Schmerzmittelgruppe Anhang 3

In health care, the primary care provider’s role is to assess and > pain by administering medications and other treatments. The nurse collaborates with other health care professionals while administering most pain relief interventions, evaluating their effectiveness, and serving as patient advocate when the intervention is ineffective. In addition, the nurse serves as an educator to the patient and family, teaching them to manage the pain relief regimen themselves when appropriate.

Physiology of Pain

Noxious stimuli activate nociceptors (= receptive neurons for painful sensations) that, together with the axons of neurons convey information to the spinal cord where reflexes are activated. Information is simultaneously transmitted to the brain supraspinally. Long-lasting changes in cells within the spinal cord afferent (ascending) and efferent (descending) pain pathways may occur after a brief noxious stimulus. Physiological responses

(such as elevated blood pressure, pulse rate, and respiratory rate; dilated pupils; pallor; and perspiration) to even a brief acute pain episode will begin showing adaptation within a short period, possibly minutes to a few

hours. Physiologically, the body cannot sustain the extreme stress response for other than short periods of time. The body conserves its resources by physiological adaptation (returning to normal or near normal blood pressure, pulse rate, and respiratory rate; normal pupil size, and dry skin) even in the face of continuing pain of the same intensity. Pain can be categorized into two types according to its pathophysiology:

Transduction of Pain = When noxious stimuli occur, tissues are damaged. Cell damage releases the following sensitizing substances:

Transmission of Pain = Movement of impulses from site of origin to the brain

The specific action of pain varies depending on the type of pain. In cutaneous pain, cutaneous nerve transmissions travel through a reflex arc from the nerve ending (point of pain) to the brain at a speed of approximately

300 feet per second, with a reflex response causing an almost immediate reaction. This explains why, when a hot stove is touched, the person’s hand jerks back before there is conscious awareness that damage is occurring

After a hot stove is touched, a sensory nerve ending in the skin of the finger initiates nerve transmission that travels through the dorsal root ganglion to the dorsal horn in the gray matter of the spinal cord. From there,

the impulse travels though an interneuron that synapses with a motor neuron, which exits the spinalcord at the same level. This motor neuron, and the stimulation of the muscle it innervates, is responsible for the swift

movement of the hand away from the hot stove. In the case of the hot stove, the sensory neuron synapses not only with an interneuron but also with an afferent sensory neuron. The impulse travels up the spinal cord to the

thalamus, where a final synapse conducts the impulse to the cortex of the brain. Efferent or descending motor neuron response is conducted from the brain through the spinal cord, where it synapses with a motor neuron that

exits the spinal cord and innervates the muscle. In visceral pain, transmission of pain impulses is slower and less localized than incutaneous pain. The internal organs (including the gastrointestinal tract) have a minimal

number of nociceptors, which explains why visceral pain is poorly localized and is felt as a dull aching or throbbing sensation. However, internal organs have extreme sensitivity to distension. In acute pain episodes,

substances released from injured tissue lead to stress hormone responses in the client. This causes an increased metabolic rate, enhanced breakdown of body tissue, impaired immune function, increased blood clotting and

water retention, and it triggers the fight-or-flight reaction, leading to tachycardia and negative emotions.

Pain Perception = Developing conscious awareness of pain

When the impulse has been transmitted to the cortex and is interpreted by the brain, the information is available on a conscious level. It is then that the person becomes aware of the intensity, location, and quality of pain.

This information is interpreted in light of previous experience, adding the affective component to the pain experience.

Modulation = The changing of pain impulses

Modulation refers to activation of descending neural pathways that inhibit transmission of pain. ³The pathways are described as descending because they involve neurons originating in the brain stem that descend to the

dorsal horn of the spinal cord´. The descending fibers release substances that produce analgesia by blocking the transmission of noxious stimuli. Pain modulation is a result of the effects of endogenous opioids, also called enkephalins and endorphins.

Prostaglandins (PG)

Bradykinin (BK)

Serotonin (5HT)

Substance P (SP)

Histamine (H)

Release of these substances alters the electrical charge on the neuronal membrane. This change in electrical charge is a result of movement of Na+ and other ions into the cells. The impulse is then ready

to be transmitted along the nociceptor fibers.

Neuropathic pain arises from damage to portions of the peripheral or central nervous system. This pain is not nociceptive pain, nor that which is due to ongoing tissue injury or inflammation. It is important to differentiate neuropathic pain from other types of pain because the treatment differs significantly. Neuropathic pain is a result of abnormal processing of sensory input by either the peripheral or central nervous system.

