What Is Pain;Medical Causes,Treatment And Referred Pain

What is Pain.It is a personal experience, and communica­tion about it depends upon the experience and vocabulary of the sufferer, just as its interpretation depends upon the experience and bias of the lis­tener. The physician, charged with alleviating suffering, must necessarily be concerned with pain. Being human, the physician experiences pain, and his attitudes toward it may modify his judgment. He may be in curiously sympathetic, too anxious to relieve pain without understanding its nature or source. He may too quickly dismiss the complaint, not recognizing its importance as a manifestation of disease. He may also fail to recog­nize that pain may be the manifestation of complex and stressful problems that face the patient. Ultimately, it is the physician who must deter­mine the source of pain and select a means of relieving it.

Pain may produce suffering, but all suffering is not pain.

A person may suffer from loneliness, fear, anxiety,, or other emotional responses to stress. However, pain.also produces fear, anxiety, and loneliness; for pain is the signal that warns of a threat to the. integrity of the organism. This threat may alter the life pattern of a person and so color his interpretation of what he is experi­encing that the exact nature of his problem is obscured. The skilled physician must learn to separate the patient’s reaction to pain from his perception of pain; and, in obtaining this separa­tion, he must view the patient in the setting  of his past, his family, and his community.

The vocabulary for describing pain is limited.

When interviewing, it is best to begin by asking the patient to describe what he feels without suggesting adjectives. Avoid leading questions, but direct the interview as necessary by asking such questions as: Where is the pain? Does it go anywhere else? Is it continuous? How does this pain interfere with your life? When the patient’s descriptive resources are exhausted, directed questions regarding quality, radiation, and tem­poral phasing may be used to round out the de­scription. Generally, the history alone distin­guishes the variety of pain, its likely source, and its cause. Examination provides corroborative data.

The alleviation of pain not only is dependent upon correction of its cause but also may require modification of the patient’s attitude toward him­self, his life situation, and his disease. The ap­proaches to treatment of pain will be dealt with after consideration of the anatomy and physiology of pain.

What Is Pain And Pain Pathways In Medication.

Until the late nineteenth cen­tury, pain was not included among the primary sensations, but was considered to arise from the intense stimulation of any afferent nerve or its terminals. The demonstration is a human that interruption of the spinothalamic tract stopped pain sensation below the level of the lesion proved that within the neuraxis the sensation of pain is conducted along a specific pathway. The exact pathways for pain conduction in the peripheral nervous system have remained open to question. However, most workers now believe that the small, finely myelinated fibers that occupy the lateral portion of the dorsal root and enter Lissauer’s tract to synapse in the substantia gelatinous and other nuclei of the dorsal gray horn are the fibers that subserve pain peripherally.

The means of transmission of the many shadings and gradations of pain remains to be clarified. Currently, it appears that pain is conducted over specific pathways, but complex integration of signals occurs at several levels. The first level is at the end organ. Finely branched, undifferentiated endings subserve pain. In skin these form an intricate, interlacing network. Partial denerva­tion of an area of skin alters the quality of pain elicited from that site because of the interruption of the normal patterns of firing of several axons when that particular area of skin is stimulated.

Painful Stimuli

Tissue injury is the adequate stimulus for pain. This is evident when skin is pierced, abraded, or burned and when deeper tis­sues are compressed and bruised. When tissue is injured, the release of various chemical products serves to excite pain. Pain may also be elicited by stretching hollow viscera or by tugging on omentum or distorting the vessels at the base of the brain. This type of pain less clearly results from tissue injury. Among the possible chemical exciters of pain are hydrogen ions, potassium ions, 5-hydroxytryptamine, histamine, polypep­tides from protein breakdown (kinins), and acetyl­choline.

It is not proper to refer to these as chemi­cal mediators of pain, for this implies a specific response between the end organ and the substance. A specific chemical mediator analogous to synap­tic transmitter substances has not been identified for sensory end organs. The local release of these chemical products of tissue injury modifies the sensitivity of the pain endings. Thus, pressure over an inflamed joint or a light touch applied to a burned area produces pain. The prolonged pain from a first-degree burn results from the accumu­lation of these products of tissue injury.

