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Hyperdynamic sepsis modifies a PEEP-mediated redistribution in organ blood flows
A D Bersten1, A A Gnidec, F S Rutledge
1Richard Ivey Critical Care Trauma Centre, University of Western Ontario, London, Canada.
The American Review of Respiratory Disease
|May 1, 1990
Summary
Positive end-expiratory pressure (PEEP) significantly reduced organ blood flow (Q) in septic sheep, with some organ flows not recovering even after fluid resuscitation. These changes suggest sepsis-induced vasculopathy impacts organ perfusion during mechanical ventilation.
Area of Science:
- Physiology
- Critical Care Medicine
- Sepsis Research
Background:
- Positive end-expiratory pressure (PEEP) is used in mechanical ventilation, but its effects on organ blood flow (Q) during sepsis are not fully understood.
- Hyperdynamic sepsis alters systemic and organ hemodynamics, potentially affecting the response to PEEP.
Purpose of the Study:
- To investigate the impact of PEEP on organ blood flow distribution in a sheep model of hyperdynamic sepsis.
- To compare the effects of PEEP on organ Q in septic versus nonseptic states.
- To assess the reversibility of PEEP-induced changes in organ Q after fluid resuscitation in sepsis.
Main Methods:
- Organ blood flow (Q) was measured using thermodilution and microsphere techniques in unanesthetized sheep.
- PEEP (20 cm H2O) was applied during baseline (nonseptic) and hyperdynamic sepsis (induced by cecal ligation and perforation) conditions.
- Systemic and organ Q were assessed before and during PEEP application, with fluid resuscitation following in the septic state.
Main Results:
- In nonseptic sheep, PEEP decreased systemic Q by 9% but maintained brain and heart flow, while reducing flow to several abdominal organs.
- In septic sheep, PEEP caused a greater decrease in systemic Q (-17%) compared to nonseptic states.
- Despite fluid resuscitation restoring systemic Q in septic sheep, organ Q, particularly to the kidney, did not recover and even decreased further.
Conclusions:
- PEEP-induced reductions in organ blood flow during hyperdynamic sepsis may be exacerbated by sepsis-related vasculopathy or altered microcirculatory function.
- The inability to restore organ Q after fluid resuscitation suggests potential persistent microvascular dysfunction.
- Alternative strategies to support organ Q during mechanical ventilation in sepsis may be necessary when PEEP acutely depresses systemic oxygen delivery.