Pathophysiology of Pain, by Catherine Dowling.
Hi.
My name is Catherine Dowling.
I'm a nurse at Children's Hospital Boston in the Cardiac ICU.
The objectives of this presentation are to understand the physiology of pain and its
effects, and to identify the sources of pain.
Introduction.
Pain is defined as an unpleasant sensory and emotional experience associated with actual
or potential tissue damage.
Pain often occurs in critical care patients, and is one of the most clinically-challenging
problems for critical care nurses.
Pain Physiology.
Pain receptors are free nerve endings that respond to painful stimuli.
Pain receptors are found throughout all tissue except the brain.
And they transmit information to the brain.
They are stimulated by biological, electrical, thermal, mechanical, and chemical stimuli.
Pain perception occurs when these stimuli are transmitted to the spinal cord and then
to the central areas of the brain.
Physiological indicators of pain can be expressed in many ways.
Tachycardia, increased blood pressure, tachypnea, diaphoresis, pallor, decreased peripheral
circulation, and pupil dilation are all physical signs of pain.
However, the majority of these signs can also be an indicator of decreased cardiac output.
Behavioral Cues to Pain.
There are many ways a child will express his or her pain.
These cues are demonstrated by both verbal and nonverbal patients.
Some of the ways a child may express their pain are facial expressions, such as a grimace,
crying or moaning, whining, clenching teeth or lips, opening eyes wide, yelling or screaming,
restlessness and agitation, lying rigidly, touching the operative site, guarding or splinting,
insomnia, combativeness, poor appetite, and withdrawal.
Sources of Pain.
There are many potential sources of pain, including incisions, invasive lines and tubes,
procedures, positioning, physical discomforts, and emotional factors.
Incision pain from surgical procedures in the cardiac intensive care unit differs depending
on the type of procedure performed.
For example, thoracotomy incisions tend to be the most painful due to rib manipulation.
Chest tubes also play a large role in discomfort of the post-operative patient and should be
considered in pain management, especially when the patient is mobile.
Patients with an inability to reposition themselves should be frequently turned at a minimum of
every two hours for comfort measures.
Emotional factors and environmental stressors may also play a role in post-operative pain
management.
If the environment of the room is loud and stressful, this may contribute to the patient's
discomfort and increase their level of stress.
Pain is always stressful, but stress is not necessarily painful.
Both require assessment.
Pain Misconceptions.
Many people have misconceptions about pain in children.
These myths still exist even though there is now evidence to support that they are not
true.
The most common myths about pain in children include the following: Infants do not feel
pain due to incomplete myelinization of nerves, a child that can play or sleep does not have
pain, pain is experienced the same in every patient, and patients who exaggerate their
pain and its effects are trying to manipulate others to obtain secondary gains.
Other misconceptions include: standard doses of pain medication work the same for every
patient, taking opioids for pain relief leads to addiction, patients and families who require
specific medications are addicted to drugs, and there is a maximum dose of narcotics that
cannot be exceeded.
Effects of Unrelieved Pain.
When pain goes untreated, there are physiological consequences.
The cardiovascular system responds to the stress of unrelieved pain by increasing sympathetic
nervous system activity, which increases heart rate, blood pressure, and peripheral vascular
resistance.
As the workload and the stress of the heart increase, tachycardia occurs, which increases
oxygen consumption of the myocardium.
When oxygen consumption is greater than oxygen supply, myocardial ischemia and myocardial
infarction may occur.
Unrelieved pain can result in a patient limiting the movement of the thoracic and abdominal
muscles in an effort to reduce pain.
When this occurs, the patient will not cough and deep breathe effectively, leading to an
increase in sputum retention, atelectasis, and hypoxemia.
The resulting hypoxemia may cause cardiac complications, disorientation, confusion,
and delayed wound healing.
This may lead to a longer length of stay.
Depression of the immune system can also be caused by unrelieved pain.
This may predispose the patient to wound infection, pneumonia, and ultimately, sepsis.
The musculoskeletal system is affected by increased fatigue and immobility as a result
of unrelieved pain.
Impaired muscle function and muscle pain can lead to immobility, causing venostasis, increased
blood coagulability, and increased risk of developing a blood clot.
Cognition is also affected.
Unrelieved pain has the potential to increase anxiety levels further, and interfere with
activities of daily living such as diet and exercise.
Pain may interrupt normal sleep patterns causing varying degrees of insomnia.
Unrelieved pain may also result in an individual experiencing distressing cognitive impairment
such as disorientation, mental confusion, and a reduced ability to concentrate.
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