Nausea is an unpleasant, diffuse sensation
of unease and discomfort, often perceived as an urge to vomit. While not painful, it can be a debilitating
symptom if prolonged, and has been described as placing discomfort on the chest, upper
abdomen, or back of the throat.Nausea is a non-specific symptom, which means that it
has many possible causes. Some common causes of nausea are gastroenteritis
and other gastrointestinal disorders, food poisoning, motion sickness, dizziness, migraine,
fainting and low blood sugar. Nausea is a side effect of many medications
including chemotherapy, or morning sickness in early pregnancy. Nausea may also be caused by anxiety, disgust
and depression.Medications taken to prevent and treat nausea are called antiemetics. The most commonly prescribed antiemetics in
the US are promethazine, metoclopramide and the newer, extremely effective ondansetron. The word nausea is from Latin nausea, from
Greek ναυσία – nausia, “ναυτία” – nautia, motion sickness, “feeling sick
or queasy”.==Causes==
Gastrointestinal infections (37%) and food poisoning are the two most common causes of
acute nausea and vomiting. Side effects from medications (3%) and pregnancy
are also relatively frequent. There are many causes of chronic nausea. Nausea and vomiting remain undiagnosed in
10% of the cases. Aside from morning sickness, there are no
sex differences in complaints of nausea. After childhood, doctor consultations decrease
steadily with age. Only a fraction of one percent of doctor visits
by those over 65 are due to nausea.===Gastrointestinal===
Gastrointestinal infection is one of the most common causes of acute nausea and vomiting. Chronic nausea may be the presentation of
many gastrointestinal disorders, occasionally as the major symptom, such as gastroesophageal
reflux disease, functional dyspepsia, gastroparesis, peptic ulcer, celiac disease, non-celiac gluten
sensitivity, Crohn’s disease, hepatitis, upper gastrointestinal malignancy, and pancreatic
cancer. Uncomplicated Helicobacter pylori infection
does not cause chronic nausea.===Food poisoning===
Food poisoning usually causes an abrupt onset of nausea and vomiting one to six hours after
ingestion of contaminated food and lasts for one to two days. It is due to toxins produced by bacteria in
food.===Medications===
Many medications can potentially cause nausea. Some of the most frequently associated include
cytotoxic chemotherapy regimens for cancer and other diseases, and general anaesthetic
agents. An old cure for migraine, ergotamine, is well
known to cause devastating nausea in some patients; a person using it for the first
time will be prescribed an antiemetic for relief if needed.===Pregnancy===
Nausea or “morning sickness” is common during early pregnancy but may occasionally continue
into the second and third trimesters. In the first trimester nearly 80% of women
have some degree of nausea. Pregnancy should therefore be considered as
a possible cause of nausea in any women of child bearing age. While usually it is mild and self-limiting,
severe cases known as hyperemesis gravidarum may require treatment.===Disequilibrium===
A number of conditions involving balance such as motion sickness and vertigo can lead to
nausea and vomiting.===Psychiatric===
Nausea may be caused by depression, anxiety disorders and eating disorders.===Potentially serious===
While most causes of nausea are not serious, some serious conditions are associated with
nausea. These include: pancreatitis, small bowel obstruction,
appendicitis, cholecystitis, hepatitis, Addisonian crisis, diabetic ketoacidosis, increased intracranial
pressure, Spontaneous Intracranial Hypotension, brain tumors, meningitis, heart attack, carbon
monoxide poisoning and many others.===Comprehensive list=======Inside the abdomen====
Obstructing disorders Pyloric obstruction
Small bowel obstruction Colonic obstruction
Superior mesenteric artery syndromeEnteric infections Viral infection
Bacterial infectionInflammatory diseases Celiac disease
Cholecystitis Pancreatitis
Appendicitis HepatitisSensorimotor dysfunction Gastroparesis
Intestinal pseudo-obstruction Gastroesophageal reflux disease
Irritable bowel syndrome Chronic idiopathic nausea
Functional vomiting Cyclic vomiting syndromeOther Non-celiac gluten sensitivity
Biliary colic Abdominal irradiation====Outside the abdomen====
Cardiopulmonary Cardiomyopathy
Myocardial infarction (heart attack)Inner-ear diseases Motion sickness
