Effect of Perioperative Vitamin C Supplementation on Postoperative Pain and the Incidence of Chronic Regional Pain Syndrome: A Systematic Review and Meta-Analysis

The Use of High-Dose Intravenous L-Ascorbate in Pain Therapy: Current Evidence from the Literature

INTRODUCTION

Pain is the most common reason for seeking medical treatment. Despite extensive research efforts and effective analgesics modulating pain, there is still a major therapeutic gap in addressing the root causes of pain. Pain is associated with tissue damage induced by oxidative stress and induction of inflammatory mediators following high consumption of antioxidants. The role of antioxidants in general, and the administration of L-ascorbate in particular, is still controversially discussed and underestimated in the daily clinical practice.

METHODS

The current literature on the therapeutic effect of L-ascorbate, ascorbic acid, and vitamin C on various pain conditions was evaluated against the background of evidence-based medicine. Those articles, obtained from systematic search in PubMed, were critically assessed and rated in terms of evidence level and methodological quality by two independent experts. The primary purpose of this work was to establish specific pain therapy guidance for intravenous L-ascorbate.

RESULTS

A PubMed search revealed 14 suitable articles comprising controlled clinical trials and meta-analyses. An additional ten publications could be identified via secondary literature. There is supporting evidence for the efficacy of ascorbate treatment in inflammatory pain conditions, in the complex regional pain syndrome, in post zoster neuralgia, in neuropathic pain, in post-operative pain conditions, and in tumor-related pain. However, the considered studies differ in the type of administration, in dosage, in duration of treatment, as well as in quality of research. Despite all study heterogeneity, it became evident that research of high scientific quality is in support of the efficacy of L-ascorbate in pain treatment.

DISCUSSION

Oxidative stress is present in almost all pain conditions. Because oral administration of most magistral formulas of vitamin C does not provide biological availability, parenteral administration should be preferred and can be supported by an oral dose with high bioavailability on days without intravenous treatment. L-ascorbate should be preferred for parenteral high dosage, rather than ascorbic acid, as it does not release acid valences under physiological conditions.

CONCLUSIONS

L-ascorbate is an effective, safe, and economically favorable integrative treatment option for various pain conditions, addressing the root cause of tissue damage and inflammatory mediator burst.

Association of dietary vitamin C consumption with severe headache or migraine among adults: a cross-sectional study of NHANES 1999-2004

Background

An antioxidant-rich diet has been shown to protect against migraines in previous research. However, little has been discovered regarding the association between migraines and vitamin C (an essential dietary antioxidant). This study assessed the dietary vitamin C intake among adult migraineurs in the United States to determine if there is a correlation between migraine incidence and vitamin C consumption in adults.

Methods

This cross-sectional research encompassed adults who participated in the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2004, providing detailed information on their dietary vitamin C intake as well as their history of severe headaches or migraines. The study used weighted multivariable and logistic regression analyses to find an independent connection between vitamin C consumption and severe headache or migraine. Tests of interactions and subgroup analysis were conducted.

Results

Among the 13,445 individuals in the sample, 20.42% had a severe headache or migraine. In fully adjusted models, dietary vitamin C consumption was substantially linked negatively with severe headache or migraine (odds ratio [OR] = 0.94, 95% confidence interval [CI] = 0.91-0.98, p = 0.0007). Compared to quartile 1, quartile 4 had 22% fewer odds of having a severe headache or migraine (OR = 0.78, 95% CI = 0.69-0.89, p = 0.0002). Subgroup analyses showed a significant difference between vitamin C intake and severe headaches or migraines by gender (p for interaction < 0.01).

Conclusion

Reduced risk of severe headaches or migraines may be associated with increased consumption of vitamin C.

Unveiling the potential impact of vitamin C in postoperative spinal pain

BACKGROUND

Spinal surgery is a common procedure associated with significant postoperative pain, and identifying effective interventions to manage this pain is crucial for optimizing patient outcomes. This review assesses the existing literature to determine the overall impact of vitamin C supplementation on spinal postoperative pain. Vitamin C, also known as ascorbic acid, is an essential nutrient that plays a vital role in numerous physiological processes. It functions as a potent antioxidant, neutralizing free radicals and reducing oxidative stress within the body. Furthermore, vitamin C is a cofactor in collagen synthesis, a crucial component of connective tissues, including those found in the spinal structures. Given its antioxidant and collagen-promoting properties, vitamin C has piqued interest as a potential therapeutic option for postoperative spinal pain. Based on the available evidence, vitamin C may have a beneficial effect on postoperative spinal pain, including reducing pain scores, analgesic consumption, and the incidence of complications such as complex regional pain syndrome. However, more research is needed to fully understand the optimal dosage and duration of vitamin C supplementation for postoperative pain management.

CONCLUSION

Vitamin C could be considered a potentially beneficial adjunctive therapy for managing spinal postoperative pain, but its routine use requires further investigation.

Exploring Ascorbic Acid's Role in Orthopedic Practices: Present Theories, Innovative Approaches, and Prospects

In the human body, ascorbic acid (AA) is known for its potent antioxidant and reducing properties and also plays a vital role in supporting the growth of bones and cartilage. It has been used extensively in orthopedic surgery. Ongoing studies under the umbrella of ascorbic acid research investigate its impact on bone and tendon physiology, as well as its influence on joint replacement and postoperative pain. The majority of both laboratory and human studies link the usage of ascorbic acid to enhanced bone health and improved tendon healing. Recent literature suggest that ascorbic acid administration may have a positive impact on the outcome of orthopedic procedures. On the other hand, controversy exists regarding the efficacy of ascorbic acid in reducing the incidence of complex regional pain syndrome. In brief, the effectiveness of ascorbic acid in enhancing orthopedic procedure outcomes remains a subject of ongoing investigation. Although certain studies have hinted at the potential positive influence of ascorbic acid on these outcomes, further research is required to validate its effectiveness and ascertain the ideal dosage and method of administration for maximizing its anticipated advantages. To establish the efficacy of ascorbic acid in improving orthopedic procedure outcomes, rigorous human trials of high quality are imperative. The aim of this review was to provide an overview of ascorbic acid's utilization in orthopedic practices and to pinpoint prospective areas for future research.

The role of diet and non-pharmacologic supplements in the treatment of chronic neuropathic pain: A systematic review

BACKGROUND/IMPORTANCE

Dietary interventions, vitamins, and nutritional supplementation are playing an increasingly important role in the management of neuropathic pain. Current pharmacological treatments are poorly tolerated and ineffective in many cases.

OBJECTIVE

This systematic review aims to study the efficacy of dietary interventions, vitamins, and nutritional supplementation in the management of chronic neuropathic pain in adults.

