1. Introduction
Pain has been defined by the International Association for the Study of Pain as “An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage” [1].
The implication of this definition is that pain may arise from any a part of the pain pathway. Frequently, however, pain is caused by trauma activating nociceptors. Conversely, the cause for a pain could also be solely within the brain, even though the sufferer will project the pain onto a specific bodily location. More often and particularly in chronic pain there could also be a mix of an initial and possibly ongoing peripheral stimulus which in turn will start off central sensitization within the central nervous system.
Most pain arises from stimulation of specialized receptors (mechanoreceptors for touch, thermoreceptors for temperature and chemoreceptors for chemical stimulation) on specific primary sensory neurons (nociceptors) that are widely distributed within the skin and musculoskeletal system [2]. Myelinated Aδ fibres convey sharp pain sensation from thermo- or mechanoreceptor stimulation and are responsible for rapid pain transmission and reflex withdrawal. Receptors responding to pressure, heat, chemical substances (e.g. histamine, prostaglandins, acetylcholine) and tissue damage (polymodal receptors) are related to unmyelinated C-fibre endings, and are responsible for dull pain sensation and immobilisation of the affected part.
Understanding the anatomical pathways and neurochemical mediators involved in noxious transmission and pain perception is vital to optimizing the management of acute and chronic pain [3]. The International Association for the Study of Pain defines pain as “an unpleasant sensory and emotional experience related to actual or potential tissue damage, or described in terms of such damage.” Although acute pain and associated responses may be unpleasant and often debilitating, they serve important adaptive purposes. They identify and localize noxious stimuli, initiate withdrawal responses that limit tissue injury, inhibit mobility thereby enhancing wound healing, and initiate motivational and affective responses that modify future behavior. Nevertheless, intense and prolonged pain transmission, additionally as analgesic undermedication, can increase postsurgical/traumatic morbidity, delay recovery, and result in development of chronic pain.
2. Materials and Methods
Regardless of the type, the pain appears suddenly. Pain is a very uncomfortable feeling that tells how the human body is damaged or injured. These are the starting points for dealing with the topic of pain that is present in all areas of medicine.
The author used the desk research method and the sources available to him.
3. Results
As already mentioned, pain can appear suddenly. There are several types of pain that differentiate in duration and intensity. The results published in this paper can help everyone: on the one hand, health professionals, and on the other hand, they can help patients.
4. Discussion
4. 1. Categorization
Pain may be categorized per several variables, including its duration (acute, convalescent, chronic), its pathophysiologic mechanisms (physiologic, nociceptive, neuropathic), and its clinical context (eg, postsurgical, malignancy related, neuropathic, degenerative) [3]. Acute pain follows traumatic tissue injuries, is mostly limited in duration, and is related to temporal reductions in intensity. Chronic pain could also be defined as discomfort persisting 3–6 months beyond the expected period of healing. In some chronic pain conditions, symptomatology, underlying disease states, and other factors could also be of greater clinical importance than definitions based on duration of discomfort.
With reference to a more moderen classification, pain states could also be characterized as physiologic, inflammatory (nociceptive), or neuropathic. Physiologic pain defines rapidly perceived nontraumatic discomfort of very short duration. Physiologic pain alerts the individual to the presence of a potentially injurious environmental stimulus, like a hot object, and initiates withdrawal reflexes that prevent or minimize tissue injury.
Nociceptive pain is defined as noxious perception resulting from cellular damage following surgical, traumatic, or disease-related injuries. Nociceptive pain has also been termed inflammatory because peripheral inflammation and inflammatorymediators playmajor roles in its initiation and development. In general, the intensity of nociceptive pain is proportional to the magnitude of tissue damage and release of inflammatory mediators.
