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

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 ((125)I-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.

Figure 1

Time scale of the experiment. PV₁, plasma volume at baseline; PV₂, plasma volume 3 h after surgical preparation just before the start of treatment; PV₃, plasma volume at the end of the experiment; ABG, arterial blood sample for analysis of blood gases, hematocrit, lactate and electrolytes.

Figure 2

Plasma volumes. Plasma volumes at baseline (PV₁), at 3 h after the surgical preparation just before the start of treatment (PV₂) and at the end of the experiment (PV₃). There was no significant difference between any of the groups at any time points. There was a significant difference between PV₁ and PV₂, and PV₂ and PV₃ for all groups. Two-way ANOVA for repeated measures followed by Bonferroni post hoc test was used for the statistical analyses (**p < 0.01).

Figure 3

Urine production. Data for urine production (mL/kg) from the end of surgical preparation to the end of the experiment. There was a significantly larger urine production in the B group compared to the S group. Student's t test was used for the statistical analyses (***p < 0.001).