EVIDENCE REVIEW

The review followed PRISMA guidelines and was registered with PROSPERO (#CRD42022300312). Ten databases and gray literature, including Embase.com, MEDLINE and Web of Science, were systematically searched using a combination of keywords and controlled vocabulary related to chronic neuropathic pain and oral non-pharmacological supplements. Studies on adult humans published between 2000 and 2021 were considered for inclusion. The Cochrane Handbook was used to assess risk of bias, and Grading of Recommendations Assessment, Development, and Evaluation was used to determine overall quality of evidence.

FINDINGS

Forty studies were included in the final review, and results were categorized according to pain type including pain related to chemotherapy-induced peripheral neuropathy (CIPN, 22 studies, including 3 prospective cohorts), diabetic peripheral neuropathy (DPN, 13 studies, including 2 prospective), complex regional pain syndrome (CRPS-I, 3 studies, including 1 prospective), and other (2 studies, both RCT). The CIPN studies used various interventions including goshajinkigan (4 studies), vitamin E (5), vitamin B12 (3), glutamine (3), N-acetyl-cysteine (2), acetyl-l-carnitine (2), guilongtonluofang (1), ninjin'yoeito (1), alpha-lipoic acid (1), l-carnosine (1), magnesium and calcium (1), crocin (1), and antioxidants (1), with some studies involving multiple interventions. All CIPN studies involved varying cancers and/or chemotherapies, advising caution for generalizability of results. Interventions for DPN included alpha-lipoic acid (5 studies), vitamin B12 (3), acetyl-l-carnitine (3), vitamin E (1), vitamin D (2), and a low-fat plant-based diet (1). Vitamin C was studied to treat CRPS-I (3 studies, including 1 prospective). Magnesium (1) and St. John's wort (1) were studied for other or mixed neuropathologies.

CONCLUSIONS

Based on the review, we cannot recommend any supplement use for the management of CIPN, although further research into N-acetyl-cysteine, l-carnosine, crocin, and magnesium is warranted. Acetyl-l-carnitine was found to be likely ineffective or harmful. Alpha-lipoic acid was not found effective. Studies with goshajinkigan, vitamin B12, vitamin E, and glutamine had conflicting results regarding efficacy, with one goshajinkigan study finding it harmful. Guilongtonluofang, ninjin'yoeito, and antioxidants showed various degrees of potential effectiveness. Regarding DPN, our review supports the use of alpha-lipoic acid, acetyl-l-carnitine, and vitamin D. The early use of vitamin C prophylaxis for the development of CRPS-I also seems promising. Further research is warranted to confirm these findings.

Complex Regional Pain Syndrome (CRPS) and the Value of Early Detection

PURPOSE OF REVIEW

The goal of this narrative review is to describe the current understanding of the pathology of Complex Regional Pain Syndrome (CRPS), as well as diagnostic standards and therapeutic options. We will then make the case for early recognition and management.

RECENT FINDINGS

CRPS remains an enigmatic pain syndrome, comprising several subtypes. Recent recommendations clarify diagnostic ambiguities and emphasize the importance of standardized assessment and therapy. Awareness of CRPS should be raised to promote prevention, early detection, and rapid escalation of therapy in refractory cases. Comorbidities and health costs (i.e., the socioeconomic impact) must also be addressed early to prevent negative consequences for patients.

Impact of vitamin C on the reduction of opioid consumption after an emergency department visit for acute musculoskeletal pain: a double-blind randomised control trial protocol

INTRODUCTION

Recent evidence has shown that vitamin C has some analgesic properties in addition to its antioxidant effect and can, therefore, reduce opioid use during recovery time. Vitamin C analgesic effect has been explored mostly during short-term postoperative context or in disease-specific chronic pain prevention, but never after acute musculoskeletal injuries, which are often seen in the emergency department (ED). The protocol's primary aim is to compare the total morphine 5 mg pills consumed during a 2-week follow-up between patients receiving vitamin C or a placebo after ED discharge for an acute musculoskeletal pain complaint.

METHODS AND ANALYSIS

We will conduct a two-centre double-blind randomised placebo-controlled trial with 464 participants distributed in two arms, one group receiving 1000 mg of vitamin C two times a day for 14 days and another one receiving a placebo. Participants will be ≥18 years of age, treated in ED for acute musculoskeletal pain present for less than 2 weeks and discharged with an opioid prescription for home pain management. Total morphine 5 mg pills consumed during the 2-week follow-up will be assessed via an electronic (or paper) diary. In addition, patients will report their daily pain intensity, pain relief, side effects and other types of pain medication or other non-pharmacological approach used. Three months after the injury, participants will also be contacted to evaluate chronic pain development. We hypothesised that vitamin C, compared with a placebo, will reduce opioid consumption during a 14-day follow-up for ED discharged patients treated for acute musculoskeletal pain.

ETHICS AND DISSEMINATION

This study has received approval from the Ethics Review Committee from the 'Comité d'éthique de la recherche du CIUSSS du Nord-de-l'Île-de-Montréal (No 2023-2442)'. Findings will be disseminated through scientific conferences and peer-reviewed journal publication. The data sets generated during the study will be available from the corresponding author on reasonable request.

TRIAL REGISTRATION NUMBER

NCT05555576 ClinicalTrials.Gov PRS.

Does the vitamin C level affect postoperative analgesia in patients who undergo orthognathic surgery?

Vitamin C has a critical role in pain management because of its antioxidative, neuroprotective, and anti-nociceptive properties. Oxidative stress caused by surgery increases the requirement for vitamin C. The aim of this study was to evaluate the change in vitamin C level and its effect on postoperative pain in patients undergoing orthognathic surgery. Thirty patients were included in the study. The relationships between the postoperative plasma vitamin C level, duration of surgery, postoperative analgesic consumption, and pain scores (visual analogue scale) were analysed. The difference between the mean pre- and postoperative vitamin C levels was found to be statistically significant (7.5 ± 2.9 mg/l vs 4.9 ± 2.3 mg/l, respectively; P = 0.001). There was no significant relationship between the duration of surgery and the vitamin C level decrease (P > 0.05). There was an inverse correlation between the postoperative vitamin C level and the amount of analgesic requested via patient-controlled analgesia (r = -0.699, P < 0.001). The findings suggest that, in patients who undergo orthognathic surgery, plasma vitamin C levels decrease significantly (34.6%), and an increase in the duration of surgery is not associated with any decrease in the vitamin C levels. A low postoperative plasma vitamin C level was found to be associated with greater postoperative analgesic consumption. In patients with preoperative plasma vitamin C levels ≤ 42 µmol/l, perioperative vitamin C administration may be considered for postoperative pain management.

