G. R. Nunns1, N. Clenenden4,7, H. B. Moore1, A. D’Alessandro4, E. Gonzalez1, M. Fragoso2, E. Peltz1, C. C. Silliman5,6, A. Sauaia1, A. Banerjee1, E. E. Moore1,2 1University Of Colorado Denver,Surgery,Aurora, CO, USA 2Denver Health Medical Center,Surgery,Aurora, CO, USA 4University Of Colorado Denver,Department Of Biochemistry And Molecular Genetics,Aurora, CO, USA 5University Of Colorado Denver,Pediatrics,Aurora, CO, USA 6Bonfils Blood Center,Research Laboratory,Denver, CO, USA 7University Of Colorado Denver,Anesthesiology,Aurora, CO, USA
Introduction:
Succinate is a citric acid cycle intermediate that accumulates during ischemia, similar to lactate. Succinate has also been linked to reperfusion injury, platelet dysfunction and immunologic modulation. Mass spectrometry (MS) has recently provided detailed descriptions of the trauma plasma metabolome, elucidating many potential pathologic mediators including succinate. To guide therapeutics the relative contribution of isolated tissue injury (TI), isolated hemorrhagic shock (HS) and organ specific metabolopathy must be elucidated. We hypothesize that TI and HS will produce distinct metabolic signatures in plasma and that organ specific ischemia will delineate the dominant source of pathologic metabolites.
Methods:
A porcine model was used to determine the role of TI vs HS with 4 experimental groups: (1) sham (anesthesia, arterial line and tracheostomy), (2) TI (femur fracture/muscle crush, laparotomy/bowel crush, thoracotomy), (3) HS (hemorrhage to mean arterial pressure of 25mm Hg for 30 minutes, 30 minutes of descending thoracic aortic cross clamp followed by reperfusion), (4) combined TI + HS. Blood was collected at baseline, 30, 60 and 90 minutes after TI, for HS it was collected at baseline, 30, 60 minutes and 5 minutes after reperfusion. Organ specific ischemia was induced without TI or HS by arterial inflow occlusion (30 min) followed by reperfusion (spleen, kidney, liver and small bowel). Blood was drawn from the femoral vein and the venous outflow of each organ at baseline, 15 and 30 minutes of ischemia and after reperfusion. Plasma samples were analyzed by MS and interpreted using principal component analysis.
Results:
Lactate and succinate are not increased in plasma following multiple TI over sham levels. HS and TI + HS each increase plasma lactate compared to sham, 1.6 and 1.5 fold respectively. HS and TI + HS each produce a 3.8 fold increase in succinate compared to sham. All organs demonstrate uniform accumulation of lactate in response to ischemia, whereas succinate is increased disproportionately in the liver. At 30 minutes of ischemia, succinate levels in the liver are 6.5 x spleen, 8.2 x small bowel, 6 x renal and 2 x systemic levels.
Conclusion:
Multiple TI alone is insufficient to elevate plasma lactate or succinate. HS and HS+TI generate marked increases in succinate and lactate. Hemorrhagic shock associated hypoperfusion is the dominant stimuli for metabolic derangement associated with trauma. The liver is the main source of succinate production in response to ischemia. These data suggest that during trauma hepatic hypoperfusion is the primary source of plasma succinate with subsequent inflammatory, coagulopathy and immunomodulatory consequences.
