Transcranial volumetric imaging using a conformal ultrasound patch.

Accurate and continuous monitoring of cerebral blood flow is valuable for clinical neurocritical care and fundamental neurovascular research. Transcranial Doppler (TCD) ultrasonography is a widely used non-invasive method for evaluating cerebral blood flow1, but the conventional rigid design severely limits the measurement accuracy of the complex three-dimensional (3D) vascular networks and the practicality for prolonged recording2. Here we report a conformal ultrasound patch for hands-free volumetric imaging and continuous monitoring of cerebral blood flow. The 2 MHz ultrasound waves reduce the attenuation and phase aberration caused by the skull, and the copper mesh shielding layer provides conformal contact to the skin while improving the signal-to-noise ratio by 5 dB. Ultrafast ultrasound imaging based on diverging waves can accurately render the circle of Willis in 3D and minimize human errors during examinations. Focused ultrasound waves allow the recording of blood flow spectra at selected locations continuously. The high accuracy of the conformal ultrasound patch was confirmed in comparison with a conventional TCD probe on 36 participants, showing a mean difference and standard deviation of difference as -1.51 ± 4.34 cm s-1, -0.84 ± 3.06 cm s-1 and -0.50 ± 2.55 cm s-1 for peak systolic velocity, mean flow velocity, and end diastolic velocity, respectively. The measurement success rate was 70.6%, compared with 75.3% for a conventional TCD probe. Furthermore, we demonstrate continuous blood flow spectra during different interventions and identify cascades of intracranial B waves during drowsiness within 4 h of recording.

A Case Report of Thalamic Infarction after Lumbar Drain: A Unique Cause of Perioperative Stroke?

In the case presented, a patient has an unexplained episode of hypertension during aneurysm clipping. Following the procedure, the patient was discovered to have bilateral thalamic infarctions unrelated to the vascular location of the aneurysm. After a review of the case, it becomes apparent that intracranial hypotension caused by lumbar over drainage of cerebrospinal fluid (CSF) is the likely cause of both the episode of intraoperative hypertension and the thalamic infarcts. It is often presumed that having an open dura protects against intracranial hypotension and subsequent herniation. We present this case to suggest that opening the dura might not be protective in all cases and anesthesiologists must pay particular attention to the rate of CSF drainage. Lumbar CSF drainage is a technique frequently employed during neurological surgery and it is important for anesthesiologists to understand the signs, symptoms, and potential consequences of intracranial hypotension from rapid drainage.

Emergency Neurological Life Support: Intracerebral Hemorrhage.

Intracerebral hemorrhage (ICH) is a subset of stroke due to spontaneous bleeding within the parenchyma of the brain. It is potentially lethal, and survival depends on ensuring an adequate airway, proper diagnosis, and early management of several specific issues such as blood pressure, coagulopathy reversal, and surgical hematoma evacuation for appropriate patients. ICH was chosen as an Emergency Neurological Life Support (ENLS) protocol because intervention within the first hours may improve outcome, and it is critical to have site-specific protocols to drive care quickly and efficiently.

Perioperative Vision Loss in Cervical Spinal Surgery.

STUDY DESIGN: Retrospective multicenter case series. OBJECTIVE: To assess the rate of perioperative vision loss following cervical spinal surgery. METHODS: Medical records for 17 625 patients from 21 high-volume surgical centers from the AOSpine North America Clinical Research Network who received cervical spine surgery (levels from C2 to C7) between January 1, 2005, and December 31, 2011, inclusive, were reviewed to identify occurrences of vision loss following surgery. RESULTS: Of the 17 625 patients in the registry, there were 13 946 patients assessed for the complication of blindness. There were 9591 cases that involved only anterior surgical approaches; the remaining 4355 cases were posterior and/or circumferential fusions. There were no cases of blindness or vision loss in the postoperative period reported during the sampling period. CONCLUSIONS: Perioperative vision loss following cervical spinal surgery is exceedingly rare.

Venous air embolus during prone cervical spine fusion: case report.

