Anesthesia Student Survival Guide.pdf - Index of

40 ● AnesthesiA student survivAl Guide
maintain hemodynamic stability, and will not negatively impact the patient’s
intraoperative course or recovery. There is no one drug that can accomplish all
these things in every patient, so multiple drugs are typically utilized in concert.
This concept is known as “balanced anesthesia.” The anesthesiologist strives to maximize
the positive actions of various drugs, while minimizing negative side effects.
Neuraxial (spinal and epidural) and peripheral nerve blockade are anesthetic
techniques requiring drug delivery to very precise locations along the body’s
neural transmission pathways. Local anesthetic drugs are primarily used for
these techniques. A full description of both neuraxial blockade and peripheral
nerve blockade appears in subsequent chapters.
The intravenous route is the primary means of delivery for most drugs
during a typical anesthetic case, owing to the ease of administration and
rapidity of transit to the drugs’ sites of action. We will consider several of the
most commonly used intravenous drugs according to their pharmacological
classes and their clinical application. The five most commonly used classes of
drugs for a typical anesthetic are benzodiazepines, opioids, induction agents,
neuromuscular blockers (NMBs), and sympathomimetics.
Benzodiazepines
The benzodiazepines utilized in anesthesia include midazolam (Versed), diazepam
(Valium), and lorazepam (Ativan) all of which exert their sedative and
hypnotic effects by enhancing GABA transmission (an inhibitory neurotransmitter).
The most commonly used perioperative benzodiazepine is midazolam
which has an elimination half-life of 3 h. With a typical sedative IV dose of
1–2 mg, the clinical effect typically lasts for 20–30 min owing to redistribution.
Benzodiazepines are used for sedation, anxiolysis, and amnesia. A beneficial
side effect of these drugs is their anticonvulsant activity, which can help
raise the seizure threshold in susceptible patients (e.g. patients receiving nerve
blocks are at risk for local anesthetic toxicity). Benzodiazepines do not
provide analgesia and can be very long-acting when used in large doses. This
is why benzodiazepines are usually used jointly with other agents during the
course of an anesthetic.
Some patients, particularly children, are so anxious that the anesthesiologist
deems it prudent to administer a benzodiazepine for anxiolysis prior to
entering the operating room. Midazolam (0.25–0.5 mg/kg orally in children)
can be administered in these situations. It is important to remember that
loss of balance and respiratory depression can occur after administration of
benzodiazepines (particularly when combined with opioids). Patients given