Alteration in Elimination

Emetogenic

Substance with potential to cause nausea/vomiting.

Constipation

Infrequent and painful expulsion of hard, dry stools; symptom not a disease

Diarrhea

Increase in the liquidity of stool or frequency of defecation to more than 3 stools per day; symptom not a disease

Cathartics

“Strong effects”, with elimination of liquid or semi-liquid stool; classified as saline or stimulant agents.

Stimulant Cathartic

Stimulates & irritates the GI mucosa and pulls water into the bowel lumen.

Saline Cathartics

Used when rapid bowel evacuation is needed; increases osmotic pressure in intestinal lumen & causes water to be retained

Laxatives

“Mild effects'“, with elimination of soft, formed stool; classified as bulk forming, lubricant, or surfactant agents.

Bulk Forming Laxatives

Swells when water is added and gel-like substance stimulates peristalsis and defecation.

Surfactant Laxatives

Decrease surface tension of fecal mass to allow water to penetrate stool & soften, used to present straining

Lubricant Laxatives

Lubricates fecal mass & slows colonic absorption of water from fecal mess; not recommended for long-term use

List The Causes For Nausea & Vomiting.

Gastrointestinal disorders

Cardiovascular, infectious, neurologic, or metabolic disorders

Adverse effects of drug therapy

Pain and other noxious stimuli

Emotional disturbances

Radiation therapy

Motion sickness

Postoperative status

Pregnancy

Migraines

List The Physiologic Pathways That Trigger N/V.

Chemoreceptor trigger zone

Cerebral Cortex (Anticipatory N/V)

Sensory organs (Noxious stimuli)

Vestibular Apparatus (Motion sickness)

List The Neurotransmitters Involved In Vomiting.

muscarinic, dopamine, histamine, hydrocytripamine, substance p/neurokinin 1 receptors

Drug Classes for N/V

Phenothiazines, antihistamines, substance P/neurokinin 1 receptor antagonists, 5-HT3 (serotonin) receptor antagonists,

Nonpharmacologic Management For N/V

Acupuncture & acupressure; herbal supplements (excluding Ginger + 5-HT3)

Drug Classes For Constipation

Laxatives & Cathartics

Nonpharmacologic Treatment of Constipation

Fiber, fluid supplementation, prebiotics, probiotics, behavioral therapy.

Drug Classes For Diarrhea

Opiate-related antidiarrheals (Risk for dependence)

Nonpharmacologic Therapy For Diarrhea

Replace lost fluid and electrolytes, 2-3 L of clear liquids 1st 24 hours.

Nausea & Vomiting – Pathophysiology

Stimulus →
Drugs, toxins, motion, noxious stimuli, anticipatory thoughts

Receptor →

• Chemoreceptor trigger zone (CTZ)

• Vestibular apparatus

• Sensory organs

• Cerebral cortex

Center →
Vomiting center in the medulla oblongata

Response →
Efferent impulses cause salivation, closure of glottis, contraction of abdominal muscles & diaphragm, relaxation of gastroesophageal sphincter, reverse peristalsis → vomiting

Constipation – Pathophysiology

Stimulus →
Repeated inhibition of urge to defecate / voluntary sphincter contraction

Receptor →
Rectal stretch receptors (reduced stimulation over time)

Center →
Cerebral cortex (voluntary control of defecation reflex)

Response →
External anal sphincter remains contracted → defecation reflex weakens → decreased urge to defecate → constipation

Diarrhea – Pathophysiology

Stimulus →
Infection, inflammation, or food intolerance

Receptor →
Intestinal mucosal receptors sense irritation and unabsorbed solutes

Center →
Enteric nervous system coordinates GI reflexes

Response →
↑ bowel motility + ↑ secretion or ↓ absorption of fluids → rapid propulsion toward rectum → limited fluid & electrolyte absorption → frequent, loose stools