What Is Referred Pain.

The referral of pain from the primary locus of stimulation to another site may occur with awareness of the primary site —for example, in a toothache, pain may be referred to the temporomandibular region —or without aware­ness of the primary site, as in referral of pain from a subdiaphragmatic abscess to the posterior shoulder region of the same side. Deep structures such as the heart and hollow viscera are not spe­cifically recognized as being painfully stimu­lated, the pain being referred to somatic areas that are more clearly recognized by the patient as a part of himself. An exhaustive catalogue of all the combinations of referred pain from deep struc­tures is not within the scope of this article. How­ever, there are common sites of pain referral worthy of consideration.Referred pain in the head is discussed in the article on Headache.

In the trunk, painful stimuli arising in the middle third of the esophagus are referred substernally. In the lower third of the esophagus, the stomach, the duodenum, and the remainder of the small intestine, pain is referred to the epigastric region. Pain arising from the large bowel is referred to the hypogastric region. Thus, the pain of duodenal ulcer is perceived as in the epigastrium, whereas the pain of appendi­citis is periumbilical and in the lower abdomen. The spread of referred pain depends upon the duration and intensity of the painful stimulus.

High intensity afferent input over a prolonged period results in spreading hyperexcitability in the segment of the cord that the afferent fibers enter and to adjacent segments. Disease processes may spread from viscera to involve the abdominal wall. When the parietal peritoneum is thus stim­ulated, pain may become more localized to the somatic region supplied by the segment involved. Hence, a posteriorly perforating duodenal ulcer causes pain radiating into the back, and acute pancreatitis localizes to the back close to the anatomic location of the pancreas.

Pain from the genitourinary tract is referred to the hypogastric area and the flanks. Ureteral colic causes pain along the border of the rectus abdominis spreading into the flank and groin. Bladder distention causes pain in the suprapubic area. Pain from the urethra is referred directly to the penis and perineum. Testicular pain is re­ferred to the suprapubic area.

Do you Know Insensitivity of Pain?

In normal persons, pain serves to protect the body from exogenous injury and internal disease. Pain demands attention; persistent pain causes withdrawal of the organism, rest of the injured part, and avoidance of further injury. These are normal reactions that protect the injured tissue and promote healing. The im­portance of these reactions is dramatized in pa­tients who are insensitive or indifferent to pain. The complete absence of any reaction to pain has been described in about 65 persons.

This rare lack of response to pain has been termed “indifference” by some and “insensitivity” by others. Both terms are probably correct. The clinical descriptions of many of the cases suggest that the patients are extraordinarily stoic and can endure remarkable pain without apparent awareness. In other cases, particularly those recognized in infancy, a true insensitivity seems more likely. These infants cut and burn them­selves without notice. Bones are broken and go unheeded. The major weight-bearing joints are destroyed by the uncommon degree of trauma that they sustain. The utter disregard for the integrity of their bodies is dramatic proof of the importance of pain as a warning of tissue injury. Only two autopsies have been reported, and in one no anatomic explanation for insensitivity to pain could be identified. In the other, Lissauer’s tract was absent, and there were no small, finely myelinated fibers in the dorsal roots.

Treatment of Pain.

Insensitivity or indifference to pain is not the common human experience. During a lifetime, man is exposed to a multitude of pain-inducing injuries-and diseases. When pain is persistent, overwhelming, or frightening, he turns to the physician for help. To the patient and to the physician, pain signifies an unnatural state that warns of tissue injury and disease. The primary attention is directed toward determining the source of the pain and correcting the cause. Generally, relief follows.

However, pain may occur as a result of disease that cannot be eradicated, as in widespread carcinoma. Pain may also be the primary manifestation of diseases of the central and peripheral nervous system, such as tic dou­loureux, postherpetic neuralgia, and causalgia. Finally, pain may be a manifestation of reaction to life stresses, as in migraine headache, tension headache, and myalgias that can involve the en­tire musculoskeletal system. Alleviating pain requires that the physician utilize his knowledge of the origin and transmission of pain and that he understand the complex interactions between perception and reaction to pain. No drug or opera­tion is a panacea for all pain.

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