Systemic function,oxygenation and microvascular correlation during treatment of hemorrhagic shock with blood substitutes

Abstract

Systemic function and oxygenation changes during hemorrhagic shock treatment were continuously monitored and correlated with real-time microvascular changes. After splenectomy, each dog (n=12) was hemorrhaged (MAP=∼50 mmHg; ∼40% blood loss=32–36 ml/kg) and randomly assigned to 4 resuscitation groups: autologous/shed blood, hemoglobin-based oxygen-carrier/Oxyglobin^®, crystalloid/saline, and colloid/Hespan^®. Systemic function and oxygenation changes were continuously monitored and measured using standard operating room protocols. Computer-assisted intravital microscopy was used to non-invasively videotape and objectively analyze and quantify real-time microvascular changes in the conjunctival microcirculation. All measurements were made during pre-hemorrhagic (baseline), post-hemorrhagic and post-resuscitation phases of the study. Pre-hemorrhagic microvascular changes were similar in all 12 dogs (venular diameter=43±12 μm; red-cell velocity=0.6±0.2 mm/s). All dogs showed similar significant (P<0.01) post-hemorrhagic microvascular changes: ∼20% decrease in venular diameter; ∼80% increase in red-cell velocity. These microvascular changes correlated with post-hemorrhagic systemic function and oxygenation changes. The resuscitations restored microvascular changes to pre-hemorrhagic values; the microvascular reversals also correlated with post-resuscitation systemic function changes in all groups. However, only shed blood resuscitation restored oxygenation level close to pre-hemorrhagic values. All 12 dogs survived resuscitation treatments despite differences in oxygen-carrying capability between groups.