Concurrent quantification of tissue metabolism and blood flow via ²h/³¹P NMR in Viva iii. alterations of muscle blood flow and metabolism during sepsis

In the conclusion of this series of reports, the application of ³¹P/²H NMR to investigate the pathophysiology of sepsis in rat hindlimb muscle is demonstrated. Sepsis decreased muscle [PCr] by 18%, 18 ± 4 SD vs 22 ± 4 SD mmol/kg tissue wet wt (P = 0.01) in control rats but [ATP] was unchanged, 6 mmol/kg tissue wet wt (P = 0.2). The derived free cytosolic [ADP] in the two groups was similar, [ADP]_septic = 0.023 ± 0.004 SD and [ADP]_control, = 0.021 ± 0.003 SD mmol/kg tissue wet wt, and not statistically different (P =0.14). Likewise [P_i] in the septic and control groups was not statistically different, [Pⁱ]_septic = 1.1 ± 0.5 SD and [P_i]_control, = 1.2 ± 0.4 SD mmol/kg tissue wet wt (P = 0.2). Septic rats presented the symptom of respiratory alkalosis evidenced by elevated blood pH. Sepsis decreased muscle blood flow by 33%, P = 0.003, but examination of individual subjects did not demonstrate a correlation with the reduction in [PCr]. Thus, a metabolic energy deficit caused by cellular ischemia/hypoxia is not a likely cause of cellular abnormality in rat hindlimb muscle during sepsis.