Anesthesia Student Survival Guide.pdf - Index of

42 ● AnesthesiA student survivAl Guide
mainly for pain control intraoperatively, longer-acting opioids such as morphine,
hydromorphone, or meperidine are usually used for postoperative pain. In
addition to varying durations of action, it is their degree of binding to different
opioid receptors and consequent side effect profiles that help in choosing the
appropriate opioid for each patient and situation. Table 4.2 shows the relative dose,
time to peak effect, and duration for the most commonly used IV opioids.
Fentanyl is a rapid-acting synthetic opioid which is about 100 times more
potent than morphine. It is often given (dose 50–150 mcg for a 70-kg adult)
during the induction of anesthesia to blunt the sympathetic response during
intubation. It can cause apparent chest wall rigidity in high doses (1,000 mcg),
which in rare cases may impair or prevent adequate ventilation.
Sufentanil and Alfentanil are both analogues of fentanyl. When compared
with sufentanil and fentanyl, alfentanil is an ultra short-acting opioid (5–10 min),
about 25% as potent as fentanyl, but has significantly faster onset than fentanyl
(1–2 min). Sufentanil is approximately 5–10 times more potent than fentanyl.
Both opioids may be used for induction and maintenance of anesthesia.
Morphine is the least lipid-soluble opioid and the most likely agent to
accumulate in the presence of renal failure. It can cause bradycardia and
histamine release in some patients. Morphine has a slower peak onset (30 min)
when compared with fentanyl. Along with hydromorphone, morphine is
the most commonly used long-acting opioid for postoperative pain control.
Usually, either 5–15 mg of morphine or 1–2 mg of hydromorphone is given
during a typical general anesthetic case.
Table 4.2 Dose, time to peak effect, and duration of analgesia for commonly
used perioperative opioids.
Opioid Dose a (mg) Peak (min) Duration (h)
morphine 10 20–30 3–4
meperidine 80 5–7 2–3
hydromorphone 1.5 15–30 2–3
fentanyl 0.1 3–5 0.5–1
sufentanil 0.01 3–5 0.5–1
Alfentanil 0.75 1.5–2 0.2–0.3
remifentanil 0.1 1.5–2 0.1–0.2
a Approximately equianalgesic dosages.