What Is Pain? What Causes Pain?
The English word 'pain' probably comes from Old French (peine), Latin (poena - meaning punishment pain), or Ancient Greek (poine - a word more related to penalty), or a combination of all three.
In medicine pain relates to a sensation that hurts. If you feel pain it hurts, you feel discomfort, distress and perhaps agony, depending on the severity of it. Pain can be steady and constant, in which case it may be an ache. It might be a throbbing pain - a pulsating pain. The pain could have a pinching sensation, or a stabbing one.
Only the person who is experiencing the pain can describe it properly. Pain is a very individual experience.
Types of painAcute pain - this can be intense and short-lived, in which case we call it acute pain. Acute pain may be an indication of an injury. When the injury heals the pain usually goes away.
Chronic pain - this sensation lasts much longer than acute pain. Chronic pain can be mild or intense (severe).
How do we classify pain?
Pain can be nociceptive, non-nociveptive, somatic, visceral, neuropathic, or sympathetic. Look at the table below.
Nociceptive Pain - specific pain receptors are stimulated. These receptors sense temperature (hot/cold), vibration, stretch, and chemicals released from damaged cells.
Somatic Pain - a type of nociceptive pain. Pain felt on the skin, muscle, joints, bones and ligaments is called somatic pain. The term musculo-skeletal pain means somatic pain. The pain receptors are sensitive to temperature (hot/cold), vibration, and stretch (in the muscles). They are also sensitive to inflammation, as would happen if you cut yourself, sprain something that causes tissue damage. Pain as a result of lack of oxygen, as in ischemic muscle cramps, are a type of nociceptive pain. Somatic pain is generally sharp and well localized - if you touch it or move the affected area the pain will worsen.
Visceral Pain - a type of nociceptive pain. It is felt in the internal organs and main body cavities. The cavities are divided into the thorax (lungs and heart), abdomen (bowels, spleen, liver and kidneys), and the pelvis (ovaries, bladder, and the womb). The pain receptors - nociceptors - sense inflammation, stretch and ischemia (oxygen starvation).
Visceral pain is more difficult to localize than somatic pain. The sensation is more likely to be a vague deep ache. Colicky and cramping sensations are generally types of visceral pain. Visceral pain commonly refers to some type of back pain - pelvic pain generally refers to the lower back, abdominal pain to the mid-back, and thoracic pain to the upper back (see below for the meaning of referred pain).
Nerve Pain or Neuropathic Pain
Nerve pain is also known as neuropathic pain. It is a type of non-nociceptive pain. It comes from within the nervous system itself. People often refer to it as pinched nerve, or trapped nerve. The pain can originate from the nerves between the tissues and the spinal cord (peripheral nervous system) and the nerves between the spinal cord and the brain (central nervous system, or CNS).
Neuropathic pain can be caused by nerve degeneration, as might be the case in a stroke, multiple-sclerosis, or oxygen starvation. It could be due to a trapped nerve, meaning there is pressure on the nerve. A torn or slipped disc will cause nerve inflammation, which will trigger neuropathic pain. Nerve infection, such as shingles, can also cause neuropathic pain.
Pain that comes from the nervous system is called non-nociceptive because there are no specific pain receptors. Nociceptive in this text means responding to pain. When a nerve is injured it becomes unstable and its signaling system becomes muddled and haphazard. The brain interprets these abnormal signals as pain. This randomness can also cause other sensations, such as numbness, pins and needles, tingling, and hypersensitivity to temperature, vibration and touch. The pain can sometimes be unpredictable because of this.
The sympathetic nervous system controls our blood flow to our skin and muscles, perspiration (sweating) by the skin, and how quickly the peripheral nervous system works.
Sympathetic pain occurs generally after a fracture or a soft tissue injury of the limbs. This pain is non-nociceptive - there are no specific pain receptors. As with neuropathic pain, the nerve is injured, becomes unstable and fires off random, chaotic, abnormal signals to the brain, which interprets them as pain.
Generally with this kind of pain the skin and the area around the injury become extremely sensitive. The pain often becomes so intense that the sufferer daren't use the affected arm or leg. Lack of limb use after a time can cause other problems, such as muscle wasting, osteoporosis, and stiffness in the joints.
