Changes in organ blood flow (Q̇) produced by 20 cm H2O positive end-expiratory pressure (PEEP) were measured before and after the induction of hyperdynamic sepsis in nine unanesthetized sheep. During the baseline nonseptic study, PEEP was associated with a 9% fall in thermodilution-measured systemic Q̇, although arterial perfusing pressures were unaffected. Concurrently, microsphere-derived Q̇ was maintained to the brain and heart, but fell to liver, spleen, pancreas, kidney, large intestine, and gastrocnemius. Twenty-four to 36 h after cecal ligation and perforation, a pre-PEEP septic study demonstrated an increase in all of the cardiac index (CI) (+43%) and systemic O2 delivery (+54%) when compared with the nonseptic study, whereas whole-body O2 extraction (-30%) was depressed. Although PEEP depressed systemic Q̇ (-17%) during the septic study to a greater extent during the nonseptic study (p<0.02), absolute organ Q̇ fell only to pancreas, liver, and spleen. Relative to the simultaneous fall in the CI, Q̇ to some splanchnic organs was not depressed by PEEP to the same magnitude in the septic as in the nonseptic study. When an infusion of Ringer's lactate (993 ± 295 ml) subsequently restored systemic Q̇ to pre-PEEP septic levels, individual flows that had been depressed by PEEP were not restored. Furthermore, Q̇-kidney continued to fall, such that the postfluid Q̇-kidney (-19%) was significantly less than was demonstrated in the pre-PEEP septic study. We postulate that difference noted in the distribution of organ Q̇ between the nonseptic and hyperdynamic septic studies after the application of PEEP were secondary to the vasculopathy of sepsis and/or an alteration in the function of specific organ microcirculations. However, these data do not address whether the changes in organ Q̇ distribution after a PEEP-mediated depression in systemic Q̇ during sepsis significantly restricted tissue DO2. The inability to acutely reverse the PEEP-mediated changes in organ Q̇ after restoring systemic Q̇ by a fluid infusion also suggests the need to evaluate alternative methods of support to organ Q̇ in acute respiratory failure secondary to sepsis when the addition of PEEP acutely depresses systemic DO2.
|Number of pages||11|
|Journal||American Review of Respiratory Disease|
|Issue number||5 Part I|
|Publication status||Published - 1 Jan 1990|