Effect of synchronized, systolic, lower body, positive pressure on hemodynamics in human septic shock. A pilot study.

The pathophysiologic disturbance observed in volume-resuscitated patients with septic shock is primarily that of hyperdynamic circulation with a markedly reduced systemic vascular resistance. We hypothesized that external, mechanically applied, phasic lower body positive pressure could increase systemic vascular resistance and, thus, blood pressure in patients with refractory septic shock. A total of nine studies were performed on seven patients with septic shock refractory to volume resuscitation and vasopressors. All pre-existing therapies were continued unaltered during the study period. Phasic lower body positive pressure was produced by rapid synchronized inflation of pneumatic fabric cuffs fitted around each lower extremity. The cuffs were inflated for 200 ms to a pressure of 150 mm Hg, and the timing of inflation was adjusted to coincide with the peak systolic arterial pressure. Hemodynamic measurements were obtained at baseline and after 15 min of phasic lower body positive pressure. This off-on cycle was repeated twice for each study. Phasic lower body positive pressure increased mean arterial pressure by 12% and cardiac index by 14% (p = 0.01) over baseline (p < or = 0.001). Heart rate, central venous pressure, pulmonary capillary wedge pressure, arterial pH, arterial pO2, and mixed venous pO2 were unchanged. Synchronized external systolic compression of the lower extremities increased mean arterial pressure and cardiac output in seven patients with refractory septic shock. This hemodynamic improvement was independent of changes in calculated systemic vascular resistance.