Marino The ICU Book 4e, IE

801

Disorders of Consciousness

1

Traumatic or Ischemic Injury Encephalopathy/Encephalitis Nonconvulsive Seizures

1

2

4

Toxic Drug Ingestion ETOH Withdrawal Dehydration

2

3

3

Thyroid Disorders

5

4

Medications, Line Sepsis

6

Hypoxia, Hypercapnia

5

7

Low cardiac Output Circuatory Shock

6

8

9 10

Hepatic Failure

7

8

Hypoglycemia

9

Adrenal Insufficiency

Uremia, Urosepsis

10

FIGURE 44.1 Sources of altered consciousness in ICU patients.

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).