Outline About Vomiting
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Vomiting (known medically as emesis and informally as throwing up and a number of other terms) is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Undesired vomiting may result from many causes, ranging from gastritis or poisoning to brain tumors, or elevated intracranial pressure. The feeling that one is about to vomit is called nausea. It usually precedes, but does not always lead to vomiting. Antiemetics are sometimes necessary to suppress nausea and vomiting, and, in severe cases where dehydration develops, intravenous fluid may need to be administered to replace fluid volume.
Vomiting is different from regurgitation, although the two terms are often used interchangeably. Regurgitation is the return of undigested food back up the esophagus to the mouth, without the force and displeasure associated with vomiting. The causes of vomiting and regurgitation are generally different.
Receptors on the floor of the fourth ventricle of the brain represent a chemoreceptor trigger zone, known as the area postrema, stimulation of which can lead to vomiting. The area postrema is a circumventricular organ and as such lies outside the blood-brain barrier; it can therefore be stimulated by blood-borne drugs that can stimulate vomiting or inhibit it.
There are various sources of input to the vomiting center:
* The chemoreceptor trigger zone at the base of the fourth ventricle has numerous dopamine D2 receptors, serotonin 5-HT3 receptors, opioid receptors, acetylcholine receptors, and receptors for substance P. Stimulation of different receptors are involved in different pathways leading to emesis, in the final common pathway substance P appears to be involved.[1]
* The vestibular system which sends information to the brain via cranial nerve VIII (vestibulocochlear nerve). It plays a major role in motion sickness and is rich in muscarinic receptors and histamine H1 receptors.
* Cranial nerve X (vagus nerve), which is activated when the pharynx is irritated, leading to a gag reflex.
* Vagal and enteric nervous system inputs that transmit information regarding the state of the gastrointestinal system. Irritation of the GI mucosa by chemotherapy, radiation, distention, or acute infectious gastroenteritis activates the 5-HT3 receptors of these inputs.
* The CNS mediates vomiting arising from psychiatric disorders and stress from higher brain centers.
Act:
The vomiting act encompasses three types of outputs initiated by the chemoreceptor trigger zone: Motor, parasympathetic nervous system (PNS), and sympathetic nervous system (SNS). They are as follows:
* Increased salivation to protect the enamel of teeth from stomach acids (excessive vomiting leads to dental erosion). This is part of the PNS output.
* A deep breath is taken to avoid aspiration of vomit.
* Retroperistalsis, starting from the middle of the small intestine, sweeping up the contents of the digestive tract into the stomach, through the relaxed pyloric sphincter.
* A lowering of intrathoracic pressure (by inspiration against a closed glottis), coupled with an increase in abdominal pressure as the abdominal muscles contract, propels stomach contents into the esophagus as the lower esophageal sphincter relaxes. The stomach itself does not contract in the process of vomiting except for at the angular notch, nor is there any retroperistalsis in the esophagus.
* Vomiting is ordinarily preceded by retching.
* Vomiting also initiates an SNS response causing both sweating and increased heart rate.
The neurotransmitters that regulate vomiting are poorly understood, but inhibitors of dopamine, histamine, and serotonin are all used to suppress vomiting, suggesting that these play a role in the initiation or maintenance of a vomiting cycle. Vasopressin and neurokinin may also participate.
Phases:
The vomiting act has two phases. In the retching phase, the abdominal muscles undergo a few rounds of coordinated contractions together with the diaphragm and the muscles used in respiratory inspiration. For this reason, an individual may confuse this phase with an episode of violent hiccups. In this retching phase nothing has yet been expelled. In the next phase, also termed the expulsive phase, intense pressure is formed in the stomach brought about by enormous shifts in both the diaphragm and the abdomen. These shifts are, in essence, vigorous contractions of these muscles that last for extended periods of time - much longer than a normal period of muscular contraction. The pressure is then suddenly released when the upper esophageal sphincter relaxes resulting in the expulsion of gastric contents. For people not in the habit of exercising the abdominal muscles, they may be painful for the next few days. The relief of pressure and the release of endorphins into the bloodstream after the expulsion causes the vomiter to feel better.
