Background and Purpose Individualizing mean arterial blood pressure (MAP) targets to a patient’s cerebral blood flow (CBF) autoregulatory range might prevent brain ischemia for patients undergoing cardiopulmonary bypass (CPB). This study compares the accuracy of real-time CBF autoregulation monitoring using near infra-red spectroscopy (NIRS) with that of transcranial Doppler (TCD). Methods Sixty adult patients undergoing CPB had TCD monitoring of middle cerebral artery blood flow velocity (MCA-FV) and NIRS monitoring. The mean velocity index (Mx) was calculated as a moving, linear correlation coefficient between slow waves of MCA-FV and MAP. The cerebral oximetry index (COx) was calculated as a similar coefficient between slow waves of cerebral oximetry and MAP. When CBF is autoregulated, Mx and COx vary around zero. Loss of autoregulation results in progressively more positive Mx and COx. Results Mx and COx showed significant correlation (r=0.55, P<0.0001) and good agreement (bias, 0.08 ± 0.18, 95% limits of agreement: −0.27 to 0.43) during CPB. Autoregulation was disturbed in this cohort during CPB (average Mx 0.38,95% CI 0.34 to 0.43). The lower CBF autoregulatory threshold (defined as incremental increase in Mx > 0.45) during CPB ranged from 45 to 80 mmHg. Conclusions CBF autoregulation can be monitored continuously with NIRS in adult patients undergoing CPB. Real-time autoregulation monitoring may have a role in preventing injurious hypotension during CPB.

Copeptin is a novel, independent prognostic marker improving currently used risk stratification of stroke patients. Ann Neurol 2009;66:799-808.

TCD pulsatility index can be easily and quickly assessed but is usually misinterpreted as a descriptor of CVR. The mathematical model presents a complex relationship between PI and multiple haemodynamic variables.