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

Point-of-Care Ultrasound and Critical Care Ultrasound use Among Providers in Neurocritical Units: A National Survey

BACKGROUND

Point-of-care ultrasound (POCUS)/critical care ultrasound (CCU) use in medical and surgical intensive care units has surged over the last few decades. It is unclear if this has similarly translated in neurocritical care (NCC) units. We designed a survey to describe the current state of POCUS/CCU use and training among NCC providers.

METHODS

An online 13-question survey was distributed nationally through newsletters and social media after endorsement by the Neurocritical Care Society. Participation was voluntary, and responses were anonymous. The survey queried respondent demographics, training, clinical use, confidence in POCUS/CCU, and barriers to POCUS/CCU use.

RESULTS

Overall, 119 NCC providers responded to the survey. Most respondents were attending neurointensivists (52.1%) and had completed neurology residency training (62.2%). Approximately 23% of respondents did not have training in POCUS/CCU, and 71% of respondents had not completed POCUS/CCU board-certified training. Fifty-five percent of respondents used POCUS/CCU in their practice frequently, and 37% used it rarely on a weekly basis. Thirty-six percent and 42% of respondents felt moderately skilled at acquiring and interpreting POCUS/CCU images, respectively. Ultrasound guidance for procedures was the most common technique used by respondents. Most respondents felt that using ultrasound for volume status, procedural guidance, and evaluation of shock influenced clinical decision-making. Lack of confidence in interpreting data/imaging and comfort in performing POCUS/CCU were the most common barriers to ultrasound use. Respondents agreed with incorporation of POCUS/CCU training in NCC fellowship milestones and creating resources for credentialing providers in POCUS/CCU to increase use of POCUS/CCU in NCC.

CONCLUSIONS

This national survey indicated that POCUS/CCU is moderately used among NCC providers. However, more formalized and robust training in POCUS/CCU is needed for trainees and practitioners in NCC to enhance comfortability with using ultrasound for clinical assessments.

Clinical applications of ultrasound in neurosurgery and neurocritical care: A narrative review

Ultrasonography (USG) has become an invaluable tool in the assessment of neurocritical patients in the operating theaters and critical care units. Due to its easy availability, reliability, safety, and repeatability, neuro-intensivists and neuro-anesthesiologists utilize USG to make a diagnosis, assess prognosis, and decide upon treatment. In neurocritical care units, USG has myriad indications for use, both systemic and neurologic. The neurological indications include the assessment of stroke, vasospasm, traumatic brain injury, brain death, acute brain damage, optic nerve sheath diameter, and pupillary reflexes to name a few. The systemic indications range from assessment of cardio-pulmonary function and intravascular volume status to detection of deep venous thromboses, vocal cord assessment in intubated patients, placement of central venous catheters, and percutaneous tracheostomy. In this narrative review, we iterate the clinical applications of USG in neuroanesthesia and neurocritical care, which we penned after searching relevant databases in PubMed, Medline, Ovid, and Google Scholar by using terms such as ‘applications of transcranial Doppler’, ‘optic nerve sheath diameter’, ‘USG applications in the critical care unit’, and so on. Our search database includes several research papers, neurocritical care books, review articles, and scientific databases. This article reviews various applications of USG in neuroanesthesia, neurosurgery, and neurocritical care.

Exploratory study to assess feasibility of intracerebral hemorrhage detection by point of care cranial ultrasound

Background

Limited studies have evaluated the use of ultrasound for detection of intracerebral hemorrhage (ICH) using diagnostic ultrasound Transcranial Doppler machines in adults. The feasibility of ICH detection using Point of care Ultrasound (POCUS) machines has not been explored. We evaluated the feasibility of using cranial POCUS B mode imaging performed using intensive care unit (ICU) POCUS device for ICH detection with a secondary goal of mapping optimal imaging technique and brain topography likely to affect sensitivity and specificity of ICH detection with POCUS.

Materials and methods

After obtaining IRB approval, a blinded investigator performed cranial ultrasound (Fujifilm, Sonosite^® Xporte, transcranial and abdominal presets) through temporal windows on 11 patients with intracerebral pathology within 72 h of last CT/MRI (computed tomography scan/magnetic resonance imaging) brain after being admitted to a neurocritical care unit in Aug 2020 and Nov 2020–Mar 2021. Images were then compared to patient’s CT/MRI to inform topography. Inferential statistics were reported.

