Expect the ordinary. Remember Occam's razor.

One common problem is hypoglycemia ( < 50) or hyperglycemia in diabetics.

Hypoglycemia is frequent in the hospital, especially if patients miss meals with tests and procedures, or eat less because they are sick.

Hypoglycemia is dangerous (permanent brain damage may occur in 2 hours). Once recognized and corrected, you must take steps to prevent recurrence of hypoglycemia.

Marked hyperglycemia ( 600+) is usually required to produce delirium by itself, though milder hyperglycemia due to other conditions like a UTI is often seen in delirium.

It is very easy to check blood sugar, so do it!

Another cause of delirium easily checked at the bedside is hypoxia (CHF, pneumonia, mucus plug, pulmonary embolus, bronchospasm, etc).

If there is any reason to suspect it, check it.

Of "electrolyte" abnormalities, some are far more likely to cause delirium than others.

For example, moderate or severe hyponatremia (< 125) may cause delirium while hypokalemia (even < 2.5) usually doesn't.

This is because potassium is important to muscle and cardiac conduction cell membranes while sodium is important for neurons.

Chloride also doesn't affect nerve function much.

It also takes a severe acidosis (pH < 7.1) or alkalosis
(pH > 7.5) to directly alter neuronal transmission.

On the other hand, moderate or severe hypercalcemia (total > 11.5, ionized > 1.5) often does cause altered mentation.

Calcium binds to albumin, so patients with low albumin can be seriously hypercalcemic with relatively low total calcium.

Magnesium is important for cardiac conduction but less so in the brain.

Phosphorous is also less important to the brain.

Standard chemistry panels also detect renal impairment, which can affect cognition.

Delirium from renal failure alone usually requires azotemia.

In older patients, especially when malnourished, remember that BUN and creatinine levels under-represent the severity of renal dysfunction.

Still, delirium from azotemia alone is uncommon with BUN < 60 or creatinine < 3.

Dehydration, and its causes (UTI, for example) may easily cause delirium with concurrent renal dysfunction.

The renal dysfunction is likely a paraphenomenon.

• Basic metabolic panel


• Look beyond mild biochemical abnormalities that are unlikely causes of delirium.

Other biochemical concerns are hepatic dysfunction from known or occult cirrhosis, and anemia.

Post-op patients are more likely to be delirious if the hemoglobin is below 10. (We don't know why.)

Occult liver disease, even quite severe, is surprisingly common.

The WBC may also point to infection.

Finally, don't forget hypo- or hyperthyroidism.

Whether due to medications (amiodarone) or diseases, thyroid abnormalities are common, and when in doubt should be checked.