Metabolic Resuscitation Using Ascorbic Acid, Thiamine, and Glucocorticoids in Sepsis.

The global burden of sepsis is substantial with an estimated 15 to 19 million cases per year; the vast majority of these cases occur in low income countries. With more timely diagnosis and improvement in supportive care the 28-day mortality from sepsis in high income countries has declined to about 25%, however, the mortality from septic shock remains as high as 45%. Moreover, the mortality from sepsis and septic shock in low income countries is reported to be as high as 60%. In addition to short term mortality, septic patients suffer from a numerous short- and long-term complications and are at an increased risk of death for up to five years following the acute event. Over the last 3 decades over 100 phase II and phase III clinical trial have been performed testing various novel pharmacologic agents and therapeutic intervention in an attempt to improve the outcome of patients with sepsis and septic shock; all of these studies have failed to show an improvement in patient outcomes. New therapeutic approaches to sepsis are desperately required; considering the global burden of sepsis these interventions should be effective, cheap, safe and readily available.

A large body of experimental data has demonstrated that both corticosteroids and intravenous vitamin C reduce activation of nuclear factor ƘB (NFƘB) attenuating the release of pro-inflammatory mediators, reduce the endothelial injury characteristic of sepsis thereby reducing endothelial permeability and improving macrocirculatory flow, augment the release of endogenous catecholamines and enhance vasopressor responsiveness. In animal models these effects have resulted in reduced organ injury and increased survival. Corticosteroids have been evaluated in several clinical trials, with meta-analysis of these trials demonstrating somewhat conflicting outcomes. Low-dose stress corticosteroids have proven to be safe with no increased risk of clinically important complications. While corticosteroids decrease vasopressor dependency the effect on survival is less clear.

Several studies have investigated the use of intravenous vitamin C in critically ill patients. Nathens et al randomized 595 surgical ICU patients (91% trauma patients) to receive intravenous vitamin C and vitamin E for up to 28 days.The vitamin combination was associated with a significant reduction in the incidence of multiple system organ failure (p=0.04) with a trend to reduced mortality and length of ICU stay. No adverse effects were noted with the vitamin combination. Fowler et al performed a pilot study in 24 patients with severe sepsis and septic shock. In this study patients were randomized to placebo (n=8), low dose intravenous vitamin C (50 mg/kg) (n=8) or high dose vitamin C (200mg/kg). Vitamin C attenuated the inflammatory response with both doses of the vitamin being devoid of any side effects. Although the Sequential Sepsis Related Organ Failure Score (SOFA) fell significantly in both treatment arms the study was underpowered to determine any outcome benefit. Zabet and colleagues performed a randomized controlled trial (RCT) in which they evaluated the role of intravenous vitamin C in a dose of 100 mg/kg/day (about 7g/day) in 28 surgical ICU patients with septic shock. In this study the mean dose of norepinephrine and duration of norepinephrine administration were significantly lower in the ascorbic acid than the placebo group. The 28-day mortality was significantly lower in the ascorbic acid than the placebo group (14% vs. 64%, p = 0.009). No side effects related to the vitamin C infusion were reported. Tanaka et al randomized 37 patients with severe burn to very high dose vitamin C (about 110g/day) or placebo. Patients who received vitamin C required less fluid resuscitation with a trend towards reduced length of stay and mortality. No adverse effects were noted with the very high dosages of vitamin C. Several studies have administered vitamin C in doses exceeding 100g/day as adjuvant therapy in patients with cancer with no discernable side effects. Vitamin C appears to be toxic to normal human cells (not cancer cells) at a concentration on greater than 25 millimole (mM). A dose of 6g/day will achieve a steady state serum concentration of about 240 micromole (uM) which is about 100 times less than the dose required to cause cellular toxicity. The package insert for vitamin C lists no contraindications or adverse effects of the drug and states that as much as "6 grams has been administered without evidence of toxicity". The only reported restriction to the use of high dose intravenous vitamin C is in patients with known glucose-6-phosphate deficiency (G6PD) in whom hemolysis has been reported. It is important to recognize that patents with sepsis predictably have very low serum vitamin C levels, which can only be corrected with intravenous vitamin C in a dose of more than 3gm per day. The low or undetectable levels of vitamin C likely result from the metabolic consumption of the molecule as well as increased renal losses. Furthermore, unlike all other mammals, primates and guinea pigs are unable synthesize vitamin C is due to mutations in the L-gulono-_-lactone oxidase (GLO) gene which codes for the enzyme responsible for catalyzing the last step of vitamin C biosynthesis. In almost all species, except humans and guinea pigs, vitamin C production increases during stress and is secreted by the adrenal gland; in these species vitamin C is best considered a stress "hormone". Vitamin C is an essential cofactor for the production of corticosteroids and catecholamines by the adrenal gland. Vitamin C has been shown to reverse adrenal suppression caused by induction doses of etomidate during anesthesia.

