Delayed ascorbate bolus protects against maldistribution of microvascular blood flow in septic rat skeletal muscle.

OBJECTIVE: Although early administration of ascorbate has been shown to protect against the microvascular dysfunction in sepsis, it is not clear if a delayed introduction of ascorbate also yields beneficial effects. The main objective was to determine the therapeutic window for treatment of an animal model of sepsis with bolus injection of ascorbate. We also determined if sepsis per se affects urinary excretion of ascorbate.
DESIGN: Prospective, controlled laboratory study.
SETTING: Animal laboratory in a university-affiliated research institute.
SUBJECTS: Male Sprague-Dawley rats, 300-400 g of body weight.
INTERVENTIONS: Rats were made septic by cecal ligation and perforation (CLP) and volume resuscitated by continuous saline infusion. Ascorbate bolus (7.6 mg/100 g of body weight) or saline vehicle was injected intravenously at 1, 6, or 24 hrs after CLP.
MEASUREMENTS AND MAIN RESULTS: At 24 hrs post-CLP, sepsis caused antidiuresis and decreased plasma ascorbate concentration, but it did not affect urinary excretion of ascorbate in rats that received only saline. Sepsis also caused maldistribution of capillary blood flow in skeletal muscle. This maldistribution of flow was prevented by ascorbate injected at 6 hrs post-CLP. At 48 hrs post-CLP, in addition to the flow maldistribution, sepsis caused systemic arterial hypotension and fever that were prevented by both immediate (1 hr post-CLP) and delayed injections of ascorbate (24 hrs post-CLP).
CONCLUSION: Despite volume resuscitation, the present model of sepsis resulted in maldistribution of capillary blood flow within 24 hrs and hypotension within 48 hrs. Our finding that intravenous bolus of ascorbate can protect against these deficits even if delayed 6-24 hrs after the septic insult shows, for the first time, that ascorbate can reverse microcirculatory dysfunction after the onset of sepsis.