Labyrinthitis MalignancyIntracerebral disorders Malignancy
Hemorrhage Abscess
Hydrocephalus Meningitis
EncephalitisPsychiatric illnesses Anorexia and bulimia nervosa
DepressionOther Post-operative vomiting====Medications and metabolic disorders====
Drugs Chemotherapy
Antibiotics Antiarrhythmics
Digoxin Oral hypoglycemic medications
Oral contraceptivesEndocrine/metabolic disease Pregnancy
Uremia Ketoacidosis
Thyroid and parathyroid disease Adrenal insufficiencyToxins Liver failure
Alcohol==Diagnostic approach=====Patient history===
Taking a thorough patient history may reveal important clues to the cause of nausea and
vomiting. If the patient’s symptoms have an acute onset,
then drugs, toxins, and infections are likely. In contrast, a long-standing history of nausea
will point towards a chronic illness as the culprit. The timing of nausea and vomiting after eating
food is an important factor to pay attention to. Symptoms that occur within an hour of eating
may indicate an obstruction proximal to the small intestine, such as gastroparesis or
pyloric stenosis. An obstruction further down in the intestine
or colon will cause delayed vomiting. An infectious cause of nausea and vomiting
such as gastroenteritis may present several hours to days after the food was ingested. The contents of the emesis is a valuable clue
towards determining the cause. Bits of fecal matter in the emesis indicate
obstruction in the distal intestine or the colon. Emesis that is of a bilious nature (greenish
in color) localizes the obstruction to a point past the stomach. Emesis of undigested food points to an obstruction
prior to the gastric outlet, such as achalasia or Zenker’s diverticulum. If patient experiences reduced abdominal pain
after vomiting, then obstruction is a likely etiology. However, vomiting does not relieve the pain
brought on by pancreatitis or cholecystitis.===Physical exam===
It is important to watch out for signs of dehydration, such as orthostatic hypotension
and loss of skin turgor. Auscultation of the abdomen can produce several
clues to the cause of nausea and vomiting. A high-pitched tinkling sound indicates possible
bowel obstruction, while a splashing “succussion” sound is more indicative of gastric outlet
obstruction. Eliciting pain on the abdominal exam when
pressing on the patient may indicate an inflammatory process. Signs such as papilledema, visual field losses,
or focal neurological deficits are red flag signs for elevated intracranial pressure.===Diagnostic testing===
When a history and physical exam are not enough to determine the cause of nausea and vomiting,
certain diagnostic tests may prove useful. A chemistry panel would be useful for electrolyte
and metabolic abnormalities. Liver function tests and lipase would identify
pancreaticobiliary diseases. Abdominal X-rays showing air-fluid levels
indicate bowel obstruction, while an X-ray showing air-filled bowel loops are more indicative
of ileus. More advanced imaging and procedures may be
necessary, such as a CT scan, upper endoscopy, colonoscopy, barium enema, or MRI. Abnormal GI motility can be assessed using
specific tests like gastric scintigraphy, wireless motility capsules, and small-intestinal
manometry.==Pathophysiology==
Research on nausea and vomiting has relied on using animal models to mimic the anatomy
and neuropharmacologic features of the human body. The physiologic mechanism of nausea is a complex
process that has yet to be fully elucidated. There are four general pathways that are activated
by specific triggers in the human body that go on to create the sensation of nausea and
vomiting. Central nervous system (CNS): Stimuli can
affect areas of the CNS including the cerebral cortex and the limbic system. These areas are activated by elevated intracranial
pressure, irritation of the meninges (i.e. blood or infection), and extreme emotional
triggers such as anxiety. Chemoreceptor trigger zone (CTZ): The CTZ
is located in the area postrema in the floor of the fourth ventricle within the brain. This area is outside the blood brain barrier,
and is therefore readily exposed to substances circulating through the blood and cerebral
spinal fluid. Common triggers of the CTZ include metabolic
abnormalities, toxins, and medications. Activation of the CTZ is mediated by dopamine
(D2) receptors, serotonin (5HT3) receptors, and neurokinin receptors (NK1). Vestibular system: This system is activated
