Dynamic Autoregulation is Impaired in Circulatory Shock.

BACKGROUND:Circulatory shock is a life-threatening disorder that is associated with high mortality, with a state of systemic and tissue hypoperfusion that can lead to organ failure, including the brain, where altered mental state is often observed. We hypothesized that cerebral autoregulation (CA) is impaired in patients with circulatory shock. METHODS:Adult patients with circulatory shock and healthy controls were included. Cerebral blood flow velocity (CBFV, transcranial Doppler ultrasound) and arterial blood pressure (BP, Finometer or intra-arterial line) were continuously recorded during 5-minutes in both groups. Autoregulation Index (ARI) was estimated from the CBFV response to a step change in BP, derived by transfer function analysis; ARI ≤ 4 was considered as impaired CA. The relationship between organ dysfunction, assessed with the Sequential Organ Failure Assessment (SOFA) score and the ARI was assessed with linear regression. RESULTS:Twenty-five shock patients and 28 age-matched healthy volunteers were studied. The mean ± SD SOFA score was 10.8 ± 4.3. Shock patients compared to control subjects had lower ARI values (4.0 ± 2.1 vs. 5.9 ± 1.5, p = 0.001). Impaired CA was more common in shock patients (44.4% vs. 7.1%, p = 0.003). There was a significant inverse relationship between the ARI and the SOFA score (R = -0.63, p = 0.0008). CONCLUSIONS:These results suggest that circulatory shock is often associated with impaired CA and that the severity of CA alterations are correlated with the degree of multiple organ failure, reinforcing the need to monitor cerebral hemodynamics in patients with circulatory shock.