Appropriate pain assessment is the foundation of effective pain treatment. Because pain is recognized as a subjective experience, the patient’s self-report is considered the most valid measure for pain and should be obtained as often as possible. Unfortunately in critical care, many factors such as the administration of sedative agents, the use of mechanical ventilation, and altered levels of consciousness may impact communication with patients. When the patient is unable to communicate in any way, observable behavioral and physiologic indicators become unique indices for pain assessment as recommended by clinical guidelines.
Pain is frequently encountered in critical care, and there is increased emphasis on the professional responsibility to manage the patient’s pain effectively. The critical care nurse must understand the mechanisms, assessment process, and appropriate therapeutic measures for managing pain.
DEFINITION AND DESCRIPTION OF PAIN
Pain - is as an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage. Specifically, the subjective characteristic implies that pain is whatever the person experiencing it says it is and that it exists whenever the patient says it does. This definition also suggests that the patient is able to self-report. However, in the critical care context, many patients are unable to self-report their pain.
Components of Pain
The experience of pain includes sensory, affective, cognitive, behavioral, and physiologic components:
· Sensory component: Perception of many characteristics of pain, such as intensity, location, and quality
· Affective component: Negative emotions such as unpleasantness, anxiety, fear, and anticipation that may be
associated with the experience of pain.
· Cognitive component: Interpretation or the meaning of pain by the person who is experiencing it.
· Behavioral component: Strategies used by the person to express, avoid, or control pain.
· Physiologic component: Nociception and the stress response
Types of Pain
Pain can be acute or chronic, with different sensations related to the origin of the pain.
Acute Pain:
Acute pain has a short duration, and it usually corresponds to the healing process (30 days) but should not exceed 6 months. It implies tissue damage that is usually from an identifiable cause.
Chronic Pain:
Chronic pain persists for more than 6 months after the healing process from the original injury, and it may or may not be associated with an illness. It develops when the healing process is incomplete or when acute pain is poorly managed. Both acute and chronic pain can have a nociceptive or neuropathic origin.
Nociceptive Pain:
· Nociceptive pain arises from activation of nociceptors, and it can be somatic or visceral.
· Somatic pain - involves superficial tissues, such as the skin, muscles, joints, and bones. Its location is well-defined.
· Visceral pain - involves organs such as the heart, stomach, and liver. Its location is diffuse, and it can be referred to
a different location in the body.
Neuropathic Pain:
· Neuropathic pain arises from a lesion or disease affecting the somatosensory system.
· The origin of neuropathic pain may be peripheral or central.
· Neuralgia and neuropathy are examples related to peripheral neuropathic pain, which implies a damage of the
peripheral somatosensory system.
· Central neuropathic pain involves the central somatosensory cortex and can be experienced by patients after a
cerebral stroke.
· Difficult to manage and frequently requires a multimodal approach that combines several pharmacological and/or
nonpharmacological treatments.
Physiology of Pain
Nociception
Nociception represents the neural processes of encoding and processing noxious stimuli but are not sufficient for pain. Pain results from the integration of the pain-related signal into specific cortical areas of the brain associated with higher mental processes and consciousness. In other words, pain is the conscious experience that may emerge from nociception.
Four processes are involved in nociception:
1. Transduction:
· refers to mechanical (e.g., surgical incision), thermal (e.g., burn), or chemical (e.g., toxic substance) stimuli that
damage tissues.
· These stimuli, also called stressors, stimulate the liberation of chemical substances, such as prostaglandins,
bradykinin, serotonin, histamine, glutamate, and substance P.
· These neurotransmitters stimulate peripheral nociceptive receptors and initiate nociceptive transmission.
2. Transmission:
· An action potential is produced and is transmitted by nociceptive nerve fibers in the spinal cord that reach higher
centers of the brain.
· It represents the second process of nociception. The principal nociceptive fibers are the A-delta and C fibers.
· Large-diameter, myelinated Aδ fibers transmit welllocalized, sharp pain, are involved in “first pain,” and lead to
reflex withdrawal.
· Small-diameter, unmyelinated C fibers transmit diffuse, dull, aching pain, often referred to as“second pain.” These
fibers transmit the noxious sensation from the periphery through the dorsal root of the spinal cord.
· With the liberation of substance P, these fibers then synapse with ascending spinothalamic fibers to the central
nervous system (CNS). These spinothalamic fibers are clustered into two specific pathways: neospinothalamic (NS)
and paleospinothalamic (PS) pathways. Generally, the Ad fibers transmit the pain sensation to the brain within the
NS pathway, and the C fibers use the PS pathway.
