”Pain” refers to residual pain; “ache” refers to an injurious sensation within the patient’s body. The so-called pain in modern medicine is a complex physiological and psychological activity, and is one of the most common clinical symptoms. It includes the pain sensation caused by injurious stimuli acting on the organism, and the pain response of the organism to injurious stimuli (somatomotor response and/or visceral vegetative response, often accompanied by strong emotional overtones). Nociception can serve as a warning that the organism is being harmed, eliciting a series of defensive protective responses from the organism. But on the other hand, pain has its limitations as an alarm (e.g., cancer, etc., when pain appears too late). And certain long-term severe pain has become an unbearable torture for the organism. Therefore, analgesia is an important task facing medical practitioners.
Etiology.
Pain is usually caused by injurious stimuli that lead to tissue damage. Mechanical stimuli such as cuts and blows, electrical currents, high temperatures, and physicochemical factors such as strong acids and bases can all be injurious stimuli. The release of potassium ions, 5-hydroxytryptamine, acetylcholine, bradykinin, histamine and other biologically active substances into the extracellular fluid during tissue cell inflammation or injury can also cause pain or nociceptive sensitization. The presence of local prostaglandins greatly enhances the nociceptive effect of these chemicals, while drugs that inhibit prostaglandin synthesis, such as aspirin, have an analgesic effect. The least differentiated free nerve endings in the skin and related tissues throughout the body act as injurious receptors, converting injurious stimuli of various energy forms into nerve impulses of a certain coding pattern, which are transmitted along the slow-conducting fine diameter myelinated and finest unmyelinated afferent nerve fibers, via the dorsal root ganglion to the relevant neurons in the posterior horn of the spinal cord or the nucleus of the spinal tract of the trigeminal nerve, and then via the contralateral ventral lateral cord to the higher pain center, the The higher pain centers, the thalamus, other brain regions and the cerebral cortex, cause pain sensation and response. At the same time, the non-painful information such as touch and pressure transmitted by the fast-conducting thicker diameter afferent nerve fibers has reached the relevant brain regions of the CNS first and interacted with the painful information transmitted by the fine fibers.
Mechanism.
The gate control theory of pain emerged in 1965, suggesting that certain nerve cells in the posterior horn glia of the spinal cord have a gate effect on the transmission of pain information and control the inward transmission of pain information, and are themselves influenced by the activity of coarse and fine afferent fibers of peripheral nerves and the action of higher central downward control. The contrast between the coarse and fine afferent fiber activity regulates the opening and closing of the gate: afferent impulses from fine fibers open the gate and transmit pain information inward; afferent impulses from coarse fibers close the gate and interrupt the transmission of pain information, while activating the higher centers of the brain to control the gate activity through the downstream control system. In 1970, it was further discovered that mild electrical stimulation of the periaqueductal gray matter of the midbrain or microinjections of morphine into the area could cause a significant analgesic effect, and the concept of endogenous pain suppression system was proposed. Then, it was found that the nerve cells in the periaqueductal gray matter were rich in enkephalin receptors, and a large amount of enkephalins were present around them. The reason why endogenous enkephalins and exogenous morphine have powerful analgesic effects is that these substances can bind to the opioid receptors on nerve cells. In addition to endogenous peptides such as enkephalins, endorphins, and prednisolone and their receptors, neurotransmitters such as 5-hydroxytryptamine and their corresponding receptors are also involved in the downstream control or endogenous pain suppression system. It is a sensation usually caused by an injurious stimulus and accompanied by an unpleasant emotional experience. The stimulus may come from an external source and act on the surface of the body, such as a blow from an external object or contact with extreme temperatures, and the sensation is precisely localized and transmitted to the brain via free nerve endings via specific nerve channels. Stimuli can also originate from within the body and be transmitted via afferent parts of visceral nerves, which are more ambiguously localized. In adults, pain is also often due to psychological causes without an obvious direct physical cause. In general, pain is said to be susceptible to moods such as attention, suggestion, and anticipation; both a person’s past experiences and the prevailing situation introduce a great deal of variability into pain.
Biological significance.
Pain is a signal symbolizing danger, prompting people to act urgently to avoid danger and remove harm. In medicine, pain is one of the most common symptoms, the location of the pain often indicates the location of the lesion, and the nature of the pain indirectly indicates the type of pathological process. On the other hand, it is the responsibility of the physician to help the patient to eliminate pain without interfering with the observation of the condition. Thus, both anesthetic pain relief and general analgesic measures are an important subject of medical research.