Effect of Perioperative Vitamin C on the Incidence of Complex Regional Pain Syndrome: A Systematic Review and Meta-Analysis

Complex regional pain syndrome type 1 (CRPS-I) is a complex complication that occurs after limb extremity surgeries. Controversy exists regarding the effectiveness of vitamin C in reducing that condition. Therefore, we conducted this systematic review and meta-analysis to assess the role of vitamin C on CRPS-I and functional outcomes after distal radius, wrist, foot, and ankle surgeries. We searched Medline (via PubMed), Embase, the Cochrane Library, Clinicaltrial.gov, and Google Scholar for relevant studies comparing perioperative vitamin C versus placebo after distal radius, wrist, foot, and ankle surgeries from infinity to May 2021. Continuous data such as functional outcomes and pain scores were pooled as mean differences, while dichotomous variables such as the incidence of complex regional pain syndrome and complications were pooled as odds ratios, with 95% confidence interval, using R software (meta package, version 4.9-0) for Windows. Eight studies were included. The timeframe for vitamin C administration in each study ranged from 42 to 50 days postinjury and/or surgical fixation. The effect size showed that vitamin C was associated with a decreased rate of CRPS-1 than placebo (odds ratio 0.33, 95% confidence interval [0.17, 0.63]). No significant difference was found between vitamin C and placebo in terms of complications (odds ratio 1.90, 95% confidence interval [0.99, 3.65]), functional outcomes (mean difference 6.37, 95% confidence interval [-1.40, 14.15]), and pain scores (mean difference -0.14, 95% confidence interval [-1.07, 0.79]). Overall, vitamin C was associated with a decreased rate of CRPS-I than placebo, while no significant difference was found regarding complications, functional outcomes, and pain scores. These results hold true when stratifying fracture type (distal radius, ankle, and foot surgeries) and vitamin C dose (500 mg or 1 g).

Opioids and Vitamin C: Known Interactions and Potential for Redox-Signaling Crosstalk

Opioids are among the most widely used classes of pharmacologically active compounds both clinically and recreationally. Beyond their analgesic efficacy via μ opioid receptor (MOR) agonism, a prominent side effect is central respiratory depression, leading to systemic hypoxia and free radical generation. Vitamin C (ascorbic acid; AA) is an essential antioxidant vitamin and is involved in the recycling of redox cofactors associated with inflammation. While AA has been shown to reduce some of the negative side effects of opioids, the underlying mechanisms have not been explored. The present review seeks to provide a signaling framework under which MOR activation and AA may interact. AA can directly quench reactive oxygen and nitrogen species induced by opioids, yet this activity alone does not sufficiently describe observations. Downstream of MOR activation, confounding effects from AA with STAT3, HIF1α, and NF-κB have the potential to block production of antioxidant proteins such as nitric oxide synthase and superoxide dismutase. Further mechanistic research is necessary to understand the underlying signaling crosstalk of MOR activation and AA in the amelioration of the negative, potentially fatal side effects of opioids.

The Impact of General Anesthesia on Redox Stability and Epigenetic Inflammation Pathways: Crosstalk on Perioperative Antioxidant Therapy

Worldwide, the prevalence of surgery under general anesthesia has significantly increased, both because of modern anesthetic and pain-control techniques and because of better diagnosis and the increased complexity of surgical techniques. Apart from developing new concepts in the surgical field, researchers and clinicians are now working on minimizing the impact of surgical trauma and offering minimal invasive procedures due to the recent discoveries in the field of cellular and molecular mechanisms that have revealed a systemic inflammatory and pro-oxidative impact not only in the perioperative period but also in the long term, contributing to more difficult recovery, increased morbidity and mortality, and a negative financial impact. Detailed molecular and cellular analysis has shown an overproduction of inflammatory and pro-oxidative species, responsible for augmenting the systemic inflammatory status and making postoperative recovery more difficult. Moreover, there are a series of changes in certain epigenetic structures, the most important being the microRNAs. This review describes the most important molecular and cellular mechanisms that impact the surgical patient undergoing general anesthesia, and it presents a series of antioxidant therapies that can reduce systemic inflammation.

Complex Regional Pain Syndrome: A Comprehensive Review

Complex regional pain syndrome (CRPS) is a chronic pain condition often involving hyperalgesia and allodynia of the extremities. CRPS is divided into CRPS-I and CRPS-II. Type I occurs when there is no confirmed nerve injury. Type II is when there is known associated nerve injury. Female gender is a risk factor for developing CRPS. Other risk factors include fibromyalgia and rheumatoid arthritis. Unfortunately, the pathogenesis of CRPS is not yet clarified. Some studies have demonstrated different potential pathways. Neuropathic inflammation, specifically activation of peripheral nociceptors of C-fibers, has been shown to play a critical role in developing CRPS. The autonomic nervous system (ANS) is involved. Depending on whether it is acute or chronic CRPS, norepinephrine levels are either decreased or increased, respectively. Some studies have suggested the importance of genetics in developing CRPS. More consideration is being given to the role of psychological factors. Some association between a history of depression and/or post-traumatic stress disorder (PTSD) and the diagnosis of CRPS has been demonstrated. Treatment modalities available range from physical therapy, pharmacotherapy, and interventional techniques. Physical and occupational therapies include mirror therapy and graded motor imagery. Medical management with non-steroidal anti-inflammatory drugs (NSAIDs) has not shown significant improvement. There have been supporting findings in the use of short-course steroids, bisphosphonates, gabapentin, and ketamine. Antioxidant treatment has also shown some promise. Other pharmacotherapies include low-dose naltrexone and Botulinum toxin A (BTX-A). Sympathetic blocks are routinely used, even if their short- and long-term effects are not clear. Finally, spinal cord stimulation (SCS) has been used for decades. In conclusion, CRPS is a multifactorial condition that still requires further studying to better understand its pathogenesis, epidemiology, genetic involvement, psychological implications, and treatment options. Future studies are warranted to better understand this syndrome. This will provide an opportunity for better prevention, diagnosis, and treatment of CRPS.

Multivitamin Use in Enhanced Recovery After Surgery Protocols: A Cost Analysis

INTRODUCTION

Enhanced Recovery After Surgery (ERAS) protocols have shown significant benefits in multiple areas including early mobilization, improved pain control, and early oral intake. Deficient nutritional states may compromise the operative outcomes. Several essential vitamins, e.g., B12, C, D, and E, have demonstrated anti-inflammatory properties and may promote wound healing. Given the low risk of oral multivitamin supplementation and the potential benefits, we hypothesized that adding a multivitamin to our institution's ERAS protocols would be a low-cost perioperative intervention accounting for a very small fraction of the annual pharmacy budget.

