Pain management is key to ensuring optimal recovery from illness or injury, however accurately assessing pain levels in non-communicative patients is a major challenge. Several tools are currently used to address this, including the Behavioural Pain Scale (BPS), Critical Care Pain Observation Tool (CPOT) and Non-Verbal Pain Scale (NVPS) – but which is most reliable? In a study in Critical Care, Gerald Chanques from the University of Montpellier, France, and colleagues, analysed the psychometric properties of each of these pain scales in non-communicative patients in intensive care units. Here Chanques discusses the challenges and importance of pain assessment in critically ill patients, and how these latest findings may impact clinical practice.
From a physiological standpoint, how much pain can be experienced when a patient is not fully conscious, such as during critical illness?
Pain is a frequent event in Intensive Care Unit (ICU) patients, with an incidence of up to 50 percent in medical as well as surgical and trauma patients. If pain intensity cannot be self-reported in some patients with an impaired level of consciousness (delirium, sedation, coma), the acute stress-response associated with pain can be assessed: pain behaviour (grimacing), agitation, changes in heart and respiratory rates, blood pressure, and pupil size.
From a physiological standpoint, these changes in neuro-vegetative system activity and brain functioning may be associated with higher oxygen consumption, cardiac arrhythmia, ischemic events, and patient/ventilator asynchrony. Also, there might be an increased risk of developing a chronic pain syndrome if high intensity pain events are repeated while in the ICU.
Why is it important to measure pain levels in critically ill patients?
Pain assessment is the first step precluding an accurate diagnostic and treatment of pain that consists of a good match between a patient’s needs and the analgesics dose i.e. providing effective analgesia while avoiding the side effects associated with an overdose of analgesics.
Pain protocols based on a validated measure of pain intensity in critically ill patients allows for decreasing adverse physiological events during painful nursing procedures. Also, reports from large observational and high quality sequential ‘before and after’ studies showed a significant association between pain assessment and patients’ outcomes in the ICU: decreased duration of mechanical ventilation, decreased length of stay in ICU, and decreased nosocomial complications. Explanations are multiple, including better prevention of the acute stress response and analgesics side effects, but also a decreased use of sedatives.
How is pain currently measured in critically ill patients, and are different approaches taken in different settings?
Pain assessment is well standardised in critically ill patients. As widely recommended by national critical care societies, pain should be assessed by self-reporting scales in patients able to communicate, or by behavioural pain scores in patients unable to communicate. However, such pain assessment using accurate clinical tools remains below average in 50 percent of ICU patients. This is mainly determined by differences in the implementation of recommended practices into routine care.
What problems do you encounter when trying to measure pain in critically ill patients?
Pain assessment is basically clinical in most ICU patients (self-reporting pain scales, behavioural pain scores), so education and training of nurses and physicians is paramount to insure standardised and reliable use of such subjective tools. An important inter-observer agreement is necessary before implementing analgesia protocols based on a subjective assessment of pain in a multidisciplinary ICU team with a number of professionals.
What were the key findings from your study? Were you surprised by any of the results?
The key findings are that some behavioural pain scores (BPS, CPOT) have significantly higher psychometric properties (inter-rater reliability, internal consistency and responsiveness) than others (NVPS). This was not so surprising because BPS and CPOT are the two behavioural pain scores recommended for practice by the Society of Critical Care Medicine (SCCM). However, though these two scores had been very well validated separately, they had never been evaluated comparatively. The purpose of this study was to address this and also compare these two scores, which are routinely used, to another score i.e. NVPS.
What are the implications of your study for current clinical practice?
Our study definitively suggests that either BPS or CPOT appear to be superior tools and should be chosen in ICUs where no behavioural pain scale has been implemented yet – this is consistent with the recent practice guidelines.
What’s next for your research?
This is the most difficult question. We should probably better understand why some ICU teams succeed in implementing these tools while others don’t. What are the barriers and facilitators to successfully implement a behavioural (subjective) pain tool? What are the most appropriate education and training methods?
Also, beyond assessment of pain in patients who are unable to communicate but still have the possibility of demonstrating a pain behaviour (e.g. grimacing, moving the limbs), we should now determine which pain assessment tool is recommended in other selected critically ill patients, especially brain injured patients and patients receiving neuromuscular blocking agents.