The quantification and monitoring of intraoperative nociception levels in thoracic surgery: a review

Nociception is the unconscious perception of a stimulus applied by trauma or surgery and expressed through a response of the autonomous nervous system. Local anaesthetics (LAs), opioids and other modulating agents such as ketamine are usually utilised to blunt nociception as a component during general anaesthesia (GA) and surgery. The effectiveness of these measures, however, are still difficult to quantify and monitoring of anti-nociception has been confined to assess variation of heart rate (HR) or blood pressure (BP). Recently, various monitoring concepts have been introduced to quantify nociception more systematically and on the other hand guide anti-nociceptive interventions more appropriately. This review describes the various technologies, their performance in clinical studies and provides a critical appraisal with particular application to thoracic anaesthesia and surgery and their relevance in the context of chronic pain after surgery.