Marcelo de Lima Oliveira

Cerebral Microdialysis in Traumatic Brain Injury and Subarachnoid Hemorrhage: State of the Art

Cerebral microdialysis (CMD) is a laboratory tool that provides on-line analysis of brain biochemistry via a thin, fenestrated, double-lumen dialysis catheter that is inserted into the interstitium of the brain. A solute is slowly infused into the catheter at a constant velocity. The fenestrated membranes at the tip of the catheter permit free diffusion of molecules between the brain interstitium and the perfusate, which is subsequently collected for laboratory analysis. The major molecules studied using this method are glucose, lactate, pyruvate, glutamate, and glycerol. The collected substances provide insight into the neurochemical features of secondary injury following traumatic brain injury (TBI) and subarachnoid hemorrhage (SAH) and valuable information about changes in brain metabolism within a short time frame. In this review, the authors detail the CMD technique and its associated markers and then describe pertinent findings from the literature about the clinical application of CMD in TBI and SAH.

Brain metabolic crisis in traumatic brain injury: what does it mean?

Cerebral microdialysis (CMD) has allowed the identification of cellular biochemical states in traumatic brain injury (TBI), including metabolic crises. Although there is controversy over the definition of metabolic crises associated with TBI, their identification can be important for guiding the therapeutic approach taken with these patients. Vespa and colleagues published an important article addressing the issue of cerebral metabolic crisis in patients with severe TBI. These authors reported that cerebral metabolic crises associated with ischemic events are uncommon in severe TBI and that the increase in CMD lactate/pyruvate ratio (LPR) permits the identification of impairment in oxidative metabolism, irrespective of the cause (ischemic or non-ischemic). 1 Later, David and colleagues found no correlation between LPR elevation and ischemic events in most severe TBI patients. 2

Cerebral blood flow autoregulation in ischemic heart failure

Patients with ischemic heart failure (iHF) have a high risk of neurological complications such as cognitive impairment and stroke. We hypothesized that iHF patients have a higher incidence of impaired dynamic cerebral autoregulation (dCA). Adult patients with iHF and healthy volunteers were included. Cerebral blood flow velocity (CBFV, transcranial Doppler, middle cerebral artery), end-tidal CO2 (capnography), and arterial blood pressure (Finometer) were continuously recorded supine for 5 min at rest. Autoregulation index (ARI) was estimated from the CBFV step response derived by transfer function analysis using standard template curves. Fifty-two iHF patients and 54 age-, gender-, and BP-matched healthy volunteers were studied. Echocardiogram ejection fraction was 40 (20-45) % in iHF group. iHF patients compared with control subjects had reduced end-tidal CO2 (34.1 ± 3.7 vs. 38.3 ± 4.0 mmHg, P < 0.001) and lower ARI values (5.1 ± 1.6 vs. 5.9 ± 1.0, P = 0.012). ARI <4, suggestive of impaired CA, was more common in iHF patients (28.8 vs. 7.4%, P = 0.004). These results confirm that iHF patients are more likely to have impaired dCA compared with age-matched controls. The relationship between impaired dCA and neurological complications in iHF patients deserves further investigation.

Surgical technique of retrograde ventricle-sinus shunt is an option for the treatment of hydrocephalus in infants after surgical repair of myelomeningocele

INTRODUCTION Treatment of hydrocephalus is accomplished primarily through a ventricular-peritoneal shunt (VPS). This study aims to describe the application of retrograde ventricle-sinus shunt (RVSS) in patients with hydrocephalus after surgical treatment of myelomeningocele. METHOD A prospective, randomized and controlled pilot study. We consecutively enrolled 9 patients with hydrocephalus after surgical repair of myelomeningocele from January 2010 to January 2012. These patients underwent elective RVSS or VPS. Five underwent RVSS and 4 underwent VPS. Patients were followed for one year with quarterly evaluations and application of transcranial Doppler. RESULTS RVSS group showed outcomes similar to those of VPS group. Doppler revealed significant improvement when comparing preoperative to postoperative period. RVSS group had significantly higher cephalic perimeter than VPS group. Neuropsychomotor development, complications and subjective outcomes did not differ between groups. CONCLUSION RVSS shunt is viable; it is an alternative option for the treatment of hydrocephalus.

Intraoperative ultrasonography for presumed brain metastases: a case series study

UNLABELLED Brain metastases (BM) are one of the most common intracranial tumors and surgical treatment can improve both the functional outcomes and patient survival, particularly when systemic disease is controlled. Image-guided BM resection using intraoperative exams, such as intraoperative ultrasound (IOUS), can lead to better surgical results. METHODS To evaluate the use of IOUS for BM resection, 20 consecutive patients were operated using IOUS to locate tumors, identify their anatomical relationships and surgical cavity after resection. Technical difficulties, complications, recurrence and survival rates were noted. RESULTS IOUS proved effective for locating, determining borders and defining the anatomical relationships of BM, as well as to identify incomplete tumor resection. No complications related to IOUS were seen. CONCLUSION IOUS is a practical supporting method for the resection of BM, but further studies comparing this method with other intraoperative exams are needed to evaluate its actual contribution and reliability.

