Anesthesia Student Survival Guide.pdf - Index of

PhArmAcoloGy of intrAvenous Anesthetic AGents ● 47
Table 4.4 Cardiovascular effects of IV induction agents.
Drug Mean
arterial
pressure
Systemic
vascular
resistance
Cardiac
output
Contractility Heart
rate
Propofol ¯¯ ¯¯ ¯¯ ¯¯ ¯¯ ¯
thiopental ¯ ¯ ¯ ¯
etomidate – – – – – ¯
Ketamine – –
Intracranial
pressure
use of etomidate, due to enzyme inhibition. The drug should therefore be used
with caution or in concert with corticosteroid administration in those patients
demonstrating adrenal insufficiency. Other side effects include myoclonus, pain
on injection, and a high incidence of postoperative nausea and vomiting.
Ketamine is a dissociative anesthetic agent that is related to PCP (phencyclidine)
and acts as an NMDA receptor antagonist. Its major drawback is
the consequent perceptual distortions and illusory phenomena patients experience
after administration. It is the only induction agent that is a cardiovascular
stimulant, owing to inhibition of norepinephrine reuptake at sympathetic
nerve endings, and also has minimal effects on respiratory drive. Of additional
benefit is the fact that ketamine is both a potent analgesic and a bronchodilator
(it is often administered in the emergency room to patients in status asthmaticus).
Ketamine is ideal for many trauma inductions (sedation, analgesia, amnesia,
and cardiovascular support), and for use in pediatrics (where perceptual
distortions are not as frequently viewed with apprehension by the patient). It
is typically avoided in situations where cardiac stimulation could be deleterious
(arrhythmias, hypertension), and in cases where the patient is expected
to emerge from anesthesia soon after administration (again due to expected
deleterious psychological effects and cognitive disarray). Further side effects
include increased salivation and intracranial pressure elevations (relative contraindication
in patients with intracranial hypertension). Table 4.4 shows the
cardiovascular effects of the most commonly used IV induction agents.
Neuromuscular Blocking Agents
Neuromuscular blockers (NMBs) or “paralytics” are frequently utilized during
the administration of a general anesthetic. They are used to facilitate intubation
and to improve surgical conditions by inducing relaxation of skeletal muscle.