Lecture 7: Pain and pain management

Why do we have pain?

Pain is a phenomenon which occurs in a wide variety of medical conditions, but it also occurs in the absence of any physical problems. Pain warns us that something is wrong with our bodies and therefore we can act in certain ways to prevent injuries from getting worse. Of all psychical symptoms presented in practice, 50% of the symptoms are pain, 20-30% are respiratory related symptoms and 20-25% of the symptoms are non-pain and non-respiratory in nature, for example fatigue and dizziness.

Pain can be defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage. Pain has a sensory and emotional component (fear and anxiety of developing pain and actual physical pain). Tissue damage is not necessary to experience pain: pain may occur in the absence of any physical problem.

The two most frequently reported reasons for consulting a primary care physician are common colds, low back pains (in 85% of patients consulting for low back pains, only minor pathology is present) and headaches (usually no clear physical can be determined).

How can pain be classified?

Pain can be classified either according to cause or according to duration.

According to cause there are four types of pain. Nociceptive pain is (musculoskeletal) pain due to tissue damage and causes pain in muscles, bones, joints and/or skin. For example a fracture, burn wounds or RA cause pain receptors to be activated and therefore cause the feeling of pain.

Neuropathic pain is a consequence of damage to (or pathology of) the central/peripheral nervous system. It causes changes at the level of the nervous system to become permanent in nature over time and it therefore is difficult to treat. Many compare it to a sensation of needle pricks, electrical shocks, burning or freezing sensation or the sensation as if ants are crawling up and under their skin. Allodynia is when pain is experienced as a consequence of a stimulus that does not normally cause pain, for example rubbing a cotton swab on your skin causing excruciating pain. It is a painful response to an innocuous stimulus. Hyperalgesia is when pain is experienced as disproportional to the pain stimulus. The pain stimulus is painful to begin with, but it is experienced way worse in hyperalgesia. For neuropathic pain, the pain threshold often becomes very low for any kind of pain.

Mixed pain is a mixture of neuropathic and nociceptive pain. An example is when a buffer disci in the spinal cord has been damaged (herniated disc, nociceptive element), causing fluid to drip in the spinal canal, causing inflammation of the nerves and then eventually causing dull pain in the lower back (neuropathic element) which can lead to paralysis.

Idiopathic pain is pain for which no clear organic cause can be found. There is no diagnosis referring to a clear structural (organic) problem. An example of idiopathic pain is fibromyalgia. This is a long-term condition which causes pain all over the body.

According to duration pain can be acute or chronic. Acute pain is pain lasting for less than 3 to 6 months. Some episodes of acute pain, usually involving injury, may occur only once. Generally the pain disappears once the injury has healed, for example after a bone has healed after being fractured. Acute pain may also be recurrent, for example migraine headaches.

Chronic pain is pain that continues for more than 3 to 6 months. Chronic pain can be with an identifiable cause, for example RA, but it can also be with no identifiable cause, for example fibromyalgia or chronic lower back pain.

What are consequences of chronic pain?

Consequences of chronic pain on an economical level are (having to pay for) doctor visits, medical investigations, medical/surgical treatments and medication intake. Also one can be unable to work and therefore a higher sickness absence.

Psychological consequences of chronic pain can be anxiety (fear, worry, rumination), frustration/irritation, sleeping difficulties and depression. Both depression and sleeping difficulties have reciprocal relationships with chronic pain. Chronic pain can lead to depressive feelings and sleeping difficulties, but the other way around is possible as well. Depression, sleeping difficulties and chronic pain can also lead to one another in a vicious circle and can increase each other.

Social consequences are lesser qualitative relationships with partner, children and friends. Social isolation often occurs as well because many in chronic pain conditions can often not participate in social activities.

What are explanatory models?

Biological explanatory models describe how a pain stimulus can lead to pain perception through activated pain receptors in the body. When pain receptors are activated they transmit information to a centre in the brain that processes pain-related information. This will cause the assumption that the pain experience is a direct representation of the injury sustained by a person. Sometimes people may experience pain in the absence of injury and there may be injury without pain.