METHODS

A cost analysis for vitamin supplementation for all adult orthopedic surgical cases for the fiscal year 2018 was conducted. To assess the potential cost for multivitamin supplementation in the perioperative period, the fiscal year 2018 pharmacy budget and current costs of multivitamins were obtained from the hospital pharmacy. Medication costs were obtained from the medical logistics ordering system at per unit (i.e., bottle) and per tablet levels for all formulary oral multivitamins. We also determined the number of adult orthopedic surgical cases for our facility in the fiscal year 2018 from our surgery scheduling system. The cost for supplementation for a single day (day of surgery), 1 week (first postoperative week), 6 weeks plus 1 week preop, and 6 months plus 1 week preop for all cases was then calculated.

RESULTS

Our institution's pharmacy budget for the fiscal year 2018 was $123 million dollars with two oral multivitamins on formulary. Prenatal tablets, containing vitamins A-E, calcium, iron, and zinc, cost $1.52 per bottle of 100 tablets and $0.0152 per tablet, while renal formulation tablets, containing water-soluble vitamins B and C, cost $2.79 per bottle of 100 tablets and $0.0279 per tablet. For one fiscal year, the medication cost to supplement every adult orthopedic surgery patient with an oral multivitamin for 1 day, 1 week, 6 weeks plus 1 week preop, and 6 months plus 1 week preop would range from $60.47 to $110.99, from $423.29 to $776.93, from $2,963.03 to $5,438.51, and from $10,582.25 to $19,423.25, respectively, depending on which multivitamin was prescribed. These costs would represent between 0.00005% and 0.00009% of the annual pharmacy budget for 1 day, between 0.0003% and 0.0006% for 1 week, between 0.00245% and 0.441% for 6 weeks plus 1 week preop, and between 0.00875% and 1.575% for 6 months plus 1 week preop, respectively.

DISCUSSION/CONCLUSIONS

The relative nutrient-deficient state in the perioperative patient from decreased oral intake contributes to the metabolic derangements resulting from the surgery. The current ERAS protocols help to mitigate this with early feeding, and the addition of multivitamin supplementation may enhance this process. Multivitamins are safe, widely accessible, and inexpensive, and early investigations of pain control and healing have shown encouraging results. Further prospective studies are needed for incorporating multivitamins into ERAS protocols in order to elucidate the effective dosages, duration of treatment, and effect on outcomes.

Micronutrients May Be a Unique Weapon Against the Neurotoxic Triad of Excitotoxicity, Oxidative Stress and Neuroinflammation: A Perspective

Excitotoxicity has been implicated in many neurological disorders and is a leading cause of oxidative stress and neuroinflammation in the nervous system. Most of the research to date has focused on each of these conditions individually; however, excitotoxicity, oxidative stress, and neuroinflammation have the ability to influence one another in a self-sustaining manner, thus functioning as a "neurotoxic triad." This perspective article re-introduces the concept of the neurotoxic triad and reviews how specific dietary micronutrients have been shown to protect against not only oxidative stress, but also excitotoxicity and neuroinflammation. Future dietary interventions for neurological disorders could focus on the effects on all three aspects of the neurotoxic triad.

Vitamin C prevention of complex regional pain syndrome after foot and ankle surgery: a prospective randomized study of three hundred and twenty nine patients

PURPOSE

Complex regional pain syndrome (CRPS) after foot and ankle surgery has a significant impact on the ability to walk. As the symptomatic treatment of this disaster complication is poor and has low efficacy, a preventive treatment would be beneficial. Vitamin C has been reported to be efficient in preventing CRPS in elective scheduled surgery. Few authors explored this efficiency in foot and ankle surgery. We, therefore, evaluated the efficacy of vitamin C in preventing this complication after foot and ankle surgeries for both trauma and elective surgery.

MATERIAL AND METHODS

Between January 2018 and December 2019, 329 patients were included in the study. We conducted a prospective randomized study on the efficiency of vitamin C (one group with and one without vitamin C) to prevent CRPS risk in patients operated in our institution on foot or ankle surgery. The incidence of CRPS after foot and ankle surgery was evaluated in both groups; the diagnostic of CRPS was made using the Budapest criteria associated with three-phase bone scintigraphy.

RESULTS

Among the 329 patients included in the study (232 women and 97 men), 121 patients were included in the vitamin C group and 208 in the control group (without vitamin C). Vitamin C was statistically linked with a decreased risk of CRPS (OR 0.19; CI 95% from 0.05 to 0.8; p = 0.021). Alcoholism and cast immobilization were increased risks factors of CRPS (respectively p = 0.001 and p = 0.034).

CONCLUSION

Taking 1 g per day of vitamin C during 40 days after a foot or ankle surgery reduces the risk of CRPS.

Parenteral high‑dose ascorbate - A possible approach for the treatment of glioblastoma (Review)

For glioblastoma, the treatment with standard of care therapy comprising resection, radiation, and temozolomide results in overall survival of approximately 14-18 months after initial diagnosis. Even though several new therapy approaches are under investigation, it is difficult to achieve life prolongation and/or improvement of patient's quality of life. The aggressiveness and progression of glioblastoma is initially orchestrated by the biological complexity of its genetic phenotype and ability to respond to cancer therapy via changing its molecular patterns, thereby developing resistance. Recent clinical studies of pharmacological ascorbate have demonstrated its safety and potential efficacy in different cancer entities regarding patient's quality of life and prolongation of survival. In this review article, the actual glioblastoma treatment possibilities are summarized, the evidence for pharmacological ascorbate in glioblastoma treatment is examined and questions are posed to identify current gaps of knowledge regarding accessibility of ascorbate to the tumor area. Experiments with glioblastoma cell lines and tumor xenografts have demonstrated that high-dose ascorbate induces cytotoxicity and oxidative stress largely selectively in malignant cells compared to normal cells suggesting ascorbate as a potential therapeutic agent. Further investigations in larger cohorts and randomized placebo-controlled trials should be performed to confirm these findings as well as to improve delivery strategies to the brain, through the inherent barriers and ultimately to the malignant cells.

Dimethyl Fumarate Reduces Oxidative Stress and Pronociceptive Immune Responses in a Murine Model of Complex Regional Pain Syndrome

BACKGROUND

Complex regional pain syndrome (CRPS) is a highly disabling cause of pain often precipitated by surgery or trauma to a limb. Both innate and adaptive immunological changes contribute to this syndrome. Dimethyl fumarate (DMF) works through the nuclear factor erythroid 2-related factor 2 (Nrf2) transcription factor and other targets to activate antioxidant systems and to suppress immune system activation. We hypothesized that DMF would reduce nociceptive, functional, and immunological changes measured in a model of CRPS.

