Assessment and quantification of cytokine changes following surgery

Cytokines are ubiquitous small proteins which act as chemical messengers in nearly all biological processes, including facilitating the normal healing process in the postoperative period. Following aseptic surgery outside the central nervous system (CNS), there is a growing appreciation that cytokine levels increase in the brain. In the CNS, cytokines are mainly released from microglia, the resident immune cell of the brain. The increased cytokine levels likely contribute to neuroinflammation, but the complex mechanisms through which this occurs are incompletely understood. These CNS cytokine changes may play a part in the normal healing process, or they may have a role in driving peri-operative neurocognitive disorders such as post-operative delirium. This thesis covers three separate studies. The first, influenced by the pandemic, considers serum cytokine changes in patients who were previously infected with SARSCoV- 2. This study also included an investigation highlighting how initial viral load and serial antibody levels are not related to post-Covid-19 syndrome (PCS). The second study considers cytokine changes in blood and cerebrospinal fluid (CSF) after emergency surgery for a hip fracture. This demonstrated that there are marked increases in IL-6 and IL-8 following surgery. These changes were more marked in CSF than in blood. The third study analyses cytokine changes in the blood and CSF in patients undergoing elective vascular surgery. This replicated the findings of the second study, demonstrating significant increases in CSF cytokines, particularly in IL-6 and IL-8. A comparison was then made between the two surgical groups. This showed that the CSF cytokine foldchanges were more marked in the hip fracture group than the vascular surgery group. There was no correlation between blood and CSF cytokine changes in each group. This suggests that measuring blood cytokines cannot be used as a surrogate marker for CSF cytokine changes.Open Acces