JC Pharmacology Wk 7 Chapter 38

Causes of Nausea and Vomiting

• Gastrointestinal disorders like GI tract infection and inflammation, including liver, gallbladder, and pancreas, can cause nausea and vomiting.
• Impaired GI motility or muscle tone may result in nausea and vomiting.
• Overeating or ingesting irritating foods or fluids can cause nausea and vomiting.
• Cardiovascular, infectious, neurologic, and metabolic disorders can induce nausea and vomiting.
• Drug therapy is the most common adverse effect that causes nausea and vomiting.
• Noxious stimuli, including pain, unpleasant sights, or odors can cause nausea and vomiting.
• Emotional disturbances or physical/mental stress may result in nausea and vomiting.
• Radiation therapy as well as motion sickness are also causes.
• Postoperative status (pain, drugs, and impaired GI motility), pregnancy and migraines are causes for Vomiting and Nausea

Antiemetics

• These medications are used to prevent or treat nausea and vomiting.
• Nausea is an unpleasant sensation of abdominal discomfort accompanied by a desire to vomit.
• Vomiting is the expulsion of stomach contents through the mouth.

Physiology of Nausea and Vomiting

• During pregnancy the activation of the chemoreceptor trigger zone (CTZ) plays a role.
• With motion sickness, inner ear receptors are stimulated
• Vomiting occurs when the vomiting center (in the medulla oblongata) is stimulated.
• The signals are provided by the CTZ, cerebral cortex, sensory organs, and vestibular apparatus.

Question #1

• Nausea and vomiting are the most common adverse effect of medication, True.

Phenothiazines

• Central nervous system (CNS) depressants like promethazine are used for many conditions, from prevention to treatment of nausea and vomiting.
• Common side effects with promethazine include blurred vision, urinary retention, dry mouth, photosensitivity, drowsiness, and confusion.
• Additional side effects are orthostatic hypotension and exacerbation of asthma, and alteration of the Q wave and T wave.

Antihistamines

• These are primarily to prevent histamine from impacting body tissues.
• Used as antiemetic agents are classic antihistamines or H1 receptor blocking agents.
• Adverse anticholinergic effects of Hydroxyzine, include drowsiness, dizziness, confusion, dry mouth, thickened respiratory secretions, blurred vision, urinary retention, tachycardia and possible prolonged QT interval as well as torsades de pointes.

5-HT3 Receptor Antagonists

• Prototype: ondansetron.
• Considered the cornerstones of therapy for control of acute emesis from chemotherapy with moderate to high emetogenic potential.
• Usually the first choice drugs for postoperative nausea and vomiting.
• Adverse effects of ondansetron are usually mild to moderate like diarrhea, headache, dizziness, constipation, fatigue, transient elevation of liver enzymes, and pain at the injection site.

Substance P/Neurokinin 1 Antagonists

• Substance P is a peptide neurotransmitter in the neurokinin family, prototype aprepitant.
• Plays a role in mediating acute chemotherapy-induced nausea and vomiting, along with serotonin.
• Believed to be the primary mediator of delayed nausea and vomiting associated with chemotherapy
• Aprepitant is well tolerated, the most common adverse effects being fatigue, weakness, dizziness, abnormal heart rhythm, headache, and hiccups, and IV infusion site pain.

Nonpharmacologic Techniques

• Nonpharmacologic techniques have become an acceptable adjunct to antiemetic drug therapy.
• Herbal supplements are also supported
• Techniques include acupuncture, acupressure, and different herbal supplements.

Assessment

• Identify risk factors for nausea and vomiting, such as digestive/other disorders where nausea and vomiting are symptoms and also identify drugs associated with nausea and vomiting.
• Interview patients about frequency, duration, and precipitating causes of nausea and Vomiting.
• Question patients about sign & symptoms, characteristics of vomitus (amount, color, odor, abnormal components like blood)
• Ask patients what relieves the vomiting/nausea and when possible, observe and measure the vomitus.

Nursing Interventions

• Use measures to prevent or minimize nausea and vomiting.
• Assist patients in identifying situations that cause/aggravate nausea and vomiting.
• The patient should avoid exposure to stimuli when feasible: unpleasant sights and odors, alcohol, excessive food ingestion, or NSAIDs.
• Administer analgesics before painful diagnostic tests, dressing changes, or other therapeutic measures to help, as pain may cause nausea and Vomiting.
• Administer antiemetic drugs 30-60 minutes before emetic events like radiation therapy, travel, or cancer chemotherapy.
• If possible, adjust timing of oral drugs that cause gastric irritation, nausea, and vomiting by taking with solid food or just after food.
• Check reference sources to determine if drugs likely to cause nausea/vomiting can be given with food without altering beneficial effects.
• Assess the patient's condition and report to the health care provider if vomiting/nausea occurs.
• A drug like digoxin or antibiotics may need to be discontinued or reduced in dosage.
• Restriction of oral intake and nasogastric intubation are preferred treatments for paralytic ileus, GI obstruction, etc.
• Eating dry crackers before rising and ingesting small, frequent, higher protein meals, can prevent nausea and vomiting associated with pregnancy.
• Avoid administering oral intake of food, fluids, and drugs during acute episodes of nausea and vomiting because oral intake may increase vomiting and the risks of fluid and electrolyte imbalances.
• Minimize activity during acute episodes of nausea and vomiting, resting quietly are helpful.
• Provide supportive care during vomiting episodes.
• Provide replacement fluids and electrolytes.
• Offer to feed & hydrate a small amount of food & fluids when tolerated and according to the patient's preference.
• Record vital signs, intake and output, and body weight at regular intervals if nausea or vomiting occurs frequently.
• Decrease environmental stimuli when possible (e.g., noise, odors).
• Decreasing motion may decrease stimulation of the vomiting center in the brain by allowing the patient to lie quietly in bed when nauseated.
• After vomiting, rinsing the mouth decreases the bad taste and corrosion of tooth enamel caused by gastric acid.
• Provide requested home remedies when possible like providing a cool, wet washcloth to the face and neck.
• Give appropriate education for any drug therapy.

Explore the various causes of nausea and vomiting, including gastrointestinal disorders, impaired GI motility, overeating, and certain medical conditions. Learn about the role of drug therapy and noxious stimuli in inducing these symptoms. Also, understand how antiemetics are used to prevent or treat nausea and vomiting.