Understanding Anesthesiology - The Global Regional Anesthesia ...

Sedation
Sedation involves the delivery of agents (usually intravenous)
for the purpose of achieving a calm, relaxed patient,
able to protect his own airway and support his
own ventilation. The range of physiologic effects of sedation
is varied and is dependent on the depth of sedation
provided: minimal, moderate or deep. A patient
under minimal sedation will be fully responsive to verbal
commands although his or her cognitive functions
and coordination would be impaired. He or she would
appear calm and relaxed and would have normal cardiorespiratory
function. At the other extreme, a patient
receiving deep sedation would be rousable only to repeated
or painful stimuli. In some instances, the patient
may require assistance in maintaining a patent airway.
In this case, the line between deep sedation and general
anesthesia is not easily identifiable. Table 9 outlines the
physiologic effects of each of the three levels of sedation
as defined by the American Society of Anesthesiologists
(ASA). Sedation may be used alone for minimally
painful procedures such as endoscopy. Often it is
used in combination with local or regional anesthesia
to provide a more palatable experience for the patient.
In any case, the sedated patient must be monitored due
to the depressant effects of the agents used. Care must
be taken to reduce the dose administered to the frail,
elderly or debilitated patient, in whom depressant effects
may be exaggerated. In any patient, sedation may
cause disinhibition, resulting in an uncooperative, agitated
patient.
Many different agents have been used for sedation. The
term “neurolept anesthesia” refers to the (now historical)
use of high doses of droperidol (a butyrophenone,
in the same class as haloperidol) in combination with
fentanyl (an opioid). Side effects were prominent. Currently,
agents are chosen with specific effects in mind.
Opioids. such as fentanyl or remifentanil, may be given
alone if analgesia is the primary goal. The short-acting
benzodiazepine, midazolam, is a popular choice because
it provides amnesia as well as anxiolysis. Propofol,
an anesthetic induction agent, can be infused in
sub-anesthetic doses to produce a calm, euphoric patient.
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