gms | German Medical Science

Objective: Intraoperative monitoring of cerebral blood perfusion is a useful technique that gives the neurosurgeon immediate feedback during the operation. As the application of such a method is time-consuming and challenging, we wanted to test the feasibility of a novel non-invasive measurement device during routine neurosurgical procedures and present our preliminary results.

Method: In this prospective, single-institution, non-randomized trial we studied local cerebral perfusion using the non-invasive laser-Doppler spectrophotometry system „Oxygen-to-see(O₂C)“ in 30 consecutive patients who underwent supratentorial neurosurgical operations. Capillary venous oxygenation (SO₂), post-capillary venous filling pressures (rHb) and blood flow (flow) were measured in 7 mm tissue depth using a thin subdural and/or epidural fiber optic probe. The cortical measurement site corresponded to the distal anterior or middle supply territory of the underlying pathology. Monitoring was performed real-time between dural opening and closure at 50 Hz with pulsed synchronous measurements. To compare our results with standard neuromonitoring procedures, we performed additional monitoring of somatosensory evoked potentials (SEP) with median and tibial nerve stimulation throughout all procedures.

Results: Data were acquired successfully in all patients and rendered reliable and valid results within the investigated samples. Parameters of local cerebral tissue perfusion changed during the following procedures:

1.

placement and removal of the self-retaining retractor,

2.

brain swelling,

3.

partial vessel occlusion during clipping of a cerebral aneurysm,

4.

use of indocyanine green (ICG) angiography during aneurysm surgery, and

5.

application of magnesium (Mg²⁺).

In conditions 1–3, local SO₂ and flow decreased while rHb increased as a sign of impeded venous outflow. Application of ICG and Mg²⁺, however, lead to an increase of all parameters, indicating local tissue hyperperfusion. SEP monitoring was uneventful in this patient cohort, and no neurological or surgical complications occurred.

Conclusions: Compared to other available techniques for non-invasive measurement of cerebral microcirculation, this novel approach allows real-time monitoring with no extensive delay in routine neurosurgical procedures. Keeping in mind the limitations of the method, we are planning to add this useful device in our surgical routine for intraoperative detection of local hypoperfusion or cerebral ischemia.