Chapter 039. Nausea, Vomiting, and Indigestion (Part 4) pdf

Chapter 039. Nausea, Vomiting, and Indigestion (Part 4) Diagnostic Testing For intractable symptoms or an elusive diagnosis, selected diagnostic tests can direct clinical management. Electrolyte replenishment is indicated for hypokalemia or metabolic alkalosis. Detection of iron-deficiency anemia mandates a search for mucosal injury. Pancreaticobiliary disease is indicated by abnormal pancreatic enzymes or liver biochemistries, whereas endocrinologic, rheumatologic, or paraneoplastic etiologies are suggested by specific hormone or serologic testing. If luminal obstruction is suspected, supine and upright abdominal radiographs may show intestinal air-fluid levels with reduced colonic air. Ileus is characterized by diffusely dilated air-filled bowel loops. Anatomic studies may be indicated if initial testing is nondiagnostic. Upper endoscopy detects ulcers or malignancy, while small-bowel barium radiography diagnoses partial small-bowel obstruction. Colonoscopy or contrast enema radiography can detect colonic obstruction. Abdominal ultrasound or computed tomography (CT) defines intraperitoneal inflammatory processes, while CT or magnetic resonance imaging (MRI) of the head can delineate intracranial disease. Mesenteric angiography or MRI is useful when ischemia is considered. Gastrointestinal motility testing may detect a motor disorder that contributes to symptoms when anatomic abnormalities are absent. Gastroparesis commonly is diagnosed using gastric scintigraphy, by which emptying of a radiolabeled meal is measured. Isotopic breath tests and telemetry capsule methods also have been validated. Electrogastrography, a noninvasive test of gastric slow-wave activity using cutaneous electrodes placed over the stomach, has been proposed as an alternate means of diagnosing gastroparesis. The diagnosis of intestinal pseudoobstruction often is suggested by abnormal barium transit and luminal dilation on small-bowel contrast radiography. Small-intestinal manometry can confirm the diagnosis and further characterize the motor abnormality as neuropathic or myopathic based on contractile patterns. Such investigation can obviate the need for open intestinal biopsy to evaluate for smooth muscle or neuronal degeneration. Nausea and Vomiting: Treatment General Principles Therapy of vomiting is tailored to correction of medically or surgically remediable abnormalities if possible. Hospitalization is considered for severe dehydration especially if oral fluid replenishment cannot be sustained. Once oral intake is tolerated, nutrients are restarted with liquids that are low in fat, as lipids delay gastric emptying. Foods high in indigestible residues are avoided as these also prolong gastric retention. Antiemetic Medications The most commonly used antiemetic agents act on sites within the central nervous system (Table 39-2). Antihistamines such as meclizine and dimenhydrinate and anticholinergic drugs like scopolamine act on labyrinthine- activated pathways and are useful in motion sickness and inner ear disorders. Dopamine D 2 antagonists treat emesis evoked by area postrema stimuli and are useful for medication, toxic, and metabolic etiologies. Dopamine antagonists freely cross the blood-brain barrier and cause anxiety, dystonic reactions, hyperprolactinemic effects (galactorrhea and sexual dysfunction), and irreversible tardive dyskinesia. Table 39-2 Treatment of Nausea and Vomiting Treatm ent Mechanism Examples Clinical Indications Antieme tic agents Antihistamine rgic Dimenhydrinate, meclizine Motion sickness, inner ear disease Anticholinergi c Scopolamine Motion sickness, inner ear disease Antidopamine rgic Prochlorperazine, thiethylperazine Medication- , toxin- , or metabolic-induced emesis 5-HT 3 antagonist Ondansetron, granisetron Chemothera py- and radiation- induced emesis, postoperative emesis NK 1 antagonist Aprepitant Chemothera py- induced nausea and vomiting Tricyclic antidepressant Amitriptyline, nortriptyline Chronic idiopathic nausea, functional vomiting, cyclic vomiting syndrome Prokinet ic agents 5-HT 4 agonist and antidopaminergic Metoclopramide Gastroparesi s Motilin agonist Erythromycin Gastroparesi s, ?intestinal pseudoobstruction Peripheral antidopaminergic Domperidone Gastroparesi s 5-HT 4 agonist Tegaserod ?Gastropares is, ?intestinal pseudoobstruction Somatostatin analogue Octreotide Intestinal pseudoobstruction Special settings Benzodiazepi nes Lorazepam Anticipatory nausea and vomiting with chemotherapy Glucocorticoi ds Methylprednisolo ne, dexamethasone Chemothera py-induced emesis Cannabinoids Tetrahydrocanna binol ?Chemother apy-induced emesis Other drug classes exhibit antiemetic properties. Serotonin 5-HT 3 antagonists such as ondansetron and granisetron exhibit utility in postoperative vomiting, after radiation therapy, and in the prevention of cancer chemotherapy– induced emesis. The usefulness of 5-HT 3 antagonists for other causes of emesis is less well established. Low-dose tricyclic antidepressant agents provide symptomatic benefit in patients with chronic idiopathic nausea and functional vomiting as well as in diabetic patients with nausea and vomiting whose disease is of long standing. . Chapter 039. Nausea, Vomiting, and Indigestion (Part 4) Diagnostic Testing For intractable symptoms or an elusive diagnosis,. Antihistamines such as meclizine and dimenhydrinate and anticholinergic drugs like scopolamine act on labyrinthine- activated pathways and are useful in motion sickness and inner ear disorders. Dopamine. emesis evoked by area postrema stimuli and are useful for medication, toxic, and metabolic etiologies. Dopamine antagonists freely cross the blood-brain barrier and cause anxiety, dystonic reactions,