Two types of neuropathic pain:

Allodynia (a nonpainful stimulus is felt as painful in spite of the tissue appearing normal)

Paresthesia (abnormal sensation such as burning, prickling, or tingling.

Gate Control Theory of Pain

The gate control theory combines cognitive, sensory, and emotional components²inaddition to the physiological aspects²and proposes that they can act on a gate controlsystem to block the individual’s perception of pain.

Bezkor and Lee (1997, p. 181) describe gate control as ³regulation of pain perception through a gating mechanism at the dorsal horn of the spinal cord. Vasoconstriction and decreased nerve conduction velocity result in

reduced transmission of noxious stimuli to the µgate.´ As a result, the level of conscious awareness of painful sensation is altered. The gate control theory is based on the premise that pain impulses travel through either

small-diameter nerve cells or large-diameter nerve cells, both of which pass through the same gate. The large-diameter cells have the ability, when properly stimulated, to ³closethe gate´ and thus block transmission of

the pain impulse to the brain. Stimulants such as cutaneous massage, opioid release, and excessive stimulation all activate the large-diameter cells to close the gate. Clinically, the effectiveness of several non

pharmacologic modalities (massage, accupuncture, accupressure) supports gate control theory.

Cultural Norms and Attitudes

Cultural diversity in pain responses can easily lead to problems in pain management. There are no significant differences among groups in the level of intensity at which pain becomes appreciable or perceptible. However,

the level of intensity or duration of pain the client is willing to endure is culturally determined. Expression of pain is also governed by cultural values. In some cultures, tolerance to pain, and therefore suffering in silence,

is expected; in others, full expression of pain may include animated physical and emotional responses. The nurse must be careful not to equate the level of expression of pain with the level of actual pain experienced, but to

instead consider cultural influences that affect the expression of pain.

Age

Can greatly influence a client’s perception of the pain experience. Infants are sensitive to pain and typically exhibit discomfort through crying or physical movement. Toddlers also use crying and physical movement to

indicate pain, and they begin to develop the skills needed to verbally describe pain or point to the area that is hurting. Children often do not understand why pain occurs and can therefore be frightened or resentful of the pain experience; in some cases, children revert to habits of their younger years (regression) as a coping mechanism when faced with pain they cannot otherwise manage.

Adolescents often sense great peer pressure and may be reluctant to admit having pain for fear of being called weak or sensitive. Adults may continue pain behavior they learned as children and may also be reluctant to admit

pain or seek medical care because of fear of the unknown or fear of the impact that treatment may have on their lifestyle. Older adults may often ignore their pain, viewing it as an unavoidable consequence of aging;

family and health care members may inadvertently support this stereotype and be less than responsive to an older client’s complaints of pain. Pain related to chronic disease is prevalent among the elderly population.

Up to 70% of non institutionalized older adults report the occurrence of pain. Frequently, pain is undertreated in older people.

Previous Experience with Pain

Clients’ previous exposures to pain will often influence their reactions. Coping mechanisms that were used in the past may affect clients’ judgments as to how the pain will affect their lives and what measures they can

use to successfully manage the pain on their own. Client teaching about pain expectations and management methods can often allay client fears and lead to more successful pain management (in clients who do not have

previous pain experience or who have memories of a previous devastating pain) experience that they do not wish to repeat.

Intensity

The intensity of pain ranges from none to mild discomfort to excruciating. There is no correlation between reported intensity and the stimulus that produced it. The reported intensity is influenced by the person’s

pain threshold and pain tolerance

Pain threshold is the smallest stimulus for which a person reports pain, and the tolerance is the maximum amount of pain a person can tolerate. To understand variations, the nurse can ask about the present pain intensity

as well as the least and the worst pain intensity. Various tools and surveys are helpful to patients trying to describe pain intensity.

Timing

Sometimes the aetiology of pain can be determined when time aspects are known. Therefore, the nurse inquires about the onset, duration, relationship between time and intensity, and whether there are changes in rhythmic

patterns. The patient is asked if the pain began suddenly or increased gradually. Sudden pain that rapidly reaches maximum intensity is indicative of tissue rupture, and immediate intervention is necessary. Pain from

ischemia gradually increases and becomes intense over a longer time. The chronic pain of arthritis illustrates the usefulness of determining the relationship between time and intensity, because people with arthritis usually

report pain < in the morning.

