Degenerative changes in body systems and the coexistence of multiple diseases with increasing age lead to an increased prevalence of chronic pain in the elderly. Studies have shown that the prevalence of chronic pain affecting quality of life in community-dwelling older adults ranges from 20% to 46%, while the prevalence of chronic pain in older adults living in residential homes is as high as 73%.
Maxwell et al. surveyed 2779 patients aged ≥65 years receiving home treatment from 1999-2011 for follow-up and found that about half (1329) suffered from pain on a daily basis; of all these study subjects, about a quarter (21.6%) did not receive any pain medication or other analgesic treatment. The diagnosis and treatment of chronic pain has failed to receive adequate attention, which is particularly prominent in the elderly population.
The diagnosis of pain in older adults is often overlooked or delayed, and treatment is missed or not effectively implemented. Chronic persistent pain can severely affect the quality of daily life of older adults, leading to behavioral, psychological and cognitive dysfunction, and ultimately causing a range of complications such as falls, fractures, depression, deep vein thrombosis and pulmonary embolism, which can be life-threatening. Pain in the elderly may bring heavy medical and economic burdens to families and society, therefore, timely and effective pain control in the elderly is necessary. However, timely and effective diagnosis and management of pain in the elderly faces challenges due to the characteristics of pain in the elderly.
I. Difficulty of pain assessment for the elderly
The decline in language function, cognitive impairment, depression or other coexisting conditions such as stroke and dementia in the elderly make it more difficult to assess pain accurately and effectively. Experience has shown that patients with dementia have a higher prevalence of chronic pain and less access to pain management, so obtaining a history from different sources and a targeted, detailed physical examination are particularly important for assessing chronic pain in older adults; in addition, it is important to choose an objective and valid assessment tool for patients with cognitive dysfunction and dementia.
Pain is subjective and self-reported, but when a self-reported history is not available, careful observation by medical personnel and the application of appropriate assessment scales become essential tools, combining visuals such as the facial expression scale (pain face scale), pain thermometer and multifunctional scales such as the McGill Pain Questionnaire to assess Patients’ pain level, emotional activity, mental status, functional level, and social skills were evaluated. In addition, the same assessments are applied when observing the progress of treatment and the effect of medications.
II. Relationship between physiopathological changes and pain
The aging process is accompanied by a series of physiological alterations that are the pharmacological basis for the selection of drugs to treat pain in the elderly. The proportion of body mass accounted for by fat increases in the elderly, the water content decreases, the volume of distribution of fat-soluble drugs increases and clearance slows, while the blood concentration of water-soluble drugs increases, so that for elderly patients the effect of fentanyl is prolonged and morphine-like drugs are more likely to cause respiratory depression.
Reduced cardiac function and decreased cardiac index in the elderly are likely to cause similar adverse reactions to drug overdose, which should be considered more in patients with chronic heart failure. In addition, reduced cerebral blood flow, neuronal atrophy, reduced density of opioid receptors and reduced neurotransmitter synthesis in the elderly make them more sensitive to pain.
When selecting analgesic drugs, the changes in digestive function and liver and kidney function in the elderly should be considered comprehensively, starting with small doses, gradual dosing, titration, close observation, repeated assessment, and adjustment according to age and liver and kidney function.
The authors once treated an 87-year-old female patient who was hospitalized due to post-lumbar fusion syndrome, lumbar back pain radiating to the left lower extremity with increased numbness and pain in the left toe, and the patient’s pain was significantly relieved after treatment with selective nerve root block on the left side of L4 and L5, but the patient could not be discharged with persistent muscle spasm in the lumbar back; laboratory tests for liver and kidney function were normal, and the patient was given oral baclofen (baclofen) 5 mg once a night, and the muscle spasm was relieved after 3 d. On the 4th day, the patient’s sanity changed and he was transferred to the intensive care unit in a shallow coma, which was diagnosed as baclofen poisoning, baclofen was discontinued, and sanity was restored after 2 d.
After analysis, 70%-80% of baclofen was excreted by kidney and about 20% was metabolized by liver. Although the dose of baclofen treatment in this case was adjusted accordingly to age, the pain was increased, the gastrointestinal passage time was prolonged and the bioavailability was increased; coupled with dehydration, reduced hepatic and renal blood flow, weakened hepatic drug metabolism (P450) and reduced glomerular filtration rate, the blood concentration increased sharply. Even though the dose was small, it led to a toxic reaction in this case that was not easily produced in general patients, so individualized medication and individualized medical treatment embody an irreplaceable role in pain management in the elderly.
The relationship between coexisting diseases and pain
The coexistence of multiple diseases increases the complexity of pain diagnosis and treatment in the elderly. For example, in a 75-year-old diabetic patient with coronary heart disease (after cardiac stenting), chronic heart failure, hypertension, stroke, end-stage renal disease, pulmonary heart disease, arthritis and obesity, the patient had severe burning pain in both feet due to diabetic peripheral neuropathy, pain in both knees due to obesity and arthritis, central pain in the left trunk due to stroke, as well as Chronic low back pain and nerve root pain in the lower extremities made it extremely challenging to effectively manage the complex pain in this patient.
