Critically ill patients in the Intensive Care Unit (ICU) frequently endure pain, both from necessary medical procedures and at rest. Procedures like chest tube removal, tracheal suctioning, wound care, repositioning, and arterial line insertion are documented as particularly painful. If acute pain is not properly managed in adult ICU patients, it can lead to serious short-term and long-term complications, including postoperative myocardial infarction, sleep disturbances, and post-traumatic stress disorder. Clinical guidelines emphasize the importance of individualized and goal-directed pain management, which starts with systematic pain assessment using validated pain scales appropriate for the patient’s consciousness level. However, assessing pain in critically ill patients is often complicated by factors such as mechanical ventilation, severe illness, the use of sedatives and analgesics, and altered levels of consciousness. When patients cannot self-report their pain, clinical guidelines recommend using validated behavioral pain scales for assessment.
Two independent systematic reviews evaluating pain assessment tools for non-verbal ICU patients highlighted the Critical-Care Pain Observation Tool (CPOT) and the Behavioral Pain Scale (BPS) as having the strongest psychometric properties. These reviews, along with recent clinical practice guidelines, recommend both CPOT and BPS for assessing pain in nonverbal, critically ill adults. The CPOT was specifically designed for pain assessment in this challenging patient population. This tool evaluates four behavioral categories: facial expression, body movements, muscle tension, and, for intubated patients, compliance with ventilation, or vocalization for extubated patients. Each category is scored from 0 to 2, resulting in a total score range of 0 (no pain) to 8 (maximum pain). A CPOT score cutoff of >2 is indicative of pain during nociceptive procedures.
One noted limitation of the CPOT is the limited research on its effectiveness in critically ill patients experiencing delirium. Delirium is a common complication in the ICU, with incidence rates after cardiac surgery ranging from 3–55%, and an average overall incidence in critically ill patients between 30–50%. Self-reporting of pain is particularly challenging in delirious patients due to communication difficulties, fluctuating consciousness, and potentially altered pain presentation. Therefore, validating behavioral pain scales like the CPOT in this specific population is crucial. Kanji and colleagues addressed this gap by investigating the validity and reliability of the CPOT in adult critically ill patients with delirium. Their study included 40 ICU patients diagnosed with delirium using the Confusion Assessment Method-ICU (CAM-ICU). Patients unable to demonstrate a reliable physical response to pain were excluded. The researchers rigorously assessed several key psychometric properties of the CPOT, including discriminant validity, interrater reliability, and internal consistency. Discriminant validity assesses a scale’s ability to differentiate between different states, often tested by comparing scores during painful versus non-painful procedures. Interrater reliability measures the consistency of scores when different raters assess the same patient. In their study, non-invasive blood pressure measurement served as a non-painful procedure, while repositioning, endotracheal suctioning, or dressing changes were considered painful. The average score difference between baseline and painful procedures was 3.13±1.56 (P<0.001). Kanji et al. concluded that their findings suggest the CPOT is a valid and reliable instrument for detecting pain in non-comatose, delirious adult ICU patients.
Despite the meticulous design and execution of the Kanji et al. study, definitive conclusions about CPOT’s use in delirious patients remain cautious. A significant concern is the absence of data regarding delirium severity, delirium subtypes, and the correlation between the Richmond Agitation-Sedation Scale (RASS) score and CPOT score. The DSM-V categorizes delirium into three subtypes: hyperactive, hypoactive, and mixed. Hyperactive delirium is characterized by heightened vigilance, restlessness, aggression, and intense emotions like anger or anxiety. Hypoactive delirium presents with reduced alertness, sparse speech, and apathy. The mixed form involves alternating periods of hyperactive and hypoactive delirium. Peterson et al. defined these subtypes based on RASS scores, with hyperactive delirium indicated by a persistently positive RASS score (+1 to +4). In delirious patients, pain and agitation can be intertwined, potentially leading to elevated CPOT scores due to agitation rather than pain. Furthermore, the influence of sedation requires further investigation. Kanji et al.’s study reported a median RASS of 0, ranging from -3 to +3, indicating inclusion of patients exhibiting anxious or apprehensive movements (RASS +1), frequent non-purposeful movements or patient-ventilator dyssynchrony (RASS +2), or aggressive behavior towards staff (RASS +3). All four CPOT domains could be affected by high RASS scores, potentially resulting in inappropriately elevated CPOT scores. These inflated scores might lead to unnecessary analgesic administration when anti-delirium medication would be more appropriate. A recent validity study of CPOT and BPS in a subgroup of seven agitated patients (RASS +1) showed non-significant increases in CPOT scores between rest and painful procedures, and no difference between non-painful and painful procedures. Baseline CPOT scores were also higher in this small subgroup compared to patients with RASS < +1. Although a small sample, this suggests that CPOT validity in patients with hyperactive delirium and/or RASS > +1 needs further study.
