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Pain is a frequent source of stress in the ICU and is experienced by nearly all critically ill patients during their stay.1 Inadequate recognition and management of pain is associated with an increased risk of hemodynamic instability, hyperglycemia, alterations in immune system functioning, and release of catecholamines, cortisol, and antidiuretic hormone.2
In addition, it's possible for untreated acute pain to produce neurohumoral changes, neuronal remodeling, and long-lasting psychological and emotional stress, which may lead to prolonged chronic pain states.3 Yet, the under treatment of pain is common in the ICUs due to lack of recognition and concerns about the adverse effects of medications (respiratory depression and hemodynamic compromise).4 This is especially troubling as pain and anxiety in the critically ill are inextricably linked, with both contributing to poor outcomes in the critically ill patient.
The recent DOLOREA study highlighted the importance of pain management in the ICU by demonstrating a reduction in the use of hypnotics, midazolam, duration of mechanical ventilation, and ICU length of stay with a standardized assessment of pain.5
The assessment and treatment of pain is mandated by multiple regulatory bodies including The Joint Commission, and the Centers for Medicare and Medicaid Services, and is now a publically reported quality measure.6,7 In addition, multiple best practice organizations, including the American Society for Pain Management Nursing (ASPMN), the Society for Critical Care Medicine (SCCM), and the American Association of Critical Care Nurses (AACN), have developed guidelines to arm nurses with the information needed to perform an evidence-based approach to pain management in the critically ill (see The pathophysiology of acute pain).8-10 The purpose of this article is to summarize the most recent evidence on the assessment of pain in the critically ill adult and provide specific clinical practice recommendations for critical care nurses.
Nerve function, as well as psychological, emotional, spiritual, and environmental factors, all play a role in how pain is ultimately perceived by the patient. The variability of this process is exemplified in the different perception of pain from one person to the next; providing further evidence that each person's pain is subjective. Patients present with differing developmental levels, language barriers, cognitive and emotional variances that affect the perception of pain. These differences, combined with the complexity of critical illness, give rise to challenges in adequately assessing and treating pain.
Often, it's left to the caregivers, physicians, and nurses, to determine if symptoms are managed well. It's nurses who are at the bedside and are generally responsible for advocating for the patient's well-being. The nurse's understanding of the patient's comfort level can help the nurse better care for the patient and avoid under or overtreatment.
Unfortunately, clinician perception of pain is often skewed. This issue is well established through studies over the years in which patient pain intensity reports don't correlate with the nurses' assessments.13 A study published in 2013 amplifies this concern that nurses' perceptions of patients' pain are underestimated compared with patient experiences.13 A study of a cross section of 86 ICU nurses in three different hospitals was designed to describe the nurses' perceptions of unpleasant signs and symptoms in mechanically ventilated adults. They were asked to estimate the likelihood of the occurrence of certain unpleasant symptoms among their patients. While previous studies have established that most ICU patients report pain, more than half of the surveyed nurses reported that pain, anxiety, or dyspnea occurred in less than 20% of the patients. The authors considered this to be an underestimation of pain.
With increasing complexity of technology and advances in the science of critical illness, patients in the ICU possess varying levels of ability to report their needs. As the trend toward minimal sedation has proceeded, the population of the ICU has changed. While some patients may be alert and able to respond verbally, others may have varying levels of consciousness or mental clarity. It's with these patients that the approach to pain management is most challenging. The fact that pain exists and is perceived no matter the level of consciousness has been established.
The critically ill patient experiences pain due to varying causes, including: disease process, surgery, trauma, and medical interventions. The range of procedures, spanning from patient turning and repositioning to mechanical ventilation and endotracheal suctioning, inherently cause some level of discomfort.
Critical care patients in a landmark study done by Puntillo were asked about their pain experiences after transfer from the ICU. A majority reported moderate-to-severe pain from such causes as incisions, movement, coughing, suctioning, and chest tube removal.14
More recently, a multinational study of 3,851 patients in ICUs who were able to self-report, cited chest tube removal, wound drain removal, and arterial line insertion as the most painful procedures experienced.15 Other causes of pain in the ICU are immobility and infection.