The choice of gabapentin for treatment must take into account that the dose can only be limited to 300 mg per day due to renal failure; the adverse effects of water and sodium retention that exacerbate heart failure; and the sedative effects that contribute to respiratory failure. Therefore, the choice of analgesic drugs for elderly patients with multiple systemic diseases should be considered in a comprehensive manner, weighing the pros and cons. Is minimally invasive treatment more appropriate for this patient? Firstly, anticoagulation in this patient increases the complexity and risk of injection therapy; secondly, the adverse effects of increased blood glucose and blood pressure caused by long-acting glucocorticoids should be considered.
Fourth, the impact of the application of multiple drugs on pain treatment
The coexistence of multiple diseases in the elderly leads to the application of multiple drugs, and sometimes the choice of analgesic drugs for the treatment of pain in the elderly faces a dilemma, on the one hand, analgesic drugs can effectively control pain, on the other hand, they can lead to unbearable adverse reactions, and the existence of coexisting diseases and complications increases the complexity of the disease itself and the risk of drug interactions.
For example, an 82-year-old patient with bone metastases from prostate cancer had a history of chronic atrial fibrillation, epilepsy, Alzheimer’s disease, and depression, and was taking more than 10 drugs such as long-acting morphine (30 mg, twice/d), nortriptyline (50 mg, once a night), pregabalin, and warfarin, with stable epilepsy control and no seizures in the past 3 years; in the past 2 weeks, the pain had increased due to herpes zoster infection, and the physician added oral tramadol The patient died 5 d later due to a sudden seizure and fall, and no occupying lesion was found on cranial CT.
In the pain clinic where the authors work, about half of the elderly patients aged 70 years and older take more than 10 medications, and the adverse effects caused by appropriate and inappropriate multiple drug applications, especially the combination of analgesic and antipsychotic drugs, pose a great challenge to pain management in the elderly.
V. Application of minimally invasive treatment in pain management of the elderly
The aging process is accompanied by degenerative changes in the spine and bone joints, which is one of the important causes of spinal-derived pain and bone and joint pain. In addition, vertebral compression fractures due to osteoporosis and neoplastic lesions are another culprit of low back pain. For these pain minimally invasive treatments such as selective nerve root block, radiofrequency therapy, vertebroplasty, percutaneous vertebroplasty decompression, other nerve blocks and peripheral joint injections have an irreplaceable role for pharmacological treatment.
However, elderly patients do not have a thorough understanding of minimally invasive treatment and are worried about the complications of surgery, so they cannot make the decision to receive treatment in a timely manner; at the same time, medical personnel believe that minimally invasive surgery in the elderly will have greater risks and cannot accurately grasp the indications, thus preventing elderly patients from receiving timely and effective treatment for their pain.
The following is an example of the importance of minimally invasive treatment in the treatment of pain in the elderly: an 80-year-old female patient, previously in good health, presented with numbness in the dorsum and toes of both feet with no apparent cause 6 months ago, followed by lumbosacral pain radiating to the posterior lateral aspect of the fibula, which was not taken seriously.
The spinal MRI showed a bulging disc at L5-S1. The patient refused surgical treatment and asked the pain physician to perform a double L5 nerve root block. Selective nerve root block is simple, safe, reliable and effective in the treatment of radiculopathy, and it is especially suitable for elderly patients who do not want to undergo surgery, and should be promoted.
In another case, a 69-year-old male patient with bilateral lower extremity pain and activity limitation due to L4-L5 spinal stenosis underwent laminectomy and decompression 3 years ago, and the pain was relieved; one year ago, the right lung was removed due to lung cancer, and 3 months ago, the pain recurred in both lower extremities with intermittent claudication; CT examination of the spine showed that the patient had thickened L3-L4 ligament and soft tissue hyperplasia with scar formation nearby, resulting in severe spinal stenosis at L3-L4. However, the patient could not undergo open surgery again. The pain doctor explained in detail to the patient and his family about the minimally invasive percutaneous spinal canal decompression and shaping procedure, and the patient underwent this treatment, which significantly reduced his pain and greatly improved his quality of life.
VI. Other factors associated with pain in the elderly
Many people, including medical professionals, believe that pain is part of the aging process and that overemphasis on analgesia can mask the condition or delay diagnosis; this, combined with patients’ fear of opioids and physicians’ lack of sufficient confidence in the use of such drugs in the elderly, has left pain management in the elderly in a negative and passive state. For this reason, the British Geriatrics Society (BGS) and the American Geriatrics Society (AGS) have made detailed recommendations on the treatment and application of medications for pain in the elderly, and medical practitioners in China are now paying more attention to the treatment of pain in the elderly.