Using the relationship between brain tissue regional saturation of oxygen and mean arterial pressure to determine the optimal mean arterial pressure in patients following cardiac arrest: A pilot proof-of-concept study☆

Abstract Introduction Prospectively assess cerebral autoregulation and optimal mean arterial pressure (MAP OPT ) using the dynamic relationship between MAP and regional saturation of oxygen (rSO 2 ) using near-infrared spectroscopy. Methods Feasibility study of twenty patients admitted to the intensive care unit following a cardiac arrest. All patients underwent continuous rSO 2 monitoring using the INVOS ® cerebral oximeter. ICM+ ® brain monitoring software calculates the cerebral oximetry index (COx) in real-time which is a moving Pearson correlation coefficient between 30 consecutive, 10-s averaged values of MAP and correspond rSO 2 signals. When rSO 2 increases with increasing MAP (COx ≥0.3), cerebral autoregulation is dysfunctional. Conversely, when rSO 2 remains constant or decreases with increasing MAP (COx ® fits a U-shaped curve through the COx values plotted vs. MAP. The MAP OPT is nadir of this curve. Results The median age was 59 years (IQR 54–67) and 7 of 20 were female. The cardiac arrest was caused by myocardial infarction in 12 (60%) patients. Nineteen arrests were witnessed and return of spontaneous circulation occurred in a median of 15.5 min (IQR 8–33). Patients underwent a median of 30 h (IQR 23–46) of monitoring. COx curves and MAP OPT were generated in all patients. The mean overall MAP and MAP OPT were 76 mmHg (SD 10) and 76 mmHg (SD 7), respectively. MAP was outside of 5 mmHg from MAP OPT in 50% (SD 15) of the time. Out of the 7672 5-min averaged COx measurements, 1182 (15%) were at 0.3 or above, indicating absence of autoregulation. Multivariable polynomial fractional regression demonstrated an increase in COx with increasing temperature ( P  = 0.008). Conclusions We demonstrated the feasibility to determine a MAP OPT using cerebral oximetry in patients after cardiac arrest.