Comparison of buccal microcirculation between septic and hemorrhagic shock.

Objective: Microcirculatory perfusion is disturbed in sepsis, and global hemodynamics does not necessarily reflect microcirculatory blood flow. In this study, we investigated the effect of the same level of mean arterial pressure (MAP) or cardiac index on the changes in buccal microcirculation between septic and hemorrhagic shock.

Design: Prospective, controlled laboratory study.

Setting: University-affiliated research laboratory.

Interventions: A total of 20 Sprague-Dawley rats were divided into four groups: 1) septic shock induced by cecal ligation and perforation: when MAP decreased to 80 mm Hg, saline was infused at a rate of 25 mL.kg.hr for 2 hrs; 2) both time- and MAP-matched hemorrhagic shock: approximately 30% of total blood volume was withdrawn during the corresponding interval, followed by infusion aiming to restore MAP as required when MAP decreased to 80 mm Hg; 3) both time- and cardiac index-matched hemorrhagic shock: approximately 40% of total blood volume was withdrawn during the corresponding interval until MAP decreased to 50 mm Hg, which generally generated a cardiac index similar to those in septic animals, followed by infusion at the same rate for 2 hrs; and 4) sham control: animals underwent the same procedure except no cecal ligation and perforation, bleeding, and infusion.

Measurements And Main Results: Buccal microcirculation was visualized with the aid of an orthogonal polarization spectral image device. A semiquantitative score was calculated for vessels of <20 mum, primarily representing the capillaries. Impaired buccal capillary blood flows in septic animals were more severe than those in MAP-matched hemorrhagic animals and were similar to those in cardiac index-matched hemorrhagic animals during the hypoperfusion period before infusion. Significantly improved global hemodynamics after resuscitation cannot effectively improve the buccal capillary blood flows in septic animals, in contrast to those in MAP-matched and cardiac index-matched hemorrhagic animals.

Conclusions: Impaired microcirculatory alteration in septic shock is more severe than hemorrhagic shock; microcirculation is relatively independent of improved systemic hemodynamics, in contrast to those in hemorrhagic shock.