Nature.
The nature of pain is sometimes extremely difficult to describe; one can usually indicate the site and extent of pain, but it is more difficult to state its nature precisely. People usually describe it by analogy, such as complaining of stabbing, burning, throbbing, dull, or cramping pains. Pain can cause somatic behaviors such as avoidance, complaints of pain, crying, and shouting, and can be accompanied by physiological responses such as increased blood pressure, increased heart rate, and dilated pupils, but none of these are unique to pain. Pain as a sensory activity can be measured with a pain meter. The lowest pain experience that the body can perceive is called the pain threshold, and its value varies by age, sex, occupation, and site of measurement. Pain as a subjective sensation does not have any kind of neurophysiological or neurochemical changes that can be considered as specific indications to determine the presence or absence or intensity of pain, especially chronic pain. The diagnosis of pain relies heavily on the patient’s chief complaint. Pain can be classified as headache, chest pain, abdominal pain and low back pain according to the location of the pain source. However, some visceral disease stimuli are received by visceral receptors, afferent by sympathetic nerve fibers and enter the posterior roots of spinal nerves and sensory cells of the posterior horn of the spinal cord through the sympathetic trunk and traffic branches, and pain appears in the skin of the corresponding segment, that is, the pain site is not at the source of pain but in a body surface area quite far from the real pain source, and this kind of pain is called involved pain, such as the pain of angina pectoris often radiates to the left shoulder, arm and wrist. According to the system of pain appearance, pain can be divided into cutaneous pain, neuralgia, etc., in which pain caused by damage to central nerve structures is called central pain. Pain can also be divided into acute pain, chronic pain and mild, moderate and severe pain according to the time course and degree of appearance. According to the cause of pain, inflammatory pain, cancer pain, etc. can be distinguished. Some amputees and even patients with congenital limb deformities can still feel pain in limbs that no longer exist or never existed at all, which is called juvenile limb pain. Pain in people who are extremely depressed and in some people with schizophrenia or epilepsy may be one of their hallucinatory symptoms.
Classification.
According to the current state of development involving pain diagnosis and treatment items.
1. acute pain: pain from acute injuries to soft tissues and joints, post-surgical pain, obstetric pain, acute herpes zoster pain, gout.
2, chronic pain: soft tissue and joint strain pain or degenerative pain, discogenic pain, neurogenic pain.
3, intractable pain: trigeminal neuralgia, post-herpetic neuralgia, disc herniation, intractable headache.
4, cancer pain: advanced tumor pain, tumor metastasis pain.
5. special pain categories: thrombotic vasculitis, intractable angina pectoris, idiopathic chest and abdominal pain.
6, related disciplinary diseases: early retinal vascular embolism, sudden deafness, vasospastic diseases, etc.
Classification of pain level.
1.Micropain seems to be painful but not painful, and often appears in compound with other sensations. Such as itching, soreness, heaviness, discomfort, etc.
2.Light pain pain limitation, pain response appears.
3.Very painful pain is more intense, and the pain response is strong.
4, severe pain pain is unbearable, pain response is strong.
Classification of the nature of pain.
1, dull pain, soreness, swelling, boring pain.
2.Sharp pain, stabbing pain, cutting pain, burning pain, colic.
Classification of pain forms.
1.drill-top-like pain.
2, violent crack-like pain.
3. throbbing-like pain.
4.tearing-like pain.
5.drawing-like pain.
6.pressure-like pain.
Levels of pain.
The World Health Organization (WHO) classifies pain into 5 degrees as follows.
1.0 degree: no pain.
2. degree I: mild pain, intermittent pain without medication.
3. degree II: moderate pain, continuous pain that affects rest and requires painkillers.
4. Ⅲ degree: severe pain, persistent pain that cannot be relieved by non-medication.
5.Degree IV: severe pain, continuous pain with changes in blood pressure and pulse rate.
Prevention and treatment.
