gms | German Medical Science

Objective: Monitoring of cerebral autoregulation (AR) and cerebral pressure reactivity (PRx) has previously been demonstrated to be of diagnostic and prognostic value in neurocritical care patients. Continuous long-time monitoring requires either transcranial Doppler (TCD) for assessing index of autoregulation (Mx) or invasive intracranial pressure (ICP) monitoring for determination of PRx. Near infrared spectroscopy (NIRS) is, compared to TCD, very robust in long-term monitoring, and, compared to ICP monitoring, non invasive. We studied the association between the dynamic index of autoregulation using TCD (Mx), and tissue oxygenation reactivity (TOx) calculated using NIRS tissue oxygenation index; and the association between the PRx and the total haemoglobin reactivity (THxa) derived from NIRS total haemoglobin index (THI).

Methods: Nineteen patients with head injury and eight patients with intracerebral or subarachnoid haemorrhage were enrolled in the study and monitored daily for up to six consecutive days. The mean age was 43 years, mean Glasgow Coma Score at admission was 8. ICP, TOI, THI, mean arterial blood pressure (ABP) and blood flow velocity (FV) were recorded. Average recording time was 74 minutes. Mx and TOx were calculated as the moving correlation coefficients between 10-second averaged values of FV, TOI and CPP over moving 5 minute time-windows. Similarly, PRx and THxa were calculated as moving correlation coefficients between ABP and ICP, or THI and ABP, respectively. Mx, Tox, PRx and THxa were averaged for each patient.

Results: The autoregulation indices Mx and TOx demonstrated significant correlation with each other (R=0.66; p<0.001) in the whole group of patients. A similar correlation could be demonstrated with PRx and THxa (R=0.69, p<0.001).

Conclusions: NIRS shows promise for continuous assessment of cerebral autoregulation. Non-invasive assessment of pressure reactivity seems to be feasible.