We all know that physical pain can immensely affect our quality of life. However, as much as it is an undesirable experience, pain is also a fundamental aspect of our existence. Remarkably, our bodies have devised an outstanding defensive mechanism to protect our organs from injury and the potential accompanying pain1.
The term pain is by definition reserved for a conscious perception of actual or potential tissue damage and cannot be used during an unconscious state. Therefore, the term nociception was introduced and describes the neural process of encoding noxious stimuli2.
Nociception refers to the peripheral (PNS) and central nervous system (CNS)3 processing of information about the internal or external environment, as generated by activation of nociceptors. Typically, noxious stimuli, including tissue damage, activate nociceptors that are present in peripheral structures and transmit information to the spinal cord dorsal horn.
Pain management is an essential element in the medical health system and in patient care. Medicine has advanced in uncovering the physiological process of pain, and more recently the underlying mechanisms of nociception have gained increasing attention in the medical community1,4.
Managing analgesia during surgery impacts outcomes, length of stay (LOS) and cost of treatment. It is a major challenge as each patient has a different pain threshold and different physiological responses to the same painful stimulus. Furthermore, studies have shown a wide range of opioid administration practice across physicians, depending on their personal beliefs and experiences. Therefore it is vital to monitor each patient’s personal response and personalise the treatment experiences5.
How can you treat pain if it cannot be measured? Anti-nociceptive agents (analgesic medications) are given to patients as part of the general anaesthesia drug regimen, yet physicians have testified that with current methods and technologies, it is extremely difficult to estimate the level of nociception in an anaesthetised patient6. Maintaining the balance between nociception and analgesia (the ‘nociception-antinociception balance’) is critical to avoid postoperative complications7.
Physicians are familiar with the traditional nociception detection methods in anaesthetised patients, which have mainly relied on monitoring blood pressure and heart rate. Yet these have been shown to be suboptimal indicators for nociception monitoring, since vital signs are influenced by a variety of other health conditions8. Various other methods have been used to assess the effectiveness of anti-nociceptive drugs, such as assessment of patient movement and sweating. Nevertheless, these surrogate parameters are largely inaccurate since several anaesthetic components, such as neuromuscular blockers, prevent the patient’s ability to move in response to pain9.
The lack of accurate nociception monitoring during surgery may lead to administering inadequate doses of analgesics. Opioids are widely used as intraoperative antinociceptive agents. However, administering an insufficient dose of opioids may lead to abnormal recovery, delayed hospital discharge, and in some cases, chronic postoperative pain (CPOP). On the other hand, administering too much opioids may cause nausea, vomiting, and life-threatening respiratory depression10.
When nociception monitoring is more accurate, such complications could be avoided. Currently, up to 75% of patients experience moderate to severe pain immediately after surgery4. This increases risk of hemodynamic instability, debilitated wound healing and the development of persistent pain that may lead to reduced mobility11. Specifically, one meta-analysis revealed that 57% and 47% of thoracic surgery patients experience pain that lasts for 3 and 6 months respectively12. In addition, it is worth noting that nociceptive stimulation has been demonstrated to be partially responsible for this thoracic pain response7.
Monitoring nociception levels is a relatively new branch of medical science that has evolved to address the need for better pain management during and after surgical procedures. The Nociception Level index (NOL® index) is a novel technology developed by Medasense Biometrics Ltd. that enables objective measurement of patient’s nociception by analysing multiple patient parameters and overcoming the limitations of individual surrogates for measurement. A non-invasive finger probe with four sensors (photoplethysmography wave amplitude, galvanic skin response, peripheral temperature, and accelerometery) extracts multiple pain-related physiological signals. Algorithms analyse the data in real-time and identify the patient’s pain-related pattern, which is displayed on a numerical scale. Widely adopted by physicians, this device provides close monitoring of anaesthetised patients’ nociception response and enables surgical teams to provide personalised analgesic treatment for each patient. NOL® provides multiple benefits, including smoother procedures13, better patient outcomes13 and cost savings14.
A recent study found that monitoring pain response levels during surgery with NOL® can even help reduce postoperative pain by 33%. Furthermore, the patient’s stress hormone levels (ACTH and cortisol), reported as % of baseline, were up to 50% lower in the NOL®-guided group, both during and after surgery. This provides objective validation that titrating analgesia through NOL® monitoring improves pain-control13.
Other evidence15 showed that NOL®-guided opioid administration was associated with a 30% reduction in intraoperative opioids usage (remifentanil) and 80% fewer hypotensive events. Considering the evidence, that intraoperative hypotension increases the risk of myocardial injury, acute kidney injury and mortality, this study demonstrates the potential of NOL® to reduce the probability of postoperative complications.
The need for nociception management also extends beyond the OR. Despite decades of research, pain management in the ICU remains a challenge to this day, especially for critically ill and non-communicating patients. Unrelieved pain in patients has significant physiological and psychological consequences, such as prolonged mechanical ventilation, hemodynamic deregulation, delirium, increased infection rate and suppression in the immune system16. Currently, ICU doctors use various behavioural pain scores to assess pain levels in patients unable to communicate their pain levels.
Practice guidelines do not recommend the use of vital signs for this purpose. The NOL® index can measure pain in sedated and mechanically ventilated patients in the Intensive Care Unit. As indicated in several guidelines, NOL® technology allows physicians to identify different levels of painful stimuli in deeply sedated or paralysed patients for optimal pain control17.
Treating pain is at the core of medicine. Tackling the clinical gap of proper intraoperative nociception management is a critical responsibility of healthcare professionals towards patients. With a new, state-of-the-art solution for continuous intraoperative nociception monitoring now available, anaesthesiologists, surgeons and other health care professionals can offer personalised analgesia to their patients. This is a significant step forward towards better management of patients’ intraoperative pain, as well as improving postsurgical outcomes and patient safety.
Rachel Weissbrod - VP Clinical, Regulatory & Quality Medasense
Yassmin Sherif - Digital Marketing Specialist Medtronic
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