic that lists many of the possible causes of altered mental state is AEIOU TIPS (1). Each letter stands for a possible cause of an altered mental status (Table 1).

Table 1. Causes of an altered mental status.
A — Alcohol/Acidosis.
E — Endocrine/Epilepsy/Electrolytes/Encephalopathy.
I — Infection- meningitis, encephalitis, sepsis, septic shock; pneumonia, urinary tract infection, occult osteomyelitis.
O — Opiates, Overdose.
U — Uremia/Underdose.
T — Trauma - head injury, blood loss (shock).
I — Insulin.

Because the differential is so large, a generalized workup is initially indicated. This includes a CBC and electrolytes and a UA but would also include a urinalysis (UA), blood sugar and arterial blood gas. It is common to give naloxone and glucose on initial evaluation because narcotic overdose and hypoglycemia are so common.

The patient’s CBC is unremarkable. However, the electrolytes are Na+ 147 mEq, K+ 5.0 mEq, bicarbonate 9 mEq, and Cl- 113 mEq.

The electrolytes reveal? (Click on the correct answer to proceed to the third of six pages)

  1. A high anion gap metabolic acidosis
  2. A metabolic alkalosis
  3. A normal anion gap metabolic acidosis
  4. 1 and 3
  5. All of the above

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