Breakthrough Pain In Non-Cancer Patients
Breakthrough pain (BTP) has been defined as a transitory exacerbation of pain that occurs on a background of otherwise stable pain in cancer patients receiving chronic opioid therapy.1 Additional opioids, such as short-acting breakthrough narcotic medications, with half-lives typically lasting three to four hours, are commonly advocated for BTP in cancer patients with a shortened life expectancy.2,3 While several studies have examined, in depth, the phenomenon of BTP that is related to malignancy in cancer patients,1,4-7 the same has not yet been accomplished for non-cancer chronic pain patients. Patients treated with maintenance doses of opioids for chronic non-cancerous pain also experience transitory flares on a background of otherwise stable pain. To date, characteristics of non-cancerous BTP have been assumed to be the same as cancer-related BTP.
A limited number of studies have begun to examine BTP in the non-cancerous population. The objective of this study was to describe characteristics of BTP in a non-cancerous group of patients with low back pain refractory to one or more surgical interventions. Thirty patients, whose pain was controlled by pharmacological methods that included a long-acting maintenance dose of opioid analgesic for chronic pain supplemented with other medications (both opioid and non-opioid) for breakthrough episodes, were enrolled in this study.
|N (% or ±SD)|
|African American||2 (6.7)|
|50 (±12) years|
|Body Mass Index||29.8 (±7.1)|
|Employment Status||Disabled||18 (60.0)|
|Retired or unemployed||7 (23.3)|
|Employed (full- or part-time)||5 (16.7)|
|Number of surgical attempts to correct low back pain||2.7 (Range 1-5)|
|Average per day dose of long-acting opioid (N=28*)||261 (±325) mg morphine equivalents|
|Average per day dose of short-acting opioid (N=15)||76 (±78) mg morphine equivalents|
|*Two patients did not record the dose of their long-acting opioid.|
The study was approved by the Washington University Human Studies Committee and utilized a waiver of consent. This pilot study used a survey to evaluate a patient’s perception of chronic and breakthrough pain experienced over the previous 30 days. Eligible patients attending the author’s pain management practice from March 2004 to July 2004 were invited to participate. Enrolled patients had chronic non-cancerous low back pain for a minimum of one year, failed back surgery, used a long-acting maintenance dose of opioid that patients subjectively reported provided at least a 50% reduction in pain, and experienced intermittent episodes of BTP. The patient’s pain management had been optimized using either long acting opioids or around the clock short acting opioids. In some cases the maintenance medication was supplemented with short acting medications (opioids, anti-epileptics, muscle relaxants, antidepressants, and NSAIDS). Patients with cancer, chronic pain not related to the back, or a long-acting opioid dose adjustment in the previous 30 days were excluded from this study.
Validated questionnaires were unavailable for the assessment of BTP in this patient group. Therefore, a questionnaire, adapted from two cancer BTP questionnaires, was designed to elicit information regarding the patients’ perception of both chronic pain and BTP.1,5 Much of the information collected relied on patient recall for a thirty day period prior to administration of the questionnaire. The data collected included: demographic information (see Table 1), descriptive terms of pain (see Table 2), characteristics of BTP (see Table 3), pharmacological and non-pharmacological treatments used for the chronic low back pain (Table 4), and precipitating events of BTP (Table 5).
All analyses were carried out using the software program SPSS 13.0 for Windows (SPSS Inc., Chicago, IL). Both descriptive and inferential statistical methods were employed. All testing was based on determining statistical significance at a two-sided alpha level of 0.05. The study sample was described using measures of central tendency (mean and median) and dispersion (standard deviation and range) for continuous variables and frequency and percentage for categorical variables. Spearman’s rho statistic was used to evaluate the association between continuous/ ordinal scaled variables. Chi-square or Fisher’s Exact tests were used, as appropriate, to compare categorical variables. Mann-Whitney tests were used to compare the distribution of continuous and ordinal scaled variables between 2 categories of categorical variables (see Table 6).