What is referred pain?Also known as reflective pain. When pain is felt either next to, or at a distance from the origin of an injury it is called referred pain. For example, when a person has a heart attack, even though the affected area is the heart, the pain is sometimes felt around the shoulders, back and neck, rather than in the chest. We have known about referred pain for centuries, but we still do not know its origins and what causes it.
How do you measure pain?It is virtually impossible to measure a person's pain objectively. Most experts say that the best way to find out how much pain a person is enduring is by a subjective pain report. A comprehensive assessment of pain should include:
- The identification of all the pains. This must include the most important ones.
- The site, quality, and radiation of pain
- What factors aggravate and relieve the pain
- When the pain occurs throughout the day
- What impact the pain has on the person's function
- What impact the pain has on the person's mood
- The sufferers' understanding of their pain
Here is a list of some pain measures used today:
Numerical Rating Scales
The patient is given a form which asks him to tick from 0 to 10 what his level of pain is. 0 is no pain, 5 is moderate pain, and 10 is the worst pain imaginable.
|Please rate the pain you have right now|
|No pain||Moderate pain||Worst pain imaginable|
The Numerical Rating Scales are useful if you want to measure any changes in pain, as well as gauging the patient's response to pain treatment. If the patient has dyslexia, autism, or is very elderly and has dementia this may not be the best tool (see the ones below).
Verbal Descriptor Scale
This type of scale exists in many different forms. The patient is asked questions and responds verbally choosing from such terms as mild, moderate, severe, no pain, mild pain, discomforting, distressing, horrible, and excruciating.
Elderly patients with cognitive impairment, very young children, and people who respond better to verbal stimuli tend to have better completion rates with this type of scale, compared to the written numerical scale. Children respond even better to the faces scale (description below).
The patient sees a series of faces. The first one is calm and happy, the second less so, etc., and the final one has an expression of extreme pain. This scale is used mainly for children, but can also be used with elderly patients with cognitive impairment. Patients with autism may respond better to this type of approach - people with autism tend to respond to visual stimuli well.
Brief Pain Inventory
This is a much more comprehensive written questionnaire. Not only does it gauge current level of pain, but also records the peaks and troughs of pain during previous days, how pain has affected mood, activity, sleep patterns, and how the pain may have affected the patient's interpersonal relationship. The questionnaire also has diagrams which the patient shades - the shaded parts being where the pain is located and where it is most severe.
McGill Pain Questionnaire
This questionnaire measures the intensity (severity) of the pain, the quality of the pain, mood, and understanding of the pain. It is also known as the McGill Pain Index. It is a scale of rating pain developed at McGill University by Melzack and Torgerson (1971).
Look at the 20 groups below.
- Circle one word in each group that best describes your pain.
- Circle only three words from Groups 1 to 10 that best describe your pain response.
- Choose just two words in Groups 11 to 15 that best describe your pain.
- Just pick the one in Group 16.
- Finally, choose just one word from Groups 17-20.
Group 1 - Flickering, Pulsing, Quivering, Throbbing, Beating, Pounding
Group 2 - Jumping, Flashing, Shooting
Group 3 - Pricking, Boring, Drilling, Stabbing
Group 4 - Sharp, Gritting, Lacerating
Group 5 - Pinching, Pressing, Gnawing, Cramping, Crushing
Group 6 - Tugging, Pulling, Wrenching
Group 7 - Hot, Burning, Scalding, Searing
Group 8 - Tingling, Itching, Smarting, Stinging
Group 9 - Dull, Sore, Hurting, Aching, Heavy
Group 10 - Tender, Taunt, Rasping, Splitting
Group 11 - Tiring, Exhausting
Group 12 - Sickening, Suffocating
Group 13 - Fearful, Frightful, Terrifying
Group 14 - Punishing, Grueling, Cruel, Vicious, Killing
Group 15 - Wretched, Binding
Group 16 - Annoying, Troublesome, Miserable, Intense, Unbearable
Group 17 - Spreading, Radiating, Penetrating, Piercing
Group 18 - Tight, Numb, Squeezing, Drawing, Tearing
Group 19 - Cool, Cold, Freezing
Group 20 - Nagging, Nauseating, Agonizing, Dreadful, Torturing
Measuring pain when the patient is cognitively impaired
In this case doctors say that the patient's subjective pain report is the most effective and accurate way of evaluating pain. If the severely cognitively impaired patient is observed carefully it is possible to pick out clues as to the presence of pain, e.g. restlessness, crying, moaning, groaning, grimacing, resistance to care, reduced social interactions, increased wandering, not eating, and sleeping problems.