The Gate-Control Theory is a psychobiological explanatory model. This theory by Melzack & Wall (1965) used the analogy of a gate to explain the pain experience. The essence is that the degree of pain that we experience is the result of an interaction between two processes:

• Pain signals are transmitted from the site of an injury to the spinal ‘gate’ by nociceptors
  • Nerves in the spinal column transmit these pain signals to pain centres in the brain
• Pain-related cognitions and emotions activate nerves taking information from the brain down the spinal column to the ‘gate’

Activation of both systems results in a variety of chemicals being produced within the gate. Some open the gate and increase the pain experience (for example, anxious thoughts), and some close the gate and decrease the pain (for example, calming thoughts).
Pain related to cognitions and emotions also activate nerves. These nerves send information down from the brain to the spinal cord to the ‘gate’.
The gate-control theory explains why psychological variables can influence (inhibit or facilitate) the pain experience. These psychological variables can for example past experiences, attention and mood aspects. The gate-control theory made the influence of psychology upon pain credible, also to medical doctors.

The learning theory contains the law of effect by Thorndike and operant conditioning by Skinner. The law of effect describes that when a specific response is followed by a reward, the probability of (re)occurrence of this response in the future increases. Operant conditioning are learning processes that take place by giving rewards, eliminating negative consequences, eliminating rewards or administering punishment. The learning theory does not consider the cognitive and emotional aspects of pain and it is restricted to behaviour only.
Fordyce applied operant conditioning to pain. According to him, pain responses are learned and maintained by reinforcement. Grimacing and complaining about pain may be maintained because of the attention the patient receives from others (positive reinforcement). The use of medication and avoidance of activity lead to pain relief (negative reinforcement).

The Cognitive Behaviour Model describes how cognitive factors influence coping and behaviour and emotions, such as anxiety, depression and frustration. These cognitive factors are attention (paying attention to the pain will have other consequences than diverting your attention and focusing on something else), attributions concerning the cause of pain (e.g. brain tumour vs. hangover) and expectations, for example about the ability to tolerate pain, about the ability to control the pain (can I do something about the pain?), about the ability to engage certain activities despite the pain and about the pain relief.

How can pain be assessed?

It is important to measure pain to have a clear picture of the pain problem, the magnitude of the pain problem and to get an evaluation of the effect of treatment.

Pain is a subjective experience and cannot be observed directly. Self-report measures are often used. Pain behaviours are observed when individuals cannot express their pain verbally, for example in toddlers, infants and cognitively impaired people.

Pain is a complex phenomenon. Therefore multidimensional assessment is important. This multidimensional assessment consists of:

• Pain perception
• Psychological dimensions
• Behavioural dimensions

During the first interview, the focus should be on the pain perception, because at this stage pain is the primary problem. You ask about pain intensity, duration of the pain, the frequency of the pain, the type of pain the patient experiences and the pattern of frequency and duration. Pain perception is a unidimensional thing. A scale is often used in which severity/intensity of pain is represented by a number. A pain diary is often used during and at the end of the treatment. The McGill Pain Questionnaire is a well-known questionnaire which is often used in scientific research to get a clear picture of the patient’s pain. A picture of the human body is shown so the patient can point out where he or she is feeling pain. Then 20 word groups are given, each describing a specific pain ‘quality’ with increasing intensity so the patient can tell what the pain feels like (jumping – flashing – shooting, sharp – cutting – laceration). The patient is asked how the pain changes, which things relieve the pain (e.g. medication) and which things increase the pain (e.g. lack of sleep). Finally, the patient is asked how the strong the pain is now, at its worst and at its least.

In the psychological dimension you can ask about the emotional and cognitive dimensions (does the patient experience anxiety or depression? What are their coping strategies?). This can be done by using different questionnaires/checklists. The Symptom Checklist-90 R measures 9 subscales, like anxiety, depression, sleep and somatic complaints. The Hospital Anciety and Depression Scale (HADS) is developed for patients with a medical condition. It does not contain any somatic items as it only measures anxiety and depression. The Pain Catastrophising Scale measures 3 subscales: rumination (“I Can’t seem to keep it out of my mind”), magnification (“I become afraid that the pain may get worse”) and helplessness (“It’s terrible and I think it’s never going to get any better”). The Pain Coping Strategies Questionnaire has 6 subscales: diverting attention (“I try to think of something pleasant”), reinterpreting the pain sensation (“I don’t think of it as pain but rather as a dull or warm feeling”), catastrophizing (“It’s awful and I feel that it overwhelms me”), ignoring sensations (“I don’t think about the pain”), praying or hoping (“I pray to God it won’t last long”) and coping self-statements (“I tell myself that I can overcome the pain”).

