1. Anesthesia for bedside procedures in the intensive care unit (ICU) is accomplished with total intravenous anesthesia (TIVA).

2. Selecting the proper dose of an analgesic to administer is challenging because of

a. Difficulty in assessing the effectiveness of pain relief (delirium, obtundation, endotracheal intubation).

b. Pharmacokinetic (PK) differences between critically ill and other patients.

c. Physiologic changes associated with aging (decrease in lean body mass, increase in volume of distribution of lipid-soluble drugs, decrease in drug clearance rates, increased sensitivity to hypnotics and analgesics).

1. PK behavior in critically ill patients is unlike that in normal subjects for the following reasons (see also Dershwitz 2012, in Suggested Readings, for more detail).

a. ICU patients frequently have renal and/or hepatic dysfunction; therefore, drug metabolism and elimination may be significantly impaired.

b. Hypoalbuminemia, common in critical illness, can decrease protein binding and increase free (active) drug concentration.

1. Procedures performed in the ICU can be differentiated according to their associated levels of discomfort.

a. Mild to moderately uncomfortable (esophagogastroscopy, paracentesis).

b. Moderately to severely uncomfortable (endotracheal intubation, thoracostomy, flexible bronchoscopy).

c. Extremely painful (rigid bronchoscopy, orthopedic manipulations, tracheotomy).

2. Specific disease states should be considered so that safety and effectiveness are maximized.

a. Head trauma.

i. Effective yet brief anesthesia is desirable so that the capacity to assess neurologic status is not lost for extended periods.

ii. The technique should not adversely affect cerebral perfusion pressure.

iii. If the effects of the medications dissipate too rapidly, undesirable episodes of agitation and increased intracranial pressure (ICP) may occur.

b. Coronary artery disease: Sufficient analgesia is necessary during and after invasive procedures to minimize tachycardia (which is a major determinant of ischemia) and reduce plasma catecholamine and stress hormone levels.

c. Renal or hepatic failure.

i. The risk of an adverse drug reaction is at least three times higher in patients with azotemia compared to those with normal renal function.

ii. Liver failure alters the volume of distribution of many drugs by impairing synthesis of albumin and α₁-acid glycoprotein.

iii. Reductions in hepatic blood flow and hepatic enzyme activity decrease drug clearance rates.

A. Hypnotics: The characteristics of commonly used hypnotics are listed in Table 18-1.

a. Propofol is an extremely popular hypnotic agent for the following reasons.

i. It is readily titratable and has more rapid onset and offset kinetics than midazolam.

ii. The rapid recovery of neurologic status makes propofol a good sedative in ICU patients, especially those with head trauma.

iii. Spontaneously breathing patients anesthetized with propofol may maintain normal end-tidal carbon dioxide values during minor surgical procedures.

b. Maintenance infusion rates of 100 to 200 µg/kg/min are adequate in younger subjects, which should be reduced by 20% to 50% in elderly individuals.

c. Adverse effects of propofol administration include

i. Hypotension from depressed ventricular systolic function and/or decreased afterload.

ii. In patients with coronary artery disease, propofol administration may be associated with a reduction in coronary perfusion pressure.

iii. The emulsion used as the vehicle for propofol supports bacterial growth; iatrogenic contamination leading to septic shock is possible.

iv. Hyperlipidemia with prolonged infusions can occur, particularly in infants and small children.