Location

The location of pain is best determined by having the patient point to the area of the body involved. Some general assessment forms have drawings of human figures, and the patient is asked to shade in the area involved.

This is especially helpful if the pain radiates (referred pain). The shaded figures are helpful in determining the effectiveness of treatment or change in the location of pain over time.

Quality

The nurse asks the patient to describe the pain in his or her own words without offering clues. For example, the patient is asked to describe what the pain feels like. Sufficient time must be allowed for the patient to describe

the pain and for the nurse to carefully record all words that are used. If the patient cannot describe the quality of the pain, words such as burning, aching, throbbing, or stabbing can be offered. It is important to document the

exact words used to describe the pain and which words were suggested by the nurse conducting the assessment.

No-one really wants pain. Once you have it you want to get rid of it. This is understandable because pain is unpleasant. But the unpleasantness of pain is the very thing that makes it so effective and an essential part of life.

Pain protects you, it alerts you to danger, often before you are injured or injured badly. It makes you move differently, think differently and behave differently, which also makes it vital for healing. It is usually really

sensible to hurt. Occasionally the pain system appears to act oddly - like the nail in your toe that may not even hurt until you notice blood at the injury site. Other times, the pain system actually fails -some life-threatening

cancers aren’t painful, which is the very reason they can go undetected and be so nasty. We believe that all pain experiences are normal and are an excellent, though unpleasant, response to what your brain judges to be a threatening situation. We believe that even if problems do exist in your joints, muscles, ligaments, nerves, immune system or anywhere else, it won’t hurt if your brain thinks you are not in danger. In exactly the same way,

even if no problems whatsoever exist in your body tissues, nerves or immune system, it will still hurt if your brain thinks you are in danger. It is as simple, and as difficult, as that.

Most commonly, pain occurs when your body’s alarm system alerts the brain to actual or potential tissue damage. But this is only part of a big story. Pain actually involves all of your body systems and all of the

responses that occur are aimed at protection and healing. However, when most of us think of pain we think of the experience of pain - that unpleasant and sometimes downright horrible experience that makes you take

notice and motivates you to do something about the situation. In fact, pain can be so effective that you can’t think, feel or focus on anything else. If the brain thinks that experiencing pain is not the best thing for your

survival (imagine a wounded soldier hiding from the enemy)you may not experience pain at the time of even very severe injury. There are many myths, misunderstandings and unnecessary fears about pain. Most people,

including many health professionals, do not have a modern understanding of pain. This is disappointing because we know that understanding pain helps you to deal with it effectively. Here are two important things we now

know about explaining pain: the physiology of pain can be easily understood by men and women in the street

1. understanding pain physiology changes the way people think about pain, reduces its threat value

2. and improves their management of it. Hopefully, you will find this journey as exciting, fascinating and empowering as we have.

Pain is normal

It’s sensible to have a system which protects and preserves

Of course things hurt; life can hurt. There are many kinds of pain. In the unlikely event that a monkey happens to bite your nose, as it has bitten Norman’s in the Zoo, then it will hurt and you will probably remember the

incident for the rest of your life – Norman probably won’t show off like next time they go to the zoo; the story of Norman’s nose holes will be retold at countless family gatherings; it will change the way the family thinks

about monkeys; and may even become the topic of nursery rhymes (e. g. ‘Norman’s nose got bit by the chimp… ever since then the chimp’s had a limp, Norman’s son knows dad is a whimp… Poor old nosey Norman’).

You get the message. You can have pain with much less obvious damage. It may just emerge over time as it has with the computer-bound Mr Lee. Pain is useful here and will hopefully encourage him to get up and move.

But pain is often unpredictable, which can make us frightened of it. Sometimes you can lift an object a thousand times without a problem. Then, all of a sudden, one lift causes extreme pain. Why would Sidney over the

page ever want to throw Rene Descartes’ bust into the bin again? By the way, Rene is the French philosopher who invented the mind-body split. There is no doubt that Rene Descartes was extremely clever, but it is 400

years since he proposed his theories. We now know enough to be sure that this mind-body split does not exist.

Explain pain

Pains from bites, postural pain and sprains are simple ‘everyday’ pains that can be easily related to changes in tissues. The brain concludes that the tissues are under threat and that action is required, incl. healing behaviours.