Somatic nociceptive pain is well localized and generally follows a dermatomal pattern. it's usually described as sharp, crushing, or tearing in character. Visceral nociceptive pain defines discomfort related to peritoneal irritation as well as dilation of smooth muscle surrounding viscus or tubular passages. It's generally poorly localized and nondermatomal and is described as cramping or colicky. Moderate to severe visceral pain is observed in patients presenting with bowel or ureteral obstructions, in addition as peritonitis and appendicitis. Visceral pain radiating during a somatic dermatomal pattern is described as referred pain. referred pain is also explained by convergence of noxious input from visceral afferents activating second-order cells that are normally responsive to somatic sensation. because of convergence, pain emanating from deep visceral structures is also perceived as well-delineated somatic discomfort at sites either adjacent to or distant from internal sites of irritation or injury.
4. 2. Character
It is worth taking some time to understand the character of the patient’s pain [4]. Cardiac pain is also severe but is rarely felt as ‘sharp’: the patient will frequently describe a sensation of pressure as if there's a significant weight on their chest. Pleuritic chest pain is often because of inflammation of the pleura and should be caused by pneumonia, less specific infection (e.g. viral pleurisy), embolism, or chest wall pain due to trauma or localised inflammation. Severe, sharp or tearing pain of sudden onset suggests dissecting thoracic aneurysm, though it's worth noting that during this condition the pain is slightly more likely to be within the anterior chest than within the classically described location of the back. Pain reproduced by specific movements may have a musculoskeletal cause like a muscle injury or nerve root irritation, but, chest wall tenderness is generally unhelpful and may even be misleading.
Pain that radiates into the neck, jaw, one arm or both arms often suggests a cardiac cause. In some patients, particularly the elderly or diabetic patient where autonomic function is impaired, chest pain or discomfort is also entirely absent and jaw or arm pain may be the only symptom of significant cardiac ischaemia. Pain radiating into the back suggests aortic dissection, but isn't uncommon in acute coronary syndrome. Pleuritic pain rarely radiates, but some nerve entrapment syndromes may cause a shooting ‘electric’ pain to or from the shoulder or spine. Oesophageal pain sometimes radiates to the shoulder or jaw, whilst diaphragmatic irritation secondary to intra-abdominal pathology (such as bowel perforation or ruptured ectopic pregnancy) may be felt as pain within the shoulder tip. This can be a type of referred pain because the nerve roots that supply the diaphragm also supply the shoulder.
4. 3. Perception
It is a typical belief that the intensity of pain is closely, if not directly, associated with the extent of injury [5]. This belief is grossly untrue since pain and suffering are more closely related to the meaning of pain and psychosocial factors, including learning history.
While injury severity or degree of tissue damage isn't consistently associated with pain ratings, there are variety of other factors that have consistent relations.
All things considered, demographic factors, like age, education, and marital status, have fairly weak relations with pain intensity ratings across studies. There are, however, two noteable exceptions. First, men tend to have higher pain tolerance and rate similar sorts of pain as less intense as compared to women. There could also be several reasons for this discrepancy, including differences in learning histories, in addition as psychological, social, and biological factors. Second, there's a moderate amount of evidence that race tend to rate pain experiences as less intense and less distressing compared to other ethnicities, particularly black and Hispanic individuals. Perhaps most concerning, several studies have found evidence of disparities among the ethnicities in access to pain treatment.
Across studies, settings, and populations, psychosocial factors are the strongest predictors of pain. the foremost studied emotional experiences include depression and anxiety (including anxiety specific to pain), although anger has been the topic of study as well. In general, as these emotional experiences worsen, pain ratings are higher.
Other factors which can influence the perception, and thus the assessment, of pain are atmospheric condition and time of day when the measurement is carried out. Patients suffering from chronic pain often have exacerbations of their symptoms because the weather changes. Many of those observations are reflected in folklore – e.g. ‘‘aches and pains, coming rains.’’ the foremost frequently reported meteorological factors which alter pain complaint are temperature and humidity. These climatic conditions alter pain perception mostly in disorders involving joints, muscles, and postoperative scars. Most patients are tuned in to a fluctuation in pain intensity according to the time of day. Those patients who don't convey regular trends of pain intensity throughout the day also report significantly higher ratings of emotional stress. Ideally, patients should rate their pain at the identical time of day. there's no control over atmospheric condition but the observer should be aware that it may affect pain scores.
