Pain is, according to I.A.S.P. (International Association for the Study of Pain) an unpleasant sensory and emotional sensation and experience associated with, or described as, existing or potential tissue damage.
This definition involves both sensory (e.g. nociception) and emotional (e.g. distress) factors. “Actual” but also “potential” events are also formulated.
Pain usually signals a present or imminent tissue injury allowing prevention or worsening of the injury having a protective role. The only external stimulus causing injury that is not recognized until very late by pain is radiation.
The same nociceptive stimulus evokes different responses in the brain according to whether the subject is alert, awake, drowsy, in deep sleep, or under the influence of drugs/medication.
There are no objective measurements for pain. We can tell that a person is “in pain” just by their statements or actions. These actions can be measured objectively, but these measurements cannot assess the events that led to their occurrence. Nociceptive impulses can theoretically be measured but cannot define the degree of suffering nor the personal response. Measuring the response does not allow the stimulus to be identified and the stimulus cannot be measured.
Pain initiates a complex neuro-humoral response that initially helps maintain homeostasis in the presence of acute injury or disease. If these lesions are excessive, pain can become morbid. The physiological response of tissues to injury and acute pain is similar regardless of whether the source is surgery, trauma, burn or visceral damage. The intensity depends on the extent of the injury but also on each person’s experience.
Classification of pain
• Acute pain: defined as pain of short duration or with an identifiable source. Acute pain is the mechanism by which the body warns of tissue damage or disease. It is quick, sharp followed by a sharp pain. It is initially localized in a well-defined area, after which it spreads. This type of pain usually responds very well to medication.
• Chronic pain is that type of pain lasting longer than 6 months, usually associated with some type of injury or disease. This pain is either constant or intermittent and does not help the body to prevent the condition. The medication must be administered by specialized personnel.
• Physiological pain can be grouped according to the source and nociceptors (neurons that detect pain)
o Skin pain, caused by injury to the superficial tissues of the skin. The nerve endings of nociceptors end almost under the dermis, and because of the relatively high concentration of nerve endings they produce a well-localized, well-defined and short-lasting pain. Such pain occurs with accidental cuts, 1st degree burns or ulcerations.
o Somatic pain originates in ligaments, tendons, bones, blood vessels. It is detected by means of somatic nociceptors. Due to the small number of receptors in this area, the pain produced is “dull”, slightly localized and lasting longer than skin pain; it is usually found in dislocations or bone fractures.
o Visceral pain, pain due to internal organs. Visceral nociceptors are located inside internal organs or cavities. The more pronounced lack of nociceptors in this area causes the pain felt to be more intense and of longer duration compared to somatic pain. Visceral pain is extremely difficult to localize, and possible injuries of various organs cause the pain to be erased, that is, localized in a completely different part from the source. Cardiac ischemia is one such example of visceral pain. The pain sensation is usually located in the upper part of the chest, with limited localization, or as pain in the left shoulder, left arm, or even the fingers of the left hand. This can be explained by the fact that visceral receptors excite spinal cord neurons that also receive signals from skin tissues. The brain associates these excitations of the respective neurons as due to signals transmitted by the skin or muscles, the transmission of signals by visceral receptors is interpreted by the brain as coming from the skin. This theory that visceral and somatic receptors transmit signals to the same area of the spinal cord is called the Ruch hypothesis.
o Phantom limb pain occurs in people who have had a limb amputated, or in people who do not perceive physical stimuli. It occurs in amputees or paraplegics.
o “Neuropathic pain” or neuralgia is the pain resulting from the destruction of the neuron or its damage. This type of pain leads to the interruption of the ability of the nerve sensors to correctly transmit information to the thalamus, and from here the brain is the one that interprets the painful stimuli, it is obvious that the cause of the pain is not known.
Drug dynamics
To combat the pain, you can intervene:
- Preventing the formation of nerve influx, in sensitive endings: local anesthetics, muscle relaxants, vasodilators, anti-inflammatories.
- Preventing the transmission of nerve impulses, through sensitive fibers – the case of local anesthetics.
- Preventing the perception of pain, at the level of integration centers: general anesthetics, antipyretic analgesics, morphinomimetic analgesics.
Pharmacotherapy
Acute pains:
- Analgesics plus adjuvants (NSAIDs, antispasmodics, transchilisants).
- Non-opioid analgesics + adjuvants – mild or moderate pain.
- Weak opioids like codeine + non-opioids + adjuvants – persistent pain.
- Strong opioids – intense pain.
Postoperative pains:
– opioids: morphine, tramadol, codeine, pentazocine (Fortral)
– non-opioids: paracetamol (intravenous injectable – Perfalgan), metamizole (Algocalmin)
Neuralgia physiopathological medication (carbamazepine is used for trigeminal neuralgia).
Migraine: in the case of a crisis, aspirin + metoclopramide, ergotamine, dihydroergotamine, sumatriptan can be used.
Analgesics N 02 are divided into:
N 02 A -Opioids, N 02 B -Analgesics and antipyretics,
N 03 C -Antimigraines.
