Constipation
Constipation is a symptom commonly experienced by terminally ill patients because of low fluid intake or dehydration, low fiber intake, impaired mobility or inactivity, and medical conditions such as bowel obstruction, hemorrhoids, hypercalcemia, hypothyroidism, autonomic dysfunction, and spinal cord involvement by tumors. Constipation is also a result of drug therapies that impair gut motility, with common culprits being opioids, anticholinergic agents, ondansetron, iron, vinca alkaloids, and antihypertensives.
Constipation is such a common side effect of opioid use that nearly all patients receiving opioid therapy should be placed on preventive regimens. There may be a slightly lower risk for patients receiving transdermal fentanyl. There are opioid receptors in the bowel as well as the central nervous system. As a result, opioids cause a reduction in the propulsive peristalsis of the intestines, an increase in intestinal fluid absorption (causing a thickening and hardening of the stool), and a decrease in intestinal, biliary, and pancreatic secretions.
Although there are no definitive trials demonstrating the superiority of one bowel regimen over another, a combination of a softening agent (e.g., docusate sodium) and a stimulant laxative (e.g., bisacodyl or senna) is commonly used. Dosages should be increased as opioid dosages increase. In general, the goal should be one bowel movement every or two days, but this should be adjusted according to patient comfort.
Assessment of Constipation
On admission, each patient should be carefully assessed for constipation. The assessment should include a detailed history that includes information about:
Stool frequency and consistency
Diet and eating habits
Abdominal pain or sensation of fullness
Previous laxative use and its effectiveness
Other potentially constipating medications
Associated problems, such as lack of privacy or long distances to the toilet
After taking a history, an abdominal examination should be performed, followed by a rectal examination, if indicated, to rule out impaction and assess anal tone.
Suggested Laxative Regimen
Avoid bulk-forming agents such as psyllium or methylcellulose, because they tend to form impactions when patients can no longer take adequate amounts of fluids. Patients with no previous history of constipation can try docusate or a combination of docusate with senna or a similar gentle laxative. Most patients require individually titrated doses of potent bowel stimulants, such as senna (with a maximum dose of 8 tablets a day) or bisacodyl.
The physician must specify the initial laxative regimen step on admission orders (e.g., docusate sodium 100 mg orally twice a day and senna 8.6mg orally twice a day) and specify that an ongoing laxative regimen must be instituted. If the patient has not had a bowel movement in two days, the laxative dosage should be increased to the next level. If the patient has not had a bowel movement in 3 days, one of the following treatments should be given once or twice daily until results are obtained: an osmotic agent (ie, lactulose 30cc, sorbitol 30cc, polyethylene glycol 17g in 8oz. water), digital disimpaction followed by two bisacodyl suppositories, or soapsuds or sodium phosphate enema (this last option should not be used for patients with renal failure). After successful treatment, the patient should resume the stepwise regimen at the initial treatment level.
A milk and molasses enema can be effective when all else fails. Add 3oz. powdered milk to 8oz. warm water in a jar. Close the jar and shake it until fully mixed. Add 4.5oz. molasses and shake again until evenly colored. Pour the mixture into an enema bag and administer rectally.
Social and Psychological Aspects of Constipation
The social and psychological aspects of constipation can interfere with its treatment and prevention. Attention must be paid to privacy; a private commode with easy access is essential. Also, patients may not tolerate opposite-sex relatives or caretakers administering suppositories or enemas. Cost is another concern, as the high cost of some laxatives can interfere with compliance.