Peripheral vascular resistance in septic shock: its relation to outcome

To support the concept that patients who die of septic shock have a persistent defect in peripheral vascular tone irrespective of cardiac index (CI), a retrospective study was undertaken of 42 patients with documented septic shock. From the patient records, the single lowest CI (t=2) measured after initial values (t=1) with concomitantly obtained haemodynamic and metabolic variables was taken. Group 1 consisted of 21 survivors and group 2 of 21 patients, who had died in shock. Initial haemodynamic and metabolic variables were comparable between the groups, reflecting shock with a hyperdynamic circulation and lactic acidemia. At t=2, median CI measured 3.21·min-1·m-2 in both groups, but mean arterial pressure (MAP) and systemic vascular resistance index (SVRI) were higher in group 1 than 2 (p<0.0005). Changes in arterial blood lactate levels also differed significantly. The rankcorrelation between CI and SVRI at t=2 was significant in group 1 (r s=-0.69, p<0.005) but not in group 2 (r s=-0.34). Our data suggest that when CI decreases in septic shock, patients with a fatal outcome have less capability to augment vascular resistance than survivors. Hence, peripheral vascular failure, even if complicated by inability to maintain an elevated CI, may be a major haemodynamic determinant of mortality in septic shock.