you treat postoperative nausea and vomiting (PONV)?
PONV continues to be a problem. In ambulatory
anes-thesia, where early discharge is an important issue, PONV can be a
limiting factor in home readiness.
The first step in dealing with PONV is the
identification of the high-risk patient. This particular patient is in the
high-risk category because of gender (female), use of intra-operative opioids,
and type of surgery. Other risk factors for PONV include being a non-smoker,
history of PONV/ motion sickness, use of volatile anesthetics, use of nitrous
oxide, duration of surgery, and type of surgery (laparoscopy, ear-nose-throat,
neurosurgery, breast, strabismus, laparo-tomy, and plastic surgery). Once the
high-risk patient is identified, strategies to decrease the risk, such as use
of regional anesthesia when appropriate, use of propofol for induction and
maintenance of anesthesia, intraoperative supplemental oxygen, avoidance of
volatile anesthetics and nitrous oxide, no to minimal use of opioids, and
hydration should be employed.
Since the cause of PONV is considered to be
multifacto-rial in nature, treatment and/or prophylaxis should be sim-ilarly
directed. There are several drugs currently being used for PONV prophylaxis in
adults. These include serotonin receptor antagonists, dexamethasone, and
metoclopramide. Older anti-emetics such as promethazine, haloperidol, and
perchlorperazine may be used as well. Combination therapy with drugs from different
classes has been shown to be superior to treatment with a single drug. The
serotonin receptor antagonists (5-HT3), ondansetron, dolasetron,
granisetron, and tropisetron, are most effective when given at the end of
surgery. According to Gan et al. (2003) there is no difference amongst the
various serotonin (5-HT3) recep-tor antagonists in their efficacy
and safety profiles.
Dexamethasone (2.5–5 mg intravenously) has also
been shown to be effective as prophylactic treatment for PONV and is most
effective when given before induction.
Low doses (0.625 mg) of droperidol are also
effective as prophylactic therapy when given at the end of surgery. It is of
note that the US Food and Drug Administration (FDA) issued a “black box”
warning that droperidol may cause death or life-threatening events associated
with QT prolongation and torsades de pointes. This warning is based on 10
reported cases. Gan et al. state that had it not been for the FDA warn-ing,
droperidol would have been their panel’s first choice for PONV prophylaxis.
Treatment of patients with PONV in whom
prophylaxis has failed includes the administration of small doses of sero-tonin
receptor antagonists (ondansetron 1 mg, dolasetron 12.5 mg, granisetron 0.1 mg,
or tropisetron 0.5 mg). In general, the rescue drug should be selected from a
different class than was used for prophylaxis.