Relationship Between Brain Tissue Oxygen and Near-Infrared Spectroscopy in Patients with Nontraumatic Subarachnoid Hemorrhage

BACKGROUND

Continuous monitoring of cerebral oxygenation is one of the diagnostic tools used in patients with brain injury. Direct and invasive measurement of cerebral oxygenation with a partial brain oxygen pressure (PbtO₂) probe is promising but invasive. Noninvasive assessment of regional transcranial oxygen saturation using near-infrared spectroscopy (NIRS) may be feasible. The aim of this study was to evaluate the interchangeability between PbtO₂ and NIRS over time in patients with nontraumatic subarachnoid hemorrhage.

METHODS

This retrospective study was performed in a neurocritical care unit. Study participants underwent hourly PbtO₂ and NIRS measurements over 72 h. Temporal agreement between markers was described by their pointwise correlation. A secondary analysis assessed the structure of covariation between marker trajectories using a bivariate linear mixed model.

RESULTS

Fifty-one patients with subarachnoid hemorrhage were included. A total of 3362 simultaneous NIRS and PbtO₂ measurements were obtained. The correlation at each measurement time ranged from - 0.25 to 0.25. The global correlation over time was - 0.026 (p = 0.130). The bivariate linear mixed model confirmed the lack of significant correlation between the PbtO₂ and NIRS measurements at follow-up. NIRS was unable to detect PbtO₂ values below 20 mm Hg (area under the receiver operating characteristic curve 0.539 [95% confidence interval 0.536-0.542]; p = 0.928), and percentage changes in NIRS were unable to detect a decrease in PbtO₂ ≥ 10% (area under the receiver operating characteristic curve 0.615 [95% confidence interval 0.614-0.616]; p < 0.001).

CONCLUSIONS

PbtO₂ and NIRS measurements were not correlated. There is no evidence that NIRS could be a substitute for PbtO₂ monitoring in patients with nontraumatic subarachnoid hemorrhage.

[Multimodal neuromonitoring in traumatic brain injury: contribution of PTiO2]

The main goal of exhaustively monitoring neurocritical patients is to avoid secondary injury. In the last few years we have witnessed an increase in brain monitoring tools, beyond the checking of intracranial and brain perfusion pressures. These widely used systems offer valuable but possibly insufficient information. Awareness and correction of brain hypoxia is a useful and interesting measure, not only for diagnostic purposes but also when deciding treatment, and to predict an outcome. In this context, it would be of great interest to use all the information gathered from brain oxygenation monitoring systems in conjunction with other available multimodal monitoring devices, in order to offer individualized treatment for each patient.

[Cortical spreading depolarization phenomena in patients with traumatic and ischemic brain injuries. Results of a pilot study]

OBJECTIVES

To determine the frequency and duration of cortical spreading depolarization (CSD) and CSD-like episodes in patients with traumatic brain injury (TBI) and malignant middle cerebral artery infarction (MMCAI) requiring craniotomy.

DESIGN

A descriptive observational study was carried out during 19 months.

SETTING

Neurocritical patients.

PATIENTS

Sixteen patients were included: 9 with MMCAI and 7 with moderate or severe TBI, requiring surgical treatment.

INTERVENTIONS

A 6-electrode subdural electrocorticographic (ECoG) strip was placed onto the perilesional cortex.

MAIN VARIABLES OF INTEREST

An analysis was made of the time profile and the number and duration of CSD and CSD-like episodes recorded from the ECoGs.

RESULTS

Of the 16 patients enrolled, 9 presented episodes of CSD or CSD-like phenomena, of highly variable frequency and duration.

CONCLUSIONS

Episodes of CSD and CSD-like phenomena are frequently detected in the ischemic penumbra and/or traumatic cortical regions of patients with MMCAI who require decompressive craniectomy or of patients with contusional TBI.