Venous air embolism (VAE) is a known neurosurgical complication classically and most frequently occurring in patients undergoing posterior cranial fossa or cervical spine surgery in a sitting or semi-sitting position. The authors present a case of VAE that occurred during posterior cervical spine surgery in a patient in the prone position, a rare intraoperative complication. The patient was a 65-year-old man who was undergoing a C1-2 fusion for a nonunion of a Type II dens fracture and developed a VAE. While VAE in the prone position is uncommon, it is a neurosurgical complication that may have significant clinical implications both intraoperatively and postoperatively. The aim of this review is 2-fold: 1) to improve the general knowledge of this complication among surgeons and anesthesiologists who may not otherwise suspect air embolism in patients positioned prone for posterior cervical spine operations, and 2) to formulate preventive measures as well as a plan for prompt diagnosis and treatment should this complication occur.

Randomized pilot trial of intensive management of blood pressure or volume expansion in subarachnoid hemorrhage (IMPROVES).

BACKGROUND: Volume expansion and hypertension are widely used for the hemodynamic management of patients with subarachnoid hemorrhage. OBJECTIVE: To investigate the feasibility, adherence, and retention in a trial of volume expansion and blood pressure manipulation to prevent delayed cerebral ischemia. METHODS: A randomized pilot trial using a 2-way factorial design allocating patients within 72 hours of subarachnoid hemorrhage to either normovolemia (NV) or volume expansion (HV) and simultaneously to conventional (CBP) or augmented blood pressure (ABP) for 10 days. The study endpoints were protocol adherence and retention to follow-up. The quality of endpoints for a larger trial were 6-month modified Rankin Scale score, comprehensive neurobehavioral assessment, delayed cerebral ischemia, new stroke, and discharge disposition. RESULTS: Twenty patients were randomized and completed follow-up. The overall difference in daily mean intravenous fluid intake was 2099 mL (95% confidence interval [CI]: 867, 3333), HV vs NV group. The overall mean systolic blood pressure difference was 5 mm Hg (95% CI: -4.65, 14.75), ABP vs CBP group. Adverse events included death (n=1), delayed cerebral ischemia (n=1), and pulmonary complications (n=3). There were no differences in modified Rankin Scale score between HV and NV (difference 0.1; 95% CI: -1.26, 1.46, P=.87) or between ABP and CBP groups (-0.5, 95% CI: -1.78, 0.78, P=.43). Neuropsychological scores were similar between HV vs NV, but tended to be worse in ABP (57±27) vs CBP group (85±21, P=.04). CONCLUSION: This pilot study showed adequate feasibility and excellent retention to follow-up. Given the suggestion of possible worse neurobehavioral outcome with ABP, a larger trial to determine the optimal blood pressure management in this patient population is warranted. (ClinTrials.gov NCT01414894.)

An epidural blood patch causing acute neurologic dysfunction necessitating a decompressive laminectomy.

OBJECTIVES: One risk with placement of an epidural blood patch (EDBP) is spinal cord or nerve root compression resulting from the epidural blood volume injected, a complication necessitating immediate surgical decompression. We could not find a previous report of this in the literature. Here, we review and discuss one such case. CASE REPORT: A patient was treated with 2 EDBPs for a presumptive cerebrospinal fluid leak 3 weeks after an epidural steroid injection. The second EDBP was performed under direct fluoroscopic guidance, yet resulted in spinal cord compression with radiologic evidence of an epidural hematoma. The patient developed acute cauda equina syndrome and required an emergent decompressive laminectomy resulting in partial resolution of neurological symptoms. One year after the procedure, the patient has recovered most of her motor function but with some persistent numbness below the left knee and a left foot drop. CONCLUSIONS: A cauda equina syndrome from an epidural hematoma may occur as a rare complication of an EDBP, even with direct fluoroscopic guidance. Early diagnosis of symptoms and prompt surgical evacuation of an epidural hematoma is essential and may result in the resolution of symptoms. This complication remains a rare occurrence and should not deter the performance of an EDBP, when indicated.

Ultrasound-based imaging in neurocritical care patients: a review of clinical applications.