by disturbances to the vestibular apparatus in the inner ear. These include movements that cause motion
sickness and dizziness. This pathway is triggered via histamine (H1)
receptors and acetylcholine (ACh) receptors. Peripheral Pathways: These pathways are triggered
via chemoreceptors and mechanoreceptors in the gastrointestinal tract, as well as other
organs such as the heart and kidneys. Common activators of these pathways include
toxins present in the gastrointestinal lumen and distension of the gastrointestinal lumen
from blockage or dysmotility of the bowels. Signals from these pathways travel via multiple
neural tracts including the vagus, glossopharyngeal, splanchnic, and sympathetic nerves.Signals
from any of these pathways then travel to the brainstem, activating several structures
including the nucleus of the solitary tract, the dorsal motor nucleus of the vagus, and
central pattern generator. These structures go on to signal various downstream
effects of nausea and vomiting. The body’s motor muscle responses involve
halting the muscles of the gastrointestinal tract, and in fact causing reversed propulsion
of gastric contents towards the mouth while increasing abdominal muscle contraction. Autonomic effects involve increased salivation
and the sensation of feeling faint that often occurs with nausea and vomiting.==Treatment==
If dehydration is present due to loss of fluids from severe vomiting, rehydration with oral
electrolyte solutions is preferred. If this is not effective or possible, intravenous
rehydration may be required. Medical care is recommended if: a person cannot
keep any liquids down, has symptoms more than 2 days, is weak, has a fever, has stomach
pain, vomits more than two times in a day or does not urinate for more than 8 hours.===Medications===
Many pharmacologic medications are available for the treatment of nausea. There is no medication that is clearly superior
to other medications for all cases of nausea. The choice of antiemetic medication may be
based on the situation during which the person experiences nausea. For people with motion sickness and vertigo,
antihistamines and anticholinergics such as meclizine and scopolamine are particularly
effective. Nausea and vomiting associated with migraine
headaches respond best to dopamine antagonists such as metoclopramide, prochlorperazine,
and chlorpromazine. In cases of gastroenteritis, serotonin antagonists
such as ondansetron were found to suppress nausea and vomiting, as well as reduce the
need for IV fluid resuscitation. The combination of pyridoxine and doxylamine
is the first line treatment for pregnancy-related nausea and vomiting. Dimenhydrinate is an inexpensive and effective
over the counter medication for preventing postoperative nausea and vomiting. Other factors to consider when choosing an
antiemetic medication include the person’s preference, side-effect profile, and cost.===Alternative medicine===
In certain people, cannabinoids may be effective in reducing chemotherapy associated nausea
and vomiting. Several studies have demonstrated the therapeutic
effects of cannabinoids for nausea and vomiting in the advanced stages of illnesses such as
cancer and AIDS.In hospital settings topical anti-nausea gels are not indicated because
of lack of research backing their efficacy. Topical gels containing lorazepam, diphenhydramine,
and haloperidol are sometimes used for nausea but are not equivalent to more established
therapies.Ginger has also been shown to be potentially effective in treating several
types of nausea.==Prognosis==
The outlook depends on the cause. Most people recover within few hours or a
day. While short-term nausea and vomiting are generally
harmless, they may sometimes indicate a more serious condition. When associated with prolonged vomiting, it
may lead to dehydration or dangerous electrolyte imbalances or both. Repeated intentional vomiting, characteristic
of bulimia, can cause stomach acid to wear away at the enamel in teeth.==Epidemiology==
Nausea and or vomiting is the main complaint in 1.6% of visits to family physicians in
Australia. However, only 25% of people with nausea visit
their family physician. In Australia, nausea, as opposed to vomiting,
occurs most frequently in persons aged 15–24 years, and is less common in other age groups.==See also==
Cancer and nausea Vasodilation

Leave a Reply

Your email address will not be published. Required fields are marked *