Analgesia/nociception monitoring for opioid guidance: meta-analysis of randomized clinical trials

INTRODUCTION: The adequate suppression of nociception is, besides induction of unconsciousness and immobility, the main objective during anesthesia. Analgesics, most commonly opioids, are usually titrated by established clinical surrogates of nociception. Recently, monitoring techniques became available to evaluate analgesia/nociception during anesthesia and provide better measures then clinical evaluation alone. They are primarily derived from autonomic response on physiologic standard measures. EVIDENCE ACQUISITION: A literature search and systematic review of randomized controlled trials was performed. Trials enrolling patients undergoing general anesthesia and comparing the effects of opioids guided by analgesia/nociception monitoring were considered. Studies were analyzed regarding the outcome effects of opioid therapy, intraoperative events and postoperative pain. Meta-analyses were performed for each outcome separately using a fixed-effects model and random effects models. EVIDENCE ANALYSIS: Seven applicable randomized clinical trials using three different methods for analgesia/nociception monitoring and opioid guidance during anesthesia were found. All but one trial were single centre studies, with a high heterogeneity between the trials and differences in predefined primary outcome. This meta-analysis found that the use of analgesia/nociception monitoring was associated with a significant reduction of movement events, a nonsignificant trend towards reduction of intraoperative administered opioids and emergence time, but was inconclusive with regard to effects on hemodynamic events, postoperatively reported pain and opioid consumption. CONCLUSIONS: Monitoring analgesia/nociception is often reliant on regular physiologic conditions, like sinus rhythm. Opioid guidance dependent on analgesia/nociception monitoring during anesthesia may have beneficial and clinically relevant effects, however the number of currently available randomized controlled studies is low and conclusions are hampered by heterogeneity. More studies with focussed clinical endpoints are therefore needed.