An added benefit is that memories of the pain will hopefully protect you from making the same mistake twice. Maybe the monkey bite nursery rhyme provides future protective behaviours for a whole family. But we all

know that pain can be a more complex experience. The word ‘pain’ is also used in relation to grief, loneliness and alienation. What is it about the pain of lost love that makes it as debilitating as any acute low back pain?

This emotionally laden pain helps us to grasp a big picture for understanding pain. All pain (in fact, all experiences!) involves many thoughts and emotional contributions. We need the brain in order to really understand

pain (that persists, spreads or seems unpredictable). We need the brain to help us understand why emotions, thoughts, beliefs and behaviours are important in pain. If you are in pain right now, then you are not alone.

In fact, at any one time on the face of the earth, around 20% of people have pain that has persisted for more than 3 months. That’s 2 million Londoners!

When pain persists and feels like it is ruining your life, it is difficult to see how it can be serving any useful purpose. But even when pain is chronic and nasty, it hurts because the brain has somehow concluded, for some

reason or another, often completely subconsciously, that you are threatened and in danger - the trick is finding out why the brain has come to this conclusion.

Some warning system!

Pain really is an amazing experience. Most of us have heard stories where people have had severe injury and no pain at the time of injury. As the rat suggests - what happened to the warning system? Severe injury creates

lots of loud alarm signals that pour into the brain, but these do not necessarily result in pain.

The amount of pain you experience does not necessarily relate to the amount of tissue damage you have sustained.

Look at Norman (still nursing his sore nose) with an arrow through his neck. While the monkey bite hurt a great deal, this comparatively serious injury may not hurt at all. In emergency rooms all around the world, patients

present impaled by various objects. Many are lucky because the object may not have interfered with vital organs and many report little or no pain.

There are many stories from wartime.

Take the World War II veteran who had some routine chest x-rays done. They revealed a bullet that had been lodged in his neck for 60 years - he never knew.

Many stories involve soldiers in wartime who have a severe injury, even losing a whole limb, yet who report little or no pain

Those who suffered traumatic amputations in wartime and commented that there was no pain usually reported the injury in innocuous terms, such as a‘bump’ or a ‘thump’

In other situations, severely burnt people have run back into burning houses to save children; sportsmen and women have accomplished amazing feats despite severe injury. But the ratio of the amount of injury to the

amount of pain swings the other way too. What is it about a paper cut? It’s not deep, there’s not much damage, but it really hurts, it stings, it makes you annoyed and you can’t believe that a paper cut could hurt that much.

Obviously what’s happening in your tissues is just one part of the amazing pain experience. Let’s contemplate a few more amazing pain stories. . .

The brain is obviously involved

Low back pain and headache are among the most common pains in humans. In low back pain, research has shown that the amount of disc and nerve damage rarely relates to the amount of pain experienced

In fact many of us have scary sounding disc bulges, even squashed nerves, yet may never have any symptoms. This can be a bit frightening, but it is really quite relieving. Many changes in tissues are just a normal part of

being alive and don’t have to hurt. What’s more, these changes don’t necessarily have to stop anyone leading a very functional and active life. It is very likely that an x-ray of an older person’s spine will reveal changes

which could be described as arthritic or degenerative, as you see in the yogi. They can still function very well.

Simply, if there is no pain it means that these changes in tissues are not perceived by your brain to be a threat.

We couldn’t resist another common example of extreme forces on the body yet no complaints of pain. A football player who scores a significant goal is likely to have his entire team jump on him; a weight of nearly a tonne.

Yet he will always jump up smiling and keep playing, often better than before. But under different circumstances a minor injury may be sufficient to lead a person into a life of chronic pain. Look at Sidney on his surfboard

waiting for the perfect wave at Bondi Beach. Surfers who have had their legs bitten off by sharks have reported feeling nothing more than a bump at the time

Even more intriguing

What about these true stories? Pain is indeed complex. There is a well reported syndrome called the Couvade syndrome, in which the father experiences labour pain. In some societies people believe that the more pain the

father displays the better father he will be. Some wives actually look after the husband while delivering the child

Acupuncture can reduce pain, but it doesn’t always work. In fact it is thought that acupuncture works best if it is performed by a Chinese man on a Chinese woman in China and worst if it is performed by a non-Chinese

woman, on a Chinese man, somewhere other than China.

