Retching, an involuntary attempt to vomit, consists of rhythmic, labored spasmodic movement of the diaphragm and abdominal muscles causing regurgitation into the esophagus (Woodruff, 2004). Retching often follows nausea and precedes vomiting. Descriptors include “dry heaves.”

Vomiting, often confused with nausea, is the forceful contraction of the abdominal muscles (stomach), to cause the expulsion of stomach contents through the mouth (National Comprehensive Cancer Network [NCCN], 2005). Common descriptors include “throwing up.”

Nausea and vomiting (N/V) are two of the most frequently reported and feared side effects experienced by patients throughout their cancer experience. N/V affects 60% to 80% of cancer patients undergoing active treatment (Cunningham, 2005), 50% to 60% of patients with advanced disease (Herndon, Jackson, & Hallin, 2002), and as many as 40% of terminally ill patients within in their last week of life (Kazanowski, 2001). If untreated, complications can lead to unnecessary hospitalizations and diminished quality of life (Figure 31-1). N/V is particularly prevalent in persons with breast, stomach, and gynecological cancers, as well as persons with AIDS (Kazanowski, 2001). At end-of-life, N/V is commonly seen as a result of certain conditions such as bowel obstruction, hypercalcemia, constipation or impaction, use of opioids, uremia, and increased intracranial pressure secondary to metastatic disease in the brain. Effective management of these individual symptoms during initial and continued therapy profoundly influences symptom response throughout the cancer trajectory (Rhodes & McDaniel, 2001).

Still not well defined, the physiological mechanisms for N/V are complex and may involve one or more mechanisms and can occur from one or more neurotransmitters (Wickham, 2005). The vomiting center (VC), located in the brainstem along with the chemoreceptor trigger zone (CTZ), located in the area postrema of the fourth ventricle of the brain, coordinate the processes involved in N/V. The CTZ is stimulated by chemicals and neurotransmitters found in the cerebrospinal fluid and blood. The CTZ, the VC, and the gastrointestinal tract have many neurotransmitter receptors. Activation of these receptors by noxious stimuli results in the symptoms of N/V. The principal neuroreceptors involved in the emetic response include dopamine and serotonin (5-hydroxytryptamine ₃ [5-HT ₃]) receptors. Other receptors involved in signal transmission include acetylcholine, corticosteroid, histamine, cannabinoid, opiate, and neurokinin-1 (NK-1), which are located in the VC and vestibular center of the brain (NCCN, 2005) (Table 31-1).

The VC is located in the lateral reticular formation of the medulla oblongata and is situated close to areas in the brain responsible for respiration, salivation, vasomotor processes, and vestibular apparatus (Ezzone, 2000). The VC, which coordinates the process of N/V, receives signals from the cerebral cortex and higher brainstem, thalamus, hypothalamus, and the vestibular system. It also receives emetic impulses via the vagus and splanchnic nerves from the pharynx and gastrointestinal tract when enterochromaffin cells in the upper gastrointestinal tract are stimulated (Figure 31-2). The VC also receives signals from the CTZ, which can initiate vomiting only via the VC (Mannix, 1999).

Vomiting occurs when efferent impulses are sent from the VC to the salivation center, abdominal muscles, respiratory center, and cranial nerves. Box 31-1 lists common causes of N/V in the palliative care setting; the causes most frequently identified in persons with end-stage disease are identified by an asterisk.

Identification of the possible cause(s) of N/V begins with a detailed history and physical examination. In patients with advanced cancer, N/V is frequently due to multiple causes (Woodruff, 2004). Questions about onset, precipitating and aggravating factors, quality (duration, frequency, and severity), and relieving factors should be documented so that an individualized approach to management can be implemented. Assessment of the gastrointestinal status, that is, abdominal distention, presence of bowel sounds, and presence of other associated symptoms such as constipation, should be part of the total process. It is also very important to remember that the most reliable way to assess nausea is through the patient’s report.