OBJECTIVE: To analyze the diagnostic, monitoring, and procedural applications of ultrasound (US) imaging in neurocritical care (NCC) patients. METHOD: US imaging has been extensively validated in various subset of critically ill patients, but not specifically in the NCC population. We reviewed the clinical applications of US imaging for heart, vascular, brain, and lung evaluation and for possible procedural uses in NCC patients. Major neurosurgical books, journals, testimonials, authors' personal experience, and scientific databases were analyzed. RESULTS: Cardiac US imaging provides accurate information at NCC arrival to stratify risk factors, including presence of atrial septal defect/patent formen ovale, abnormal ventricular function, or pericardial effusion, and to monitor cardiac anatomy and function during the NCC stay for guiding goal-directed therapy. Vascular US in NCC patients has three especially relevant indications: to screen anatomy and flow in extracranial supra-aortic arteries, to diagnose deep vein thrombosis, and to optimize the safety of central venous catheterization. Brain US has important clinical applications in the NCC, including transcranial Doppler and emerging techniques for cerebral blood flow evaluation with contrast-enhanced US imaging. Lung US, as demonstrated in other intensive care unit patients, provides accurate diagnosis of anatomical and functional abnormalities and enables diagnosis of pleural effusion, pneumothorax, lung consolidation, pulmonary abscess and interstitial-alveolar syndrome, and lung recruitment/derecruitment. US imaging can effectively guide percutaneous tracheostomy. CONCLUSION: In conclusion, US imaging is an important diagnostic tool that provides real-time information at the bedside to stratify risk, monitor for complications, and guide invasive procedures in NCC patients.

Cerebral blood flow and the injured brain: how should we monitor and manipulate it?

PURPOSE OF REVIEW: Cerebral ischemia plays a major role in the pathophysiology of the injured brain, including traumatic brain injury and subarachnoid hemorrhage, thus improvement in outcome may necessitate monitoring and optimization of cerebral blood flow (CBF). To interpret CBF results in a meaningful way, it may be necessary to quantify cerebral autoregulation as well as cerebral metabolism. This review addresses the recent evidence related to the changes in CBF and its monitoring/management in traumatic brain injury. RECENT FINDINGS: Recent evidence on the management of patients with traumatic brain injury have focused on the importance of cerebral autoregulation in maintaining perfusion, which necessitates the measurement of CBF. However, adequate CBF measurements alone would not indicate the amount of oxygen delivered to neuronal tissues. Technologic advancements in measurement devices have enabled the assessment of the metabolic state of the cerebral tissue for the purpose of guiding therapy, progress as well as prognostification. SUMMARY: Current neurocritical care management strategies are focused on the prevention and limitation of secondary brain injury where neuronal insult continues to evolve during the hours and days after the primary injury. Appropriately chosen multimodal monitoring including CBF and management measures can result in reduction in mortality and morbidity.

Clinical experience with transcranial Doppler ultrasonography as a confirmatory test for brain death: a retrospective analysis.

BACKGROUND: Transcranial Doppler (TCD) ultrasonography to demonstrate cerebral circulatory arrest (CCA) is a confirmatory test for brain death (BD). The primary aim of this retrospective study was to evaluate the practical utility of TCD to confirm BD when clinical diagnosis was not feasible due to confounding factors. Secondary aims were to evaluate the reasons for inability of TCD to confirm BD and to assess the outcome of patients not brain dead according to the TCD criteria. METHODS: TCD waveforms and medical records of all the patients examined to confirm suspected BD between 2001 and 2007, where clinical diagnosis was not possible, were analyzed. BD was diagnosed based on CCA criteria recommended by the Task Force Group on cerebral death of the Neurosonology Research Group of the World Federation of Neurology. Final outcome of patients and the use of other ancillary tests were noted. RESULTS: Ninety patients (61 males), aged 40 ± 21 (range 3-84) years underwent TCD examination for confirmation of suspected BD. TCD confirmed BD in 51 (57%) patients and was inconclusive in 38 (43%), with no flow signals on the first examination in 7 (8%) patients and the waveform patterns in 31 (35%) being inconsistent with BD. Fourteen of the 19 patients who had CCA pattern in at least one artery but did not meet all the criteria for BD were subsequently found brain dead according to SPECT/clinical criteria or suffered cardiovascular death. CONCLUSION: Using the conventional criteria, TCD confirmed BD in a large proportion, of patients where clinical diagnosis could not be made. The presence of CCA pattern in one or more major cerebral artery may be prognostic of unfavorable outcome, even when BD criteria are not satisfied.

Adenosine-induced transient asystole for intracranial aneurysm surgery: a retrospective review.

