Authors: Matsumoto S et al.
Cureus. 17(10): e95199, October 22, 2025. DOI: 10.7759/cureus.95199
Summary:
This prospective observational study evaluated whether real-time measurements of oxidative stress using electron spin resonance (ESR) can predict postoperative complications. The authors focused on ascorbyl free radical (AFR) in plasma, expressed as AFR/DMSO, as a rapid surrogate marker of ascorbate (vitamin C) consumption and oxidative stress.
A total of 145 adult patients undergoing elective surgery at a single university hospital were studied. All patients had arterial lines placed; arterial blood was sampled immediately before and immediately after surgery. Plasma was rapidly processed in the operating room, mixed with dimethyl sulfoxide (DMSO), and analyzed with an ESR device to quantify AFR/DMSO within about 12 minutes of sampling. Clinical data included demographics, comorbidities, type and duration of surgery, blood loss, fluids, laboratory values (AST, ALT, BUN, creatinine, CRP), intraoperative hemodynamics, the surgical Apgar score (SAS), and 30-day postoperative complications defined by NSQIP.
Postoperative AFR/DMSO values were significantly lower than preoperative values, indicating increased perioperative oxidative stress with consumption of ascorbate. Lower postoperative AFR/DMSO correlated with worse surgical physiology: longer surgery time, greater fluid administration and blood loss, higher postoperative CRP, and other indices of greater surgical invasiveness. Multivariate analysis showed that preoperative AFR/DMSO, surgery duration, and postoperative CRP were independent predictors of postoperative AFR/DMSO, suggesting that both baseline antioxidant status and intraoperative stress shape postoperative oxidative balance.
Postoperative AFR/DMSO levels showed a significant positive correlation with SAS and a negative correlation with the number of NSQIP-defined major complications. Patients with lower postoperative AFR/DMSO tended to have lower SAS and more postoperative complications, many classified as SIRS or other serious events. These findings suggest that rapid depletion of ascorbate (reflected by reduced AFR/DMSO) is associated with higher perioperative risk and worse short-term outcomes.
The authors place their work in the context of previous oxidative stress markers such as malondialdehyde and F2-isoprostanes, which reflect cumulative damage but are not suited for real-time monitoring. ESR-based AFR/DMSO offers faster turnaround and may be more practical as a point-of-care tool. They also discuss the nuanced role of antioxidants: although animal data suggest that ascorbate can protect against ischemia-reperfusion and organ injury, clinical trials of blanket antioxidant supplementation have been inconclusive, and high-dose antioxidants can be harmful if given indiscriminately. The authors argue that real-time AFR/DMSO monitoring could eventually allow targeted, individualized antioxidant therapy, focusing on patients with demonstrable antioxidant depletion rather than routine supplementation.
Limitations include the single-center design, relatively small sample size, short follow-up focused on early complications, and the specialized requirement for ESR equipment, which may limit widespread adoption. Long-term prognostic value of AFR/DMSO was not assessed.
Overall, the study suggests that ESR-based AFR/DMSO is a sensitive, real-time biomarker of perioperative oxidative stress that correlates with surgical severity and postoperative complications, and it may have future utility in risk stratification and guiding tailored antioxidant interventions.
What You Should Know
• Oxidative stress increases with surgical stress and is implicated in postoperative organ dysfunction and complications.
• AFR/DMSO measured by ESR provides a rapid, real-time index of ascorbate consumption and oxidative stress in the OR.
• Lower postoperative AFR/DMSO is associated with longer surgeries, higher postoperative CRP, lower surgical Apgar scores, and more NSQIP-defined complications.
• AFR/DMSO may be more practical than traditional oxidative stress markers, which are slower and reflect cumulative damage rather than real-time changes.
• Indiscriminate antioxidant supplementation is not clearly beneficial and may be harmful; targeted therapy guided by real-time biomarkers may be a better approach.
• Larger, multicenter studies and long-term follow-up are needed to confirm prognostic value and guide clinical integration.
Key Points
• Postoperative AFR/DMSO falls significantly compared with preoperative levels, indicating increased oxidative stress and ascorbate consumption during surgery.
• Lower postoperative AFR/DMSO correlates with worse physiological status (lower SAS) and more major postoperative complications.
• Surgery duration and postoperative inflammatory burden (CRP) are key drivers of reduced postoperative AFR/DMSO.
• ESR-based AFR/DMSO is a promising real-time biomarker for perioperative oxidative stress and short-term postoperative risk.
• Future use may include identifying patients who truly need targeted antioxidant therapy rather than applying supplementation universally.
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