4. 4. Chronic Pain
Chronic pain is a complex condition with multiple physical, physiological, psychological, emotional, and social components [6]. It's usually related to significant impairment of well-being and limitations on relationships between the affected individual and his or her family and friends, though the impact of chronic pain varies greatly among affected individuals.
Over the past few decades, the understanding of chronic pain and therefore the available management options have vastly improved, but many limitations, challenges, and opportunities for improvement persist. as an example, many patients report positive impact from the increased use of opioid medications, but there has been growing concern and alarm about an epidemic of misuse and abuse. A lack of documented long-term efficacy and significant adverse events affecting 30–40% of patients are some of the opposite concerns. The interventional techniques, on the other hand, have shown efficacy in a subset of patients, though many still suffer from intractable, severe pain despite the use of all currently available treatments.
Intrathecal drug delivery systems (IDDS), known as pain pumps, offer an alternate treatment option within the management of chronic, severe pain for those patients who haven't responded well to less invasive, more commonly used lines of treatment. Recently published reports have presented an algorithmic protocol utilizing IDDS within the management of chronic, severe pain that's not responsive to other treatment, showing good success in terms of pain relief and functional improvement. It's very clear that patient selection could be a crucial element in achieving good outcomes from the use of a drug delivery system for chronic, severe pain. The important point is matching the right patient with the right therapy at the right time. Selecting a suitable patient and ensuring that the patient is ready and optimized for the proposed therapy will positively impact outcomes. The clinician cannot change other aspects of the disease process, like the previous occurrence of an injury, the predisposition to disease progression, or how the patient has dealt with the pain within the past, but patient selection that matches the right patient with the right therapy at the right time can have the best impact in producing positive outcomes.
4. 5. fMRI
Brain functional MRI (fMRI) and positive emission tomography (PET) have helped clinicians better understand central sites of pain processing by revealing, in real time, discrete cortical and thalamic regions that are activated by noxious input [3]. Cortical pain processing could also be divided into sensory-discriminative and affective-motivational components. The neocortical sensory discriminative domain localizes the stimulus and determines its intensity. This domain can be assessed using visual analog scales or numerical rating scales. The limbic affective-motivational domain determines the unpleasantness and other qualities of pain. Connections made with cells in frontal area and amygdala also underlie emotional and behavioral responses like fear, anxiety, helplessness, and learned avoidance.
Cortical sensory, behavioral, cognitive, and motor responses to peripheral noxious stimuli is studied by brain imaging. Brain imaging studies, including fMRI and PET scanning and brain spectroscopy, offer a bridge between basic research and understanding mechanisms underlying clinical pain states. These techniques have provided evidence that experimental pain is processed at interconnected cortical regions, with each having distributed functions. Functional imaging (PET scan and fMRI) techniques allow clinicians to visualise neuronal targets related to pain modulation and perception in real time. Considering the multidimensional subjective experience of pain, functional imaging studies have revealed those CNS (central nervous system) regions that are primarily involved in controlling the sensory discriminative, attentional cognitive aspects, behavioral/affective reactions, and motor responses to pain. Positron emission scan images will be used to visualize changes in regional cerebral blood flow (rCBF) induced by localizing and subjective aspects of noxious perception, whereas fMRI has higher spatial and temporal resolution and may measure both the change in rCBF in addition because the change in neuronal activity in response to pain perception. Considering that the PET scan is that the gold standard for rCBF measurement, regions identified or linked to pain perception have demonstrated fairly consistent noxious-induced alterations across several studies. In these trials, a standardized nociceptive stimulus consistently activated several well-connected regions within the CNS, including the contralateral insula, secondary somatosensory cortex (S2), and also the anterior cingulate cortex (ACC). Primary somatosensory cortex (S1), is primarily responsible for acute noxious localization, whereas the insular cortex plays a task in pain anticipation. Thalamus, brain stem, cerebellum (CBLM), supplementary motor area (SMA), and also the primary motor cortex are some of the other regions that become activated, although not as consistently as the insula, S1, and ACC.