Content:
Gastric secretions and likewise vomit are highly acidic. Recent food intake will be reflected in the gastric vomit. Irrespective of the content, vomit tends to be malodorous.
The content of the vomitus (vomit) may be of medical interest. Fresh blood in the vomit is termed hematemesis ("blood vomiting"). Altered blood bears resemblance to coffee grounds (as the iron in the blood is oxidized) and, when this matter is identified, the term "coffee ground vomiting" is used. Bile can enter the vomit during subsequent heaves due to duodenal contraction if the vomiting is severe. Fecal vomiting is often a consequence of intestinal obstruction or a gastrocolic fistula and is treated as a warning sign of this potentially serious problem ("signum mali ominis"); such vomiting is sometimes called "miserere."
If the vomiting reflex continues for an extended period with no appreciable vomitus, the condition is known as non-productive emesis or dry heaves, which can be painful and debilitating.
Complications:
1.Aspiration of vomit:
Vomiting can be dangerous if the gastric content gets into the respiratory tract. Under normal circumstances the gag reflex and coughing will prevent this from occurring, however these protective reflexes are compromised in persons under the influences of certain substances such as alcohol or anesthesia. The individual may choke and asphyxiate or suffer an aspiration pneumonia.
2.Dehydration and electrolyte imbalance:
Prolonged and excessive vomiting will deplete the body of water (dehydration) and may alter the electrolyte status. Gastric vomiting leads to the loss of acid (protons) and chlorine directly. Combined with the resulting alkaline tide, this leads to hypochloremic metabolic alkalosis (low chloride levels together with high HCO3 and CO2 and increased blood pH) and often hypokalemia (potassium depletion). The hypokalemia is an indirect result of the kidney compensating for the loss of acid. With the loss of intake of food the individual may eventually become cachectic. A less frequent occurrence results from a vomiting of intestinal contents, including bile acids and HCO3- which can lead to metabolic acidosis.
3.Mallory-Weiss tear:
Repeated or profuse vomiting may cause erosions to the esophagus or small tears in the esophageal mucosa (Mallory-Weiss tear). This may become apparent if fresh red blood is mixed with vomit after several episodes.
4.Recuurent Vomiting:
Recurrent vomiting, such as observed in bulimia nervosa, may lead to destruction of the tooth enamel due to the acidity of the vomit. Digestive enzymes can also have a negative effect on oral health, by degrading the tissue of the gums.
Causes:
Vomiting may be due to a large number of causes, and protracted vomiting has a long differential diagnosis.
1.Digestive tract:
* Gastritis (inflammation of the gastric wall, usually by viruses)
* Gastroenteritis
* Pyloric stenosis (in babies, this typically causes a very forceful "projectile vomiting" and is an indication for urgent surgery)
* Bowel obstruction
* Overeating
* Acute abdomen and/or peritonitis
* Ileus
* Cholecystitis, pancreatitis, appendicitis, hepatitis
* Food poisoning
* In children, it can be caused by an allergic reaction to cow's milk proteins (Milk allergy or lactose intolerance)
2.Sensory system:
* Movement: motion sickness (which is caused by overstimulation of the labyrinthine canals of the ear)
* Ménière's disease
3.Causes in the brain:
* Concussion
* Cerebral hemorrhage
* Migraine
* Brain tumors, which can cause the chemoreceptors to malfunction
* Benign intracranial hypertension and hydrocephalus
4.Metabolic disturbances (these may irritate both the stomach and the parts of the brain that coordinate vomiting)
* Hypercalcemia (high calcium levels)
* Uremia (urea accumulation, usually due to renal failure)
* Adrenal insufficiency
* Hypoglycemia
* Hyperglycemia
5.Pregnancy
* Hyperemesis, Morning sickness
6.Drug reaction (vomiting may occur as an acute somatic response to)
* alcohol (being sick while being drunk or being sick the next morning, suffering from the after-effects, i.e., the hangover).
