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Effects of isoflurane anesthesia on hyperpolarized 13C metabolic measurements in rat brain

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Abstract

Purpose

Commonly used anesthetic agents such as isoflurane are known to be potent cerebral vasodilators, with reported dose-dependent increase in cerebral blood flow and cerebral blood volume. Despite the widespread use of isoflurane in hyperpolarized 13C preclinical research studies, a quantitative assessment of its effect on metabolic measurements is limited. This work investigates the effect of isoflurane anesthesia dose on hyperpolarized 13C MR metabolic measurements in rat brain for [1-13C]pyruvate and 2-keto[1-13C]isocaproate.

Methods

Dynamic 2D and 3D spiral chemical shift imaging was used to acquire metabolic images of rat brain as well as kidney and liver following bolus injections of hyperpolarized [1-13C]pyruvate or 2-keto[1-13C]isocaproate. The impact of a “low dose” vs. a “high dose” of isoflurane on cerebral metabolite levels and apparent conversion rates was examined.

Results

The cerebral substrate signal levels, and hence the metabolite-to-substrate ratios and apparent conversion rates, were found to depend markedly on isoflurane dose, while signal levels of metabolic products and their ratios, e.g. bicarbonate/lactate, were largely insensitive to isoflurane levels. No obvious dependence on isoflurane was observed in kidney or liver for pyruvate.

Conclusion

This study highlights the importance of careful attention to the effects of anesthesia on the metabolic measures for hyperpolarized 13C metabolic imaging in brain. Magn Reson Med, 70:1117–1124, 2013. © 2012 Wiley Periodicals, Inc.

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