Transcranial, Non-Invasive Evaluation of Potential Misery Perfusion During Hyperventilation Therapy of Traumatic Brain Injury Patients.

Hyperventilation (HV) therapy uses vasoconstriction to reduce intracranial pressure (ICP) by reducing cerebral blood volume. However, as HV also lowers cerebral blood flow (CBF), it may provoke misery perfusion (MP), in which the decrease in CBF is coupled with increased oxygen extraction fraction (OEF). MP may rapidly lead to the exhaustion of brain energy metabolites, making the brain vulnerable to ischemia. MP is difficult to detect at the bedside, which is where transcranial hybrid, near-infrared spectroscopies are promising because they non-invasively measure OEF and CBF. We have tested this technology during HV (∼30 min) with bilateral, frontal lobe monitoring to assess MP in 27 sessions in 18 patients with traumatic brain injury. In this study, HV did not lead to MP at a group level (p > 0.05). However, a statistical approach yielded 89 events with a high probability of MP in 19 sessions. We have characterized each statistically significant event in detail and its possible relationship to clinical and radiological status (decompressive craniectomy and presence of a cerebral lesion), without detecting any statistically significant difference (p > 0.05). However, MP detection stresses the need for personalized, real-time assessment in future clinical trials with HV, in order to provide an optimal evaluation of the risk-benefit balance of HV. Our study provides pilot data demonstrating that bedside transcranial hybrid near-infrared spectroscopies could be utilized to assess potential MP.

Percutaneous implantation of cerebral microdialysis catheters by twist-drill craniostomy in neurocritical patients: description of the technique and results of a feasibility study in 97 patients.

Cerebral microdialysis is increasingly used to monitor several types of neurocritical patients. This study presents the technique used in our unit for percutaneous implantation of cerebral microdialysis catheters using a small twist-drill craniostomy that can be performed in the intensive care unit (ICU). We also present the results of this technique in 89 head-injured patients and in eight patients with a malignant middle cerebral artery (MCA) infarction. One hundred and twenty-two cerebral microdialysis catheters were implanted in the 97 patients included in this study. One cerebral microdialysis catheter was implanted in the less damaged hemisphere of 67 head-injured patients with a diffuse brain injury. An additional microdialysis catheter was inserted in the pericontusional parenchyma of 22 patients with brain contusions. In five of the eight patients with a malignant MCA infarction, only one microdialysis probe was inserted in the penumbral zone. In the remaining three patients, two cerebral microdialysis catheters were implanted in the same hemisphere (one in the ischemic core and the other in the penumbra). Technical problems were detected in 18 (15%) of the 122 microdialysis catheters implanted and were more frequent during the initial period of using microdialysis in our unit. In four patients (3% of implanted catheters), follow-up computed tomography (CT) scans showed a small intracerebral blood collection (always