Nausea and Vomiting Health Article

Description

Nausea and vomiting are recognized as two separate and distinct conditions. Nausea is the subjective, unpleasant feeling or urge to vomit, which may or may not result in vomiting. Vomiting is the forceful expelling of the contents of the stomach and intestines through the mouth. To some, nausea is a more distressing symptom than vomiting. Nausea and vomiting are major problems for patients being treated with cancer, with approximately 50% of patients experiencing nausea and vomiting as a result of cancer treatments even though antiemetics (anti-nausea and vomiting medications) were used. In addition, more than 50% of cancer patients experience nausea and vomiting as a result of progression of the disease, or as a result of exposure to other therapies used to treat the cancer.

Not all patients diagnosed with cancer will experience nausea and vomiting. However, nausea and vomiting remain two of the side effects associated with cancer and cancer treatment that patients and their families fear the most. The negative aspects of nausea and vomiting can influence all facets of a patient's life. If nausea and vomiting are not controlled in the patient with cancer, the result can be serious metabolic problems such as disturbances in fluid and electrolyte balance and nutritional status. Psychological problems associated with nausea and vomiting include anxiety and depression. Uncontrolled nausea and vomiting can also lead to the decision by the patient to stop potentially curative cancer therapy.

Causes

The most common causes of nausea and vomiting in cancer patients include treatment with chemotherapy and radiation therapy; tumor spread to the gastrointestinal tract, liver, and brain; constipation; infection; and use of some opioids which are drugs used to treat cancer pain. The mechanisms that control nausea and vomiting are not fully understood, but both are controlled by the central nervous system. Nausea is thought to arise from stimulation of the autonomic nervous system. It is theorized that chemotherapy causes vomiting by stimulating areas in the gastrointestinal tract and the brain. The areas in the brain that are stimulated are the chemoreceptor trigger zone (CTZ) and the emetic or vomiting center (VC). When the VC is stimulated, muscular contractions of the abdomen, chest wall, and diaphragm occur, which result in the expulsion of stomach and intestinal contents.

Chemotherapy-induced nausea and vomiting

Not all chemotherapeutic agents cause nausea and vomiting. Chemotherapy drugs vary in their ability or potential to cause nausea and vomiting. This variation is known as the emetogenic potential of the drug, or the potential of the drug to cause emesis. Chemotherapy drugs are classified as having severe (greater than 90% of patients exposed to this drug will experience nausea and vomiting), high (60-90% of patients will experience nausea and vomiting), moderate (30-60% will experience nausea and vomiting), low (10-30% will experience nausea and vomiting), and very low (less than 10% experience nausea and vomiting) emetogenic potential.

The incidence and severity of chemotherapy-induced nausea and vomiting varies and is related to the following factors: the emetogenic potential of the drug, the drug dosage, the schedule of administration of the drug, and the route of the drug. For example, even a drug with a low emetogenic potential may cause nausea and vomiting if given at higher doses. Factors that are associated with increased nausea and vomiting after chemotherapy include female gender, age greater than six in children, age less than 50 in adults, history of motion sickness, and history of vomiting in pregnancy.

When nausea and vomiting result from chemotherapy administration, the nausea and vomiting can be classified as anticipatory, acute, or delayed. Anticipatory nausea and vomiting occur prior to the actual chemotherapy treatment and is a response primarily to an environmental stimulus, such as a specific odor, which is then associated with the chemotherapy treatment in the future. That is, the smell of the odor alone can be enough to induce or trigger nausea and vomiting in the sensitized patient. Acute nausea and vomiting occur within 24 hours of administration of the chemotherapeutic agent. Delayed nausea and vomiting occur after the acute phase and may last 48 or more hours after chemotherapy administration.

Radiation therapy induced nausea and vomiting

Although not all patients receiving radiation therapy will experience nausea and vomiting, patients receiving radiation therapy to the gastrointestinal tract and brain are most likely to experience those side effects. Radiation therapy to the brain is believed to stimulate the CTZ, the VC, or both. The higher the radiation therapy dose and the greater the body surface area irradiated, the higher the potential for nausea and vomiting. Also, the larger the amount of gastrointestinal tract tissue exposed to radiation the more likely nausea and vomiting will occur. Nausea and vomiting associated with radiation therapy usually occurs one half to several hours after treatment and usually does not occur on the days when the patient is not undergoing treatment.