Each advance in the study of theoretical mechanisms of pain brings new strategies and measures to the practice of pain prevention and treatment. Any measures that attenuate fine fiber afferents and/or enhance fiber afferents can help treat or relieve pain. In addition to sealing or blocking the fine fiber activity of afferent pathways with traditional local anesthetics, physical therapies such as tui na, massage, heat therapy, and electrotherapy can also relieve pain. Therapies such as acupuncture and mild electrical nerve stimulation have been widely used in the treatment of pain, especially chronic pain. In drug therapy, in addition to non-narcotic analgesics that inhibit prostaglandin synthesis (e.g. aspirin) and narcotic analgesics that bind to opioid receptors (e.g. morphine), which are commonly used for pain relief, some non-steroidal anti-inflammatory drugs have also started to be applied. The discovery of 5-hydroxytryptamine, norepinephrine, and certain peptides involved in the downstream inhibitory pathway has also provided new application prospects for pain control. Based on the influence of psychological factors in pain production and control, psychotherapy such as placebo, hypnosis, suggestion, relaxation training and biofeedback to enhance positive emotional activity, as well as any other medication or treatment that enhances confidence and alleviates fear, can help relieve or reduce pain. Even the joy of childbirth, concentration of attention, intense fighting, and certain special rituals can relieve the sensation of pain and suffering to some extent. Surgical treatments that permanently disrupt or interrupt the upstream anatomical pathways of pain, used in some cases of last resort, can hardly achieve long-term pain relief. Surgeons are thus increasingly favoring non-invasive treatments that use instruments to electrically stimulate the relevant parts of the endogenous pain inhibitory system (e.g., the posterior cord of the spinal cord in which the thick fibers travel upward). This stimulation therapy can produce encouraging results.
Since pain has defensive and protective significance for physical health and not all pain is a consequence of a serious disease, not all pain requires pain relief. In cases where the diagnosis of the disease would be in doubt if the pain were eliminated, analgesics should not be used lightly until the diagnosis is confirmed. In order to relieve the pain of long-lasting chronic pain, it is also advisable for the patient to first develop confidence in overcoming pain and learn the art of living a normal life and even maintaining work in the presence of pain and suffering, with appropriate rest and physical therapy if necessary. Superficial pain of body surface structures can generally be relieved with non-narcotic painkillers. Deep somatic pain as well as visceral pain often requires the use of less addictive synthetic analgesics, such as pethidine. The most powerful morphine for pain relief is often used for intractable pain caused by advanced cancer, but its addictive properties are not necessary; pain-relieving surgery can be used if necessary. For pain patients with strong mental tension or psychological factors, sedative drugs and psychotherapy can be applied.
Cancer pain treatment.
Cancer pain patients are traditionally classified as cancer pain, non-cancer pain or both. Treatment of these patients is mainly based on different tumors, different anatomical locations and familiar typical symptom characteristics, and understanding the etiology related to cancer pain so as to recognize the complexity of cancer pain and its treatment. Explosive pain is defined as a sudden onset of pain during the treatment with effective analgesic drugs. Eruptive pain can be classified as somatic pain, visceral pain, neuropathic pain, and mixed pain. 38% of these pains are severe or intense, with an average of 4 episodes per day ranging from 1 to 14, most patients are unpredictable, 72% last less than 30 minutes, and 75% are unsatisfied with pain control. In conclusion, explosive pain is common among cancer pain patients, frequent, short duration, unpredictable, not necessarily related to chronic pain, and more difficult to treat.
The treatment of explosive pain is predicated on the importance of nurse detection, the application of measurement tools, accurate assessment, and the requirement for rapid onset and short maintenance of medication control for the explosive nature. The application of sublingual fentanyl titration (SLFC) has been reported to be effective in patients, with 6 patients having pain relief in 10 minutes, 9 patients having relief in 15 minutes, 18% of patients having very good results, 36% better, 28% fair and 18% poor results. Compared with commonly used analgesic drugs, sublingual fentanyl drops had an excellent rate of 46%, an average rate of 36% and a poor rate of 18%. The advantages of sublingual fentanyl drops are easy application, rapid onset of action, and no systemic systemic side effects such as associated drowsiness. Only 2 patients reported dry and bitter mouth, 2 cases found it difficult to retain the drug under the tongue, and 64% of patients agreed to continue applying this drug. Although sublingual fentanyl drops are safe and effective, randomized double-blind comparative studies and dose ranges need to be further explored.
Transoral mucosal fentanyl titration (OTFC) is also an option. Compared to morphine tablets, OTFC is fast-acting and effective, with side effects of drowsiness, dizziness, nausea, vomiting, and confusion, and its dosage form can be made into a good taste or lollipop, which is extremely attractive to pediatric patients but should be prevented from being accidentally ingested. OTFC can be tried when immediate morphine is not effective in controlling explosive pain, and some people have tried intranasal sufentanil treatment, which is also effective.