A Symptom Review: Nausea and Vomiting in HIV.

Nausea and vomiting are symptoms often experienced by individuals with HIV disease. The etiologies are multifactorial, yet the symptoms have not been well studied in HIV research. Interventions currently used are adapted from the oncology setting and remain to be tested on patients with HIV. The purpose of this article is to review and discuss the symptoms of nausea and vomiting and to emphasize the need for research in this area.

Key words: nausea and vomiting, symptom management, nursing interventions

Nausea and vomiting are symptoms commonly associated with human immunodeficiency virus (HIV) disease. Nausea has been reported as one of the 12 most frequent and bothersome symptoms in patients with HIV disease (Whalen, Antani, Carey, & Landefeld, 1994). Nausea and vomiting are often nonspecific symptoms that cause patients much distress and discomfort. In HIV disease, pharmacologic side effects and opportunistic infections are the most probable causes of nausea and vomiting. Additionally, excessive nausea and vomiting can lead to discontinuation of drug therapies, substantially affecting a patient's physical and psychologic status.

Research on the symptom management of nausea and vomiting has primarily focused on cancer patients, pregnancy, and the postoperative emetic response. Current attempts at controlling nausea and vomiting have focused on dietary management, pharmacologic therapy, behavior modification, and complementary therapies, such as acupressure and acupuncture. Methods to control nausea and vomiting in patients with HIV have not been well studied. Understanding the complexity of this issue is critical because nausea and vomiting can have multifactorial etiologies and potentially can affect the success of HIV therapies. This article will review the symptoms of nausea and vomiting. Discussions will include the following: defining the symptoms, pathophysiology, prevalence, causes, effects, and implications for nursing.

Defining Nausea and Vomiting

Nausea is an ill-defined and subjective sensation (Porth, 1994). It is often a prodrome to vomiting; however, vomiting can occur without the prodromal sensation to nausea (Fessele, 1996). Nausea is the conscious awareness of the stimulation of the vomiting center located in the medullary reticular formation of the brain (Porth, 1994). It can be caused by irritation of the gastrointestinal (GI) tract due to certain foods and drugs, motion sickness, pregnancy, and endocrine pathologies. Nausea is frequently accompanied by salivation, pallor, sweating, and tachycardia (Porth, 1994).

Vomiting can be defined as a sudden and forceful expulsion of the gastric contents through the mouth (Fessele, 1996). It is usually preceded by nausea but can occur without it. The act of vomiting is caused by stimulation of the vomiting center. The vomiting center can receive stimulation from the GI tract, from the vestibular apparatus responsible for motion sickness, and from the chemoreceptor trigger zone stimulated by various drugs and endogenous and exogenous toxins (Porth, 1994). Vomiting can be accompanied by dizziness, bradycardia, and a decrease in blood pressure.

Nausea and vomiting are common manifestations of many GI disorders. These symptoms are protective when the presence of nausea signals a disease process, and the main function of an occurrence of vomiting is to remove noxious agents from the body (Porth, 1994). Nausea and vomiting become problematic symptoms when they impair intake and/or lead to a loss of fluids and nutrients (Porth, 1994).

Pathophysiology of Nausea and Vomiting

Multiple neural pathways are involved in stimulating the vomiting center. A basic understanding of the neural pathways involved in nausea and vomiting can provide the foundation for approaching and managing these symptoms. The vomiting center is responsible for the coordination of emesis and can be activated in a number of ways. Commonly involved pathways are the following: the vagal afferents, the chemoreceptor trigger zone (CTZ), the pharyngeal afferents, the midbrain afferents, and the vestibular afferents (Hogan, 1997).

The vagus afferents are composed of two types of sensory fibers that originate in the GI tract. The fibers are capable of sensing either a mechanical or chemical change in this area (Hogan, 1997). These fibers are the most important route for GI information to reach the brain stem and stimulate an emetic response. For example, mechanical causes can include an intestinal obstruction or gastric distention caused by stasis, resulting in the stimulation of the vomiting center via the vagus nerve (Fessele, 1996).

Once the vagus nerve is activated, this information is relayed to the CTZ (Naylor & Inall, 1994). The CTZ is located at the area postrema in the fourth ventricle of the brain stem. The CTZ is surrounded by a rich blood supply and cerebrospinal fluid. If toxic agents are absorbed, toxins will be detected in the circulating blood and cerebrospinal fluid, thus activating the CTZ (Naylor & Inall, 1994). The GI tract also contains numerous chemoreceptors found in the stomach, which are sensitive to noxious chemicals (Hogan, 1997). Chemoreceptors located in the G1 tract and responsible for emesis are dopamine and serotonin, specifically chemoreceptor 5-HT3 (Ettinger, 1995). Activation of these chemoreceptors by a noxious agent will trigger the vomiting center.

The pharyngeal afferents (glossopharyngeal nerve) is activated with mechanical irritation, as in excessive coughing (Hogan, 1997). Excessive coughing may result in gagging or vomiting (Hogan, 1997).

The midbrain afferents is activated with increased intracranial pressure (ICP). Other causes of ICP are central nervous system malignancies and meningitis. Activation of the vestibular system can also stimulate the vomiting center.

The vestibular system is located in the inner ear and is linked to the perception of balance and motion (Fessele, 1996). Dysfunction in this area is responsible for nausea and vomiting associated with motion sickness and labyrinthitis.

Prevalence of Nausea and Vomiting in HIV

The overall prevalence of nausea and vomiting in patients with HIV …