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FOUNDATION OVERVIEW

Nausea and vomiting may be caused by a number of factors, with two of the most common factors being chemotherapy and surgery. Nausea and vomiting can lead to serious medical complications such as dehydration, electrolyte imbalances, and esophageal tears. It is easier to prevent nausea and vomiting than to treat it once it has started. Although significant progress has been made in the management of nausea and vomiting, these side effects are some of the most worrisome and undesirable effects reported by patients receiving chemotherapy and may cause patients to avoid further chemotherapy.

The etiology of nausea and vomiting is complex. The chemoreceptor trigger zone (CTZ), located outside of the blood-brain barrier, is activated by chemotherapy and other irritants. The CTZ is triggered by various neurotransmitters including dopamine, serotonin, histamine, and neurokinin-1 (substance P) which then stimulates the vomiting center (Figure 42-1). In addition to the CTZ, the gastrointestinal (GI) tract releases these neurotransmitters in response to stimulants such as chemotherapy and anesthesia, which can activate the vomiting center, also causing nausea and vomiting. Current antiemetic medications block the neurotransmitter receptors with the intent to mitigate nausea and vomiting.

FIGURE 42-1

Chemoreceptor trigger zone and activating neurotransmitters with the vomiting center.

There are several risk factors that increase the possibility of experiencing chemotherapy-induced nausea and vomiting (CINV) and postoperative nausea and vomiting (PONV). Female gender, age below 50 years, a history of motion sickness or nausea with pregnancy, and a history CINV or PONV increase the risk of CINV and PONV despite adequate antiemetic treatment. In terms of CINV, the emetic potential of the chemotherapy agent or agents is the most important factor. Chemotherapy agents are classified into high, moderate, low, or minimal risk for causing CINV (Table 42-1). Dose of the chemotherapy agent can also affect the risk (the higher the dose, the higher the risk of CINV). For PONV, certain anesthesia agents, how the anesthesia is delivered, duration of anesthesia, and nonsmokers tend to have a higher incidence of PONV.

TABLE 42-1Emetic Risk of Commonly Administered Chemotherapy Agents

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