Propofol
Propofol (Diprivan) is rapidly acting, has a short
recov-ery time, and possesses antiemetic properties. A rapid onset of
anesthesia (50 seconds) is achieved, and if no other drug is administered,
recovery will take place in 4 to 8 minutes. The recovery is attributed to
redistribution of the drug and rapid metabolism to glucuronide and sulfate
conjugates by the liver and extrahepatic tissues, such as intestine and kidney.
Rapid recovery and its
antiemetic properties make propofol anesthesia very popular as an induction
agent for outpatient anesthesia. Propofol can also be used to supplement
inhalational anesthesia in longer proce-dures. Both continuous infusion of
propofol for con-scious sedation and with opioids for the maintenance of
anesthesia for cardiac surgery are acceptable techniques.
Propofol is primarily a
hypnotic drug with substantial cardiorespiratory depressant actions and with no
ability to produce neuromuscular blockade. While propofol lacks analgesic
properties, its use permits lower doses of opioids. Likewise, less propofol is
required for adequate hypnosis when it is administered with opioids. Thus, it
is said that propofol and opioids interact synergistically.
The dose of propofol should
be reduced in older pa-tients; however, it does have a relatively linear dose–
response characteristic, and patients generally can besafely titrated. The pain
on injection, especially when small veins are used, can be considerably reduced
if li-docaine 20 mg is administered first.
Anesthesia induction with
propofol causes a signifi-cant reduction in blood pressure that is proportional
to the severity of cardiovascular disease or the volume sta-tus of the patient,
or both. However, even in healthy pa-tients a significant reduction in systolic
and mean arte-rial blood pressure occurs. The reduction in pressure appears to
be associated with vasodilation and myo-cardial depression. Although propofol
decreases sys-temic vascular resistance, reflex tachycardia is not ob-served.
This is in contrast to the actions of thiopental. The heart rate stabilization
produced by propofol rela-tive to other agents is likely the result of either
resetting or inhibiting the baroreflex, thus reducing the tachy-cardic response
to hypotension.
Since propofol does not
depress the hemodynamic response to laryngoscopy and intubation, its use may
permit wide swings in blood pressure at the time of in-duction of anesthesia.
Propofol should be used with ut-most caution in patients with cardiac disease.
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