Postoperative Nausea & Vomiting PONV
Without any prophylaxis, PONV occurs in approx-imately 20–30% of the general surgical population and up to 70–80% in patients with predisposing risk factors (Table 17–3). As anesthetic duration increases, so, too, does PONV risk. When the risk is sufficiently great, prophylactic antiemetic medications are administered and strategies to reduce its incidence are initiated. The Society of Ambulatory Anesthesia (SAMBA) provides sim-plified risk scoring systems, which assign points for specific risk factors, as well as guidelines that assist in the management of at-risk patients (Table 17–4). Obesity, anxiety, and reversal of neuromuscular blockade are not independent risk factors for PONV.
Drugs used in the prophylaxis and treatment of PONV include 5-HT3 antagonists, butyrophe-nones, dexamethasone, neurokinin-1 receptor antagonists (aprepitant, Emend); antihistamines and transdermal scopolamine may also be used. At-risk patients often benefit from one or more prophylactic measures.