Methods
This study was approved by the institutional review board at the Mayo Clinic Rochester. All patients who were initiated on intravenous analgesia with an electronic patient-controlled opioid pump (PCA) while admitted to a general medicine service in 2011 and 2012 were identified. Patients who received PCA therapy were identified through a pharmacy database. Only patients older than 18 years of age were included in the study. PCA therapy was selected for our analysis because PCA therapy is not regularly administered on an outpatient basis. All of these patients, therefore, had a change in their narcotic regimen on admission to the hospital. Patients were excluded from the study if they were on a PCA for less than 24 hours; had a PCA initiated on a service other than a general medicine service; were on a scheduled laxative regimen prior to admission; or carried a diagnosis of bowel obstruction, chronic diarrhea, constipation, or intestinal discontinuity (eg, those with previous diversions or ostomies).
A retrospective review of each patient’s chart was conducted with the assistance of a team of nurse abstractors. Basic demographic data were recorded for each patient. Date of hospital admission and discharge; scheduled laxatives ordered and administered (any dose of sennosides, polyethylene glycol, docusate, bisacodyl, lactulose, or magnesium citrate); abdominal X-rays and abdominal CT scans performed for constipation; and any administration of enemas were recorded. Fiber supplements were not considered laxatives. If a patient was documented to have constipation during their hospitalization this was recorded. Patients were classified as having severe constipation if an abdominal CT or x-ray was performed for the indication of constipation; if abdominal distension, pain, or bloating were documented due to constipation; or if an enema was performed during the hospitalization.
For analysis purposes, patients who started receiving scheduled laxatives (as opposed to laxatives “as needed”)on or before the day of PCA initiation were classified as receiving prophylactic laxatives. Baseline patient characteristics and outcomes were compared using the chi-square test for nominal variables and the rank sum test for continuous variables. In all cases, 2-tailed tests were performed with P values ≤ 0.05 considered statistically significant. A nominal logistic regression model was utilized to assess for independent association of risk factors with the outcome of constipation.
Results