Results

Mean age was 57 (28–77 years) and 6/11 were female. Six patients were diagnosed with ICH, 3 with ischemic stroke, 1 subarachnoid hemorrhage, and 1 brain tumor. The sensitivity and specificity of point of care diagnosis of ICH compared to CT/MRI brain was 100% and 50%, respectively. Mean time between ultrasound scan and CT/MRI was 13.3 h (21 min–39 h). Falx cerebri, choroid calcification and midbrain-related artifacts were the most reproducible hyperechoic signals. Abdominal preset on high gain yielded less artifact than Transcranial Doppler preset for cranial B mode imaging. False positive ICH diagnosis was attributed to intracerebral tumor and midbrain-related artifact.

Conclusions

Our exploratory analysis yielded preliminary data on use of point of care cranial ultrasound for ICH diagnosis to inform imaging techniques, cranial topography on B mode and sample size estimation for future studies to evaluate sensitivity and specificity of cranial POCUS in adult patients. This pilot study is limited by small sample size and over representation of ICH in the study. Cranial POCUS is feasible using POCUS machines and may have potential as a screening tool if validated in adequately powered studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13089-022-00289-z.

Role of Ultrasound in Neurocritical Care

Bedside point of care ultrasound has acquired an extremely significant role in diagnosis and management of neurocritical care, just as it has in other specialties. Easy availability and increasing expertise have allowed the intensivists to use it in a wide array of situations, such as confirming clinical findings as well as for interventional and prognostic purposes. At present, the clinical applications of ultrasonography (USG) in a neurosurgical patient include estimation of elevated intracranial pressure (ICP), assessment of cerebral blood flow (CBF) and velocities, diagnosis of intracranial mass lesion and midline shifts, and examination of pupils, apart from the systemic applications. Transcranial sonography has also found use in the diagnosis of the cerebral circulatory arrest. An increasing number of clinicians are now relying on the use of ultrasound in the neurointensive care unit for neurological as well as non-neurological indications. These uses include the diagnosis of shock, respiratory failure, deep vein thrombosis and performing bedside procedures.

Contrast-Enhanced Ultrasound Imaging in Detection of Changes in Cerebral Perfusion

Contrast-enhanced ultrasonography (CEU) is a non-invasive imaging technique that provides real-time, bedside information on changes in global and segmental organ perfusion. Currently, there is a lack of data concerning changes in the distribution of segmental brain perfusion in acute ischemic stroke treated by decompressive craniectomy. The aim of our case series was to assess the role of CEU after decompressive craniectomy in patients with acute ischemic stroke. CEU was performed in 12 patients at baseline and after any one of the following interventions was performed as dictated by the patient's clinical condition: vasoactive drug administration (in order to achieve cerebral perfusion pressure ≥70 mm Hg and mean arterial pressure <100 mm Hg for management of arterial blood pressure) and mild hyperventilation (carbon dioxide arterial pressure = 30-35 mm Hg). CEU was able to detect a significant variation in cerebral contrast distribution in both normal and pathologic hemispheres after induced hyperventilation (difference in time to peak [dTTP] = -38.4%), vasodilation (dTTP = -6.6%) and vasoconstriction (dTTP = +31.2%) (p < 0.05). CEU can be useful in assessing real-time cerebral perfusion changes in neurocritical care patients.

Advances in cerebral monitoring for the patient with traumatic brain injury

A brief overview of the most common invasive and noninvasive monitoring tools collectively referred to using the term "multimodal monitoring" is provided. Caring for the critically ill patient with traumatic brain injury requires careful monitoring to prevent or reduce secondary brain injury. Concurrent to the growth of the subspecialty of neurocritical care, there has been a concerted effort to discover novel mechanisms to monitor the physiology of brain injury. The past 2 decades have witnessed an exponential growth in neurologic monitoring in terms of intracranial pressure, blood flow, metabolism, oxygenation, advanced neuroimaging, and electrophysiology.