* opioids
* selective serotonin reuptake inhibitors
* many chemotherapy drugs
* some entheogens (such as peyote or ayahuasca)
Illness:
* Norwalk virus
Miscellaneous:
* Self-induced
o Eating disorders (anorexia nervosa or bulimia nervosa)
o To eliminate an ingested poison (some poisons should not be vomited as they may be more toxic when inhaled or aspirated; it is better to ask for help before inducing vomiting)
o Some people who are engaged in binge drinking will induce vomiting in order to make room in their stomachs for further alcohol consumption.
* After surgery (postoperative nausea and vomiting)
* Disagreeable sights, smells or thoughts (such as decayed matter, others' vomit, thinking of vomiting), etc.
* Extreme pain, such as intense headache or myocardial infarction (heart attack)
* Violent emotions
* Cyclic vomiting syndrome (a poorly-understood condition with attacks of vomiting)
* High doses of ionizing radiation will sometimes trigger a vomit reflex in the victim
* Violent fits of coughing, hiccups, or asthma
* Nervousness
* Performing physical activity (such as swimming) shortly after a meal.
* Being struck hard in the stomach.
* Overexertion (doing too much strenuous exercise can lead to vomiting shortly afterwards).
* Rumination syndrome, an underdiagnosed and poorly understood disorder that causes sufferers to regurgitate food shortly after ingestion.
Unusual types:
Fecal vomiting is a kind of emesis in which half-digested matter is expelled from the intestines into the stomach, by spasmodic contractions of the gastric muscles, and then subsequently forcefully expelled from the stomach up into the esophagus and out through the mouth and sometimes nasal passages. Though it is not actual fecal matter that is expelled, it smells similar. Alternative medical terms for fecal vomiting are copremesis and stercoraceous vomiting.[2] This form of aspiration usually leads to a severe aspiration pneumonia, secondary to the massive number of bacteria present in the fecal matter.[citation needed] This form of pneumonia is often severe enough to be fatal.
Vomiting is different from regurgitation, although the two terms are often used interchangeably. Regurgitation is the return of undigested food back up the esophagus to the mouth, without the force and displeasure associated with vomiting. The causes of vomiting and regurgitation are generally different.
Receptors on the floor of the fourth ventricle of the brain represent a chemoreceptor trigger zone, known as the area postrema, stimulation of which can lead to vomiting. The area postrema is a circumventricular organ and as such lies outside the blood-brain barrier; it can therefore be stimulated by blood-borne drugs that can stimulate vomiting or inhibit it.
There are various sources of input to the vomiting center:
* The chemoreceptor trigger zone at the base of the fourth ventricle has numerous dopamine D2 receptors, serotonin 5-HT3 receptors, opioid receptors, acetylcholine receptors, and receptors for substance P. Stimulation of different receptors are involved in different pathways leading to emesis, in the final common pathway substance P appears to be involved.[1]
* The vestibular system which sends information to the brain via cranial nerve VIII (vestibulocochlear nerve). It plays a major role in motion sickness and is rich in muscarinic receptors and histamine H1 receptors.
* Cranial nerve X (vagus nerve), which is activated when the pharynx is irritated, leading to a gag reflex.
* Vagal and enteric nervous system inputs that transmit information regarding the state of the gastrointestinal system. Irritation of the GI mucosa by chemotherapy, radiation, distention, or acute infectious gastroenteritis activates the 5-HT3 receptors of these inputs.
* The CNS mediates vomiting arising from psychiatric disorders and stress from higher brain centers.
Act:
The vomiting act encompasses three types of outputs initiated by the chemoreceptor trigger zone: Motor, parasympathetic nervous system (PNS), and sympathetic nervous system (SNS). They are as follows:
* Increased salivation to protect the enamel of teeth from stomach acids (excessive vomiting leads to dental erosion). This is part of the PNS output.
