The ‘Analgoscore’: A Novel Score to Monitor Intraoperative Pain and its Use for Remifentanil Closed-Loop Application

Abstract

Background: Measuring pain during general anesthesia is difficult because communication with the patient is impossible. The focus of this project is the development of an objective score (‘Analgoscore’TM) of intraoperative pain based on mean arterial pressure (MAP) and heart rate (HR). The Analgoscore TM is used for closed-loop application of remifentanil.

TM
Methods: The Analgoscore ranges from -9 (too

profound analgesia) to 9 (too little analgesia) in increments of 1, with -3 to + 3 representing excellent pain control, -3 to -6 and 3 to 6 good pain control, and -6 to -9 and 6 to 9 as insufficient pain control. According to the zone of pain, a remifentanil infusion was either closed-loop-administered (Closed-loop Group) or manually administered by the same anesthesiologist (Control Group). The percentage of anesthetic time within the different control zones was recorded as well as the variability of MAP and HR and compared between the two groups. Data as mean ± standard deviation.

Results: In the closed-loop group, 16 patients (5 f, 11 m; age 49 ± 21 y) received a dose of remifentanil of 0.13 ± 0.08 μg/kg/min. During 84%, 14% and 0.5% of the total anesthesia time, the AnalgoscoreTM showed excellent, good or insufficient pain control, respectively. Artifacts were recorded only 1.5% of the time. The control group of eleven patients (4 f, 7 m; age 48 ± 17 y) received remifentanil of 0.17 (0.1) μg/kg/min. Excellent control was obtained 79% of the time, whereas good control and insufficient control yielded 16% and 0%, respectively. Artifacts were recorded 5% of the time.

Discussion: The AnalgoscoreTM is a novel score of intraoperative pain. Remifentanil was successfully closed-loop-administered.