Cardiopulmonary changes with intermittent endotoxin administration in sheep

Area of Science:

• Cardiovascular Physiology
• Sepsis Pathophysiology
• Endotoxemia Research

Background:

• Sepsis is a life-threatening condition characterized by dysregulated host response to infection.
• Endotoxemia, caused by bacterial endotoxins like lipopolysaccharide (LPS), is a key factor in sepsis.
• Understanding the chronic effects of endotoxemia is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the chronic cardiopulmonary and hemodynamic effects of repeated lipopolysaccharide (LPS) administration in a sheep model.
• To assess the development of refractoriness to endotoxemia over time.
• To examine changes in plasma and lymph concentrations of thromboxane B2 (TxB2) and the kallikrein-kallikrein inhibitor system.

Main Methods:

• Chronic sepsis was induced in sheep (n=7) by administering lipopolysaccharide (LPS) every 12 hours for 5 days.
• Pulmonary arterial pressure (PAP), cardiac index (CI), systemic vascular resistance, and lung lymph flow were monitored.
• Plasma and lymph thromboxane B2 (TxB2) concentrations, prekallikrein, and C1-esterase inhibitor levels were measured.

Main Results:

• Initial LPS doses increased PAP, systemic vascular resistance, TxB2, and lung lymph flow, while decreasing CI.
• Repeated LPS administration led to attenuated and eventually absent elevations in PAP and TxB2.
• Chronic endotoxemia resulted in elevated pulmonary microvascular permeability and a hyperdynamic circulation tendency, with reduced C1-esterase inhibitor levels.

Conclusions:

• Chronic endotoxemia in sheep induces pulmonary microvascular changes and a hyperdynamic circulatory state.
• The animals developed refractoriness to the hemodynamic and eicosanoid effects of repeated LPS administration.
• These findings highlight the complex and adaptive responses to sustained endotoxemia.