Hypnosis is fascinating. There are many records of people who have undergone major surgery while hypnotised, without medical anaesthesia

How can this be? The alarm bells in the tissues would still ring as the scalpel slices through skin and muscle, yet there is no pain. A little trivia - people around the world consume around 100 billion aspirin tablets per year.

If you put them all in line, the line would be one million kilometres long (that’s to the moon and back)

It’s a known fact that the shape of the tablet plays a part in the effectiveness of the drug. Transparent capsules with coloured beads work better than capsules with white beads, which work better than coloured tablets, which

work better than square tablets with the corners missing, which work better than round tablets

Many and varied cues may relate to the pain experience, but it is the brain which decides whether something hurts or not, 100% of the time, with no exceptions.

Children can have phantom limbs even if they are born without limbs

What this tells us is that there must be a virtual body in the brain from birth. This virtual body is further constructed, refined and added to as we grow and do new things. Take, for example, learning to kick a ball. The map

of the leg would link to areas in your brain that are involved in balance and coordination and the use of particular muscles. Perhaps the only good side-effect of a minor brain injury is that pre-existing phantom pains may go.

Some studies using brain imaging have shown that phantom pain is associated with extensive alterations in the way that the brain is organised. In fact, imaging studies show that marked changes occur in the brain with any

chronic pain situation, not just phantom pain

These alterations result in changes in the virtual body. For example, in the case of phantom leg pain, the brain area related to the leg actually ‘smudges’ so that there is no longer a clearly outlined virtual leg in the brain.

Age, gender, culture and pain

The exact effects of age, culture and gender on pain are difficult to study and are not fully understood.

AGE

The medical view has often been that older and younger people feel less pain than middle-aged people. This is not true.

Generally speaking, if a railway crossing boom gate falls evenly on a 10 year old, a 45 year old and a 62 year old, they will all say it hurts at about the same amount of force. That said, the response to being struck will

vary according to age. A baby will scream, a child will cry, an adult may react in various ways. The prevalence of some pains, such as back pain, varies throughout the lifetime

For example, the over 60’s have less back pain than the under 60s. This shows again that pain is not necessarily related to the amount of degeneration in tissues. We begin attributing meaning to pain from a very early age.

Have you ever noticed that when infants hurt themselves, they often look to their parents before screaming with pain? Parents can ‘inform’ infants about the meaning of the sensory input they are receiving (health professionals also inform patients about the meaning of sensory inputs). The early impact of meaning has been investigated in association with injections: the second injection a child receives usually causes more pain behaviour (e. g. screaming, avoidance) than the first. Also, during immunisation the pain behaviours of a young circumcised boy are more obvious than a non-circumcised boy

GENDER

Differences in pain experiences might be due to reproductive organs and/or societal gender roles. For example, they might follow stereotypes: mother or father roles, women wearing high heels, men with beer bellies,

women with big breasts, stereotypical job demands, hobbies or sports played. These differences in pain are usually caused by different societal roles not different physiology. There is a popular myth that females have a

lower pain threshold and tolerance than males, at least until females go through labour, at which time their pain threshold and tolerance ‘magically’ rises. It is more likely many females will report pain more honestly until

they have experienced labour, at which time they feel ‘obliged’ to be ‘tougher’. There is still a tendency to undermedicate female pain patients in comparison to males, which suggests health professionals may

‘psychologise’ the pain of females more than the pain of males

We should also acknowledge that most pain research to date has been done on male animals by male researchers. Perhaps our understanding of pain will change when these conventions of research change.

CULTURE

Initiations are a great example of cultural influences - they often involve severe injury but are rarely described as painful. Why would pain be a sensible response when the point of the initiation is to enter manhood?

What about the Easter crucifixions (voluntary) in the Philippines - little or no pain is reported. Now, why would pain be sensible when the point of the crucifixion is to get closer to God?

Many studies report differences in pain thresholds and responses between people in different cultures. For example, the level of radiant heat found to be painful to Mediterranean peoples is merely regarded as warm to

northern Europeans.

Do Mediterranean people have greater reason to consider radiant heat to be dangerous?

Your pain will never be the same pain as that experienced by your health professional or anyone else for that matter.

Recapatulation:

All pain experiences are a normal response to what your brain thinks is a threat.

The amount of pain you experience does not necessarily relate to the amount of tissue damage.

The construction of the pain experience of the brain relies on many sensory cues.

Phantom limb pain serves as a reminder of the virtual limb in the brain.

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