Performance Assessment of the PMD-200 Under General Anesthesia

The primary efficacy objective of this study is to demonstrate that the NOL Index of the PMD-200 monitor (Medasense Biometrics Ltd., Ramat Gan, Israel) is correlated with the responses to noxious stimuli and analgesic administration during the surgical procedure (prior and following a stimuli or titration), and the secondary efficacy objective of the study is to determine whether the NOL values can be correlated to other nociception predictors (e.g., increase in heart rate or blood pressure) following a noxious stimuli. The primary safety objective of this study is to assess the rate of any adverse reaction related to the study device. This device will not be used to make any clinical decision.

General anesthesia is the combination of various components including lack of movement, hypnosis, amnesia, control of autonomic responses, and attenuation of the response to noxious stimulation. Some anesthetic components, such as muscle relaxation and absence of movement are easy to assess with a twitch monitor. Similarly, hypnotic state can be estimated using processed electroencephalographic signals, but the anesthetic component that remains the most challenging to assess is the nociceptive/antinociceptive state. Typically, intraoperative nociception is estimated from autonomic responses (such as change in blood pressure and heart rate) and clinical signs such as tearing and sweating, but these variables can be very unreliable in predicting pain such as in patients who take beta blockers for treatment of high blood pressure whose heart rate may not increase in response to pain, patients with significant bleeding during surgery whose blood pressure may not increase in response to pain, etc. Effective antinociception is an important component of balanced anesthesia and appears to enhance postoperative outcomes. The most obvious potential consequence of insufficient intraoperative antinociceptive treatment is excessive postoperative pain, but inadequate treatment may also promote inflammatory, hormonal, and immunologic imbalances.

A novel measure of nociception is the nociception level (NoL) index. The NoL index ranges from 0 to 100 and is based on a nonlinear combination of nociception-related physiologic variables, specifically heart rate (HR), heart rate variability at the 0.15- to 0.4-Hz band power, photoplethysmograph wave amplitude (PPGA), skin conductance level, number of skin conductance fluctuations, and their time derivatives. The NoL index estimates the nociceptive/antinociceptive state from these components measures using random forest regression. Previous experimental work on a small number of patients showed that the NoL index is superior to each individual component and to a linear combination of the components. However, it remains unknown whether the NoL index accurately quantifies patients' intraoperative responses to noxious stimuli of varying intensities. The investigators therefore wish to evaluate the ability of the NoL index to discriminate noxious from nonnoxious stimuli, respond to analgesic administration, and progressively increase in response to increasing intensity of noxious stimulation.

In this observational study, The investigators attempt to learn the proper use of the PMD-200 and assess safety and efficacy of this device as mentioned above; however, no clinical decision will be based on the NoL index obtained.