Examination of Nurse-Modifiable Risk Factors for Chronic Post-Surgical Pain after Cardiac Surgery

Abstract

Background: Thousands of Canadians undergo cardiac surgery each year with the aim of relieving symptoms (e.g., angina) and improving health-related-quality-of-life (HRQoL). Despite the demonstrated symptom-related benefits of these surgeries, evidence suggests that the development of chronic post-surgical pain (CPSP) is a major clinical problem. To date, several perioperative factors have been examined for their potential to confer risk for CPSP. Purpose: The purpose of the study was to explore the association between preoperative moderate to severe anxiety and depressive symptoms; moderate to severe acute postoperative pain; and cumulative opioid dose consumption with the development of CPSP at six months and 12 months after cardiac surgery. Method: Design. This thesis was a prospective observational cohort sub-study of adults undergoing cardiac surgery in a tertiary care hospital setting (n=735), recruited from Hamilton Health Sciences, Canada over a five year period. Measures. The independent variables included state anxiety, depressive symptoms, acute postoperative pain intensity, and opioid dose consumption. At baseline, the Spielberger State-Trait Anxiety Inventory (STAI) assessed state anxiety and the Hospital Anxiety and Depression Scale (HADS) assessed depressive symptoms. The Brief Pain Inventory-Short Form (BPI-SF) assessed acute postoperative pain intensity on postoperative days three (in-hospital) and 30 (at home via telephone). All instruments have established reliability and validity in cardiac surgery patients (e.g., STAI Cronbach’s alpha (α) =0.82; HADS α=0.81; BPI-SF α=0.87). Medical records were reviewed and total dose of opioids consumed up to three days postoperatively, were collected via analgesic chart audit and converted into milligrams of parenteral morphine equivalent dose using standard dosage tables. Dependent variable. The primary outcome of CPSP was assessed dichotomously (i.e., yes/no) at six months and 12 months after cardiac surgery. If present, CPSP was assessed via the BPI-SF. At baseline, data was collected on pre-specified model covariates (e.g., age, sex). Data Analyses. Logistic regression was used to model the primary outcome with the presence of CPSP at six months and 12 months, while adjusting for model covariates. Secondary linear regression models were constructed to examine the effect of the independent variables on the severity of CPSP with statistical significance set at p-values <0.05. Results: The incidence of CPSP was 8.7% at six months and 4.1% at 12 months after cardiac surgery. Baseline demographics (i.e., age, sex) and medical status (i.e., diabetes mellitus) were significantly associated with the presence of CPSP. Moderate to severe preoperative anxiety was not significantly associated with CPSP at six months (adjusted OR 0.629, 95% CI [0.300, 1.322], p=0.222) or 12 months (adjusted OR 0.743, 95% CI [0.242, 2.285], p=0.604). Moderate to severe preoperative depressive symptom was not significantly associated with CPSP at six months (adjusted OR 0.676, 95% CI [0.152, 3.005], p=0.607) or 12 months (adjusted OR 3.216, 95% CI [0.835, 12.382], p=0.089). Acute postoperative pain rated as pain ‘right now’ on day three was significantly associated with CPSP at six months (adjusted OR 2.263, 95% CI [1.255, 4.081], p=0.007) and 12 months (adjusted OR 2.749, 95% CI [1.174, 6.441], p=0.020). Acute postoperative pain ‘right now’ on day 30 was significantly associated with CPSP at six months (adjusted OR 2.913, 95% CI [1.304, 6.505], p=0.009). Cumulative opioid dose consumed was significantly associated with the development of CPSP at six months (adjusted OR 1.001, 95% CI [1.000, 1.002], p=0.003) and 12 months (adjusted OR 1.001, 95% CI [1.000, 1.001], p=0.033) after cardiac surgery. Significance: The findings demonstrate that acute postoperative pain ‘right now’ and cumulative opioid dose consumed are risk factors for CPSP after cardiac surgery. These findings offer targets for nursing staff to identify potentially at-risk patients, implement evidence-based pain management strategies, as well as contribute to nursing-led research designed to target CPSP after cardiac surgery.