* A deep breath is taken to avoid aspiration of vomit.
* Retroperistalsis, starting from the middle of the small intestine, sweeping up the contents of the digestive tract into the stomach, through the relaxed pyloric sphincter.
* A lowering of intrathoracic pressure (by inspiration against a closed glottis), coupled with an increase in abdominal pressure as the abdominal muscles contract, propels stomach contents into the esophagus as the lower esophageal sphincter relaxes. The stomach itself does not contract in the process of vomiting except for at the angular notch, nor is there any retroperistalsis in the esophagus.
* Vomiting is ordinarily preceded by retching.
* Vomiting also initiates an SNS response causing both sweating and increased heart rate.
The neurotransmitters that regulate vomiting are poorly understood, but inhibitors of dopamine, histamine, and serotonin are all used to suppress vomiting, suggesting that these play a role in the initiation or maintenance of a vomiting cycle. Vasopressin and neurokinin may also participate.
Phases:
The vomiting act has two phases. In the retching phase, the abdominal muscles undergo a few rounds of coordinated contractions together with the diaphragm and the muscles used in respiratory inspiration. For this reason, an individual may confuse this phase with an episode of violent hiccups. In this retching phase nothing has yet been expelled. In the next phase, also termed the expulsive phase, intense pressure is formed in the stomach brought about by enormous shifts in both the diaphragm and the abdomen. These shifts are, in essence, vigorous contractions of these muscles that last for extended periods of time - much longer than a normal period of muscular contraction. The pressure is then suddenly released when the upper esophageal sphincter relaxes resulting in the expulsion of gastric contents. For people not in the habit of exercising the abdominal muscles, they may be painful for the next few days. The relief of pressure and the release of endorphins into the bloodstream after the expulsion causes the vomiter to feel better.
Content:
Gastric secretions and likewise vomit are highly acidic. Recent food intake will be reflected in the gastric vomit. Irrespective of the content, vomit tends to be malodorous.
The content of the vomitus (vomit) may be of medical interest. Fresh blood in the vomit is termed hematemesis ("blood vomiting"). Altered blood bears resemblance to coffee grounds (as the iron in the blood is oxidized) and, when this matter is identified, the term "coffee ground vomiting" is used. Bile can enter the vomit during subsequent heaves due to duodenal contraction if the vomiting is severe. Fecal vomiting is often a consequence of intestinal obstruction or a gastrocolic fistula and is treated as a warning sign of this potentially serious problem ("signum mali ominis"); such vomiting is sometimes called "miserere."
If the vomiting reflex continues for an extended period with no appreciable vomitus, the condition is known as non-productive emesis or dry heaves, which can be painful and debilitating.
Complications:
1.Aspiration of vomit:
Vomiting can be dangerous if the gastric content gets into the respiratory tract. Under normal circumstances the gag reflex and coughing will prevent this from occurring, however these protective reflexes are compromised in persons under the influences of certain substances such as alcohol or anesthesia. The individual may choke and asphyxiate or suffer an aspiration pneumonia.
2.Dehydration and electrolyte imbalance:
Prolonged and excessive vomiting will deplete the body of water (dehydration) and may alter the electrolyte status. Gastric vomiting leads to the loss of acid (protons) and chlorine directly. Combined with the resulting alkaline tide, this leads to hypochloremic metabolic alkalosis (low chloride levels together with high HCO3 and CO2 and increased blood pH) and often hypokalemia (potassium depletion). The hypokalemia is an indirect result of the kidney compensating for the loss of acid. With the loss of intake of food the individual may eventually become cachectic. A less frequent occurrence results from a vomiting of intestinal contents, including bile acids and HCO3- which can lead to metabolic acidosis.
