Disorders of Consciousness
801
lation of ammonia and aromatic amino acids (e.g., tryptophan) in the
central nervous system (4,5). The origins of septic encephalopathy may
be the actions of inflammatory mediators to increase the permeability of
the blood-brain barrier, which then allows ammonia and other toxic sub-
stances to gain entry into the central nervous system. This is similar to
the capillary leak that promotes peripheral edema in septic and anaphy-
lactic shock.
DELIRIUM
Delirium is reported in 16 – 89% of ICU patients (6), and is particularly
prevalent in ventilator-dependent patients (7), and elderly postoperative
patients (8). The delirium that accompanies alcohol withdrawal is a dif-
ferent entity than hospital-acquired delirium, and is described in a sepa-
rate section.
Clinical Features
The clinical features of delirium are summarized in Figure 44.2 (9).
Delirium is an acute confusional state with attention deficits, disordered
thinking, and a fluctuating course (the fluctuations in behavior occur
over a 24-hour period). Over 40% of hospitalized patients with delirium
have psychotic symptoms (e.g., visual hallucinations) (10); as a result,
delirium is often inappropriately referred to as “ICU psychosis” (11).
Traumatic or Ischemic Injury
Encephalopathy/Encephalitis
Nonconvulsive Seizures
Medications, Line Sepsis
Low cardiac Output
Circuatory Shock
Thyroid Disorders
Adrenal Insufficiency
Toxic Drug Ingestion
ETOH Withdrawal
Dehydration
Hypoglycemia
Hepatic Failure
Hypoxia, Hypercapnia
Uremia, Urosepsis
1
2
3
4
5
6
7
8
9
10
1
2
4
5
6
7
8
9
10
3
FIGURE 44.1
Sources of altered consciousness in ICU patients.
