Nausa and Vomiting reading.pdf

Nausa and Vomiting Vomiting (emesis) is the involuntary, forceful expulsion of the contents of the stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenteritis, pregnancy, motion sickness, or it can be an after effect of diseases such...

Nausa and Vomiting Vomiting (emesis) is the involuntary, forceful expulsion of the contents of the stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenteritis, pregnancy, motion sickness, or it can be an after effect of diseases such as brain tumors, elevated intracranial pressure, or overexposure to ionizing radiation. The feeling that one is about to vomit is called nausea; it often precedes, but does not always lead to vomiting. In severe cases, where dehydrationdevelops, intravenous fluid may be required. Antiemetics are sometimes necessary to suppress nausea and vomiting. Self-induced vomiting can be a component of an eating disorder such as bulimia, and is itself now classified as an eating disorder on its own, purging disorder. Vomiting is controlled by the brainstem that coordinates a series of actions involving the gut and skeletal muscle, resulting in the forceful ejection of the contents of the upper gut. Essentially, vomiting is a reflex designed to expel potentially harmful substances from the body. It is important to distinguish between the various symptoms that may be described as ‘vomiting’. Nausea is the unpleasant sensation of being about to vomit and is often associated with mouth watering. Vomiting is the forceful expulsion of gastric contents via the mouth. Retching is contraction of the abdominal muscles without the expulsion of gastric contents. In contrast, regurgitation is the effortless appearance of gastric contents into the mouth, usually without nausea, and may be a symptom of gastro-oesophageal reflux disease or rumination syndrome. The causes and plan for investigation of nausea and vomiting can be conveniently divided into whether the symptoms are acute or chronic. Chronic symptoms are defined as those lasting 1 month or more. Complications 1. Aspiration Vomiting is dangerous if gastric content enters the respiratory tract. Under normal circumstances the gag reflex and coughing prevent this from occurring; however, these protective reflexes are compromised in persons who are under the influence of certain substances (including alcohol) or even mildly anesthetized. The individual may choke and asphyxiate or develop aspiration pneumonia. 2. Dehydration and electrolyte imbalance Prolonged and excessive vomiting depletes the body of water (dehydration), and may alter the electrolyte status. Gastric vomiting leads to the loss of acid and chloride directly. Combined with the resulting alkaline tide, this leads to hypochloremic metabolic alkalosis (low chloride levels together with high HCO−and increased blood pH) and often hypokalemia (potassium depletion). The hypokalemia is an indirect result of the kidney compensating for the loss of acid.. 3. Mallory–Weiss tear (Mallory–Weiss syndrome) 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. Dentistry Recurrent vomiting, such as observed in bulimia nervosa, may lead to the 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. Pathophysiology 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. Detailed illustration of the receptors and central control of vomiting is in this link: https://www.youtube.com/watch?v=LTjbp5xdwf4 The vomiting 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 tooth enamel from stomach acids. (Excessive vomiting leads to dental erosion.) This is part of the PNS output. The body takes a deep breath to avoid aspirating vomit. Retroperistalsis starts from the middle of the small intestine and sweeps up digestive tract contents into the stomach, through the relaxed pyloric sphincter. Intrathoracic pressure lowers (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 also initiates an SNS response causing both sweating and increased heart rate. Contents Gastric secretions and likewise vomit are highly acidic. Recent food intake appears 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. 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 duodenalcontraction 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. Color of vomitus Bright red in the vomit suggests bleeding from the esophagus Dark red vomit with liver-like clots suggests profuse bleeding in the stomach, such as from a perforated ulcer  Coffee-ground-like vomit suggests less severe bleeding in the stomach because the gastric acid has had time to change the composition of the blood Yellow or green vomit suggests bile, indicating that the pyloric valve is open and bile is flowing into the stomach from the duodenum. This may occur during successive episodes of vomiting after the stomach contents have been completely expelled. Acute nausea and vomiting Aetiology The most common cause of acute nausea/vomiting (Table1) is viral gastroenteritis or bacterial food poisoning. Gastrointestinal infections are more common in autumn and winter and in children and young adults. Viruses include rotavirus, adenovirus and norovirus (especially during epidemics). Preformed bacterial toxins ingested in food may cause vomiting alone, and are often due to ingestion of poorly cooked and inappropriately stored food contaminated with Staphylococcus aureus or Bacillus cereus. An infective cause is supported by the presence of diarrhoea, mild abdominal pain, fever, malaise, a potential cause/contact (eg. travel, sick family member, ‘dodgy’ meal) and an absence of significant