Are changes in cerebrovascular autoregulation following cardiac arrest associated with neurological outcome? Results of a pilot study.

PURPOSE

To investigate the association between impaired cerebrovascular autoregulation (CVAR) and outcome in comatose survivors of cardiac arrest.

METHODS

The correlation in the time domain between cerebral tissue oxygenation (cStO2) using near infrared spectroscopy (NIRS) and mean arterial pressure was used to determine the tissue oxygenation index (TOx) as a reflection of normal (TOx<0) or impaired (TOx>0) CVAR. Daily measurements (>1h recording time) were performed in the first three days post cardiac arrest. Survival and neurological outcome was assessed at three months following cardiac arrest. A control group of healthy volunteers was also investigated.

RESULTS

23 patients and 28 volunteers were studied. All survivors (n=8) of cardiac arrest had a good neurological outcome. The TOx (median [interquartile range] for days 1-3) was higher (Mann Whitney test, p<0.001) in non-survivors (0.04 [-0.02 to -0.16]) compared to survivors (-0.11 [-0.19 to -0.02]) and healthy volunteers (-0.15 [-0.27 to -0.04]) on every day and for days 1-3 following cardiac arrest. The TOx was not significantly different between survivors and healthy volunteers. The cStO2 did not discriminate survivors (67 [62-72]%) from non-survivors (71 [65-75]%). Logistic regression analysis demonstrated TOx to be independently associated with survival at three months post cardiac arrest (odds ratio [95% confidence interval] 0.01 [0.01-0.50], p=0.04).

CONCLUSIONS

Early impairment of CVAR following cardiac arrest is independently associated with mortality at three months follow-up. Assessments of CVAR could add to the management and prognostication during post-resuscitation care and should be further investigated as a guide to optimise cerebral perfusion pressure.