Nausea & Vomiting Flashcards
nausea
noxious psychophysiological sensation that suppresses appetite and induces urge to vomit
vomiting
*forceful retrograde ejection of material in the upper jejunum and stomach out of the body
*medical term = emesis
evolutionary significance of nausea & vomiting
*plants use phytotoxins to defend themselves against predators (neurotoxins that poison insect, avian, and mammalian predators)
*many of these defensive chemicals are perceived as BITTER
*layered defense vs. phytotoxins:
1. sight/smell = don’t eat it
2. bitter taste = spit it out
3. gut sensors = nausea, stop eating it
4. CNS sensors = vomiting, get rid of it
how does taste act as a gatekeeper of the gut
*3 tastes identify beneficial foods
-sweet = contains sugars (provide energy)
-salty = contains mineral salts (needed for cellular fxn)
-umami = contains amino acids (provides protein for growth)
*2 tastes identify potentially dangerous foods:
-sour = acids made by fermentation (could contain infectious organisms)
-bitter = may contain toxic phytochemicals (25 distinct bitter receptors)
physiology of nausea & vomiting
*if food contains toxins, drugs, or microorganisms, the visceral afferents communicate from the gut to the brain and induces vomiting
*multiple higher cortical centers in the brain, NTS and CTZ nuclei, and info from the cochlea/balance system communicate their info with the vomiting center in the brainstem
*phase 1 = reverse peristalsis and pyloric relaxation
*phase 2 = pylorospasm & gastric contraction
causes of nausea & vomiting
*enteric infections (acute; usually self-limited)
*pregnancy (morning sickness, hyperemesis gravidarum)
*gastric inflammation or ulceration
*DRUGS (very common)
*GI tract obstruction
*metabolic abnormalities
serious consequences related to nausea/vomiting
*dehydration, hypokalemia, alkalosis
*aspiration, choking, aspiration pneumonia
*oropharyngeal problems (vocal cord dysfunction; accelerated tooth decay)
*Mallory-Weiss syndrome (esophageal mucosal tear)
*Boerhaave syndrome (esophageal rupture)
*weight loss and chronic malnutrition
goals of drug treatment of nausea & vomiting
- control vomiting to enable hydration (scheduled medication dosing is better than PRN)
- suppress nausea for comfort
- diagnose and treat root cause
anti-nausea medication choice
*PPI or H2-blockers if gastric inflammation is present
*start with drugs that have fewer/milder side effects
*consider 5-HT3 antagonists or antihistamines before using dopamine antagonists and other agents
ondansetron - overview
*drug class: 5-HT3 antagonist
*MOA: antagonist of 5-HT3 receptors in the vagus and chemoreceptor trigger zone
*drug use: highest effectiveness against chemotherapy nausea & vomiting
*side effects: constipation, diarrhea, headache, dizziness
promethazine - overview
*drug class: antihistamine
*MOA: H1 receptor antagonist
*drug use: broad spectrum use for nausea & vomiting
*side effects: drowsiness, fatigue, dry mouth, sedation
prochlorperazine - overview
*drug class: dopamine antagonists
*MOA: antagonists of D2 receptors in the GI tract and CNS
*drug use: broad spectrum use for nausea & vomiting
*side effects: dry mouth, diarrhea, sedation, dystonia, extrapyramidal sx, hyperprolactinemia
dronabinol - overview
*drug class: antiemetic drug
*MOA: CB1 cannabinoid receptor agonist
*drug use: chemo Rx nausea; refractory nausea
*side effects: drowsiness, dry mouth, euphoria, tachycardia
evaluation of nausea & vomiting
- detailed history
-onset, patterns, pregnancy, weight loss
-review of meds (chronic vs. recently added)
-associated sx (vertigo, headache, neuro) - metabolic assessment (electrolytes, liver fxn, glucose, A1c, cortisol)
- EGD and biopsy
- gastric emptying scan
- small bowel imaging
- other (brain imaging, tilt table, breath tests, ENT evaluation)