What are the treatments for pain?An underlying disorder, if treated effectively, will also get rid of the pain, or at least reduce it. If you have an infection and take antibiotics, the antibiotics may get rid of that infection, resulting also in the elimination of pain. Even if an underlying problem can be treated, you may still need analgesics (pain relievers).
Analgesics are good at relieving nociceptive pain, but not neuropathic pain. Chronic pain - long-lasting pain - may need other non-drug treatments as well.
Opioid analgesics are also known as narcotics. These are the strongest painkillers and are commonly used after surgery, for cancer, broken bones, burns, and various other situations. Even though opioids are not commonly used to treat non-cancer pain, their usage for non-cancer pain is becoming more widespread and acceptable. Some patients do not respond well to opioids and should not take them.
The patient will be given opioids in gradually increasing dosages. The ideal dose is reached when the pain is relieved and the side-effects are tolerable (increase any higher and the side effects become too much for the patient). Dosages should be generally much lower for older patients and infants.
The patient is administered opioids every few hours - each dose coinciding with the moment just before the pain starts becoming severe. Some patients are given higher dosages if the pain becomes more intense, while others are given other medications alongside the opioid. Pain can become more intense if the patient needs to move about, or if a wound dressing needs to be changed.
The dosage goes down if the pain intensity drops, until if possible, the doctor switches to a non-opioid analgesic.
People with kidney failure, liver problems, COPD (chronic obstructive pulmonary disease, dementia, tend to have more side effects when given opioids. The most common opioid side effects are drowsiness, constipation, nausea, vomiting, and itching. Generally, the side effects lessen as after time. Taking too much opioid can be dangerous. Patients who take opioids for long period become physically dependent and will have withdrawal symptoms when treatment is stopped - it is important that their dosage is tapered off gradually.
Nonopioid analgesics are used generally for mild to moderate pain. They are not addictive and their pain-relieving effects do not dwindle over time.
NSAIDs (nonsteroidal anti-inflammatory drugs)
These may be obtained either OTC (over-the-counter) or as a prescription medication, it depends on the dosage. Low dosage NSAIDs are effective for headaches, muscle aches, fever, and minor pains. At a higher dose they help reduce joint inflammation. There are three main types of NSAIDs, and they all block prostaglandins - hormone-like substances that cause pain, inflammation, muscle cramps, and fever.
- Traditional NSAIDs - the largest subset of NSAIDs. As is the case with most drugs, they do carry a risk of side-effects, such as stomach upset and gastrointestinal bleeding. The risk of side effects is significantly higher if the patient is over 60. At higher doses, they should only be taken when monitored by a doctor.
- COX-2 inhibitors - these also reduce pain and inflammation. However, they are designed to have fewer stomach and gastrointestinal side-effects. In 22004/2005 Vioxx and Bextra were withdrawn from the market after major studies showed Vioxx carried increased cardiovascular risks, while Bextra triggered serious skin reactions. Some other COX-2 inhibitors are also being investigated for side-effects. The FDA told makers of NSAIDs to highlight warnings on their labels in a black box.
- Salicylates - these include aspirin which continues to be a popular medication for many doctors and patients. If your plan to take aspirin more than just occasionally you should consult your doctor. Long term high dosage usage of aspirin carries with it a significant risk of serious undesirable side effects, such as kidney problems and gastrointestinal bleeding. For effective control of arthritis pain and inflammation frequent large doses are needed. Nonacetylated salicylate is designed to have fewer side effects than aspirin. Some doctors may prescribe nonacetylated salicylate if they feel aspirin is too risky for their patient. Nonacetylated salicylate does not have the chemical aspirin has which protects against cardiovascular disease. Some doctors prescribe low dose aspirin along with nonacetylated salicylate for patients who they feel need cardiovascular protection.