· Through synapsing of nociceptive fibers with motor fibers in the spinal cord, muscle rigidity can appear because of
a reflex activity.
· Muscle rigidity can be a behavioral indicator associated with pain. It can contribute to immobility and decrease
diaphragmatic excursion.
· This can lead to hypoventilation and hypoxemia. Hypoxemia can be detected by a pulse oximeter (SpO2) and by
oxygen arterial pressure (PaO2) monitoring. An intubated patient’s activation of alarms or fighting the ventilator
may indicate the presence of pain.
3. Perception:
· The pain message is transmitted by the spinothalamic pathways to centers in the brain, where it is perceived.
· Pain sensation transmitted by the NS pathway reaches the thalamus, and the pain sensation transmitted by the PS
pathway reaches brainstem, hypothalamus, and thalamus.
· Pain sensation transmitted by the NS pathway reaches the thalamus, and the pain sensation transmitted by the PS
pathway reaches brainstem, hypothalamus, and thalamus - contribute to the initial perception of pain.
· Projections to the limbic system and the frontal cortex - allow expression of the affective component of pain.
· Projections to the sensory cortex located in the parietal lobe - allow the patient to describe the sensory
characteristics of pain, such as location, intensity, and quality.
4. Modulation:
· Modulation is a process by which painful messages that travel from the nociceptive receptors to the CNS may be
enhanced or inhibited.
· A typical example of ascending pain modulation is rubbing an injury site, thus activating large A-beta fibers in the
periphery.
· In the descending pain modulation mechanism, the efferent spinothalamic nerve fibers that descend from the brain
can inhibit the propagation of the pain signal by triggering the release of endogenous opioids in the brainstem and
in the spinal cord.
· Serotonin and norepinephrine are important inhibitory neurotransmitters that act in the CNS.
· These substances are also released by the descending fibers of the descending spinothalamic pathway.
· The use of distraction, relaxation, and imagery techniques facilitate the release of endogenous opioids and have
been shown to reduce the overall pain experience.
PAIN ASSESSMENT
Pain assessment is an integral part of nursing care. It is a prerequisite for adequate pain control and relief.
Pain assessment has two major components:
1) non observable or subjective
2) observable or objective.
The complexity of pain assessment requires the use of multiple strategies.
Pain Assessment: The Subjective Component
Pain is a subjective experience.it refers to the patient’s self-report of pain, and this must be obtained whenever possible. A simple yes or no (presence versus absence of pain) is considered a valid self-report.
Mechanical ventilation should not be a barrier for nurses to document patients’ self-reports of pain. Many mechanically ventilated patients can communicate that they have pain or can use pain scales by pointing to numbers or symbols on the scale. Sufficient time should be allowed for the patient to respond to the questions. If sedation and cognition levels allow the patient to give more information about pain, a multidimensional assessment can be documented.
Multidimensional pain assessment tools, including the sensorial, emotional, and cognitive components, are available such as:
· the Brief Pain Inventory,
· the Initial Pain Assessment Tool
· the McGill Pain Questionnaire–Short Form.
The patient’s self-report of pain can also be obtained by questioning the patient using the mnemonic PQRSTU:
P: provocative and palliative or aggravating factors - indicates what provokes or causes the patient’s pain, what he or she was doing when the pain appeared, and what makes the pain worse or better.
Q: quality - the quality of the pain or the pain sensation that the patient is experiencing.
R: region or location, radiation - ask that the patient point to the location on himself or herself or on a simple anatomic drawing.
S: severity - denotes pain severity or intensity.
T: timing - to documenting the onset, duration, and frequency of pain
U: understanding - the patient’s perception of the problem or cognitive experience of pain.
Pain Assessment: The Observable or Objective Component
When the patient’s self-report is impossible to obtain, nurses can rely on the observation of behavioral indicators, which are strongly emphasized in clinical recommendations and guidelines for pain management in nonverbal patients. Similarly, fluctuations in physiologic indicators (i.e., vital signs) can be used as a cue to begin further assessment for pain.
Pain-related behaviors have been described in critically ill patients and were studied in the AACN Thunder Project II. Patients who experienced pain during nociceptive procedures were three times more likely to have tense facial expressions, muscle rigidity, and vocalization than patients without pain. Patients who experienced pain during turning showed significantly more intense facial expressions (e.g., grimacing), muscle rigidity, and less compliance with the ventilator (e.g., fighting the ventilator) compared with patients without pain.
Behavioral indicators are strongly recommended for pain assessment in nonverbal patients, and several tools are recommended in guidelines for critically ill adults, including the Behavioral Pain Scale (BPS) and the Critical-Care Pain Observation Tool (CPOT). Implementation of the BPS and the CPOT in the critical care unit has improved pain practices and patient outcomes, with shorter duration of mechanical ventilation and shorter length of stay.