In contrast to previous research, Kanji et al. reported interrater reliability for each of the four CPOT domains rather than for different procedures (painful vs. non-painful or rest). This approach deviates from typical ICU practice, where CPOT is used as a composite score across domains during various situations like tracheal suctioning or rest. Consequently, the interrater reliability of CPOT in delirious patients during different procedures remains unclear.
A close-up view of the Critical-Care Pain Observation Tool (CPOT) assessment form
Furthermore, in Kanji et al.’s study and previous research, assessments often involved investigators or physicians. However, in routine clinical practice, nurses are the primary assessors of pain in the ICU. Bedside nurses may have a more nuanced understanding of patient reactions due to longer contact times. Future interrater reliability studies should include a broader range of raters. Finally, the existence of at least six versions of the Intraclass Correlation Coefficient (ICC), which can yield different results with the same data, poses another concern. Kanji et al. did not specify which ICC model was used in their analysis, making it unclear if the chosen model was appropriate.
In conclusion, the study by Kanji et al. represents a valuable initial step in validating the CPOT for pain assessment in critically ill patients with delirium. However, future assessments of CPOT interrater reliability should better reflect daily ICU practice. Larger studies with sufficient representation of delirium subtypes and patients with RASS > +1 are necessary before definitively concluding that the CPOT is a valid and reliable pain assessment tool for ventilated, critically ill patients with delirium.
References
1 Chanques G, Jaber S, Barriere E, et al. Pain assessment in critically ill patients: comparison of 5 self-report scales. J Crit Care 2010;25:417–24.
2 Puntillo KA, Morris AB, Thompson CL, et al. Pain behaviors observed during six common procedures: results from multicenter critical care pain observation tool validation study. Crit Care Med 2004;32:421–7.
3 Gordon DB, Dahl J, Phillips P, et al. The use of ‚Äúpain as the 5th vital sign‚Äù across health care settings: lessons learned and future directions. Pain Med 2005;6:241–7.
4 Fletcher D, Breivik H, Rosseland LA, et al. Factors predictive of chronic pain persistence‚Äî‚Äîevidence from a篩n international survey of patients undergoing surgery. Pain 2015;156:2238–47.
5 Weinhouse GL, Schwab RJ. Sleep in the intensive care unit: общие considerations. Sleep Med Clin 2015;10:203–15.
6 Devlin JW, Skrobik Y, Gélinas C, et al. Clinical practice guidelines for the prevention and management of pain, agitation, delirium, immobility, and sleep disruption in adult patients in the ICU. Crit Care Med 2018;46:e825–e873.
7 Gélinas C. Pain assessment in the critically ill ventilated adult: validation of the critical-care pain observation tool and physiologic indicators. Pain 2006;125:47–54.
8 Rijkenberg S, Stilma CR, Ouwerkerk J van, et al. Assessment of pain in critically ill adults who cannot self-report. Pain Manag 2018;8:377–93.
9 Barr J, Fraser GL, Puntillo K, et al. Clinical practice guidelines for the management of pain, agitation, and delirium in adult patients in the intensive care unit. Crit Care Med 2013;41:263–306.
10 Chanques G, Gélinas C, Savelli D, et al. Pain assessment in the intensive care unit: nurses’ adherence to recommendations and barriers. Intensive Care Med 2010;36:1684–91.
11 Kreutzer MJ, Poklepovich J, Riley B, et al. Society of Critical Care Medicine, American College of Chest Physicians, American Society of Health-System Pharmacists. Clinical practice guidelines for sustained neuromuscular blockade in the adult critically ill patient. Crit Care Med 2016;44:e117–e159.
12 Odhner M, Wegman D, Freeland N, et al. Assessing pain in nonverbal patients after cardiac surgery. Pain Manag Nurs 2003;4:158–67.
13 van den Boogaard M, টেক্সট সুরকার M, Peters ML, et al. The impact of delirium after cardiac surgery on cognitive functioning. Int J Geriatr Psychiatry 2009;24:125–34.
14 Ouimet P, Kavanagh BP, Gottfried SB, et al. Incidence, risk factors and consequences of ICU delirium. Intensive Care Med 2007;33:66–80.
15 Kanji F, Singh A, Katz J, et al. Validity and reliability of the critical-care pain observation tool in critically ill patients with delirium. J Crit Care 2020;57:13–20.
16 Koo TK, Li MY. A guideline of selecting and reporting intraclass correlation coefficients for reliability research. J Chiropr Med 2016;15:155–63.
17 Peterson JF, Pun BT, Dittus RS, et al. Delirium and its motor subtypes: a study of 614 critically ill patients. J Am Geriatr Soc 2006;54:479–83.
18 De Jonghe B, Cook D, Appere-De-Vecchi C, et al. Using and understanding pain and sedation scales throughout the ICU stay. Intensive Care Med 2019;45:847–9.
19 McGraw KO, Wong SP. Forming inferences about some intraclass correlation coefficients. Psychol Methods 1996;1:30–46.
