Pain,
nausea and
vomiting are frequently listed by patients as their most important perioperative concerns. With the change in emphasis from an inpatient to outpatient hospital and office-based medical/surgical environment, there has been increased interest in the 'big little problem' of
postoperative nausea and vomiting (
PONV). Currently, the overall incidence of
PONV is estimated to be 25 to 30%, with severe, intractable
PONV estimated to occur in approximately 0.18% of all patients undergoing surgery.
PONV can lead to delayed postanaesthesia care unit (PACU) recovery room discharge and unanticipated hospital admission, thereby increasing medical costs. The aetiology and consequences of
PONV are complex and multifactorial, with patient-, medical- and surgery-related factors. A thorough understanding of these factors, as well as the neuropharmacology of multiple
emetic receptors [dopaminergic,
muscarinic,
cholinergic,
opioid,
histamine,
serotonin (5-hydroxy-
tryptamine; 5-HT)] and physiology [cranial nerves VIII (acoustic-vestibular), IX (glossopharyngeal) and X (vagus), gastrointestinal reflex] relating to
PONV are necessary to most effectively manage
PONV. Commonly used older, traditional
antiemetics for
PONV include the
anticholinergics (
scopolamine),
phenothiazines (
promethazine),
antihistamines (
diphenhydramine),
butyrophenones (
droperidol) and
benzamides (
metoclopramide). These
antiemetics have adverse effects such as dry mouth, sedation,
hypotension, extrapyramidal symptoms, dystonic effects and
restlessness. The newest class of
antiemetics used for the prevention and treatment of
PONV are the
serotonin receptor antagonists (
ondansetron,
granisetron,
tropisetron,
dolasetron). These
antiemetics do not have the adverse effects of the older, traditional
antiemetics.
Headache and
dizziness are the main adverse effects of the
serotonin receptor antagonists in the dosages used for
PONV. The
serotonin receptor antagonists have improved
antiemetic effectiveness but are not as completely efficacious for
PONV as they are for
chemotherapy-induced
nausea and
vomiting. Older, traditional
antiemetics (such as
droperidol) compare favourably with the
serotonin receptor antagonists regarding efficacy for
PONV prevention. Combination
antiemetic therapy improves efficacy for
PONV prevention and treatment. In the difficult-to-treat
PONV patient (as in the
chemotherapy patient), suppression of numerous emetogenic peripheral stimuli and central neuroemetic receptors may be necessary. This multimodal
PONV management approach includes use of: (i) multiple different
antiemetic medications (double or triple combination
antiemetic therapy acting at different neuroreceptor sites); (ii) less emetogenic anaesthesia techniques; (iii) adequate intravenous hydration; and (iv) adequate
pain control.