3.Mallory-Weiss tear:
Repeated or profuse vomiting may cause erosions to the esophagus or small tears in the esophageal mucosa (Mallory-Weiss tear). This may become apparent if fresh red blood is mixed with vomit after several episodes.
4.Recuurent Vomiting:
Recurrent vomiting, such as observed in bulimia nervosa, may lead to destruction of the tooth enamel due to the acidity of the vomit. Digestive enzymes can also have a negative effect on oral health, by degrading the tissue of the gums.
Causes:
Vomiting may be due to a large number of causes, and protracted vomiting has a long differential diagnosis.
1.Digestive tract:
* Gastritis (inflammation of the gastric wall, usually by viruses)
* Gastroenteritis
* Pyloric stenosis (in babies, this typically causes a very forceful "projectile vomiting" and is an indication for urgent surgery)
* Bowel obstruction
* Overeating
* Acute abdomen and/or peritonitis
* Ileus
* Cholecystitis, pancreatitis, appendicitis, hepatitis
* Food poisoning
* In children, it can be caused by an allergic reaction to cow's milk proteins (Milk allergy or lactose intolerance)
2.Sensory system:
* Movement: motion sickness (which is caused by overstimulation of the labyrinthine canals of the ear)
* Ménière's disease
3.Causes in the brain:
* Concussion
* Cerebral hemorrhage
* Migraine
* Brain tumors, which can cause the chemoreceptors to malfunction
* Benign intracranial hypertension and hydrocephalus
4.Metabolic disturbances (these may irritate both the stomach and the parts of the brain that coordinate vomiting)
* Hypercalcemia (high calcium levels)
* Uremia (urea accumulation, usually due to renal failure)
* Adrenal insufficiency
* Hypoglycemia
* Hyperglycemia
5.Pregnancy
* Hyperemesis, Morning sickness
6.Drug reaction (vomiting may occur as an acute somatic response to)
* alcohol (being sick while being drunk or being sick the next morning, suffering from the after-effects, i.e., the hangover).
* opioids
* selective serotonin reuptake inhibitors
* many chemotherapy drugs
* some entheogens (such as peyote or ayahuasca)
Illness:
* Norwalk virus
Miscellaneous:
* Self-induced
o Eating disorders (anorexia nervosa or bulimia nervosa)
o To eliminate an ingested poison (some poisons should not be vomited as they may be more toxic when inhaled or aspirated; it is better to ask for help before inducing vomiting)
o Some people who are engaged in binge drinking will induce vomiting in order to make room in their stomachs for further alcohol consumption.
* After surgery (postoperative nausea and vomiting)
* Disagreeable sights, smells or thoughts (such as decayed matter, others' vomit, thinking of vomiting), etc.
* Extreme pain, such as intense headache or myocardial infarction (heart attack)
* Violent emotions
* Cyclic vomiting syndrome (a poorly-understood condition with attacks of vomiting)
* High doses of ionizing radiation will sometimes trigger a vomit reflex in the victim
* Violent fits of coughing, hiccups, or asthma
* Nervousness
* Performing physical activity (such as swimming) shortly after a meal.
* Being struck hard in the stomach.
* Overexertion (doing too much strenuous exercise can lead to vomiting shortly afterwards).
* Rumination syndrome, an underdiagnosed and poorly understood disorder that causes sufferers to regurgitate food shortly after ingestion.
Unusual types:
Fecal vomiting is a kind of emesis in which half-digested matter is expelled from the intestines into the stomach, by spasmodic contractions of the gastric muscles, and then subsequently forcefully expelled from the stomach up into the esophagus and out through the mouth and sometimes nasal passages. Though it is not actual fecal matter that is expelled, it smells similar. Alternative medical terms for fecal vomiting are copremesis and stercoraceous vomiting.[2] This form of aspiration usually leads to a severe aspiration pneumonia, secondary to the massive number of bacteria present in the fecal matter.[citation needed] This form of pneumonia is often severe enough to be fatal.
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