Self-report of pain is the gold standard of pain assessment and should be the primary assessment method in critically ill patients who're capable of providing the information to the provider.8-10 However, many patients in the intensive care unit are incapable of self-report by nature of their illness (shock, respiratory failure, cerebral insult) or by nature of the therapies being provided (mechanical ventilation, sedation). Healthcare professionals are bound by ethical principles to provide comfort to all patients whether they're able to speak for themselves or not.10
Foremost to the approach to pain should be a plan for a systematic assessment.12 An established and routine monitoring and assessment of pain improves treatment, communication, and patient satisfaction. It's necessary to provide ongoing assessment not only to determine the approach toward management, but also to evaluate the outcomes. Within the ASPMN guidelines from 2006 are recommendations for a hierarchical approach to the intubated and/or unconscious person unable to self-report.10 Self-report should be elicited with every assessment for pain. The variability of consciousness in this population makes it sometimes possible to obtain a self-report, while other times not. The ASPMN guidelines further provide for a step-wise approach to treat pain when the self-report isn't feasible.
The next step in this hierarchical approach is to identify diagnoses or procedures that would be considered painful in the fully conscious, verbal patient. As noted previously, many procedures associated with critical illness are painful, some more than others. It's assumed that the nonverbal patient also has pain due to these potential causes of pain. Pasero and McCaffery in 2002 introduced the concept "assume pain is present" as a means of documenting this unconfirmed pain based solely upon the fact that procedures or pathologies exist in this patient that are normally considered painful.16
Patient behaviors may be observed as clues to pain assessment. Behaviors have been correlated with pain intensity scales in the patient who's able to self-report.17 When appropriate, behavioral assessment through the use of tools can help provide consistent systematic evaluation between clinicians over time. In patients incapable of self-report, a multitude of tools exist to identify the presence of pain. The optimal behavioral assessment tool is valid, meaning its variables measure what it's designed to measure (pain, in this case) and reliable, meaning that it identifies what it's intended to identify all of the time, regardless of who administers the tool. The best tools are also highly sensitive, meaning that if pain is present, it's detected, and specific, meaning that the tool identifies only pain and isn't subject to interference from other clinical conditions (such as anxiety or delirium).
It's important to remember that observational pain scales require the presence of a spontaneous, neuromuscular-mediated physical response that can be observed by a third party in order to be effective. Therefore, patients with quadriplegia, neuromuscular disorders, and those receiving neuromuscular blocking agents, are unable to be assessed with these tools.
Additionally, patients with significant neurologic injury, hemodynamic compromise, or delirium were commonly excluded in the testing of these tools, making it difficult to conclude if the tools are valid and reliable in these patient populations.21,23,28
Obtaining the perspective of the family or caregivers of the patient is another element in the assessment of pain. While the opinion of a family member cannot be solely used as an accurate interpretation of the patient's pain, it's important to include their opinions in the assessment based upon their familiarity and past experiences with the patient.
Finally, if the observations made previously provide sufficient data that pain is present, an analgesic trial may be initiated. This is because several of the behaviors (for example, body movement, ventilator dysynchrony) found on behavioral assessment tools are nonspecific for pain, and can indicate the presence of other conditions, such as anxiety or dyspnea.
While analgesics are initiated, the patient's behaviors are observed for any changes that would indicate some positive response. After the analgesic trial, the continuation of the analgesic regimen is determined based upon the response, and other goals of care. Different medications may be more appropriate in certain situations. For example, the ASPMN guidelines suggest weighing the risks and benefits of increasing opioids in the brain-injured patient who needs neurologic assessments. In this case, shorter acting opioids may be used. Similarly, nonopioid medications may be just as useful for certain types of pain without the sedative adverse reactions.
Pain assessment in the critically ill is challenging, but exceedingly important work. Guidelines have been put forth by three national organizations to meet the challenge of assessing pain in this population. Within these guidelines, general recommendations for utilization of a hierarchy of pain assessment techniques are supported, as outlined earlier.