METHODS

Male C57BL/6 mice were used in the well-characterized tibial fracture model of CRPS. Some groups of mice received DMF 25 mg/kg/d orally, per os for 3 weeks after fracture versus vehicle alone. Homozygous Nrf2 null mutant mice were used as test subjects to address the need for this transcription factor for DMF activity. Allodynia was assessed using von Frey filaments and hindlimb weight-bearing data were collected. The markers of oxidative stress malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) were quantified in the skin of the fractured mice using immunoassays along with the innate immune system cytokines IL-1β and IL-6. The accumulation of IgM in the fractured limbs and lymph node hypertrophy were used as indexes of adaptive immune system activation, and the passive transfer of serum from wildtype fractured mice to B cell-deficient fractured muMT mice (mice lacking B cells and immunoglobulin) helped to assess the pronociceptive activity of humoral factors.

RESULTS

We observed that oral DMF administration strongly prevented nociceptive sensitization and reduced uneven hindlimb weight bearing after fracture. DMF was also very effective in reducing the accumulation of markers of oxidative stress, activation of innate immune mediator production, lymph node hypertrophy, and the accumulation of IgM in fractured limbs. The sera of fractured vehicle-treated but not DMF-treated mice conferred pronociceptive activity to recipient mice. Unexpectedly, the effects of DMF were largely unchanged in the Nrf2 null mutant mice.

CONCLUSIONS

Oxidative stress and immune system activation are robust after hindlimb fracture in mice. DMF strongly reduces activation of those systems, and the Nrf2 transcription factor is not required. DMF or drugs working through similar mechanisms might provide effective therapy for CRPS or other conditions where oxidative stress causes immune system activation.

A meta-analysis of randomized clinical trials on the impact of oral vitamin C supplementation on first-year outcomes in orthopedic patients

This meta-analysis aimed at investigating the impact of oral vitamin C supplementation on the post-procedural recovery of orthopedic patients, including functional outcomes and complex regional pain syndrome type I (CRPS I). Literature search using the Medline, Cochrane Library, and Embase databases from inception till March 2021 identified seven eligible randomized controlled trials with 1,361 participants. Forest plot revealed no significant difference in the functional outcomes at 6–12 months [standardized mean difference (SMD) = −0.00, 95% CI − 0.19 to 0.18, 467 patients], risk of overall complications (RR = 0.98, 95% CI 0.68 to 1.39, 426 patients), and pain severity at 3–6 months (SMD = − 0.18, 95% CI − 0.49 to 0.12, 486 patients) between patients with and without oral vitamin C supplementation. Pooled analysis showed that vitamin C treatment reduced the risk of CRPS I regardless of dosage (RR = 0.46, 95% CI 0.25 to 0.85, 1143 patients). In conclusion, the current meta-analysis demonstrated that oral vitamin C supplementation may reduce the risk of complex regional pain syndrome type I but did not improve the functional outcomes in orthopedic patients. Nevertheless, because of the small number of trials included in the present study, further large-scale clinical studies are warranted to support our findings.

Vitamin C in orthopedic practices: Current concepts, novel ideas, and future perspectives

Vitamin C (ascorbic acid), is an important antioxidant that has been applied broadly in the field of orthopaedics. Current research on vitamin C examines the molecule's role in bone and tendon physiology, as well as joint replacement and Postoperative pain. Most laboratory and human studies associate the use of vitamin C with improved bone health and tendon healing. Recent literature moderately supports the use of vitamin C to improve functional outcomes, decreased postoperative pain, and prevent complex regional pain syndrome following orthopaedic procedures. The perioperative use of vitamin C in patients undergoing joint replacement surgery and anterior cruciate ligament reconstruction is still under investigation. Overall, there is need for high-quality human trials to confirm whether vitamin C can potentiate the outcomes of orthopaedic procedures and to determine optimal dosage and means of administration to maximize its proposed benefits. The purpose of this review was to summarize the application of vitamin C in orthopaedic practices and to identify potential areas for future study.

The Effect of Perioperative Vitamin C on Postoperative Analgesic Consumption: A Meta-Analysis of Randomized Controlled Trials

Because the analgesic effect of vitamin C against acute pain remains poorly addressed, this meta-analysis aimed at investigating its effectiveness against acute postoperative pain. A total of seven randomized controlled trials with placebo/normal controls were identified from PubMed, Cochrane Library, Medline, Google Scholar, and Embase databases. Pooled analysis showed a lower pain score (standardized mean difference (SMD) = -0.68, 95% CI: -1.01 to -0.36, p < 0.0001; I2 = 57%) and a lower morphine consumption (weighted mean difference (WMD) = -2.44 mg, 95% CI: -4.03 to -0.86, p = 0.003; I2 = 52%) in the vitamin group than that in the placebo group within postoperative 1-2 h. At postoperative 24 h, a lower pain score (SMD = -0.65, 95% CI: -1.11 to -0.19, p = 0.005; I2 = 81%) and lower morphine consumption (WMD = -6.74 mg, 95% CI: -9.63 to -3.84, p < 0.00001; I2 = 85%) were also noted in the vitamin group. Subgroup analyses demonstrated significant reductions in pain severity and morphine requirement immediately (1-2 h) and 24 h after surgery for patients receiving intravenous vitamin C but not in the oral subgroup. These findings showed significant reductions in pain score and opioid requirement up to postoperative 24 h, respectively, suggesting the effectiveness of perioperative vitamin C use. Further large-scale trials are warranted to elucidate its optimal intravenous dosage and effectiveness against chronic pain in the postoperative pain control setting.

Glutathione and Glutathione-Like Sequences of Opioid and Aminergic Receptors Bind Ascorbic Acid, Adrenergic and Opioid Drugs Mediating Antioxidant Function: Relevance for Anesthesia and Abuse

Opioids and their antagonists alter vitamin C metabolism. Morphine binds to glutathione (l-γ-glutamyl-l-cysteinyl-glycine), an intracellular ascorbic acid recycling molecule with a wide range of additional activities. The morphine metabolite morphinone reacts with glutathione to form a covalent adduct that is then excreted in urine. Morphine also binds to adrenergic and histaminergic receptors in their extracellular loop regions, enhancing aminergic agonist activity. The first and second extracellular loops of adrenergic and histaminergic receptors are, like glutathione, characterized by the presence of cysteines and/or methionines, and recycle ascorbic acid with similar efficiency. Conversely, adrenergic drugs bind to extracellular loops of opioid receptors, enhancing their activity. These observations suggest functional interactions among opioids and amines, their receptors, and glutathione. We therefore explored the relative binding affinities of ascorbic acid, dehydroascorbic acid, opioid and adrenergic compounds, as well as various control compounds, to glutathione and glutathione-like peptides derived from the extracellular loop regions of the human beta 2-adrenergic, dopamine D1, histamine H1, and mu opioid receptors, as well as controls. Some cysteine-containing peptides derived from these receptors do bind ascorbic acid and/or dehydroascorbic acid and the same peptides generally bind opioid compounds. Glutathione binds not only morphine but also naloxone, methadone, and methionine enkephalin. Some adrenergic drugs also bind to glutathione and glutathione-like receptor regions. These sets of interactions provide a novel basis for understanding some ways that adrenergic, opioid and antioxidant systems interact during anesthesia and drug abuse and may have utility for understanding drug interactions.

