Lecture on Gastric Motility and Laxatives

Overview of Gastric Motility

• Gastric Motility refers to the movement of the digestive system and the transit of the contents within it.
• Peristalsis: The undulating, wave-like motion that moves contents through the intestinal tract.
  • Increased motility → Diarrhea
  • Decreased motility → Constipation

Laxatives: Types and Uses

General Information

• Purpose: Soften stool, increase stool formation, and decrease straining during bowel movements.
• Indications: Used for constipation or excessive straining.
• Precautions: Avoid stimulating the vagus nerve to prevent a decrease in blood pressure and heart rate.
  • Avoiding the Valsalva maneuver is crucial, which can lead to fainting due to vagus nerve stimulation.

Side Effects and Precautions

• Monitor fluid volume status and electrolyte balance as excessive use can lead to dehydration and electrolyte loss.
• Be informed of the patient's primary medical history, including any GI disorders or surgeries.
• Nursing actions include assessment of therapeutic and side effects and the appropriateness of the agent.

Types of Laxatives

Bulk-Forming Laxatives

• Mechanism: Water-retaining cellulose derivatives that increase water absorption into the intestines, increasing bulk and softening stool.
• Side Effects: Possible esophageal obstruction or fecal impaction.
• Example: Psyllium (Metamucil)

Emollient (Surfactant) Laxatives

• Mechanism: Act as stool softeners, increasing water and fat content in intestines to lubricate feces.
• Side Effects: Abdominal cramping and diarrhea.
• Example: Docusate Sodium (Colace)

Stimulant Laxatives

• Mechanism: Stimulate intestinal nerves to increase peristalsis.
• Side Effects: Potential for abdominal cramping and dependence.
• Example: Bisacodyl
• Note: Elderly patients may misuse or become dependent on these laxatives due to fixation on regular bowel movements.

Saline Laxatives

• Mechanism: Increase osmotic pressure in small intestines to draw water into stool.
• Side Effects: Nausea, vomiting, abdominal pain, electrolyte imbalance.
• Contraindications: Not for use in patients with renal disease.
• Example: Magnesium Hydroxide (Milk of Magnesia)

Hyperosmotic Laxatives

• Mechanism: Increase water content in the large intestine to stimulate peristalsis.
• Side Effects: Nausea, vomiting, potential for hypovolemia due to stronger action.
• Examples:
  • Lactulose: Used for constipation and to reduce ammonia levels in liver failure.
  • Polyethylene Glycol (GoLYTELY): Used for bowel prep prior to surgeries or procedures.
  • Sorbitol: Also a sweetener, helps with bowel movement stimulation.

Conclusion

• Laxatives have various mechanisms of action and are essential for treating different types of bowel function disorders.
• Understanding the type, mechanism, and potential side effects of each laxative category is crucial for appropriate use in clinical settings.