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FOUNDATION OVERVIEW

Nausea and vomiting is caused by numerous 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 or a surgical procedure.

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 serotonin 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). Things that increase the risk of both despite adequate antiemetic treatment are female gender, age less than 50, a history of motion sickness or nausea with pregnancy, and a history CINV or PONV. In terms of CINV, the emetic potential of the chemotherapy agent or agents is the most important factor. Agents are classified into high, moderate, low, or minimal risk for causing CINV (Table 42-1). Dose of the agent can also affect risk (the higher the dose, the higher the risk of CINV). Bolus infusions also tend to have higher risk of CINV than extended infusions. For PONV, certain anesthesia agents, how the anesthesia is delivered and non-smokers tend to have a higher incidence of PONV.

TABLE 42-1Emetic Risk of Commonly Administered Chemotherapy Agents

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