Vomiting, also known as emesis, is a distressing symptom that frequently affects individuals in the advanced stages of a serious illness. This involuntary expulsion of stomach contents signifies complex physiological changes as the body’s major systems begin to fail. Identifying the specific cause of vomiting is important because the underlying trigger dictates the most effective strategy for managing the symptom and maximizing comfort. The causes are often multifactorial, stemming from systemic toxicity, pharmacological effects, or direct neurological disturbances, all of which converge on the brain’s vomiting center to initiate the reflex.
Causes Related to Organ Failure and Metabolic Changes
The most common causes of vomiting in advanced illness are related to the failure of organs responsible for filtering and processing waste from the bloodstream. When kidney function declines significantly, toxins such as urea build up in the blood, a condition known as uremia. This accumulation of metabolic waste directly stimulates the chemoreceptor trigger zone (CTZ) in the brain. The CTZ detects noxious substances and initiates the reflex. Uremia often causes constant nausea and vomiting, sometimes presenting with an unpleasant metallic taste in the mouth.
Liver failure can similarly lead to a buildup of circulating toxins that trigger the CTZ. The liver’s inability to metabolize compounds means substances that would normally be neutralized remain in the circulation, causing chemical imbalances that lead to the vomiting reflex. Electrolyte imbalances, particularly hypercalcemia (an abnormally high level of calcium in the blood often seen in certain cancers), can also induce nausea.
Physical issues within the digestive tract represent another major category of causes. Severe constipation, common in advanced disease due to reduced mobility and fluid intake, can cause a mechanical backup that leads to nausea and vomiting. In patients with abdominal tumors, a malignant bowel obstruction can physically prevent the passage of food and fluid, causing significant distress and the forceful expulsion of contents.
Medication Side Effects and Pharmacological Triggers
Medications used to manage pain and other symptoms in advanced illness are frequent causes of nausea and vomiting. Opioids, the mainstay of pain management, stimulate the CTZ directly, leading to opioid-induced nausea and vomiting. This effect is a normal pharmacological response, especially when therapy is first initiated or the dose is increased.
Opioids also contribute indirectly by slowing the movement of the gastrointestinal tract, a condition called gastroparesis. Gastroparesis leads to delayed gastric emptying and a feeling of fullness or nausea. Other medications commonly used in palliative care can also be triggers, including antibiotics, non-steroidal anti-inflammatory drugs (NSAIDs), and some anticonvulsants.
The severity of drug-induced nausea often depends on the specific compound used. Fortunately, many patients develop a tolerance to the emetic effects of opioids within days to a couple of weeks of consistent dosing. Managing pain may introduce nausea, requiring careful adjustment of the medication regimen.
Neurological and Central Nervous System Causes
Vomiting can also be caused by issues that directly involve the brain and nervous system, separate from circulating toxins or drug effects. The most significant neurological cause is increased intracranial pressure (ICP), which occurs when conditions like brain tumors, metastases, or cerebral edema increase the pressure within the rigid skull. This elevated pressure directly irritates the vomiting center located in the brainstem.
Vomiting caused by high ICP often occurs suddenly without preceding nausea and sometimes presents as projectile. This sudden, forceful expulsion indicates that the cause is central rather than gastrointestinal. Conditions like hydrocephalus, an accumulation of cerebrospinal fluid, also cause increased ICP and can lead to the same symptoms.
The vomiting center, which coordinates the physical act of emesis, can be activated by direct pressure from a mass or swelling. Inner ear disturbances, known as vestibular issues, can also trigger vomiting due to their connection to the balance centers in the brain.
Managing Nausea and Vomiting for Comfort
The focus of managing vomiting in the last stages of life is on providing comfort and dignity, not cure. Non-pharmacological measures offer relief by addressing environmental triggers and physical positioning, such as maintaining a semi-upright position to reduce stomach pressure. Minimizing strong odors, providing cool compresses, and reducing movement can also help calm the reflex.
Pharmacological management involves antiemetic medications selected based on the suspected underlying cause. Dopamine receptor blockers, such as haloperidol, counteract chemical triggers stimulating the CTZ. Prokinetic agents like metoclopramide are used for delayed gastric emptying or obstruction, as they increase digestive tract movement.
Other classes, such as ondansetron, target different receptors and may be used for chemical triggers or in combination. The choice of antiemetic requires close communication with the palliative care team to ensure effective symptom control.