Wednesday, 8 January 2014

NAUSEA AND VOMITING



Nausea is usually defined as the inclination to vomit or as a feeling in the throat or epigastric region alerting an individual that
vomiting is imminent.Vomiting is defined as the ejection or expulsion of gastric contents through the mouth and is often a forceful event. Either condition may occur transiently with no other associated signs or symptoms
ETIOLOGY:-
Gastrointestinal Mechanisms
Mechanical gastric outlet obstruction
Peptic ulcer disease
Gastric carcinoma
Pancreatic disease
Motility disorders
Gastroparesis
Drug-induced gastric stasis
Chronic intestinal pseudo-obstruction
Postviral gastroenteritis
Irritable bowel syndrome
Postgastric surgery
Idiopathic gastric stasis
Anorexia nervosa
Intra-abdominal emergencies
Intestinal obstruction
Acute pancreatitis
Acute pyelonephritis
Acute cholecystitis
Acute cholangitis
Acute viral hepatitis
Acute gastroenteritis
Viral gastroenteritis
Salmonellosis
Shigellosis
Staphylococcal gastroenteritis (enterotoxins)
Cardiovascular Diseases
Acute myocardial infarction
Congestive heart failure
Shock and circulatory collapse
Neurologic Processes
Midline cerebellar hemorrhage
Increased intracranial pressure
Migraine headache
Vestibular disorders
Head trauma
Metabolic Disorders
Diabetes mellitus (diabetic ketoacidosis)
Addison’s disease
Renal disease (uremia)
Psychogenic Causes
Self-induced
Anticipatory
Therapy-induced Causes
Cytotoxic chemotherapy
Radiation therapy
Theophylline preparations (intolerance, toxic)
Anticonvulsant preparations (toxic)
Digitalis preparations (toxic)
Opiates
Amphotericin B
Antibiotics
Drug Withdrawal
Opiates
Benzodiazepines
Miscellaneous Causes
Pregnancy
Any swallowed irritant (foods, drugs)
Noxious odors
Operative procedures


Pathophysiology:-
The three consecutive phases of emesis include nausea, retching, and vomiting. Nausea, the imminent need to vomit, is associated with gastric stasis and may be considered a separate and singular symptom. Retching is the labored movement of abdominal and thoracic muscles before vomiting. The final phase of emesis is vomiting, the forceful expulsion of gastric contents caused by GI retroperistalsis. The act of vomiting requires the coordinated contractions of the abdominal muscles, pylorus, and antrum, a raised gastric cardia, diminished lower esophageal sphincter pressure, and esophageal dilatation. Vomiting should not be confused with regurgitation, an act in which the gastric or esophageal contents rise to the pharynx because of pressure differences caused by, for example, an incompetent lower esophageal sphincter. Accompanying autonomic symptoms of pallor, tachycardia, and diaphoresis account for many of the distressing feelings associated with emesis. Vomiting is triggered by afferent impulses to the vomiting center,
a nucleus of cells in the medulla. Impulses are received from sensory centers, such as the chemoreceptor trigger zone (CTZ), cerebral cortex, and visceral afferents from the pharynx and GI tract. When excited, afferent impulses are integrated by the vomiting center, resulting in efferent impulses to the salivation center, respiratory center, and the pharyngeal, GI, and abdominal muscles, leading to vomiting. The CTZ, located in the area postrema of the fourth ventricle of the brain, is a major chemosensory organ for emesis and is usually associated with chemically induced vomiting. Because of its location, blood-borne and cerebrospinal fluid toxins have easy access to the CTZ.
Clinical presentation:-
General
Depending on severity of symptoms, patients may present in mild to
severe distress
Symptoms
Simple: Self-limiting, resolves spontaneously and requires only
symptomatic therapy
Complex: Not relieved after administration of antiemetics; progressive
deterioration of patient secondary to fluid-electrolyte imbalances;
usually associated with noxious agents or psychogenic events
Signs
Simple: Patient complaint of queasiness or discomfort
Complex: Weight loss; fever; abdominal pain
Laboratory tests
Simple: None
Complex: Serum electrolyte concentrations; upper/lower Gl evaluation
Other information
Fluid input and output
Medication history
Recent history of behavioral or visual changes, headache, pain, or stress
Family history positive for psychogenic vomiting.
POSTOPERATIVE NAUSEA AND VOMITING
One of the most common complications of surgery is postoperative nausea and vomiting (PONV). Most patients undergoing an operative procedure do not require preoperative prophylactic antiemetic therapy and universal PONV prophylaxis is not cost effective. Consensus therapeutic guidelines for the prophylaxis and treatment of PONV have recently been published. Factors to be considered for PONVprophylaxis and treatment include: risk factors, potential morbidity, potential adverse events associated with various antiemetics, efficacy of antiemetics, and costs.
Risk Factors for PONV
Patient-specific factors
Female gender
Nonsmoking status
History of motion sickness/PONV
Anesthetic risk factors
Use of volatile anesthetics
Nitrous oxide
Use of opioids (intraoperative or postoperative)
Surgical risk factors
Duration of surgery
Operative procedure (intra-abdominal, ear-nose-throat, major
gynecologic, orthopedic, or laparoscopic)

ANTIEMETIC USE DURING PREGNANCY
More than one-half of pregnant women experience nausea and vomiting to some degree during the first trimester of pregnancy (nausea and vomiting of pregnancy; NVP). Teratogenicity is a major consideration for the use of antiemetic drugs during pregnancy and is the primary factor that guides drug selection. A large body of evidence suggests that the histamine1-receptor antagonists (dimenhydrinate, diphenhydramine, doxylamine, hydroxyzine, and meclizine) have no human teratogenic potential and are effective in reducing treatment failure. Whether used alone or in combination with doxylamine, pyridoxine has not been found to be teratogenic and significantly decreases the nausea score. Other commonly prescribed agents that are effective and not teratogenic include the phenothiazines prochlorperazine and promethazine. Studies using the SSRIs in NVP are limited. In a randomized controlled trial of 15 patients exposed during the first trimester to intravenous ondansetron versus promethazine for treatment of severe NVP, ondansetron was no more beneficial than promethazine with respect to the following outcome measures: severity of nausea, daily weight gain, days requiring hospitalization, treatment failures, and voluntary use of the drug. The limited safety data for ondansetron does not allow it to be recommended as first-line therapy. Nonpharmacologic interventions for NVP include ginger and acupuncture, although safety and efficacy trials for acupuncture are lacking.
Treatment :-
Antacids, Antihistaminic-Anticholinergic Agents, Histamine H2 Antagonists, Phenothiazines, Cannabinoids, Butyrophenones, Corticosteroids, Benzodiazepines, Substance P/Neurokinin1 Receptor Inhibitor