Level of Consciousness
The brain is quite sensitive to body changes, and an alteration in mental status often precedes abnormalities in other vital signs. Altered mentation may range from bizarre behavior and confusion to coma,
a state of unresponsiveness from which the patient cannot be aroused. Psychotic behavior
is usually lucid and not confused.
The person with delirium
is confused, and the onset is fairly sudden. Common causes of delirium are hypoglycemia in the diabetic, drugs, alcohol, inappropriate meds in the elderly, infection,withdrawal syndromes and hypoxemia.
Recently, the serotonin syndrome, a complication of new antidepressant drugs, may cause agitation and confusion from increased central serotonin neurotransmission. Delirium
is reversible. Untreated, it may progress to coma.
on the other hand, is a gradual loss of mental capacity, is primarily a disorder of the elderly and is rarely reversible. Alzheimer patients make up 70% of dementia cases, with multi-infarct dementia accounting for 15-20% of others. The three conditions may co-exist, particularly in the elderly. Overlaps and misinterpretations are frequent. Psychotic depression, for example, may be misdiagnosed as dementia.
On the other hand, delirium from medicines may be misdiagnosed as depression. Therefore, it is important to rule out an organic cause for altered mentation before classifying behavior as a functional disorder.
Common causes of an altered level of consciousness are alcohol and drug abuse (30%), hypoglycemia from insulin reactions (30%) and stroke (30%). In some centers the percentages vary (i.e., trauma centers, hospitals that see many elderly).