Reduction in Migraine and Headache Frequency and Intensity With Combined Antioxidant Prophylaxis (N-acetylcysteine, Vitamin E, and Vitamin C): A Randomized Sham-Controlled Pilot Study

OBJECTIVE

To investigate the preventive effects of a combined antioxidant drug (N-acetylcysteine, vitamin E, and vitamin C [NEC]) on migraine outcomes. Migraine is characterized by increased oxidative stress and neurogenic inflammation in the brain; therefore, antioxidants may have a migraine preventive effect.

DESIGN

Randomized, double-blind, sham-controlled pilot study.

SETTING

Australian community.

SUBJECTS

Adults reporting 2 to 8 migraines per month for at least a year.

METHODS

After a 1-month baseline period, 35 subjects completed 3 months of treatment with NEC (n = 19) or sham (n = 16) capsules. The primary outcome was the difference in mean number of headaches per month between baseline and final month of the trial for NEC and sham groups; secondary outcomes are listed below.

RESULTS

For NEC there was a significant decrease in mean number of headaches by 3.0 per month (P = 0.004) compared with 1.4 for sham (P = 0.073); there was no significant difference in these changes between the 2 groups (P = 0.052). Average monthly headache (P = 0.041) and migraine frequency (P = 0.018) were significantly less for NEC vs. sham. In NEC subjects, there was a significant decrease in average monthly migraine days (-3.1), moderate/severe headache days (-3.2), migraine duration, headache pain scores, and acute headache medication use.

CONCLUSIONS

This is the first randomized controlled trial to find that combined antioxidant therapy with NEC reduces headaches and migraines in adult migraineurs. Given the limitations of this pilot study, an adequately powered randomized controlled trial is planned to further investigate antioxidant prophylaxis in migraine.

The effect of β-carotene on the mortality of male smokers is modified by smoking and by vitamins C and E: evidence against a uniform effect of nutrient

A previous analysis of the Alpha-Tocopherol Beta-Carotene (ATBC) Study on male smokers found that β-carotene supplementation increased the risk of pneumonia 4-fold in those who started smoking at the age of ≥21 years and smoked ≥21 cigarettes/d (a subgroup of 7 % of the study population). The present study hypothesised that β-carotene increases mortality in the same subgroup. The ATBC Study (1985–1993) recruited 29 133 Finnish male smokers (≥5 cigarettes/d) aged 50–69 years. Cox regression models were constructed to estimate the effect of β-carotene supplementation in subgroups. β-Carotene increased mortality (risk ratio 1·56; 95 % CI 1·06, 2·3) in those who started to smoke at ≥21 years and smoked ≥21 cigarettes/d. Within this subgroup, there was strong evidence of further heterogeneity. The effect of β-carotene supplementation was further modified by dietary vitamin C intake, fruit and vegetable intake (P = 0·0004), and by vitamin E supplementation (P = 0·011). Thus, harm from β-carotene was not uniform within the study population. Interactions between β-carotene and vitamins C and E were seen only within a subgroup of 7 % of the ATBC participants, and therefore should not be extrapolated to the general population. Heterogeneity of the β-carotene effect on mortality challenges the validity of previous meta-analyses that have pooled many diverse antioxidants for one single estimate of effect using the assumption that a single estimate equally applies to all antioxidants and all people. Trial registration: ClinicalTrials.gov NCT00342992.

Comparison of the effects of preoperative melatonin or vitamin C administration on postoperative analgesia

The analgesic benefit of melatonin and vitamin C as primary or adjuvant agents has been reported in various studies; however, their analgesic effects in the treatment of postoperative pain remain unclear. Thus, we aimed to evaluate the effect of single preoperative dose of oral melatonin or vitamin C administration on postoperative analgesia. In this study, we recruited 165 adult patients undergoing elective major abdominal surgery under general anesthesia. Patients were randomly divided into three equal (n = 55) groups. One hour before surgery, patients received orally melatonin (6 mg) in group M, vitamin C (2 g) in group C, or a placebo tablet in group P. Pain, sedation, patient satisfaction, total morphine consumption from a patient-controlled analgesia device, supplemental analgesic requirement, and the incidence of nausea and vomiting were recorded throughout 24 h after surgery. The mean pain score and total morphine consumption were found significantly lower in both M and C groups compared with group P (p < 0.001). There were no significant differences between group M and C with respect to pain scores (p = 0.117) and total morphine consumption (p = 0.090). Patients requested less supplemental analgesic and experienced less nausea and vomiting in groups M and C compared with group P. In conclusion, preoperative oral administration of 6 mg melatonin or 2 g vitamin C led to a reduction in pain scores, total morphine consumption, supplemental analgesic requirement, and the incidence of nausea and vomiting compared with placebo.

Additional effect of magnesium sulfate and vitamin C in laparoscopic gynecologic surgery for postoperative pain management: a double-blind randomized controlled trial

Background

This clinical trial was conducted to determine whether combined use of magnesium sulfate and vitamin C more significantly reduced postoperative fentanyl consumption and pain than magnesium sulfate or vitamin C alone.

Methods

The prospective, double-blinded, randomized controlled study enrolled 132 patients scheduled for laparoscopic gynecologic surgery. The patients were randomly allocated to one of the four groups (n = 33 for each group; Group M [magnesium sulfate 40 mg/kg], Group V [vitamin C 50 mg/kg], Group MV [magnesium sulfate 40 mg/kg and vitamin C 50 mg/kg] and Group C [isotonic saline 40 ml]). Cumulative postoperative fentanyl consumption (primary endpoint measure), postoperative pain score by numeric rating scale, and postoperative nausea and vomiting were recorded at 1, 6, 24, and 48 h after discharge from the postanesthesia care unit.

Results

Cumulative postoperative fentanyl consumption was significantly less in Groups M, V, and MV than in Group C at all time points. Group MV showed significantly less cumulative postoperative fentanyl consumption than Group M at postoperative 24 h (mean ± standard deviation, 156.6 ± 67.5 vs. 235.6 ± 94.6 µg, P = 0.001), as well as significantly less consumption than Groups M and V at postoperative 48 h (190.8 ± 74.6 vs. 301.0 ± 114.8 or 284.1 ± 128.6 µg, P < 0.001, P = 0.003, respectively).

