Cerebral blood flow is proportional to cardiac index in patients with septic shock

Purpose: In patients with septic shock, the cardiac index is often increased. Maldistribution of blood flow and regional hypoperfusion has been implicated as a key factor in the pathogenesis of organ dysfunction in these patients. We have investigated the relationship between cerebral blood flow and cardiac index in patients with septic shock. Materials and Methods: We used Doppler ultrasound techniques to investigate limb and carotid blood flow in 15 patients with septic shock and 9 nonseptic controls. Results: In the nonseptic control patients, common femoral and brachial blood flow were proportional to cardiac index (r = 0.73 and 0.76; P = .038 and .017, respectively) reflecting a protective redistribution of flow to more vital organs. However, this relationship was absent in patients with septic shock (r = 0.23 and 0.21). Furthermore, in the septic patients but not the nonseptic controls, cerebral blood flow was correlated with the cardiac index (r = 0.66, P < .05 vs r = -0.36, NS in nonseptic controls). Carotid flow was independent of mean arterial pressure, Paco₂ and Pao₂ in patients with septic shock. Conclusions: These data are consistent with a loss of autoregulation of cerebral blood flow and a change in the control of limb blood flow in humans with septic shock.