Serum Neurofilament Light (NFL) in Surgery Under General Anaesthesia (GA) Compared to Surgery With Hypno-analgesia (Hyp)

Overview

Experimental studies have shown that inhalational anesthetics may be neurotoxic by for example causing amyloid beta deposition. Otherwise a pre-clinical study reported an increase in tau phosphorylation with the use of propofol. Whether anesthesia and surgery contribute to the development of long-term cognitive decline remains however controversial. A meta-analysis concluded that general anesthesia could increase the risk of postoperative cognitive decline (POCD) compared with regional or combined anesthesia but this was not shown for Postoperative delirium (POD). This conclusion should be interpreted with caution as these studies showed many shortcomings. Currently no study has compared the release of Neurofilament Light, a biomarker of neuronal injury, in patients undergoing surgery under general anesthesia compared to surgery with Hypno-analgesia and thus without anesthetic drugs.

POD and POCD are manifestations of cognitive dysfunction occurring in the perioperative period. Whether surgery and specifically anesthesia contribute to the development of perioperative cognitive dysfunctions is not clear. Cell culture and animal studies have suggested detrimental effects of anesthetic exposure.1,2,3 Otherwise, it has been shown in animals that surgery plus anesthesia produced worse POCD than anesthesia alone.4 Proinflammatory cytokine levels increase during surgery. These elevated levels of inflammatory markers associated with the activation of microglial cells may induce neuroinflammation enhancing ongoing neurodegeneration.5 However, anesthetics may be capable of modulating inflammation and may alter the neuroinflammatory response. Clinical studies associating the effects of general anesthesia with POCD and POD are conflicting.6 These varying results could be due to heterogeneity of patients' baseline status (e.g. cognitive status, education, associated diseases), type of surgery, as well as methods used to determine POCD and POD. The use of serum neurobiomarkers, sensitive and specific for neuronal cell injury will address the hypothesis of general anesthesia neurotoxicity. Serum Neurofilament Light (NFL) is such a neurobiomarker.Currently no study has compared the release of Neurofilament Light, a biomarker of neuronal injury, in patients undergoing surgery under general anesthesia compared to surgery with Hypno-analgesia and thus without anesthetic drugs. Our hypothesis is that surgery under GA compared to hypnosis does not statistically increase the risk of neuronal injury as measured by serum NFL.