UNLABELLED: BRIEF SUMMARY: We describe the use of adenosine-induced cardiac arrest to facilitate intracranial aneurysm clip ligation. BACKGROUND: Cerebral aneurysms are highly variable which may result in difficult surgical exposure for clip ligation in select cases. Secure clip placement is often not feasible without temporarily decompressing the aneurysm. This can be accomplished with temporary clip ligation of proximal vessels, or with deep hypothermic circulatory arrest on cardiopulmonary bypass, although these methods have their own inherent risks. Here we describe an alternate method of decompressing the aneurysm via adenosine-induced transient asystole. METHODS: We examined the records of 27 patients who underwent craniotomy for cerebral aneurysm clipping in which adenosine was used to induce transient asystole to facilitate clip ligation. Duration of adenosine-induced bradycardia (heart rate <40) and hypotension (SBP < 60) recorded on the electronic anesthesia record and outcome data including incidence of successful clipping, intraoperative and postoperative complications, and mortality were recorded. RESULTS: Satisfactory aneurysm decompression was achieved in all cases, and all aneurysms were clipped successfully. The median dose of intravenous adenosine resulting in bradycardia greater than 30 seconds was 30 mg. The median dose of adenosine resulting in hypotension greater than 30 seconds was 15 mg, and greater than 60 seconds was 30 mg. One case of prolonged hypotension after rapid redosing of adenosine required brief closed chest compressions before circulation was spontaneously restored. No other adverse events were observed. CONCLUSIONS: Adenosine cardiac arrest is a relatively novel method for decompression of intracranial aneurysms to facilitate clip application. With appropriate safety precautions, it is a reasonable alternative method when temporary clipping of proximal vessels is not desirable or not possible.

Current practices of triple-H prophylaxis and therapy in patients with subarachnoid hemorrhage.

BACKGROUND: Medical management of cerebral vasospasm following aneurysmal subarachnoid hemorrhage (SAH) includes hypertensive, hypervolemic, and hemodilution ("triple-H") therapy. However, there is little information regarding the indications and guidance used to initiate and adjust triple-H therapy. METHODS: A 43-item questionnaire was e-mailed to 375 members of the Neurocritical Care Society. Questions were designed to investigate the diagnostic approach to cerebral vasospasm and prophylactic and therapeutic administration of triple-H therapy. RESULTS: Completed surveys were received from 167 respondents (45% response proportion). Eighty-six percent of respondents worked in hospitals with neurointensive care units (NICUs). SAH patients in hospitals with a NICU had longer ICU stay (P = 0.037) and had indwelling central venous catheters for longer (P < 0.01). Centers without dedicated NICUs were more likely to induce prophylactic hypervolemia (P < 0.01). Twenty seven percent of respondents (n = 45) reported using prophylactic hypervolemia in patients with SAH, while 100% reported inducing hypervolemia for severe or symptomatic vasospasm. Twelve percent (n = 20) of respondents reported inducing prophylactic hypertension, while all reported inducing hypertension with severe or symptomatic vasospasm. Half of respondents relied on the mean arterial pressure and half on systolic blood pressure as the clinical parameter for blood pressure titration. The most widely used agents to induce hypertension were phenylephrine (48%) and norepinephrine (39%). There was little variation in the use of hemodilution therapy comparing patients with or without evidence of vasospasm. CONCLUSIONS: There are substantial differences in the administration of prophylactic triple-H, but there was high agreement on indication for therapeutic use. There was wide variability in the extent of ICU monitoring, diagnostic approach, physiologic parameters and values used as target of therapy. NICU availability was associated with more intensive monitoring. Lack of evidence and guidelines for triple-H therapy might largely explain these findings.

Paradoxical emboli secondary to hepatic pathology: common or coincidental?

Paradoxical cerebral emboli from cardiac and pulmonary sources are well described in the peer-reviewed literature. We outline a case with a hepatic etiology and describe diagnostic and management options. Though this paper represents the first documentation of such, we believe that transpulmonary shunting with concurrent paradoxical cerebral microemboli is more prevalent than recognized. We introduce this case report to compel practitioners to consider paradoxical emboli in selected cirrhotic patients since it can often be difficult to elicit subtle neurologic changes on clinical examination of patients with end stage liver disease.

Postoperative cognitive dysfunction in the elderly.

Despite improvement in surgical techniques, anesthetic management, and intensive care, a significant number of elderly patients develop postoperative cognitive decline. Postoperative cognitive dysfunction (POCD) is a postoperative memory or thinking impairment that has been corroborated by neuropsychological testing, for which increasing age is the leading risk factor. POCD is multifactorial in origin, but it remains unclear whether its occurrence is a result of surgery or general anesthesia. This article discusses the incidence, assessment, consequences, and prevention of POCD, as well as anesthetic strategies to improve cognitive outcome in elderly patients.