abdominal tenderness Toxin mediated vomiting develops 1–6 hours after ingestion of the offending food. Other infections such as otitis media, urinary tract infections (UTI), meningitis and hepatitis can also result in vomiting as part of the overall clinical picture, but rarely present with nausea and vomiting alone except in elderly or institutionalised individuals. Medication side effects usually present acutely soon after commencing the drug, but may be delayed or go unrecognised and present subacutely. A full medication history including vitamins, herbs and over-the-counter drugs should be sought, as well as an alcohol and drug history. Recent changes in medication are particularly relevant. Any recently commenced drug should be considered as a potential cause of nausea/vomiting however, some are particularly prone to cause this side effect. Mechanical gastrointestinal obstruction causes vomiting often without nausea as a prominent symptom, at least initially. The nature of the vomitus may give a clue to the level of the obstruction; undigested food and saliva in acute oesophageal obstruction, partially digested food in gastric outlet obstruction, and bile or faeculent vomiting with more distal obstructions. Small bowel obstruction is usually acute, persistent and associated with colicky pain; but may occasionally be intermittent or subacute. Vertigo, neurological symptoms, neck stiffness or headache hint at a neurological cause and should prompt appropriate investigation. Pregnancy should not be forgotten in women of childbearing age, particularly those with early morning nausea. Initial assessment In the acute setting, history, examination and simple investigations can often yield a diagnosis. The illness is commonly self limiting. The diagnostic approach focuses on identifying the cause (or at least excluding significant underlying diseases) with a view to expectant management or directing specific treatment. Complications of nausea and vomiting should be identified and acute emergencies should be excluded. Most cases are not severe enough to require hospitalisation, however intravenous (IV) therapy may be required for: Severe dehydration (inability to tolerate oral fluids) Significant metabolic abnormalities related to Vomiting (including hypokalaemia, metabolic alkalosis Or uraemia) Surgical emergencies (eg. Mechanical obstruction, Perforation or peritonitis) Other medical or social factors increasing the likelihood of complications (eg. underlying renal, cardiac or hepatic impairment). Examination Dehydration is assessed clinically by examining for dry mucous membranes, reduced skin turgor, tachycardia and postural hypotension. The abdomen should be examined for tenderness (particularly localised tenderness), distension or a succussion splash – a splashing sound heard with a stethoscope when the abdomen is shaken in intestinal or pyloric obstruction. Particular attention should be paid to areas where hernias are common. Bowel sounds may be tinkling in mechanical obstruction or absent in an ileus. The presence of abdominal signs should prompt a surgical opinion. Investigations In many cases nil investigations may be appropriate. Basic biochemistry may include (as appropriate): Electrolytes and renal function Full blood count Pancreatic and liver enzymes Glucose. If small bowel obstruction is suspected, erect and supine abdominal radiographs should be considered. Management Once surgical and major medical causes have been excluded, rehydration with oral fluids is preferred with oral or intramuscular antiemetic therapy. Patients may be discharged with instructions to return if symptoms deteriorate or do not improve. If outpatient management is not tolerated, admission for IV fluids and parenteral antiemetic treatment (IV or IM) is required. Antiemetic choices is highly dependent on the cause and the severity of the vomiting. Usually no specific follow up is required for a self limiting episode of nausea/vomiting unless there are public health issues. Summary of important points Most cases of acute nausea and vomiting are self limited and the aims of assessment are to reduce complications and screen for important treatable causes (especially surgical). In many cases, a diagnosis can be made following a thorough history, examination and/or simple investigations. Gastrointestinal infections and food poisoning make up the majority of acute presentations. Medication side effects should always be suspected with recent commencement or change in dose of medication. Pregnancy should be considered in women of childbearing age. Hospitalisation may be required for severe metabolic abnormalities, dehydration or suspected surgical causes. In chronic nausea and vomiting, with many potential causes, a comprehensive history and examination is required. Symptoms are poor predictors of functional versus pathological illness. The type and extent of investigation is heavily influenced by the clinical circumstances and presentation and must be tailored to the individual. A therapeutic trial of antiemetic or dietary modification can be undertaken while investigation and further referral is made. Source: 1. "Nausea and vomiting in adults | nidirect". www.nidirect.gov.uk. 2017-12-07. Retrieved 2024-03-08. 2. Hauser, Joshua M.; Azzam, Joseph S.; Kasi, Anup (2022-09-26). "Antiemetic Medications". StatPearls Publishing. PMID 30335336. Archived from the original on 2023-03- 30. Retrieved 2023-07-12. 3. Hebbard, G. and Metz, A., 2007. Nausea and vomiting in adults: a diagnostic approach. Australian family physician, 36(9).