This study addressed the association between frailty domains and chronic pain following cardiac surgery in older patients. Additionally, the impact of chronic pain on HRQL in older patients was evaluated. One out of three elderly reported chronic pain after one year and frail patients had a higher risk of chronic pain following cardiac surgery. Frailty domains that were associated with chronic pain following surgery were medication use, living situation, mobility, gait speed, Nagi's physical functioning and preoperative HRQL. In addition, we found that postoperative chronic pain was associated with worse physical HRQL one year after surgery.
This study confirmed that chronic pain is common in elderly cardiac surgery patients with a similar incidence reported in prior studies.[1–3] However, in our study the number of patients with postoperative chronic pain (n = 182) decreased compared to the number of patients with pain prior to surgery (n = 331), and 27% of patients (140/518) reported an improvement in pain. This might be explained by an improved functional capacity, decreased ischemic chest pain and lower levels of anxiety following cardiac surgery. Nevertheless, increased pain symptoms were common. Considering that chronic pain had a profound effect on HRQL, identification of risk factors for development of chronic pain, especially in the frail and vulnerable population, is important and might help to initiate preventive strategies. Several risk factors including younger age, psychological impairment, preexisting pain, internal mammary artery harvest, use of remifentanil and emergency surgery have been described to increase the risk of chronic pain following cardiac surgery.[1,2,26–30] In contrast to prior studies, these risk factors were not associated with higher risks of the development of chronic pain in our study. This is likely explained by differences between surgical cohorts. The AGE study consisted of a frailty-prone population undergoing a wide range of elective cardiac surgery procedures, and the mean age was higher than in other reports.
Frail patients had a higher risk of developing postoperative chronic pain following cardiac surgery. This association might be explained by impaired physical exertion as higher levels of activity have been described to reduce pain sensitivity by decreased pain facilitation and increased pain inhibition.33].Conversely, preexistent pain is well-known to have an impact on physical activity.[5,6] Furthermore, preexistent pain is known to be a risk factor for acute and chronic pain following surgery.[1,26,27] The question arises whether preexistent pain or impaired physical functioning (possibly due to pain or frailty) in these patients is the most relevant risk factor for the development of chronic pain. In our study, preexistent pain was not significantly associated with postoperative chronic pain. Also, in a post-hoc analysis, in which patients with preexistent moderate to severe pain were excluded from the chronic pain definition, our results did not change. Consistent with prior research, this underlines the association between impaired physical functioning and the development of chronic postoperative pain.
Besides impaired physical functioning, medication use, living situation and preoperative mental HRQL were associated with chronic postoperative pain. Polypharmacy is common in older patients, and might impede pain management for several reasons. Apart from age- and disease-related changes in physiology, disease-drug and drug-drug interactions might lead to a heterogeneity in response to medications and increased adverse drug effects. Frailty further increases this heterogeneity and thus frail elderly with polypharmacy may be more susceptible to adverse events. Next to this, polypharmacy leads to medication non-adherence, leading to a suboptimal effect of prescribed analgesic therapy. In our study, patients with excessive polypharmacy had a twofold risk to develop chronic pain. Finally, patients living alone are prone to social isolation, which contributes to feelings of depression or anxiety, and a more intense experience of pain.[11,26,35]
Gender has been described to interact with multiple preoperative factors as well as cardiac surgery outcomes. Female gender has been positively associated with preoperative frailty, psychological disease and dementia in cardiac surgery patients. The results of our study confirm the well-investigated relationship between female gender and chronic pain.[26,27] When defining interventions to improve outcome following cardiac surgery based on preoperative risk stratification, gender-related disparities should be taken into consideration.
Our study confirmed the existing relationship between chronic pain and HRQL. In general, polypharmacy, physical inactivity, reduced self-reliance and social isolation leads to an increase in health consumption, pain and poor HRQL.[11,27,28,37,38] In addition, several studies found that pain adversely affects recovery and HRQL, and that the impact correlated with the severity of pain.[27,28,37] In patients with chronic pain in our study, mental and physical HRQL were lower prior to surgery and physical HRQL was worse one year after surgery compared to patients without chronic pain (p < 0.001). Understanding factors that are related to HRQL in older people can be used to preoperatively accommodate patients' needs and preserve quality of life.
Risk stratification should lead to individualized evaluation and preparation for surgery. However, evidence for pre-habilitation is limited for cardiac surgery patients. However, preoperative exercise has been demonstrated to improve functional recovery. Optimization of treatment expectations by a simple psychological intervention have shown to improve disability. Currently, trials on pre-habilitation are being performed in cardiac surgery patients, but the results have to be awaited.[41,42]
Comprehensive evaluation of pharmacotherapy should be part of each preoperative assessment, but deserves additional attention of, for example, a pharmacist or geriatrician in patients with polypharmacy. Patients suffering from chronic pain preoperatively should receive an individualized perioperative pain management plan, depending on their preoperative situation. Within this plan, additional pharmacotherapy, locoregional anesthesia and/or non-pharmacological interventions including may be considered to treat acute postoperative pain and prevent the increase of chronic pain symptoms following cardiac surgery.
The following limitations should be considered. First, pain was determined by a health survey that was not specifically designed to assess pain or pain interference. This study population reported pain within the last 4 weeks at 12 months follow up after surgery, and defined it as chronic pain. Unfortunately, differentiation between thoracic pain, wound pain, chest pain, pain due to the surgical procedure or other pain, and type of pain (i.e., neuropathic, musculoskeletal, inflammatory, or mechanical pain) was not possible. Second, a single point estimate was used for the incidence of chronic pain which may have resulted in an underestimation. Besides, the ageing process may account for differences in pain signaling and perception, causing an inconsistence and variety in pain measurements. More specific, with ageing a loss in structure and function of peripheral nerves occurs.[10,44] Due to a decrease in the spread and magnitude of brain activation in response to pain in elderly, pain thresholds might be higher.[10,44] On the other hand, endogenous pain modulation in elderly shows age-related impairment.[10,44] In particular, inhibitory systems were reported to be affected, resulting in lower capacities to modulate pain. This inadequacy to modulate pain leads to an increased risk for chronic pain. Finally, we did not register age-dependent conditions such as arthrosis and neurological conditions which may be related to frailty as well as to chronic pain. Further analysis of the reason for frailty may improve the prediction of chronic postoperative pain. Future research to explore these current findings should determine pain using patient diaries with validated pain assessments.
BMC Anesthesiol. 2022;22(201) © 2022 BioMed Central, Ltd.