4. 6. Modulation
Pain modulation includes both inhibition and facilitation [6]. Dorsal reticular nucleus, also called subnucleus reticularis dorsalis (DRt) within the brain stem balances the descending inhibition and facilitation processes. DRt receives nociceptive inputs from the ascending spinoreticular pathway and communicates with the periaqueductal grey matter (PAG) and rostral ventromedial medulla (RVM) in addition because the thalamus and amygdala and sends pain modulatory projections to the spinal cord. Electrophysiologic studies and lesioning experiments propose that pain modulation occur through a PAG relay to RVM then to the spinal cord. Descending projections from RVM travel through the dorsolateral funiculus (DLF) to the dorsal horn of spinal cord, where they synapse with primary afferent fibers, secondary neurons as well as interneurons. The modulation effect is biphasic. Low intensity stimuli to RVM produce inhibitory effect of nociception, while high intensity stimuli enhance the response. Endogenous opioids, serotonin, noradrenaline are the most neurotransmitters involved within the descending pathway. Descending facilitation and loss of descending inhibition pathway is also involved in chronic pain. Understanding of pain pathways and their modulations will provide basis for multimodal analgesia and chronic pain.
4. 7. Abnormalities
It has been estimated that 35% of chronic pain patients have some form of coexistent psychological and or psychiatric abnormalities [7]. Psychological evaluation prior to implantation of a pain pump is essential. The goal of the psychological evaluation is to detect any underlying untreated or unaddressed psychological disorders; to reemphasize adequate, realistic, achievable goals and expectations; and to give the patient and therefore the family or caregiver a chance to debate the full process with a psychologist who could be a member of the care team, allowing questions and ensuring adequate understanding of the process.
The goal isn't to have all psychiatric disorders and concerns “treated” prior to implementation; we believe it's more appropriate to think about it a process of “optimization” rather than a treatment. It's not uncommon for some psychological concerns or diagnoses to coexist in chronic pain patients, but evaluation and optimization are shown to greatly enhance the outcome following implantation. The psychological evaluation should also be able to shed some light on any cognitive impairment like early dementia, early Alzheimer’s disease, or chronic brain injury conditions. Any impairment or difficulties with comprehending educational material should also be pointed out within the psychological evaluation.
4. 8. Comorbidities
Patients with chronic pain usually suffer from multiple coexisting medical disorders [3]. Understanding the character, severity, and complexity of these disorders is of great importance in determining the character and timing of the proposed intervention, a pump implant, and in maintaining optimal outcomes following implantation. the foremost common medical comorbidities of chronic pain patients are diabetes mellitus, hypertension, obesity, and sleep disorders.
The interplay between chronic deconditioning, obesity, and diabetes can't be overemphasized, as lack of activity with deconditioning fosters the onset and progression of obesity. There's no clear evidence that pain pumps are especially useful in treating diabetic neuropathy per se, but the impact of diabetes on wound infection and wound healing has been documented in multiple clinical scenarios. Patients with diabetes should be thoroughly counseled regarding the increased risk of wound infection and delayed wound healing. It's been documented that achieving glycemic control and normal hemoglobin A1c immediately prior to surgery doesn't lower the incidence of infection or delayed wound healing, but long-standing, chronic management and maintenance of adequate glycemic control for a length of time before surgery may lower the incidence of infection related to diabetes mellitus.
4. 9. Control
Pain is one of the factors that trigger the injury response, resulting in metabolic, endocrine and water and electrolyte changes that will have an adverse effect on recovery, and current evidence indicates that effective pain control is capable of modifying these responses [8]. Fractures cause significant pain, which might be exacerbated by movement, and so for patients with a fractured neck of femur, pain control within the immediate post-trauma period will be difficult to manage effectively. While the emergency management of major trauma has been extensively analysed within the last few years, trauma analgesia has received comparatively little attention. Reluctance to deliver adequate pain relief within the acute stage of trauma originates, at least in part, from a widely held belief that analgesia may precipitate or disguise cardiorespiratory deterioration. In reality, current evidence shows that uncontrolled pain may actually harm patients by impairing cardiac, pulmonary and endocrine functioning.