Conclusions

Combined use of magnesium sulfate and vitamin C provides an additional benefit in postoperative pain management after laparoscopic gynecologic surgery in comparison to single administration of magnesium sulfate or vitamin C.

Preoperative Ascorbic Acid Levels in Proximal Femur Fracture Patients Have No Postoperative Clinical Impact, While Ascorbic Acid Levels upon Discharge Have a Major Effect on Postoperative Outcome

Proximal femur fractures show a high prevalence in elderly patients and are associated with an elevated risk of multimorbidity and early mortality. Recovery is impaired by malnutrition and oxidative stress, which is affected by antioxidants such as ascorbic acid (AA). This study monitored AA levels during hospitalization of patients with a proximal femur to investigate the influence of AA status to the clinical outcome. AA levels of 25 elderly patients with a proximal femur fracture were measured during hospitalization using high performance liquid chromatography. Plasma samples were collected preoperatively, on the first day after surgery, on the third day after surgery and on the day of discharge. Nutritional Risk Screening 2002 (NRS) and Mini Nutritional Assessment (MNA) were assessed to evaluate the nutritional status. In patients with proximal femoral fractures, preoperative AA concentrations were significantly lower compared to elderly patients without an acute fracture. A significant decrease of 33.8% in AA plasma level was measured on the day after surgery with a significant recovery up to the time of discharge. The preoperative AA status did not have any significant effect on clinical outcome. However, inadequate AA levels (<50 µmol/L) upon discharge significantly increased the incidence and the severity of postoperative complications. These results indicate that the AA status upon discharge has a greater impact on clinical outcome than assumed, and therefore, AA supplementation during hospitalization should be considered.

Vitamin C Can Shorten the Length of Stay in the ICU: A Meta-Analysis

A number of controlled trials have previously found that in some contexts, vitamin C can have beneficial effects on blood pressure, infections, bronchoconstriction, atrial fibrillation, and acute kidney injury. However, the practical significance of these effects is not clear. The purpose of this meta-analysis was to evaluate whether vitamin C has an effect on the practical outcomes: length of stay in the intensive care unit (ICU) and duration of mechanical ventilation. We identified 18 relevant controlled trials with a total of 2004 patients, 13 of which investigated patients undergoing elective cardiac surgery. We carried out the meta-analysis using the inverse variance, fixed effect options, using the ratio of means scale. In 12 trials with 1766 patients, vitamin C reduced the length of ICU stay on average by 7.8% (95% CI: 4.2% to 11.2%; p = 0.00003). In six trials, orally administered vitamin C in doses of 1⁻3 g/day (weighted mean 2.0 g/day) reduced the length of ICU stay by 8.6% (p = 0.003). In three trials in which patients needed mechanical ventilation for over 24 hours, vitamin C shortened the duration of mechanical ventilation by 18.2% (95% CI 7.7% to 27%; p = 0.001). Given the insignificant cost of vitamin C, even an 8% reduction in ICU stay is worth exploring. The effects of vitamin C on ICU patients should be investigated in more detail.

Intravenous vitamin C in the treatment of allergies: an interim subgroup analysis of a long-term observational study

Objective Oxidative stress appears to be a key factor in the pathogenesis of allergic diseases and a potential therapeutic target in allergy treatment. Allergic diseases are reportedly associated with reduced plasma levels of ascorbate, which is a key physiological antioxidant. Ascorbate prevents excessive inflammation without reducing the defensive capacity of the immune system. Methods An interim analysis of a multicenter, prospective, observational study was conducted to investigate the change in disease-specific and nonspecific symptoms (fatigue, sleep disorders, depression, and lack of mental concentration) during adjuvant treatment with intravenous vitamin C (Pascorbin®; Pascoe, Giessen, Germany) in 71 patients with allergy-related respiratory or cutaneous indications. Results Between the start and end of treatment, the mean sum score of three disease-specific symptoms decreased significantly by 4.71 points and that of four nonspecific symptoms decreased significantly by 4.84 points. More than 50% of patients took no other allergy-related medication besides vitamin C. Conclusions Our observations suggest that treatment with intravenous high-dose vitamin C reduces allergy-related symptoms. Our observations form a basis for planning a randomized controlled clinical trial to obtain more definitive evidence of the clinical relevance of our findings. We also obtained evidence of ascorbate deficiency in allergy-related diseases.

TRIAL REGISTRATION

Clinical Trials NCT02422901.

Systematic Review of Intravenous Ascorbate in Cancer Clinical Trials

Background: Ascorbate (vitamin C) has been evaluated as a potential treatment for cancer as an independent agent and in combination with standard chemotherapies. This review assesses the evidence for safety and clinical effectiveness of intravenous (IV) ascorbate in treating various types of cancer. Methods: Single arm and randomized Phase I/II trials were included in this review. The PubMed, MEDLINE, and Cochrane databases were searched. Results were screened by three of the authors (GN, RP, and CJP) to determine if they met inclusion criteria, and then summarized using a narrative approach. Results: A total of 23 trials involving 385 patients met the inclusion criteria. Only one trial, in ovarian cancer, randomized patients to receive vitamin C or standard of care (chemotherapy). That trial reported an 8.75 month increase in progression-free survival (PFS) and an improved trend in overall survival (OS) in the vitamin C treated arm. Conclusion: Overall, vitamin C has been shown to be safe in nearly all patient populations, alone and in combination with chemotherapies. The promising results support the need for randomized placebo-controlled trials such as the ongoing placebo-controlled trials of vitamin C and chemotherapy in prostate cancer.

An Insight and Update on the Analgesic Properties of Vitamin C

Pain is an unpleasant subjective feeling having implications on both physical and mental realm. Multiple dimensions of pain involving behavioral, spiritual, emotional, and cognitive changes have been studied and pathways elucidated. It is stressed that the nature in which pain is modulated and perceived at a higher center is a complex phenomenon. One of the main goals of pain modulation is to modify pain to a more tolerable level, rather than its complete eradication. Different pain management interventions were tried but have effects that are more adverse. Till date, the only reliable pain blockers are analgesics and anti-inflammatory drugs in the form of opioids and non-opioids. Despite this, most of the drugs are ineffective at various levels, furthermore, adding to complications. Thus, there is an urgent need for effective intervention with minimal side effects. Ascorbic acid, popularly known as vitamin C, has shown to exhibit promising analgesic properties. The literature is sparse with the usage of the drug in various forms of pain. This review focuses on the dynamics and kinetics of vitamin C and its usage in various forms of pain. With minimal adverse effects, the drug is shown to perform well in different types of pain disorders, thus paving way for alternative interventional agent for pain management.

