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      The effect of vitamin C on plasma volume in the early stage of sepsis in the rat

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          Abstract

          Background

          Previous experimental studies have shown that vitamin C has several beneficial effects in sepsis and burns, such as decreased tissue oedema, improved endothelial barrier function and decreased transcapillary leakage of plasma markers. It has still not been investigated, though, if vitamin C has any impact specifically on plasma volume. The present study aims at testing the hypothesis that vitamin C decreases plasma volume loss in sepsis.

          Methods

          Anaesthetized male adult Sprague-Dawley rats were used in this prospective randomized study. All experiments were carried out at a university hospital laboratory. Sepsis was induced by caecal ligation and incision. After 3 h, vitamin C was given either as a bolus dose (66 mg/kg) followed by a continuous infusion (33 mg/kg/h) ( n = 9), or as a single bolus dose (200 mg/kg) ( n = 9). A sham group ( n = 9) underwent the same surgical procedure, but no vitamin C was given. Plasma volume was measured ( 125I-dilution technique) at baseline, at 3 h after end of initiation of sepsis and at the end of the experiment 3 h later. Arterial blood samples for analyses of electrolytes, blood gases, haematocrit and lactate were taken at the same time points.

          Results

          There were no significant differences in plasma volumes or the physiological parameters analysed between any of the three groups at any time point. There was a significantly larger urine production in the single bolus dose group (200 mg/kg) compared to the sham group.

          Conclusions

          Vitamin C treatment did not decrease the loss of plasma volume in the septic rat. The diuretic effect of vitamin C was in accordance with previous studies.

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          Most cited references21

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          Reduction of resuscitation fluid volumes in severely burned patients using ascorbic acid administration: a randomized, prospective study.

          High-dose ascorbic acid (vitamin C) therapy (66 mg/kg per hour) attenuates postburn lipid peroxidation, resuscitation fluid volume requirements, and edema generation in severely burned patients. A prospective, randomized study at a university trauma and critical care center in Japan. Thirty-seven patients with burns over more than 30% of their total body surface area (TBSA) hospitalized within 2 hours after injury were randomly divided into ascorbic acid and control groups. Fluid resuscitation was performed using Ringer lactate solution to maintain stable hemodynamic measurements and adequate urine output (0.5-1.0 ml/kg per hour). In the ascorbic acid group (n = 19; mean burn size, 63% +/- 26% TBSA; mean burn index, 57 +/- 26; inhalation injury, 15/ 19), ascorbic acid was infused during the initial 24-hour study period. In the control group (n = 18; mean burn size, 53% +/- 17% TBSA; mean burn index, 47 +/- 13; inhalation injury, 12/18), no ascorbic acid was infused. We compared hemodynamic and respiratory measurements, lipid peroxidation, and fluid balance for 96 hours after injury. Two-way analysis of variance and Tukey test were used to analyze the data. Heart rate, mean arterial pressure, central venous pressure, arterial pH, base deficit, and urine outputs were equivalent in both groups. The 24-hour total fluid infusion volumes in the control and ascorbic acid groups were 5.5 +/- 3.1 and 3.0 +/- 1.7 mL/kg per percentage of burn area, respectively (P<.01). In the first 24 hours, the ascorbic acid group gained 9.2% +/- 8.2% of pretreatment weight; controls, 17.8% +/- 6.9%. Burned tissue water content was 6.1 +/- 1.8 vs 2.6 +/- 1.7 mL/g of dry weight in the control and ascorbic acid groups, respectively (P<.01). Fluid retention in the second 24 hours was also significantly reduced in the ascorbic acid group. In the control group, the ratio of PaO2 to fraction of inspired oxygen at 18, 24, 36, 48, and 72 hours after injury was less than that of the ascorbic acid group (P<.01). The length of mechanical ventilation in the control and ascorbic acid groups was 21.3 +/- 15.6 and 12.1 +/- 8.8 days, respectively (P<.05). Serum malondialdehyde levels were lower in the ascorbic acid group at 18, 24, and 36 hours after injury (P<.05). Adjuvant administration of high-dose ascorbic acid during the first 24 hours after thermal injury significantly reduces resuscitation fluid volume requirements, body weight gain, and wound edema. A reduction in the severity of respiratory dysfunction was also apparent in these patients.
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            Mechanism of action of vitamin C in sepsis: ascorbate modulates redox signaling in endothelium.