A growing body of research supports the link between serious post-operative complications like deep vein thrombosis, infections, sepsis, paralytic ileus, acute renal disorder and uncontrolled pain. Additionally, pain interferes with sleep, impairs immune functioning and lowers the quality of life for the patient. The physiological changes that result from pain and injury are a results of activation of both the peripheral and also the central nervous systems. Trauma and injury induce a complex ‘stress response’ characterised by hormonal changes and an inflammatory response resulting in malaise, hyperthermia and immunosuppression. Effective analgesia is capable of modifying many of the pathophysiological responses, preventing or reducing complications and assisting recovery. Regular pain assessment and evaluation of effect are vital by nursing staff to ensure that patients don't experience severe pain and side effects from analgesia[9].
4. 10. Critically Ill Patient
Admission to a critical care setting is usually a threat to the life and wellbeing of the patient [9]. Critical care nurses often see the intensive care unit as an area where fragile lives are carefully analyzed and cared for. Patients and their families often see admission to critical care as an indication of imminent death. Understanding what the critical care setting signifies to patients may help health care professionals take care of their patients. However, communication with a critically ill patient is usually challenging and frustrating because of the barriers that exist associated with the patient’s physiological condition, or the presence of endotracheal tubes which inhibit communication, or mind altering medications, or other conditions that affect cognitive function.
Researchers have long studied the patient experience associated with an ICU (intensive care unit) stay. Many patients recall negative feelings associated with fear, anxiety, sleep disturbance, cognitive impairment, and pain or discomfort. Many patients mistakenly believe that pain is to be expected and endured or they fear opioid use will lead to addiction. Health care professionals are often unaware of a patient’s discomfort or don't understand the physiological effects of uncontrolled/unrelieved pain. Despite the advances that are made overall, unrelieved pain is still a serious problem.
Pain may be a stressor for the critically ill patient and provides significant challenges for the health care professional. Critically ill patients may suffer excessive pain from their life-threatening illnesses, injuries, or nursing care and/or procedures (turning, endotracheal suctioning, removal of a chest tube). The critically ill often are unable to effectively communicate to their caregivers, making it difficult to assess and manage their pain effectively. In an effort to solve this ongoing problem, health care professionals must be able to recognize pain particularly within the critically ill. One must assume that every one critically ill patients are in pain or are at high risk for pain.
The health care team must work along with the patient to establish common pain treatment goals. in order to select the foremost appropriate treatment, thorough pain assessment and in-depth understanding of pain physiology are needed. An understanding of how pain is processed at each stage allows the treatment arrange to be tailored for every individual patient.
In most instances, the goal of the treatment strategy may be to achieve the maximal analgesia but when that's not possible, the goal shifts to reducing pain to a level that the patient finds tolerable which allows for the performance of activities of daily living. Once that goal has been established the next step is to develop an idea to fulfill that goal.
5. Conclusion
Pain is a bodily experience of suffering, a sensation transmitted from the sensory nerves through the spinal cord and to the sensory area of the brain, where the sensation is experienced. Pain can simultaneously complement nociception, a system that transmits information about inflammation, damage, or imminent tissue damage, to the spinal cord and brain. Nevertheless, it is independently observed. Nociception transmits somatic information without the presence of consciousness, while pain is the perception of sensory information. As part of the body’s defense system, pain triggers mental and physical behaviors that try to find a way to end a painful experience as soon as possible. At the same time, pain is feedback that encourages learning, making the repetition of the same painful experience less likely. The nociceptive system can elicit signals that trigger pain, and is a way of responding to damage and is part of a rapid and warning transmission that directs certain organs and primarily the central nervous system that then initiates reactions to reduce injury.
Funding
This research received no external funding
Conflicts of Interest
The author declare no conflict of interest
