Vomiting
Study guide:
Definition:
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Vomiting (emesis): Forceful oral expulsion of gastric contents associated with contraction of the abdominal and chest wall musculature, frequently preceded by nausea and abdominal pain.
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Nausea: The unpleasant sensation of the imminent need to vomit, usually referred to the throat or epigastrium; a sensation that may or may not ultimately lead to the act of vomiting.
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Regurgitation: The act by which food is brought back into the mouth without the abdominal and diaphragmatic muscular activitythat characterizes vomiting.
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Retching: Spasmodic respiratory movements against a closed glottis with contractions of the abdominal musculature without expulsion of any gastric contents, "dry heaves".

Mechanisms:
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Neurophysiological Emesis:
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Area of Postrema (vomiting center):
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Has the “Chemoreceptor trigger zone” CTZ lies outside the BBB
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Anatomically, located in the brain stem at the caudal extremity of the floor of the fourth ventricle.
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Triggered by: systemic chemicals through the following pathways:
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Vagal Afferents:
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Mechanical or chemosensory
sensations.
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Examples of sensations that
trigger this pathway: over
distension, food poisoning, mucosal irritation, cytotoxic drugs, and radiation.
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Vestibular System:
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When vestibular input is in conflict with visual
sensations.
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Plays a role in motion sickness.
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E.g.: Irritation or labyrinthine inflammation,
motion-sickness
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Amygdala:
Receives input from the olfactory bulb andolfactory cortex.
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Somatomotor Events of Emesis (emptying out the stomach, characterized by cycles of retching followed by the forceful expulsion of gastric contents):
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Diaphragm descends and the intercostal muscles contract while the glottis is closed.
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The abdominal muscles contract and the gastric contents are forced into upper
gastric vault and lower esophagus.
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The abdominal muscle relaxes and the esophageal refluxates.
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Several cycles of retching.
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Abdominal contraction with elevation of diaphragm results in forceful expulsion of
gastric contents.
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Causes:
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Food poisoning (toxins):


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Pain-induced:
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Any deep visceral pain
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E.g.: Acute appendicitis, MI, Renal stone pain
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Obstructive:
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Pyloric or intestinal obstruction
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Cerebral or Central:
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Psychogenic: anxiety, bad odor, sight of blood, and tension.
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Fever.
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Pregnancy.
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Drugs: digitalis, salicylates, morphine, alcohol…etc..
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Increased intracranial pressure.
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Disturbance of electrolytes: ketosis, uremia.
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Labyrinthine Disturbances.
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References:
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Clinical Approach to Diagnosis Major Sign and Symptoms by Dr. Salah Ibrahim.
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Crash course Gastrointestinal System 4th edition.
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Crash course Gastroenterology 4th edition.
Written by: Roaa Amer
Reviewed by: Haifa Al-Issa
Haneen Al-Farhan
Format editor: Roaa Amer
Web publisher: Bayan Alzomaili
Salman Alahmed