Behavioral Pain Scale
The validity of its use was supported with significantly higher BPS scores during nociceptive procedures (e.g., turning, endotracheal suctioning, peripheral veinous cannulation) compared with rest or non-nociceptive procedures (e.g., arterial catheter dressing change, compression stocking applications, eye care). The authors of the BPS determined a cut-off score >5 for the presence of pain.
Critical-Care Pain Observation Tool
Validity of the CPOT use was supported with significantly higher CPOT scores during a nociceptive procedure (e.g., turning with or without other care) compared with rest or a nonnociceptive procedure (e.g., taking blood pressure).
Positive associations were found between the CPOT scores and the patient’s self-report of pain. A cut-off score >2 was established with the CPOT in postoperative adults in critical care unit. Similarly, to the BPS, good interrater reliability of CPOT scores was achieved with critical care nurses. Feasibility and satisfaction of the CPOT were positively evaluated by nurses at 12-month postimplementation of its use in the critical care unit.
Use of Cutoff Scores
A cutoff score refers to the score on a specific scale associated with the best probability of correctly ruling in or ruling out a patient with a specific condition in this case, pain. The use of a cutoff score with behavioral pain scales can help to identify when pain is highly likely to be present and guide nurses in determining whether an intervention to alleviate pain is required or not. Also, a cutoff score can help to evaluate the effectiveness of pain management interventions. It is important to highlight that cutoff scores are established using a criterion (i.e., a gold standard in the field).
Physiologic Indicators
When patients cannot react behaviorally to pain, the only possible clues left for the detection of pain are physiologic indicators (i.e., vital signs). Although vital sign values generally increase during painful procedures, they are not consistently related to the patient’s self-report of pain, nor are they predictive of pain. For example, none of the monitored vital signs (heart rate, mean arterial pressure [MAP], respiratory rate, transcutaneous oxygen saturation [SpO2], and end-tidal CO2 capnography) predicted the presence of pain in critical care patients.
The American Society for Pain Management Nursing (ASPMN) recommendations emphasize that vital signs should not be considered as primary indicators of pain because they can be attributed to other distress conditions, homeostatic changes, and medications.
Changes in vital signs offer a cue to begin further assessment of pain or other stressors.
Fifth Vital Sign
Because pain is considered the fifth vital sign, including pain assessment with other routinely documented vital signs may help ensure that pain is assessed and controlled for in all patients on a regular basis. This approach can ensure that pain is detected and treatment implemented before the patient develops complications associated with unrelieved pain.
The use of a pain flow sheet in critical care settings allows for a visible and on-going pain assessment before and after an intervention for pain. This communication tool may be in the electronic health record, or on paper, and should be accessible to all clinicians involved in the assessment and management of pain.
Patient Barriers to Pain and Assessment Management
Communication
The most obvious patient barrier to the assessment of pain in the critical care population is an alteration in the ability to communicate. The patient who is mechanically ventilated cannot verbalize a description of the pain. If the patient can communicate in any way, such as by head nodding or pointing, pain can be reported in that manner. If writing is possible, the patient may be able to describe the pain thoroughly.
With patients unable to self-report, the nurse relies on behavioral indicators to assess the presence of pain. The patient’s family can contribute significantly in pain assessment. The family is intimately familiar with the patient’s normal responses to pain and can assist in identifying clues. A family member’s impression of a patient’s pain should be considered in the pain assessment process of the critically ill patient.
Altered Level of Consciousness
The patient who is unconscious or has an altered level of consciousness presents a dilemma for all clinicians. Because pain relies on cortical response to provide recognition, the belief that the patient with a brain injury altering higher cortical function has no perception of pain may persist. Conversely, the inability to interpret the nociceptive transmission does not negate the transmission. Experts recommend assuming that patients who are unconscious or with an altered level of consciousness have pain and that they be treated the same way as conscious patients are treated when they are exposed to sources of pain.
It has been demonstrated that behavioral indicators of pain can be observed in reaction to a painful procedure in critically ill patients, no matter what their level of consciousness. Moreover, it has been shown that some cortical activation related to pain perception is still present in unconscious patients in a neurovegetative state. Knowing this, the critical care nurse can initiate a discussion with the other members of the health care team to formulate a plan of care for the patient’s comfort.
Older Patients
Many elderly patients do not complain much about pain. Some misconceptions, such as believing that pain is a normal consequence of aging or being afraid to disturb the health care team, are barriers to pain expression for the elderly.
