Pharmacologic Management of Constipation in the Critically Ill Patient

Asad E. Patanwala, Pharm.D.; Jacob Abarca, Pharm.D., M.S.; Yvonne Huckleberry, Pharm.D.; Brian L. Erstad, Pharm.D., FCCP


Pharmacotherapy. 2006;26(7):896-902. 

In This Article


Medical records of 95 patients admitted to the MICU of an academic medical center from July 1–October 31, 2004, were retrospectively reviewed. Patients included in the study were 18 years or older and had been admitted to the MICU for 96 hours or longer. Exclusion criteria were a contraindication to use of the gastrointestinal tract, diarrhea on admission, bowel surgery within 14 days of admission, ileostomy, or colostomy. Patient-specific data such as occurrence of bowel movements, days receiving enteral or oral nutrition, and drug therapy (e.g., opioids, laxatives, stool softeners, prokinetic agents, vasopressors) were recorded during the first 96 hours of MICU admission. Other information, such as age, weight, sex, Acute Physiology and Chronic Health Evaluation (APACHE) II score, admitting service, use of mechanical ventilation, and length of MICU stay were also recorded.

Patients who did not have a bowel movement during the first 96 hours of MICU admission were defined as constipated. In a previous study involving critically ill patients, constipation was defined as no bowel movement over a 72-hour period;[3] however, this definition was based on characteristics of an ambulatory patient population. The first day of MICU admission frequently involves patient stabilization and establishment of enteral access, which could delay the start of enteral nutrition or a bowel regimen during the first 24 hours. In addition, our study looked at only the first 96 hours of the MICU admission and not the entire MICU stay. Therefore, it seemed reasonable that expectations regarding frequency of bowel movements in an ambulatory population might not apply to critically ill patients. Taking these factors into consideration and based on expert opinion at our institution, we determined that no bowel movement for the first 96 hours of MICU admission would be a more practical definition of constipation. Rectal discharge recorded as a smear was not counted as a bowel movement.

The main dependent variable of interest was the occurrence of a bowel movement within 96 hours of MICU admission; this was included in the analysis as a dichotomous variable. The effect of treatment on the occurrence of a bowel movement was analyzed using logistic regression analysis. The main independent variables included in the analysis were use of stimulant or osmotic laxatives, use of prokinetic agents, use of docusate, and administration of enemas during the first 96 hours of MICU admission (for all four variables). These variables were included as dichotomous variables in the analysis. Use was defined as administration of at least one dose of an agent during the first 96 hours of MICU admission.

Also included in the analysis were independent variables for age, APACHE II score on MICU admission, oral or enteral diet for 24 hours or longer (as a dichotomous variable), and vasopressor and opioid use. All opioid use was converted to the equivalent intravenous morphine dosage. A logarithmic transformation of the morphine equivalents was performed to obtain a more normal distribution. Bivariate analyses were also conducted. Categoric variables were analyzed using the Pearson χ2 test. Continuous variables were analyzed using a two-sample t test for normally distributed variables; a Wilcoxon rank sum test was used for continuous variables that were not normally distributed. Analyses were performed using SAS, version 9.0 (SAS Institute Inc., Cary, NC) and Stata, version 8.0 (Stata Corp., College Station, TX).


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