Encephalic hemodynamic phases in subarachnoid hemorrhage： how to improve the protective effect in patient prognoses

Subarachnoid hemorrhage is frequently associated with poor prognoses. Three different hemodynamic phases were identified during subarachnoid hemorrhage: oligemia, hyperemia, and vasospasm. Each phase is associated with brain metabolic changes. In this review, we correlated the hemodynamic phases with brain metabolism and potential treatment options in the hopes of improving patient prognoses.

Experimental model of intracranial hypertension with continuous multiparametric monitoring in swine

OBJECTIVE Intracranial hypertension (IH) develops in approximately 50% of all patients with severe traumatic brain injury (TBI). Therefore, it is very important to identify a suitable animal model to study and understand the pathophysiology of refractory IH to develop effective treatments. METHODS We describe a new experimental porcine model designed to simulate expansive brain hematoma causing IH. Under anesthesia, IH was simulated with a balloon insufflation. The IH variables were measured with intracranial pressure (ICP) parenchymal monitoring, epidural, cerebral oximetry, and transcranial Doppler (TCD). RESULTS None of the animals died during the experiment. The ICP epidural showed a slower rise compared with parenchymal ICP. We found a correlation between ICP and cerebral oximetry. CONCLUSION The model described here seems useful to understand some of the pathophysiological characteristics of acute IH.

Multimodal brain monitoring in fulminant hepatic failure

Acute liver failure, also known as fulminant hepatic failure (FHF), embraces a spectrum of clinical entities characterized by acute liver injury, severe hepatocellular dysfunction, and hepatic encephalopathy. Cerebral edema and intracranial hypertension are common causes of mortality in patients with FHF. The management of patients who present acute liver failure starts with determining the cause and an initial evaluation of prognosis. Regardless of whether or not patients are listed for liver transplantation, they should still be monitored for recovery, death, or transplantation. In the past, neuromonitoring was restricted to serial clinical neurologic examination and, in some cases, intracranial pressure monitoring. Over the years, this monitoring has proven insufficient, as brain abnormalities were detected at late and irreversible stages. The need for real-time monitoring of brain functions to favor prompt treatment and avert irreversible brain injuries led to the concepts of multimodal monitoring and neurophysiological decision support. New monitoring techniques, such as brain tissue oxygen tension, continuous electroencephalogram, transcranial Doppler, and cerebral microdialysis, have been developed. These techniques enable early diagnosis of brain hemodynamic, electrical, and biochemical changes, allow brain anatomical and physiological monitoring-guided therapy, and have improved patient survival rates. The purpose of this review is to discuss the multimodality methods available for monitoring patients with FHF in the neurocritical care setting.

The role of metabolism in the ischemia associated with vasospasm following brain tumor resection

Alotaibi et al have reviewed cerebral vasospasm following resection of intracranial tumor. Vasospasm is unusual after intracranial tumor resections and is associated with high morbidity and mortality. In general, the pathogenesis of cerebral ischemia related to vasospasm is complex and may be linked to an uncoupling of cerebral blood flow and metabolism.1 – 4 We present the case of a 52-year-old woman with a 4-year history of periods of disorientation and cognitive deficits. A left sphenoid wing meningioma (figure 1) was diagnosed, and a Simpson III surgical resection was performed. On the first postoperative day, the patient developed reduced consciousness and motor deficits on the right side. CT was compatible with ischemia and swelling on left cerebral hemisphere associated with midline shift. The patient underwent a decompressive craniectomy to relieve the intracranial hypertension. On the same day, transcranial …

Embolic Signals during Routine Transcranial Doppler Ultrasonography in Aneurysmal Subarachnoid Hemorrhage

Introduction. Cerebral emboli may occur in subarachnoid hemorrhage (SAH) and intracranial aneurysm surgery. Although embolic signs (ES) have been reported in SAH, their origin remains unclear. The aim of this study was to report the detection of ES during routine TCD monitoring in patients with aneurysmal SAH. Methods. A total of 105 patients with aneurysmal SAH were submitted to TCD evaluation. Patients were monitored almost daily (5 times per week). In each monitoring session, one experienced operator performed TCD to detect or assess vasospasm and ES in arteries of the Willis polygon. Results. Four patients out of a total of 105 patients with aneurysmal SAH were found to present spontaneous cerebral embolization during routine TCD monitoring. The average age of the 4 patients (mean ± standard deviation) was 59.5 ± 8.34 years (range 49–68 ys); female patients predominated representing 75% (3/4) of subjects. Conclusion. Although detection of ES was relatively rare in this study, rates of emboli occurrence may be higher under systematic monitoring. The detection of ES after SAH surgery reinforces the need to study the role of embolus in this condition and may be an indicator for prophylactic antithrombotic treatment.