Ascorbate donates a single electron in all its redox reactions, generating the ascorbate radical. This radical is not very reactive with anything but itself. Dismutation of two ascorbate radicals forms a molecule each of ascorbate and dehydroascorbate. Hydrolysis of the lactone ring of dehydroascorbate irreversibly converts it to 2,3-diketo-1-gulonic acid which is then converted to oxalate. Oxalate is normally excreted by the kidney and serum levels will increase with renal impairment. In patients with renal impairment receiving mega-dose vitamin C, supersaturation of serum with oxalate may result in tissue deposition as well as crystallization in the kidney. Glyoxylate, a byproduct of intermediary metabolism, is either reduced to oxalate or oxidized to carbon dioxide (CO2) by the enzyme glyoxylate aminotransferase; thiamine pyrophosphate is a co-enzyme required for this reaction. Thiamine deficiency increases the conversion of glyoxylate to oxalate resulting in hyper- oxalosis. Donnino and colleagues have demonstrated that thiamine deficiency is common (32%) in patients with sepsis and that treatment with thiamine in these patients reduces mortality. In a post-hoc analysis of this study these authors demonstrated that thiamine decreased the risk of acute kidney injury and the required for renal replacement therapy in all treated patients.

It has previously been suggested that "...the best hope for therapeutic advances [in sepsis] will depend on broad-base targeting, in which multiple components are targeted at the same time." Such combination "chemo-therapy" targeting multiple biological pathways is the standard approach in the treatment of malignant disease. While the benefits of vitamin C, hydrocortisone, and thiamine alone are likely limited, the investigators believe that these medications act synergistically to reduce the risk of organ failure and death in patients with sepsis. This hypothesis is supported previous research and more recently a set of elegant experiments performed by Barabutis et al. Using a validated pulmonary endothelial monolayer model, these authors demonstrated that hydrocortisone together with vitamin C protected the vascular endothelium from damage by endotoxin while neither agent alone had this effect. Previous research has demonstrated that vitamin C reverses oxidation of the glucocorticoid receptor (GR) a likely manifestation of sepsis. Oxidation of the GR limits binding of the GR to both ligand and DNA responsive units decreasing the activity of glucocorticoids. Furthermore, glucocorticoids increase the expression of the sodium vitamin C transporter-2 (SVCT-2) which is an essential transport protein necessary for vitamin C to be transported intracellularly.

The investigators therefore propose that a "metabolic resuscitation protocol" including vitamin C, corticosteroids and thiamine will limit the development of organ failure and reduce mortality in patients with severe sepsis and septic shock. This postulate is supported by the preliminary findings by Marik et al. In a retrospective before-after clinical study, these authors compared the outcome and clinical course of consecutive septic patients treated with intravenous vitamin C, hydrocortisone and thiamine during a 7-month period (treatment group) compared to a control group treated in during the preceding 7 months. The primary outcome was hospital survival. A propensity score was generated to adjust the primary outcome. There were 47 patients in both treatment and control groups with no significant differences in baseline characteristics between the two groups. The hospital mortality was 8.5% (4 of 47) in the treatment group compared to 40.4% (19 of 47) in the control group (p < 0.001). The propensity adjusted odds of mortality in the patients treated with the vitamin C protocol was 0.13 (95% CI 0.04-0.48, p=0.002). The SOFA score decreased in all patients in the treatment group with none developing progressive organ failure. Vasopressors were weaned off all patients in the treatment group, a mean of 18.3 ± 9.8 hours after starting treatment with vitamin C protocol. The mean duration of vasopressor use was 54.9 ± 28.4 hours in the control group (p<0.001). The results of this study provide sufficient information for the design of an adequately powered, pragmatic randomized controlled trial.