Foundations Outline: Pain and Discomfort

Basic Concepts

Types of discomfort and pain:

Physical Pain:

• Nausea and Vomiting:
• Usually occurs some hours after initial dose of opioid
• adequate hydration and administration of anti emetics may decrease incidents of nausea
• opioid induced nausea usually subside within an few days
• Pruritis: 
• itching is a frequent side effect of opioids administered by any route
• it is not an allergic reaction
• can be relieved by antihistamines
• often times patients will report pruritus as an allergic reaction
• can pretreat with benadryl prior to opioid administration if pt reports past history of pruritus
• Acute Pain:
• resent onset
• commonly associated with a specific injury
• indicates damage or injury has occurred
• usually decreases as healing progresses
• can last from seconds to 6 months, though 6 months is an arbitrary time
• many acute injuries heal within a few weeks and most heal by 6 weeks
• in a situation where the injury is expected to heal within in 3 weeks but the pain continues beyond the expected healing time, the pain should be treated as chronic
• Chronic Pain:
• constant or intemittent
• extends beyond usual healing time
• can seldom be attributed to a specific cause or injury
• may have poorly defined onset
• often difficult to treat because origin is unclear
• chronic pain serves no purpose and if allowed to continue may become the patient's primary disorder
• Cancer Related Pain (Malignant Pain)
• associated with cancer
• may be acute or chronic
• can be directly associated with the cancer (bony infiltrates or nerve compression)
• can be result of treatment (surgery or radiation)
• not associated with the cancer (trauma)
• Referred Pain:
• pain that originates in one part of the body but is perceived

• Cutaneous Pain:
• superficial pain such as a paper cut
• usually produces sharp pain with a burning/stinging sensation
• Somatic Pain:
• diffuse or scattered
• originates in bones, ligaments, tendons, blood vessels, or nerves
• sprains can cause this type of pain
• Visceral Pain:
• poorly localized
• originates in body organs in the thorax, cranium, and abdomen
• pain occurs as organs stretch abnormally and become distended
• guarding reflex may occur as a protective mechanism to prevent additional trauma
• Neuropathic Pain:
• resltus from injury to or abnormal functioning of peripheral nerves or the CNS
• often described as burning or stabbing
• Allodynia is a characteristic feature of neuropathic pain
• Intractable Pain:
• pain that persists despite a variety of interventions
• Psychogenic Pain:
• usually has physical and psychogenic origins
• pain that results from a mental event can be just as intense as win that results from a physical event
• Anxiety and Pain:
• it is a misconception that anxiety makes pain worse
• anxiety is often associated with pain, but the cause and effect relationship has not been established
• pain often causes anxiety, but is not clear that pain makes anxiety more intense
• anxiety that is unrelated to the pain may actually serve as a distraction and decrease the perception of pain
• direct the treatment at the pain rather than the anxiety
• routine use of anti anxiety meds in pts with pain may prevent pts from reporting their pain and may impair their ability to take deep breaths, get out of bed, and cooperate
• anxiety can be related to pain because of fears about the underlying disease causing the pain
• acknowledging the pain helps to reduce the anxiety
• Interpretation of Pain:
• a patient that was treated for breast cancer years ago and now has hip pain may fear that the pain indicates metastasis
• in this case the anxiety may result in increased pain
• Environmental Factors:
• strangeness of healthcare environment
• lights
• noise
• lack of sleep
• cold from can increase pain perception

Physiology of Pain

• Sensation:
• A-Delta fibers
•  transmit acute, well localized pain
• are myelinated
• fast conducting
• C Fibers
• slower conduction
• not myelinated
• transmit diffuse, viseral pain that is often described as burning and aching
• Transduction of Pain:
• peripheral nerve fibers that transmit win are called nociceptors
• damaged cells release histamine which excites nerve cells
• Substance P:
• sensitizes receptors on nerves to feel pain and also increases the rate of firing of nerves
• Prostaglandins:
• send additional pain stimuli to CNS
• Stimulants:
• Mechanical Stimulant: friction, pressure
• Thermal Stimulant: sunburn, cold water on teeth
• Chemical Stimulant: acid burn
• Electric Stimulant: static charge
• Gate Control Theory:
• describes the transmission of painful stimuli and recognizes a relationship between pain and emotions
• smaller nerve fibers conduct excitatory pain stimuli toward brain
• larger nerve fibers are capable of inhibiting the transmission of pain signals to the brain
• this balance of excitatory and inhibiting signals at the gate (at the spinal cord) determine which signals enter the brain
• amount a limited amount of sensory information can be processed at any given moment
• when too much info is sent through, cells in the spinal column interrupt and close the gate to the brain
• nursing measure such as massage or warm compress stimulate the large nerve fibers to close the gate, thus blocking pain impulses from that area
• helps to explain how interventions such as distraction and music therapy relieve pain
• Pain Threshold:
• the lowest intensity of a stimulus that causes the subject to recognize pain
• some studies have reached the conclusion that women have a lower pain threshold than men
• Pain Tolerance:
• the maximum amount of pain a person can tolerate
• Endorphins and Enkephalins:
• endogenous opioid morphine like neurotransmitters/neuromodulators
• reduce nociceptive transmission
• found in the CNS
• enkephalins inhibit the real ease of Substance P
• Posoperative Pain:
• opioid analgesics are provided mostly by IV in PACU
• may also use a PCA pump which permits self administration
• patients who are controlling their own opiod administration usually become sedated and fall asleep before any significant respiratory depression occurs 

Myths about Pain:

• People with chronic pain have hypochondriasis
• Infants do not feels pain
• Old patients constantly complain
• Treating pain will lead to addiction
• Its better to put up with the pain than to treat it (this leads to sensitization which is when the pain becomes so intense that it is difficult to treat) Inteventions are more successful if initiated before pain sensitization occurs. It is easier to manage the pain and less medication is needed.