Postoperative nausea and vomiting (PONV) is the most common complication associated with anesthesia and surgery, occurring in approximately one-third of all patients and up to 70% of “high-risk” patients.1 PONV is a cause of great distress for patients, and in addition to creating a highly unpleasant experience of discomfort, it can lead to a variety of unintended consequences such as delayed discharge, wound dehiscence, dehydration, tearing of sutures, and potential pulmonary aspiration, all of which serve to greatly increase medical costs.2 Understanding the various mechanisms involved in PONV is critical for optimizing the prophylaxis and treatment of this unwanted side effect of anesthesia.
There are numerous risk factors associated with the development of PONV, and these can be divided into patient specific risk factors, anesthesia-related factors, and surgery-related factors (Table 15–1). By careful evaluation of an individual's risk factors for the development of PONV, those who will most likely benefit from prophylactic antiemetic therapy can be more easily identified.
Risk factors for postoperative nausea and vomiting (ponv) in adults.
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Table 15–1 Risk factors for postoperative nausea and vomiting (ponv) in adults.
|Type of Risk Factor ||Specific Factor Associated With Increased PONV |
|Patient-specific ||Female gender |
| ||Nonsmoking |
| ||Previous history of PONV |
| ||History of motion sickness |
|Anesthesia-related ||Use of volatile agents |
| ||Use of nitrous oxide |
| ||Use of perioperative opioids |
| ||High doses of neostigmine (> 2.5 mg) |
|Surgery-related ||Lengthy surgical procedure |
| ||Intra-abdominal surgery |
| ||Gynecologic surgery |
| ||Laparoscopic procedures |
| ||Major breast surgery |
| ||Neurologic surgery |
| ||Ear, nose, and/or throat surgery |
| ||Strabismus repair |
PHYSIOLOGIC MECHANISM OF EMESIS
The physiologic process of vomiting (emesis) involves a series of autonomic changes that operate in the brainstem at the level of the medulla oblongata. Within this region of the hindbrain, various afferent sources of emetic input are received by the area postrema, known as the chemoreceptor trigger zone (CTZ), and the vomiting center located in the nucleus tractus solitarius (NTS).3 The signals received by the CTZ and the vomiting center are mediated primarily by major neurotransmitter receptor systems. The major neurotransmitters and receptors that supply signals to the CTZ and vomiting center are serotonin (5-HT3), dopamine (D2), histamine (H1), muscarinic acetylcholine, and neurokinin (Figure 15–1). Pharmacologic antiemetic agents that work to block the neurotransmitters involved in the development of emesis have long been the mainstay of prophylaxis and treatment of PONV.
Receptor sites, receptor agonists, and receptor antagonists involved in the prophylaxis and/or treatment of postoperative nausea and vomiting. Ach, acetylcholine; D, dopamine; H, histamine; 5-HT3, serotonin; NK-1, neurokinin; RA, receptor antagonist. Numbers indicate receptor types (H1 is histamine receptor type 1).
ANTIEMETIC PHARMACOLOGIC THERAPY