Low frequency flowmotion/(vasomotion) during patho-physiological conditions.

The role of low frequency flowmotion in physiological or pathophysiological settings is unclear. We performed various series of experiments in young anesthetized New Zealand white (NZW) rabbits. Many animals exhibited flowmotion during control conditions. However, they very often seemed to be in unstable physiological conditions, and our preset inclusion criteria (as to arterial pressure and blood gases) were frequently not met.Therefore, in a first series, we correlated these systematically with the incidence of flowmotion. Eleven of 35 anesthetized rabbits, subjected to extensive surgery, showed flowmotion with a median frequency of 1.5 cpm and a relative "amplitude" of 32%. Arterial pressure was 10 mmHg lower, bicarbonate, base-excess, and PCO(2) values and relative blood flow were also significantly lower compared to animals not exhibiting flowmotion. In a second series, we tested whether flowmotion could be induced by an isolated metabolic acidosis in animals meeting the inclusion criteria and not showing flowmotion at control. Here, flowmotion was induced in 9/10 cases (p < 0.01) 30 min after the start of an HCl-infusion. In a third study, we related the onset of flowmotion to the pressure/flow autoregulation curve. At locally reduced blood pressure all 23 rabbits exhibited flowmotion (p < 0,00001) in the gastrocnemius and the tenuissimus muscles, with maximum flowmotion at a locally reduced blood pressure of 30 mmHg; the LDF-flux level showing 67% of control flow.These results support the concept that low frequency periodic hemodynamics are a characteristic of pathophysiological conditions like hypoperfusion or acidosis rather than indicating a normal physiological state.