Prominent signs of delirium include acute onset, fluctuating
course, inattention, disordered thinking or speech, and altered
level of consciousness. Level of consciousness is defined as “alert,” which
corresponds to a normal level of consciousness, “vigilant,” which
corresponds to a hyperalert level, “lethargy,” which
corresponds to a drowsy or easily arousable level, “stupor,” which corresponds
to a difficult to arouse level, and “coma,” which
corresponds to an unarousable level. The condition may include perceptual
disorders such as illusions, hallucinations, sleep disorders, and
abnormal psychomotor activity, which may be either increased or
decreased. Life-threatening causes of delirium include Wernike’s
encephalopathy (thiamine deficiency: nystagmus, ophthalmoplegia,
ataxia, confusion), hypoxia, hypertensive crisis, hypoperfusion
states, anemia or bleeding, electrolyte imbalance (hyponatremia,
hypercalcemia, hypokalemia), intracranial bleeding, edema or closed
head trauma, meningitis, poisons or other drug toxicities, and withdrawal
states such as from benzodiazepines. The list of medications associated
with delirium is too long for this brief discussion. Drugs with
anticholinergic side effects (such as found in drugs that are often
co-prescribed with opioids such as tricyclic antidepressants) are
among the drugs that most commonly cause delirium. Another common
culprit is the class of benzodiazepine drugs. If opioids are suspected
as the cause of delirium, a thorough investigation to rule out other
possible causes should nonetheless be undertaken, as opioids are
often incorrectly blamed for causing delirium. Treating the symptoms
of delirium such as agitation or unpleasant hallucinations require
use of neuroleptics. The most appropriate choice of neuroleptics
is those with the least anticholinergic side effects, such as intravenous
dosages of haldoperidol.