Technique for the simultaneous measurement of renal ATP, blood flow and pH in a large animal model of septic shock

Abstract

BACKGROUND: Simultaneous measurement of renal blood flow, renal ATP, renal pH and mean arterial pressure (MAP) might help investigators understand the mechanisms responsible for acute renal failure (ARF) in sepsis. OBJECTIVES: (1) To develop a technique to simultaneously measure MAP, renal blood flow, renal ATP and renal pH in a large mammal during severe sepsis and after circulatory arrest; and (2) To describe preliminary observations during such measurements. METHODS: We implanted a custom-made phosphorus coil around the left kidney and a magnetic resonance-compatible blood flow probe around the renal artery of an adult Merino ewe. We induced severe sepsis by intravenous administration of Escherichia coli and obtained 31P magnetic resonance spectroscopic data at 3tesla, and continuous blood flow and MAP data before and during severe sepsis over several hours. We induced circulatory arrest with potassium chloride and measured the same 31P signal immediately and again 30 minutes later. RESULTS: We successfully and simultaneously measured MAP, renal blood flow, renal ATP and renal pH in a large mammal during severe sepsis and induced circulatory arrest. With these techniques, we observed that, despite marked hypotension, there were limited changes in renal ATP and renal pH, and that renal blood flow increased. A rapid and dramatic decrease in ATP and pH occurred with circulatory arrest. CONCLUSIONS: We have developed a technique to simultaneously monitor MAP, renal blood flow, ATP and pH in a large mammal during severe sepsis. Our initial observations indicate preservation of renal ATP in septic shock.