Cognitive deficits or delirium present additional pain assessment barriers. Many elderly patients with mild-to-moderate cognitive impairments and even some with severe impairment are able to use pain intensity scales. Elderly patients with cognitive deficits should receive repeated instructions and be given sufficient time to respond. More than 24 behavioral tools have been developed for elderly patients with cognitive deficits and some of it are:
· The Pain Assessment Checklist for Seniors with Limited Ability to Communicate (PACSLAC),
· Doloplus-2,
· Pain Assessment in Advanced Dementia (PAINAD).
Cultural Influences
· Another barrier to accurate pain assessment is cultural influences on pain and pain reporting.
· Cultural influences are compounded when the patient speaks a language other than that of the health team
members.
· To facilitate communication, the use of a pain intensity scale to facilitate the communication.
Lack of Knowledge
· A relatively overlooked patient barrier to accurate pain assessment is the public knowledge deficit regarding pain
and pain management.
· Many patients and their families are frightened by the risk of addiction to pain medication. They fear that addiction
will occur if the patient is medicated frequently or with sufficient amounts of opioids necessary to relieve the pain.
· It is important to teach the family and the patient about the importance of pain control and the use of opioids in
treating pain in critical illness.
Health Professional Barriers to Pain Assessment and Management
The health professional’s beliefs and attitudes about pain and pain management are frequently a barrier to accurate and adequate pain assessment. This can lead to poor management practices. Addiction rates for patients in acute pain who receive opioid analgesics are less than 1%. Some of the false beliefs that surround addiction result from a lack of knowledge about addiction and tolerance, and other concerns are related to the possible side effects of opioids.
Addiction and Tolerance
Addiction - is defined by a pattern of compulsive drug use that is characterized by an incessant longing for an opioid and the need to use it for effects other than pain relief.
Tolerance - is defined as a diminution of opioid effects over time.
Physical dependence and tolerance to opioids may develop if the opioid is given over a long period.
If this is an anticipated problem, withdrawal may be avoided by weaning the patient from the opioid slowly to allow the brain to re-establish neurochemical balance in the absence of the opioid.
Respiratory Depression
Another concern of the health care professional is the fear that aggressive management of pain with opioids will cause critical respiratory depression. Opioids can cause respiratory depression, but when used safely, this is a rare phenomenon. The incidence of respiratory depression is less than 2%.
PAIN MANAGEMENT
The management of pain in the critically ill patient is as multidimensional as the assessment. It is a multidisciplinary task. The control of pain can be pharmacologic, nonpharmacologic, or a combination of the two therapies. Pharmacologic pain management is predominantly used in critical care.
Pharmacologic Control of Pain
Pain pharmacology is divided into three categories of action: opioid agonists, non-opioids, and adjuvants. Elements of the Pain Agitation Delirium guidelines of the Society of Critical Care Medicine (SCCM) for pharmacologic interventions in the critically ill adult are presented for each medication. How pain is approached and managed is a progression or combination of the available agents, the type of pain, and the patient response to the therapy.
Opioid Analgesics
The opioids most commonly used and recommended as first line analgesics are the agonists. These opioids bind to mu (µ) receptors (transmission process) responsible for pain relief.
1. Morphine
2. Fentanyl.
3. Hydromorphone.
4. Meperidine.
5. Codeine.
6. Methadone
Preventing and Treating Respiratory Depression
Respiratory depression is the most life-threatening opioid side effect. The risk of respiratory depression increases when other medications with CNS depressant effects (e.g., benzodiazepines, antiemetics, neuroleptics, antihistamines) are concomitantly administered to the patient. While no universal definition of respiratory depression exists, it is usually described in terms of decreased respiratory rate (fewer than 8 or 10 breaths/minute), decreased SpO2 levels or elevated end-tidal carbon dioxide (ETCO2 levels). A change in the patient’s level of consciousness or an increase in sedation normally precedes respiratory depression.
Monitoring. Recent ASPMN monitoring guidelines for patients receiving opioid analgesia recommend evaluation of respirations over 1 minute and assessed according to rate, rhythm, and depth of chest excursion. The use of technology supported monitoring (e.g., continuous pulse oximetry and capnography) are recommended in high-risk patients.
Opioid reversal. Critical respiratory depression can be readily reversed with the administration of the opioid antagonist naloxone. The usual dose is 0.4 mg, which is mixed with 10 mL of normal saline (for a concentration of 0.04 mg/mL). Naloxone is administered intravenously very slowly (0.5 Ml over 2 minutes) while the patient is carefully monitored. Naloxone administration is discontinued as soon as the patient is responsive to physical stimulation and able to take deep breaths. However, the medication should be kept nearby. Because the duration of naloxone isshorterthan most opioids, another dose of naloxone may be needed as early as 30 minutes after the first dose.
