Noninvasive monitor assesses patients’ response to painful stimulation during surgery

A novel measure for assessing the body’s response to surgery may allow for better anaesthesia management, less pain when regaining consciousness from anaesthesia and better postoperative outcomes. According to a study published in the Online First edition of Anesthesiology, the measure, called the nociception (pain) level index, allowed physicians to more accurately evaluate responses to painful stimulation in patients under general anaesthesia, compared to traditional measures.

“There’s currently no standardised, objective method for physicians to monitor the effectiveness of pain relieving drugs being administered during surgery,” said Ruth Edry, lead study author and senior physician anaesthetist at Rambam Medical Center in Haifa, Israel. “Not effectively monitoring bodily responses to painful stimulation can lead to insufficient amounts of pain medication being administered, which can result in the patient having severe pain upon regaining consciousness from anaesthesia, while too much medication may cause other side effects such as nausea and vomiting or respiratory complications.”

The nociception (pain) level index, which uses an algorithmic combination to process multiple hormonal and neurological reactions, aims to provide a better, earlier measure of the body’s reflex response to painful stimulation during surgery, compared to the traditional monitoring of individual factors such as changes in heart rate or blood pressure.

In the study, 58 patients who had general anaesthesia for a variety of different surgical procedures were examined. Routine anaesthesia monitoring was supplemented with a pain monitoring device (PMD-100; Medasense Biometrics; Ramat-Gan, Israel), which generated the nociception (pain) index. The patients’ index was compared to individual, more traditional measures, including heart rate and blood pressure. This index was assessed at several stages including intubation and skin incision, which were designated “noxious” stimuli that would be painful in the conscious person, and where then compared to other non-painful periods.

Compared to other accepted monitors for measuring the body’s response to painful stimulation during surgery, the nociception (pain) index better discriminated presumed pain-causing stimuli from non-pain-causing stimuli. The index also accurately quantified the body’s response to increasingly more painful stimulation, with high sensitivity and specificity, as well as showed a decrease when pain medication was administered.

“Our results demonstrate the superiority of combining multiple physiologic measures over any individual parameter in the evaluation of the body’s response to pain during surgery,” said Edry. “The article presents an effective index for trending the body’s response to painful stimulation in the anaesthetised patient. Once in clinical practice, we can conduct large-scale studies to better assess the influence of this monitor on patient outcomes.”

Reference: “Preliminary Intraoperative Validation of the Nociception Level Index: A Noninvasive Nociception Monitor” Ruth Edry, M.D.; Vasile Recea, M.D.; Yuri Dikust, M.D.; Daniel I. Sessler, M.D. Anesthesiology. DOI: 10.1097/ALN.0000000000001130. April 2016.