Objective: Direct observations of the microcirculation using orthogonal polarization spectral imaging have attracted attention and revealed that, especially in cardiogenic and distributive shock, there is discordance between the macrocirculation and the microcirculation. We evaluated serial changes and the effects of epinephrine on microcirculatory blood flow in the most severe form of circulatory failure, namely, cardiac arrest.
Design and setting: : Controlled laboratory animal study.
Subjects and interventions: A total of 15 pigs were subjected to 5 mins of ventricular fibrillation and 5 mins of precordial compression before electrical defibrillation was attempted. In a subset, six animals received 1 mg of epinephrine after 1 min of precordial compression.
Measurements and main results: Microcirculatory blood flow was visualized in the sublingual mucosa at baseline and 0.5, 1, and 5 mins of ventricular fibrillation, at 1 and 5 mins of precordial compression, and at 1 and 5 mins after return of spontaneous circulation. In addition, coronary perfusion pressure was recorded. Microcirculatory blood flow decreased dramatically in the 0.5 min after the onset of ventricular fibrillation. Precordial compression partially restored microcirculatory blood flow in each animal but to a significantly greater extent in animals that achieved return of spontaneous circulation. These changes were paralleled by similar changes in coronary perfusion pressure. Both variables were highly correlated. Administration of epinephrine resulted in a massive reduction of microcirculatory blood flow that lasted for >/=5 mins.
Conclusions: In this model, microcirculatory blood flow was highly correlated with macrocirculatory hemodynamics, including coronary perfusion pressure in distinction with septic shock. Administration of epinephrine dramatically decreased microcirculatory blood flow.