Uncomfortable awareness of breathing, a sensation of air hunger, or feeling breathless are common definitions for dyspnea. Dyspnea has a significant negative effect on functional capacity and quality of life. It is common in patients with advanced cancer, occurring in up to 70 percent of these patients, with approximately one fourth of them having moderate to severe dyspnea. The physical aspects of the condition affect the perception of dyspnea, but psychologic, emotional, social, and environmental factors also have an influence. LeGrand and colleagues reviewed the literature on the use of opioids in patients with dyspnea.
The first-line therapy for dyspnea is correction of the underlying cause when possible. In patients with advanced cancer, the underlying cause of dyspnea can be traced to symptoms directly or indirectly related to the tumor, to cancer treatments, or to noncancer chronic diseases. In the majority of patients with advanced cancer, correcting the underlying cause of dyspnea is not possible. In this case, an opioid is used to control the symptoms of dyspnea.
The use of opioids for treatment of dyspnea in patients undergoing palliative care has not been well studied. However, a Cochrane review of the literature found statistically strong evidence that opioids are effective in treating dyspnea in patients with cancer and chronic obstructive pulmonary disease (COPD). The authors reviewed multiple studies finding that various opioids had a significant effect on dyspnea symptoms in patients with advanced cancer. These studies also showed that in the patients treated with opioids, there was no change in the incidence of somnolence, anxiety, respiratory rate, or oxygen saturation when compared with placebo. In COPD patients with dyspnea, opioid treatment reduced the incidence of breathlessness and improved exercise tolerance.
Common side effects of opioid use include constipation, nausea, vomiting, dry mouth, and sedation. Most patients develop a tolerance for opioid side effects with the exception of constipation. Respiratory depression is one of the major concerns with opioid therapy, but the authors point out that in studies where this condition was an issue, opioid-naive persons and normal subjects were used. Most patients with advanced cancer are not opioid naive and have other conditions that might cause dyspnea. The authors also point out that if opioids are titrated appropriately to provide symptom relief, they are safe and effective.
The authors conclude that dyspnea is a common symptom in advanced illness and most often is not correctable in these patients. With appropriate titration and monitoring, opioids can be used in the treatment of dyspnea in patients with advanced diseases.