The effects of surgery on plasma vitamin C concentrations and cognitive function: a protocol for a prospective, observational study

Background: Post-operative cognitive function has recently become an area of focus for researchers. The most commonly reported perioperative neurocognitive disorders include delirium and longer-lasting post-operative cognitive dysfunctions. The contributing pathophysiology to these complications remains unclear. A number of studies have systematically revealed a significant post-operative plasma vitamin C depletion. Recent insights have also exhibited a link between plasma vitamin C and numerous biological roles in brain function, with deficiencies potentially compromising cognitive function. Aim: The present prospective, observational study will investigate whether there is a possible link between post-operative plasma vitamin C depletion and cognitive dysfunction. Methods: The cohort will consist of surgical patients, between the ages of 65 and 85 years, undergoing hip replacement surgery or a control group not exposed to surgical trauma. Participants will have their plasma vitamin C concentrations tested alongside a battery of computer-based cognitive assessments and paper and pen based cognitive tests. Further assessments will include dietary nutritional intake, serum vitamin B12 concentrations, cardiovascular biomarkers, wound healing, sleep quality, pain, mood and inflammatory cytokines. Participants will be tested at baseline (1-2 weeks prior to surgery) and subsequent testing sessions will be performed within 1 week, 4-6 weeks, 3 months and 6 months following surgery. Conclusions: Findings from this observational study will provide insight into whether there is a concomitant depletion in post-operative plasma vitamin C concentrations and cognition function. Extrapolated results may prompt future, extensive randomized controlled trials to assess whether vitamin C supplementation can alleviate or even prevent post-operative cognitive complications.