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Written by Robert J Lewis
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Pain starts at pain receptors that can be found throughout the body.
These pain receptors transmit electrical impulses along nerves to the spinal cord and onward to the brain.
Pain receptors and nerve pathways vary considerably throughout the body, and therefore the sensation of pain is different depending on its type and location. For instance, skin pain receptors are numerous and able to transmit information that is precise as to the location of the injury and its cause. The intestine can cause severe pain from something fairly harmless, such as trapped gas causing pressure inside it, but no pain should it be burned or cut. The brain can also not identify the exact location of intestinal pain or identify the exact cause of the pain.
Referred pain is pain felt in a part of the body different from where we would expect to feel it. For example heart disorders can cause pain in the left arm and fingers and a gall bladder attack can cause pain in the shoulders. This occurs because sensory nerves from different parts of the body share common pathways going to the spinal cord and brain. The medical term for referred pain is synalgia.
People’s ability to tolerate pain varies greatly. One person might complain considerably over the pain from a minor cut or graze, whereas another person may be able to withstand the pain of a major wound with little complaint.
Evaluating Pain
In analysing the cause of pain, there are several considerations:
· Where is the main site of the pain?
· How far from the main site of the pain does it radiate?
· What is the character of the pain, e.g., throbbing, aching etc
· How severe is the pain?
· How long has the pain been evident?
· How often does the pain occur – is it continuous, short sharp bursts etc
· If the pain is not continuous, how often does it occur e.g. every morning, every hour, after eating etc
· Are there any aggravating factors, e.g. pain after a hot drink, taking particular medication etc
· Is there anything that relieves the pain e.g. lying down, taking a hot bath etc
· Are there any associated factors e.g. when the pain occurs so does dizziness, a headache, nausea etc
· Sometimes a scale of one (no pain) to ten (severe) is used to help people to describe their pain. For children a chart of pictures of faces, from smiling to crying is used, so that the child can point to the picture that describes their pain.
· Neuropathic pain is caused by a problem occurring in the pathway of a nerve. The problem causes a disruption in the nerve signals, which the brain then interprets incorrectly. Neuropathic pain can cause sensitivity to touch as well as deep aching or burning type discomfort.
A good example of neuropathic pain is phantom limb pain. A person who has had a limb amputated can sometimes still feel pain in the limb, which is of course impossible; therefore the pain has got to come from nerves just above the site of the amputation, which the brain interprets as coming from the absent limb.
Pain is usually caused by an injury or disease, and therefore a treatable cause is usually sought.
However, stress for example can exaggerate pain, and some illnesses / diseases can be pyschosomatic (relating to both mind and body) but psychogenic pain (having an origin in the mind rather than in the body) may require treatment by a psychiatrist.
Drugs that relieve pain are called analgesics. Analgesics are divided into opioids and non-opioids.
Opioid analgesics are related to a poppy seed extract, opium. They block the transmission of pain signals by acting on sites within the central nervous system involved in pain perception. Opioid analgesics are the strongest analgesics and are often used to relieve severe pain, and because they also induce a feeling of euphoria and relaxation they are very good at relieving the stress that can occur with severe pain.
Non-opioids are less powerful as painkillers than the opioids and are believed to act by reducing the production of prostaglandins in the brain. Non-opioids include such drugs as paracetamol and the non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin.
Aspirin, one a number of NSAIDs (non-steroidal anti-inflammatory drugs) relieves pain, reduces fever and acts as an anti-inflammatory (reducing swelling and pain in inflamed tissue).
Paracetamol is a widely used analgesic, and if taken correctly, is one of the safest (allergic reactions are rare). However, an overdose of the drug can be extremely dangerous and cause possible fatal liver and kidney damage.
Aspirin is not recommended for children under 16 as it has been linked to Reye’s syndrome.
Aspirin can be effective in relieving the pain and inflammation of chronic rheumatoid arthritis, as well as more minor conditions such as headaches, sore throat and feverish illnesses.
Ibuprofen is also a commonly used NSAID, but one that has many fewer side effects than some of the others, and unlike aspirin it rarely causes stomach bleeding. It is an analgesic as well as an anti-inflammatory and is similar to aspirin in the way it works and can be used.
Topical anaesthetics, such as lotions, cream and ointments can be applied to the skin or used as a mouthwash to help treat a sore throat.
©Robert J Lewis 2006
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