Detection of Del Ayed Cerebral Ischemia (DCI) In Subarachnoid Haemorrhage Applying Near-Infrared Spectroscopy: Elimination Of The Extracerebral Signal By Transcutaneous And Intraparenchymatous Measurements In Parallel

Abstract

Background: Detection of delayed cerebral ischemia (DCI) in high-grade subarachnoid haemorrhage (SAH) is an unsolved issue. Conventional near-infrared spectroscopy (NIRS) with optodes applied over the skin is controversial because the NIRS signal is contaminated by extracerebral tissue. The objective is to quantify and subtract the contribution from extracerebral tissue from the signal by using measurements in parallel with a NIRS brain tissue probe and conventional NIRS. Methods: In a patient with high-grade SAH, two approaches for NIRS were applied. First, a conventional brain tissue probe for intracranial pressure (ICP) monitoring, supplied by optical fi bres, was placed into the brain tissue 2 cm deep from the dura. Second, for conventional NIRS, a plaster-based patch carrying optodes (one emitter, two detectors) was attached to the skin. Central venous injections of 0.3 mg/kg body weight (bw) indocyanine green (ICG) were performed. ICG dye dilution curves obtained with the probe and patch were collected simultaneously and analysed for blood fl ow values. Results: Twelve measurements in parallel with the probe and patch were performed. Mean cerebral blood fl ow (CBF) for the probe was higher (24.8 ± 9.1 ml/100 g/min) compared with the values obtained with the patch (for detector 1, extracerebral blood fl ow [ECBF] mean 5.1 ± 1.8 ml/100 g/min; p = 0.002; for detector 2, 6.6 ± 2.1 ml/100 g/min; p = 0.002). CBF values obtained with the probe correlated with blood fl ow values obtained with the patch (for CBF vs. ECBF detector 1, r = 0.72 [p = 0.008]; ECBF detector 2, r = 0.79 [p = 0.002]). Conclusions: Blood fl ow values obtained with conventional NIRS correlated signifi cantly with absolute CBF values obtained directly within the brain tissue. Simultaneous measurements with the NeMo Probe and NeMo Patch allow quantifi cation and subtraction of the contribution from extracerebral tissues from the signal obtained with conventional NIRS.