            Circulating levels of vitamin C (ascorbate) are low in patients with sepsis. Parenteral administration of ascorbate raises plasma and tissue concentrations of the vitamin and may decrease morbidity. In animal models of sepsis, intravenous ascorbate injection increases survival and protects several microvascular functions, namely, capillary blood flow, microvascular permeability barrier, and arteriolar responsiveness to vasoconstrictors and vasodilators. The effects of parenteral ascorbate on microvascular function are both rapid and persistent. Ascorbate quickly accumulates in microvascular endothelial cells, scavenges reactive oxygen species, and acts through tetrahydrobiopterin to stimulate nitric oxide production by endothelial nitric oxide synthase. A major reason for the long duration of the improvement in microvascular function is that cells retain high levels of ascorbate, which alter redox-sensitive signaling pathways to diminish septic induction of NADPH oxidase and inducible nitric oxide synthase. These observations are consistent with the hypothesis that microvascular function in sepsis may be improved by parenteral administration of ascorbate as an adjuvant therapy. (c) 2009 International Union of Biochemistry and Molecular Biology, Inc.
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              Ascorbate protects against impaired arteriolar constriction in sepsis by inhibiting inducible nitric oxide synthase expression.

              Compromised microvascular responsiveness is one of the key factors associated with mortality of septic patients. The present study addresses the mechanism of protection by ascorbate against impaired vasoconstriction in septic mice. Sepsis (i.e., cecal ligation and puncture (CLP) model) elevated both plasma protein carbonyl (i.e., an index of oxidative stress) and plasma nitrite/nitrate (NOx) levels, reduced baseline mean arterial blood pressure (MABP), and inhibited the MABP pressor response to angiotensin II (Ang II) at 6 h post-CLP. At the microvascular level, sepsis increased the inducible nitric oxide synthase (iNOS) mRNA level in cremaster muscle arterioles (18-25 microm diameter) at 3 h post-CLP, and impaired vasoconstriction to Ang II in these arterioles at 6 h post-CLP. At 24 h post-CLP, sepsis resulted in 9% survival. An intravenous bolus of ascorbate (200 mg/kg body wt) given 30 min prior to CLP prevented the protein carbonyl and NOx increases, partially restored the baseline arterial pressure, and completely protected against all arteriolar iNOS mRNA increases, arteriolar constriction hyporesponsiveness, and pressor response impairment. Survival increased to 65%. In septic mice, iNOS gene knockout resulted in protection of arteriolar constriction and pressor responses identical to that provided by ascorbate. Ascorbate bolus given 3 h post-CLP protected against the increase in plasma NOx concentration and against the pressor response impairment. We conclude that ascorbate may protect arteriolar vasoconstrictor responsiveness in sepsis by inhibiting excessive NO production.
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                Author and article information

                Contributors
                bjorn.bark@med.lu.se
                per-olof.grande@med.lu.se
                Journal
                Intensive Care Med Exp
                Intensive Care Med Exp
                Intensive Care Medicine Experimental
                Springer International Publishing (Cham )
                2197-425X
                6 March 2014
                6 March 2014
                December 2014
                : 2
                : 11
                Affiliations
                Department of Anaesthesia and Intensive Care, Lund University and Lund University Hospital, SE-221 85 Lund, Sweden
                Article
                9
                10.1186/2197-425X-2-11
                4512993
                c4530a0f-1d10-4aa9-a8e3-d35e10de7b45
                © Bark and Grände; licensee Springer. 2014

                This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.

                History
                : 14 October 2013
                : 2 February 2014
                Categories
                Research
                Custom metadata
                © The Author(s) 2014

                plasma volume,sepsis,sirs,vitamin c,ascorbate,ascorbic acid,caecal ligation

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