Actualizaciones en los métodos de monitorización cerebral regional en los pacientes neurocríticos: presión tisular de oxígeno, microdiálisis cerebral y técnicas de espectroscopía por infrarrojos

Avoiding brain hypoxia in severe traumatic brain injury in settings with limited resources - A pathophysiological guide

Cerebral oxygenation represents the balance between oxygen delivery, consumption and utilization by the brain, and therefore reflects the adequacy of cerebral perfusion. Different factors can influence the amount of oxygen to the brain including arterial blood pressure, hemoglobin levels, systemic oxygenation, and transfer of oxygen from blood to the cerebral microcirculation. A mismatch between cerebral oxygen supply and demand results in cerebral hypoxia/ischemia, and is associated with secondary brain damage and worsened outcome after acute brain injury. Therefore, monitoring and prompt treatment of cerebral oxygenation compromise is warranted in both neuro and general intensive care unit populations. Several tools have been proposed for the assessment of cerebral oxygenation, including non-invasive/invasive or indirect/direct methods, including Jugular Venous Oxygen Saturation (SjO2), Partial Brain Tissue Oxygen Tension (PtiO2), Near infrared spectroscopy (NIRS), Transcranial Doppler, electroencephalography and Computed Tomography. In this manuscript, we aim to review the pathophysiology of cerebral oxygenation, describe monitoring technics, and generate recommendations for avoiding brain hypoxia in settings with low availability of resources for direct brain oxygen monitoring.

[Aneurysmal subarachnoid haemorrhage: Results after introducing endovascular therapy in a medium-low volume centre]

OBJECTIVE

To evaluate the impact of introducing endovascular therapy for patients with aneurysmal subarachnoid haemorrhage (aSAH) in a medium-low volume centre.

MATERIAL AND METHODS

A retrospective observational study was conducted by comparing the clinical outcome of patients with aSAH before and after introducing endovascular therapy in our centre. The main variables analysed were: type of treatment, hospital and late mortality, intra-procedural morbidity, rate of re-bleeding and vasospasm, and clinical outcome according to the Glasgow Outcome Score (GOS).

RESULTS

Seventy-one patients were treated in two periods: 2010-2011 (32 patients; 19 clipped, 6 coiled, 7 untreated), and 2012-2013 (39 patients, 3 clipped, 34 coiled, 2 untreated). No significant differences were found in age, sex, clinical grade at admission, type and location of aneurysm, Fisher score, or in hospital mortality (28.1% vs 25.6%, P=.35), GOS (except for GOS 5: 43.37% vs 53.8%, P=.045), rate of hydrocephalus and rate of vasospasm. The second cohort obtained better results for aggregated GOS 1+2+3 (36.3% vs 43.75%, P=.034) and for GOS 4+5 (61.5% vs 56.25%, P=.078). The percentage of patients left untreated was significantly lower in the second period (5.1% vs 21.8%, P<.01), as well as the rate of re-bleeding (0% vs 9.4%, P<.01). Patients were treated earlier (2.51 vs 3.95 days), and hospital and total stay were lower (15.2 and 24.6 vs 10.3 and 18 days) in the second period, these differences not reaching statistical significance.

CONCLUSIONS

Endovascular therapy allowed treating more patients with aSAH, and with a lower re-bleeding rate. This led to a modest reduction in morbidity and mortality.

Microdialysis: is it ready for prime time?

PURPOSE OF REVIEW

This review highlights recent advances in cerebral microdialysis for investigational and clinical neurochemical monitoring in patients with critical neurological conditions.

RECENT FINDINGS

Use of microdialysis with other methods, including PET, electrophysiological monitoring and brain tissue oximetry in traumatic brain injury, subarachnoid hemorrhage with vasospasm, and infarction with refractory increased intracranial pressure have been reported. Potentially adverse neurochemical effects of nonconvulsive status epilepticus and cortical slow depolarization waves, both of which are increasingly recognized in traumatic brain injury and stroke patients, have been reported. The explosive growth in the use of cerebral oximetry with targeted management of brain tissue oxygen levels is leading to greater understanding of derangements of cerebral bioenergetics in the critically ill brain, but there remain unresolved basic issues. Understanding of the analytes that are measurable at the bedside - glucose, lactate, pyruvate, glutamate and glycerol - continues to evolve with glucose, lactate, pyruvate and the lactate-pyruvate ratio taking center stage. Analytes including inflammatory biomarkers such as cytokines and metabolites of nitric oxide are presently investigational, but hold promise for future application in advancing our understanding of basic pathophysiology, therapeutic target selection and prognostication. Growing consensus on indications for use of clinical microdialysis and advances in commercially available equipment continue to make microdialysis increasingly 'ready for prime time.'

SUMMARY

Cerebral microdialysis is an established tool for neurochemical research in the ICU. This technique cannot be fruitfully used in isolation, but when combined with other monitoring methods provides unique insights into the biochemical and physiological derangements in the injured brain.