Serum vitamin C and spinal pain: a nationwide study

Back pain brings about one of the heaviest burden of disease. Despite much research, this condition remains poorly understood, and effective treatments are frustratingly elusive. Thus, researchers in the field need to consider new hypotheses. Vitamin C (ascorbic acid) is an essential cofactor for collagen crosslinks, a key determinant of ligament, tendon, and bone quality. Recent studies have reported high frequency of hypovitaminosis C in the general population. We hypothesized that lack of vitamin C contributes to poor collagen properties and back pain. We conducted this study to examine the associations between serum concentration of vitamin C and the prevalence of spinal pain and related functional limitations in the adult general population. This study used nationwide cross-sectional data from the U.S. National Health and Nutrition Examination Survey (NHANES) 2003-2004. Data were available for 4742 individuals aged ≥20 years. Suboptimal serum vitamin C concentrations were associated with the prevalence of neck pain (adjusted odds ratio [aOR]: 1.5; 95% confidence interval [CI]: 1.2-2.0), low back pain (aOR: 1.3; 95% CI: 1.0-1.6), and low back pain with pain below knee (aOR: 1.3; 95% CI: 1.0-1.9) in the past 3 months, self-reported diagnosis of arthritis/rheumatism (aOR: 1.4; 95% CI: 1.2-1.7), and related functional limitations' score (adjusted difference of means [aB]: 0.03; 95% CI: 0.00-0.05). The prevalence of hypovitaminosis C in the general population is high. Our study shows associations between vitamin C and spinal pain that warrant further investigation to determine the possible importance of vitamin C in the treatment of back pain patients.

The role of vitamin C in the treatment of pain: new insights

The vitamin C deficiency disease scurvy is characterised by musculoskeletal pain and recent epidemiological evidence has indicated an association between suboptimal vitamin C status and spinal pain. Furthermore, accumulating evidence indicates that vitamin C administration can exhibit analgesic properties in some clinical conditions. The prevalence of hypovitaminosis C and vitamin C deficiency is high in various patient groups, such as surgical/trauma, infectious diseases and cancer patients. A number of recent clinical studies have shown that vitamin C administration to patients with chronic regional pain syndrome decreases their symptoms. Acute herpetic and post-herpetic neuralgia is also diminished with high dose vitamin C administration. Furthermore, cancer-related pain is decreased with high dose vitamin C, contributing to enhanced patient quality of life. A number of mechanisms have been proposed for vitamin C’s analgesic properties. Herein we propose a novel analgesic mechanism for vitamin C; as a cofactor for the biosynthesis of amidated opioid peptides. It is well established that vitamin C participates in the amidation of peptides, through acting as a cofactor for peptidyl-glycine α-amidating monooxygenase, the only enzyme known to amidate the carboxy terminal residue of neuropeptides and peptide hormones. Support for our proposed mechanism comes from studies which show a decreased requirement for opioid analgesics in surgical and cancer patients administered high dose vitamin C. Overall, vitamin C appears to be a safe and effective adjunctive therapy for acute and chronic pain relief in specific patient groups.

Complex regional pain syndrome: a recent update

Complex regional pain syndrome (CRPS) is a debilitating condition affecting the limbs that can be induced by surgery or trauma. This condition can complicate recovery and impair one’s functional and psychological well-being. The wide variety of terminology loosely used to describe CRPS in the past has led to misdiagnosis of this condition, resulting in poor evidence-base regarding the treatment modalities available and their impact. The aim of this review is to report on the recent progress in the understanding of the epidemiology, pathophysiology and treatment of CRPS and to discuss novel approaches in treating this condition.

An open-label pilot study of oral vitamin C as an opioid-sparing agent in patients with chronic pain secondary to cancer

PURPOSE

The purpose of this study is to assess the efficacy of oral Vitamin C as an opioid-sparing agent when used in conjunction with opioids and standard adjuvant therapy in the management of chronic cancer pain.

METHODS

An open-label pilot study of patients ≥18 years of age with chronic pain secondary to cancer and/or its treatment and a Brief Pain Inventory average pain score of ≥3/10. In addition to opioid analgesia, patients received 1 g of vitamin C twice daily over 3 days (total daily dose of 2 g). Patients' usual medications, including breakthrough medications, were continued throughout the study period. The primary endpoint was total daily opioid use during vitamin C administration compared with that immediately prior to study.

RESULTS

Thirty-four patients were enrolled in the study. Seven failed to complete the trial. Across the 17 evaluable patients, the median daily opioid consumption was 360 mg oral morphine equivalents (OME) on the days prior to vitamin C and 390 mg when administered with vitamin C.

CONCLUSION

This study failed to demonstrate any clinically significant benefit from vitamin C in conjunction with opioids in cancer-related pain and does not provide support for embarking on a larger randomised trial to determine efficacy.

[Complex regional pain syndrome following distal fractures of the radius : Epidemiology, pathophysiological models, diagnostics and therapy]

The complex regional pain syndrome (CRPS) still represents an incompletely etiologically understood complication following fractures of the distal radius. The incidence of CRPS following fractures of the distal radius varies between 1 % and 37 %. Pathophysiologically, a complex interaction of inflammatory, somatosensory, motor and autonomic changes is suspected, leading to a persistent maladaptive response and sensitization of the central and peripheral nervous systems with development of the corresponding symptoms. Decisive for the diagnostics are a detailed patient medical history and a clinical hand surgical, neurological and pain-related examination with confirmation of the Budapest criteria. Among the types of apparatus used for diagnostics, 3‑phase bone scintigraphy and temperature measurement have a certain importance. A multimodal therapy started as early as possible is the most promising approach for successful treatment. As part of a multimodal rehabilitation the main focus of therapy lies on pain relief and functional aspects.

Perioperative management in children with chronic pain

Children with chronic pain often undergo surgery and effective perioperative management of their pain can be challenging. Identification of the pediatric chronic pain patient preoperatively and development of a perioperative pain plan may help ensure a safer and more comfortable perioperative course. Successful management usually requires multiple different classes of analgesics, regional anesthesia, and adjunctive nonpharmacological therapies. Neuropathic and oncological pain can be especially difficult to treat and usually requires an individualized approach.

Does vitamin C prevent the occurrence of complex regional pain syndrome in patients with extremity trauma requiring surgery?

The complex regional pain syndrome is a neuroinflammatory pathology that affects the central and peripheral nervous system, characterized by disproportional pain in relation to the trauma experimented by the patient. It has been proposed that vitamin C could prevent the development of this syndrome in patients with limb trauma and surgery. Searching in Epistemonikos database, which is maintained by screening 30 databases, we identified two systematic reviews that indentified four primary studies, including one randomized controlled trial. We generated a summary of findings table following the GRADE approach. We concluded it is uncertain whether vitamin C prevents complex regional pain syndrome because the certainty of the evidence is very low.