The behavioural dimension focuses on pain behaviour (verbal or non-verbal) and functional limitations and Quality of Life.

Treatment of acute pain (biological dimension) can be done by medical treatment or psychological treatment. Medical treatment usually consists of pain killers. In psychological treatment, distraction, relaxation and hypnosis were demonstrated to be effective in controlling post-operative pain. Distraction and relaxation are also successfully used in children with cancer who had to undergo painful invasive procedures, such as lumbar punctures. Distraction can also be done by making use of virtual reality. The effectiveness of virtual reality can be explained by means of the Gate Control Theory (paying attention to the pain vs. focusing on something else). Conscious attention is necessary to experience pain. In virtual reality, the patient’s attention is directed away from the body/pain to the virtual world.

Treatment of chronic pain (biological dimension) can be done by medical treatment or psychological treatment. Medical treatment is about interrupting the transmission of pain signals to the brain (can be done by surgical interventions). The neural pathways that are responsible for the transmission of pain signals to the brain are severed, therefore transmission of pain signals is no longer possible. Short term effects of this intervention are finding different neural pathways for the transmissions of pain signals. Side effects are damage to the nervous system, which can cause neuropathic pain. Another form of medical treatment is Transcutaneous Electrical Nerve Stimulation (TENS). Electrodes are placed onto the skin in the area of the pain and as a small, low intensity electrical pulse is passed through the area the pain signal is blocked. It is widely used but due to lack of well-conducted trials, no conclusions can be drawn about its effectiveness and it only has a temporary effect. Pain medication for chronic pain are painkillers, narcotics, anxiolothics, corticosteroids, NSAIDS and antidepressants.

Psychological treatment consists of techniques like relaxation, biofeedback, meditation, hypnosis, behavioural interventions and Cognitive Behaviour Therapy (most often used).

• Relaxation influences the pain directly by decreasing muscle tension, therefore decreasing blood perfusion and decrease of pain. it influences pain indirectly by feeling more relaxed (stress has less impact upon the body). There are different types of relaxation.
• Biofeedback is often used in combination with relaxation. The patient receives information about his/her own biological processes and the information is subsequently used to influence these biological processes. Examples of biofeedback are measuring activity of the muscles of the forehead by means of an EMG
• Meditation incorporates focused attention and the whole field of awareness in the present moment. It involves observing, without judging, thoughts, emotions, sensations and perceptions as they arise moment by moment. In a study, positive effects were found post-treatment, but during the follow-up effects on pain disappeared.
• Hypnosis is a form of deep relaxation. The expectation of hypnosis is that it will ease the pain. During hypnosis patients are instructed to think differently about the pain. It implies distraction.
• Behavioural interventions are to increase healthy behaviour and decrease unhealthy/pain behaviour. This is done by reinforcing healthy behaviour and not paying attention to unhealthy/pain behaviour.
• CBT

What are therapies that can be used for chronic pain treatment?

Rational Emotive Therapy is about challenging irrational/dysfunctional automatic thoughts by means of the ABC schema.

A = Actual situation

B = irrational belief

C = consequences

In this therapy it is about changing those irrational thoughts into rational thoughts. An example:

Cognitive Behaviour Therapy has been found to be effective for chronic pain. Different forms have been developed:

• Individual therapy
• Group therapy
  
  • Has proven its effectiveness for treating different chronic pain problems
  • It is as effective as individual therapy
  • It is cost-effective
  • Group dynamics can be used as an additional therapeutic technique (social support from other group members)
  • It is not a good choice for those who have history of interpersonal problems (borderline), nor for cognitively impaired patients
  • Ideal group size is from 5 to 7 patients
• Self-help
  
  • Make use of behavioural and cognitives techniques to improve patients’ problem-solving skills, self-management and perceived control over the pain
  • It decreases pain intensity and limited contact with a therapist increases effectiveness
  • Stepped care approach: to what extent is this patient willing and able to actively participate in his/her own recovery/pain management?
  • It is not advisable in cases of clinical depression, cognitive impairment or social isolation.

Multidisciplinary pain rehabilitation centres

Different medical, psychological and social disciplines work together to develop an individualized treatment plan for chronic pain patients, like internal medicine, pharmacology, psychiatry, psychology, physical therapy and social work. Cognitive behaviour principles are central.