Sedative with Analgesic Properties: Dexmedetomidine
Dexmedetomidine (Precedex) is a short-acting alpha-2 agonist that is indicated for the short-term sedation (<24 hours) of mechanically ventilated patients in the critical care unit. Dexmedetomidine acts in the locus ceruleus section of the brainstem.
Nonopioid Analgesics
In the SCCM guidelines, the use of nonopioids in combination with an opioid is recommended in selected critical care patients. This may reduce the opioid requirement.
Acetaminophen
An analgesic used to treat mild-to-moderate pain. It inhibits the synthesis of neurotransmitter prostaglandins in the CNS.
Nonsteroidal antiinflammatory agents
The use of NSAIDs in combination with opioids is indicated in the patient with acute musculoskeletal and soft tissue inflammation. The mechanism of action of NSAIDs is to block the action of cyclooxygenase (COX, which has two forms: COX-1 and COX-2), the enzyme that converts arachidonic acid to prostaglandins. This inhibits the production of prostaglandins.
Ketamine
Anesthetics may be used to treat pain in the critical care setting. Ketamine is a dissociative anesthetic agent that has analgesic properties. Compared with opioids, ketamine has the benefit of sparing the respiratory drive, but it has many side effects related to the release of catecholamines and the emergence of delirium. Not recommended for routine therapy in critically ill patients.
Lidocaine
An anesthetic that can be used for procedural pain, neuropathic or non-neuropathic pain conditions. Because lidocaine is metabolized in the liver, it should be used with caution in patients with hepatic dysfunction.
Delivery Methods
The most common routes for medication administration are continuous intravenous infusion, bolus administration, or patient-controlled analgesia (PCA). The benefits of this method are the rapid onset of action and the ease of titration. This promotes a consistent level of comfort.
Patient-Controlled Analgesia
PCA is an effective method using intravenous route and an infusion pump for medication delivery. It allows the patient to self-administer small doses of analgesics.
Intraspinal Pain Control
Intraspinal anesthesia uses the concept that the spinal cord is the primary link in nociceptive transmission. The goal is to mimic the body’s endogenous opioid pain modification system by interfering with the transmission of pain and providing an opioid receptor binding agent directly into the spinal cord.
Intrathecal Analgesia
Intrathecal (subarachnoid) opioids are placed directly into the cerebral spinal fluid and attach to spinal cord receptor sites. Opioids introduced at this site act quickly at the dorsal horn.
Epidural Analgesia
Epidural analgesia is commonly used in the critical care unit after major abdominal surgery, nephrectomy, thoracotomy, and major orthopedic procedures.
Equianalgesia
When a modification of opioid is considered, the goal is to provide equal analgesic effects with the new agents. This concept is referred to as equianalgesia. Prescribed dosages must take into account the patient’s age and health status. Because of the variety of agents and routes, the professional pain organizations have developed equianalgesia charts for use by health care professionals.
Nonpharmacologic Methods of Pain Management
Nonpharmacologic methods can be used to supplement analgesic treatment, but they are not intended to replace analgesics. In most instances, these therapies may enhance the pharmacologic management of the patient’s pain.
It is crucial that critical care nurses be provided with the appropriate training and equipment required to apply nonpharmacologic methods for pain management in the critically ill.
Physical Techniques
Stimulating other non–pain sensory fibers (Aβ) in the periphery modifies pain transmission. These fibers are stimulated by thermal changes as in the application of heat or cold and simple massage.
Cold Application
Ice therapy was found to be helpful to reduce procedural pain in critically ill patients.
Massage
The effect of massage on pain relief was explored and the result is a significant decrease in pain intensity scores was obtained in patients who received a 20-minute massage intervention between postoperative day 2 and day 5 compared to a control group who received standard care and a 20-minute quiet time during the same period.
Cognitive-Behavioral Techniques
Using the cortical interpretation of pain as the foundation, several interventions can reduce the patient’s pain report.
Relaxation
Relaxation is a well-documented method for reducing the distress associated with pain. Although not a substitute for pharmacology, relaxation decreases oxygen consumption and muscle tone, and it can decrease heart rate and blood pressure.
Guided Imagery
Guided imagery is a technique that uses the imagination to provide control over pain. It can be used to distract or relax.
Music Therapy
Music therapy is a commonly used intervention for relaxation. Music that is pleasing to the patient may have soothing effects, but its effects on reducing pain are controversial.