The assessment of pain should be completed on a routine basis. Self-report of pain is the most reliable method of pain assessment and should be attempted with all patients. In patients undergoing potentially painful interventions (turning, endotracheal suctioning), preemptive treatment is recommended. If self-report is unable to be obtained, the use of a behavioral assessment tool, such as the Behavioral Pain Scale (BPS) or Critical-Care Pain Observation Tool (CPOT) should be used. Changes in vital signs can indicate the presence of pain, but shouldn't be used independently to determine the presence of pain. Additional methods such as proxy reporting or attempting an analgesic trial, can be used in patients who are unable to be assessed through behavioral assessment scales. (See Behavioral pain assessment tools.)
Since publication of the various guidelines, some issues have arisen that may benefit from further exploration. Specifically, research has been proposed to evaluate the usefulness of behavioral tools in patients with traumatic brain injuries. It may be deduced that since the brain plays a role in the perception of pain, injury to the brain could pose unique assessment challenges.
Similarly, patients receiving neuromuscular blockade or those with delirium, quadriplegia, or significant neurologic insults (such as the comatose patient) may not exhibit typical pain behaviors. Continued exploration into the objective study of pain using alternate techniques may provide evidence for pain perception in these patients.
The variability of pain perception from patient to patient is inherent in his or her own brain activity and experiences. An understanding of basic physiology of acute pain is important to provide the caregiver a foundation to support appropriate assessment and interventions.11 The process of how pain occurs normally in the body is called nociception.12
Nociception involves four steps: transduction, transmission, perception, and modulation.
The process begins with transduction, or the activation of neurons by a noxious stimulus. The activation begins with a release of chemical mediators that result in an action potential, and ultimately a pain impulse.
Next, in transmission, the impulse is transmitted from the site of the noxious stimulus, along A-delta fibers and C fibers across the spinal cord at the dorsal horn, and to the brain.
It's in the brain where pain perception becomes complex. Several areas of the brain play a role in the awareness of pain: the limbic system, responsible for behavior and emotional responses; the reticular system where motor and autonomic responses are formed; and the somatosensory cortex where memory and cognitive recognition of pain takes place. Therefore, pain is influenced through sensory input, affective response, and cognitive evaluation learned over time.11
The fourth step in the process of nociception, modulation, refers to the amplification or reduction of pain signal intensities that play a role in changing the person's reaction to the pain.
In recent years, several systematic reviews have been completed to identify the most valid and reliable tool for use in critically ill adults. In all of these reviews, the BPS and the CPOT have been identified as the superior tools.9,18,19
The BPS is designed for mechanically ventilated patients and consists of three observational domains (facial expression, upper limb movements, and compliance with mechanical ventilation) that are scored from 1 to 4, with higher numbers indicating higher levels of discomfort.
The total BPS score can range from 3 (no pain) to 12 (maximum pain). The BPS has been tested extensively in critically ill patients and found to be valid and has demonstrated high interrater agreement, and good internal consistency. From a practice standpoint, the BPS is easy to use and takes an average of 2 to 5 minutes to complete.20-25
The CPOT is designed for use in both intubated and nonintubated critical care patients. Four domains, including facial expression, body movements, muscle tension, and ventilator compliance or vocalization (extubated patients), are scored from 0 to 2, with a total score ranging from 0 (no pain) to 8 (maximal pain).
The CPOT was originally developed in French, with subsequent versions being tested in English and Spanish.26-28 Like the BPS, the CPOT has proven to be valid and reliable.28 In testing, the CPOT has demonstrated a sensitivity of 86% and a specificity of 78% during painful procedures, with the sensitivity decreasing to 83% prior to a painful procedure and 63% following the painful procedure. Specificity remained high at 83% and 97%, respectively.30 In clinical practice, 100% of the nurse respondents reported that the CPOT directives were clear and that the tool was easy to use. The majority also reported that the CPOT was quick to use (78%), and that they would recommend the use of the CPOT routinely in practice (72.7%).31
There are several limitations that need to be acknowledged when a BPS is used. It's important to note that both tools have been unable to demonstrate a consistent correlation with the patient's self-report of pain, especially when the patient was scored as having "no pain" on the BPS or CPOT. In addition, an increasing score on a behavioral pain assessment tool doesn't equate to an increasing severity of pain as on a 0 to 10 self-report tool.12 Clinical nurses are encouraged to use these tools only to indicate the presence of pain and provide analgesia when indicated.
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