Comparison of the Skin Conductance Algesimeter and the Nociception Level Index in the Paediatric Population. An Observational Study.

Intraoperative non-invasive monitors designed to detect nociception during surgery have seen a considerable development over the past few years. There are multiple commercial monitoring devices available of which most have not been extensively evaluated in the pediatric population. Adequate levels of perioperative analgesia are important as they lead to less intraoperative nociception and less post-operative pain and post-operative complications and thereby leads to improved patient recovery. Monitoring the nociceptive state of a patient by monitoring the autonomic peripheral sympathetic pathways during surgery with these monitoring methods might lead to earlier detection of nociception and therefore less nociception and perioperative pain. Most monitoring devices have not been extensively evaluated in the pediatric population and have not yet demonstrated large clinical implications such as a decrease in post-operative pain or a decrease in opioid usage by using monitor guided analgesia administration. One of the nociception monitoring methods that has not been studied extensively in the pediatric population is the Nociception level index(NOL, Medasense, Ramat Gan, Israel). This monitor is a multi-parametric non-invasive monitoring method that measures heartrate, heartrate variability, skin temperature, photoplethysmographic amplitude, skin conductance and fluctuations in skin conductance using a non-invasive finger probe. These parameters are combined in an algorithm that provides an index from 0-100 with an abstract unit. With 0 indicating no nociception and 100 indicating severe nociception. A first study in the paediatric population with the NOL monitor showed that the NOL index was able to significantly detect first incision and significantly respond to opioid administration during surgery in children 1 to 5 years of age. Another more recent study demonstrated that the NOL index can quantify nociceptive stimuli in children aged 1 to 12. Other more commonly used monitoring methods for nociception such as fluctuations in mean arterial blood pressure(MAP), heartrate(HR) and respiratory rate(RR) did not show a significant change during first incision or during opioid administration in this study, indicating that the NOL monitor might be a better method to assess and respond to intraoperative nociception than fluctuations in MAP, HR and RR alone.

Another nociception monitoring method is the skin conduction algesimeter(SCA, Medstorm, Oslo, Norway. This is a single parameter nociception monitoring device that uses three electrodes that are fixed to the skin to measure fluctuations in skin conductance in order to detect nociception. It measures the amount of bursts in the skin sympatetic nerves in peaks per second. This contrasts with the multiparametric design of the NOL monitor with an algorithm and an abstract index of 0-100. The SCA monitor system doesn't utilize heartrate and photoplethysmographic amplitude. Hypothetically making the device less susceptible to interference of intraoperative hemodynamic changes and intraoperative vasoactive medication administration in comparison with the NOL monitor which does utilizes these variables in its system and algorithm. Furthermore as the SCA monitor measures the direct burst of the palmary or plantary sympathetic nerves this could mean that it responds faster than the NOL index to nociceptive stimuli. The SCA monitor has already been studied in the unanesthetized and the sedated pediatric and neonatal population. But has not seen extensive validation during surgery under general anaesthesia. One small pilot study in the pediatric population under general anaesthesia has been performed. In this study only 12 patients were included, and these patients had a broad age range (8.4 ± 5 years) and received perioperative analgesia through means of continuous infusion of remifentanil. Furthermore the studies researchers did not use the recommended threshold value for the SCA monitor. Both monitors use different proprietary owned algorithms with the same aim of detecting nociception.

Therefore, the primary goal of this study is to evaluate the SCA in the pediatric population during general anaesthesia. As more extensive evaluation of the SCA in the pediatric population is imperative in order to assess if it the SCA can detect nociceptive stimuli during general anesthesia. Another primary objective of this study will be to compare the SCA with the NOL index during general anesthesia. Evaluation of SCA through this feasibility study and comparison with the NOL monitor at the same time, may answer the question of which monitor can better predict and monitor nociceptive stimulation in the perioperative period. This will be the basis for future interventional randomized studies to assess if perioperative monitoring of the analgesia level leads to improved post-operative outcomes. We hypothesize that the NOL monitor and SCA monitor will both be able to quantify nociceptive stimuli, and that the SCA monitor responds faster than the NOL monitor.

Another secondary aim of the current study is the comparison of the BIS to the algesimeters awakening index.

Previous studies have demonstrated that fluctuations in skin conductance with an increase of area under the skin conductance peaks curve while awakening from general anesthesia performs similar to the bispectral index (BIS) in the adult population during nociceptive stimuli.