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e5 164 Horvat CM, Ogoe H, Kantawala S, et al Development and performance of electronic pediatric risk of mortality and pediatric logistic organ dysfunction-2 automated acuity scores Pediatr Crit Care Med 2019;20(8):e372-e379 165 Gupta P, Rettiganti M, Gossett JM, Daufeldt J, Rice TB, Wetzel RC Development and validation of an empiric tool to predict favorable neurologic outcomes among PICU patients Crit Care Med 2018;46(1):108-115 166 Watson DS, Krutzinna J, Bruce IN, et al Clinical applications of machine learning algorithms: beyond the black box BMJ 2019;364:l886 167 Wiens J, Saria S, Sendak M, et al Do no harm: a roadmap for responsible machine learning for health care Nat Med 2019;25(9): 1337-1340 168 Ginestra JC, Giannini HM, Schweickert WD, et al Clinician perception of a machine learning-based early warning system designed to predict severe sepsis and septic shock Crit Care Med 2019; 47(11):1477-1484 169 Eytan D, Jegatheeswaran A, Mazwi ML, et al Temporal variability in the sampling of vital sign data limits the accuracy of patient state estimation Pediatr Crit Care Med 2019;20(7):e333-e341 170 Fartoumi S, Emeriaud G, Roumeliotis N, Brossier D, Sawan M Computerized decision support system for traumatic brain injury management J Pediatr Intensive Care 2016;5(3):101-107 171 Jha RM, Elmer J, Zusman BE, et al Intracranial pressure trajectories: a novel approach to informing severe traumatic brain injury phenotypes Crit Care Med 2018;46(11):1792-1802 172 Sorani M, Hemphill J, Morabito D, Rosenthal G, Manley G New approaches to physiological informatics in neurocritical care Neurocrit Care 2007;6:1-8 173 Hemphill J, Barton C, Morabito D, Manley G Influence of data resolution and interpolation method on assessment of secondary brain insults in neurocritical care Physiol Meas 2005;26:373-386 e6 Abstract: Much of the practice of brain-directed critical care in children is empiric, but studies in traumatic brain injury show that protocol-directed care with multidisciplinary teams in the intensive care unit improve outcome Neuromonitoring incorporates the use of technologies including electroencephalography and neuroimaging but begins with a focused neurologic examination Communication between team members, serial examinations, anticipation and early recognition of changes in the neurologic exam, or other monitoring parameters are essential The examiner should focus both on localization of a neurologic deficit and identifying mechanism(s) of injury (or potential injury) as the first step in developing a treatment approach to reduce brain injury Key words: electroencephalogram, transcranial Doppler, intracranial pressure, neurologic examination, near infrared spectroscopy, quantitative EEG 61 Neuroimaging FRANCISCO A PEREZ, HEDIEH KHALATBARI, AND DENNIS W.W SHAW PEARLS • Multiple imaging modalities are available for evaluation of the brain, head, neck, and spine of the critically ill child The most appropriate modality depends on consideration of patient pretest probability for the clinically suspected diagnosis, the modality sensitivity, and the patient’s age and condition • When ordering radiographic studies, particularly computed tomography scans, the physician should keep the radiation burden in mind, especially for infants When ordering magnetic resonance imaging for young children, one must keep in mind the risk related to sedation and general anesthesia • The ever-increasing complexity of imaging modalities and medical problems in the intensive care unit warrants liberal consultation with radiology colleagues to yield an appropriately tailored imaging protocol and a more relevant interpretation Imaging Modality Overview moderate to severe white-matter injury It is less sensitive for pathologies such as mild to moderate parenchymal ischemic changes, subarachnoid and punctate parenchymal hemorrhage, dural venous sinus thrombosis, and cerebral malformations Extraaxial collections, especially those along the lateral cerebral convexities, can be difficult to visualize on ultrasound performed through a midline fontanelle Color Doppler ultrasound uses the shift in frequency associated with reflection of the sound beam off a moving interface (the “Doppler shift” phenomenon) to detect motion in the image field, most commonly from blood in vessels Those pixels with movement are assigned a color to distinguish them from pixels without movement The color assigned (most often red and blue) depends on whether movement is away or toward the transducer and does not necessarily indicate arterial or venous flow Color Doppler allows for some investigation of the cerebral circulation, primarily through the open fontanelle Transcranial Doppler (TCD) uses the same Doppler shift to produce waveforms that give information about flow velocity and direction An advantage of TCD is that it can be performed through the thinner portions of the skull, primarily the temporal squamosa, including in older children and adults (Fig 61.2) TCD has been used in the evaluation of cerebral perfusion in patients with sickle cell disease1 and vasospasm secondary to subarachnoid hemorrhage (SAH).2 TCD is generally sensitive to vessel stenosis greater than 50% in the central cerebral circulation, with the highest sensitivity and specificity being in the middle cerebral artery (MCA).3,4 The role of TCD in the ICU is expanding because it enables noninvasive bedside monitoring of cerebral perfusion parameters in various conditions,5 including in patients on extracorporeal membrane oxygen therapy.6 However, the utility of TCD in critically ill children requires additional investigation Moreover, performance of TCD requires specially trained technologists and interpreting physicians Multiple imaging modalities are available to investigate the neurologic status of children in the intensive care unit (ICU) To select the most appropriate imaging modality, many factors need to be considered, including the pathologies suspected in a particular case, sensitivity of the imaging modality for the suspected pathologies, complexity of the imaging examination, and the child’s clinical condition This chapter reviews available imaging modalities and the disease processes that are more commonly evaluated with neuroimaging Radiography The most commonly performed radiographic study in neuroimaging is the radiographic shunt series The cerebrospinal fluid (CSF) shunt is imaged in the frontal and lateral projections to evaluate the location and course of the proximal catheter, reservoir, valve, and distal catheter in order to detect complications such as disconnection, fracture, improper placement, and migration (Fig 61.1) Ultrasound Standard cranial ultrasound is a mainstay in the neonatal ICU Ultrasound generates grayscale digital images using sound waves reflecting off tissue interfaces There is no ionizing radiation and bedside imaging can be performed Because sound waves cannot readily penetrate the bones of the skull, cranial ultrasound has a restricted window through which sound waves can be used to visualize the brain, primarily through an open anterior fontanelle Therefore, it is mostly limited to the first few months of life Ultrasound is sensitive to the detection of germinal matrix hemorrhage, assessment of ventricular size, and identification of 735 736 S E C T I O N V I Pediatric Critical Care: Neurologic A B • Fig 61.1 Improper placement of distal catheter of a cerebrospinal fluid (CSF) shunt in the large bowel Fourteen-year-old female with history of multiple prior CSF shunt revisions and intraperitoneal adhesions underwent CSF shunt revision Anteroposterior abdominal radiograph (A) from a radiographic shunt series obtained the same day demonstrates the distal catheter of a ventriculoperitoneal shunt coursing along the descending colon and sigmoid colon (arrows) and pneumoperitoneum (best appreciated in the right upper and lower quadrants, asterisk) Coronal image (B) from a subsequent abdominal computed tomography scan confirms the improper placement of the distal catheter in large bowel (arrow) Computed Tomography Computed tomography (CT) scanning has higher sensitivity compared with ultrasound for many intracranial pathologies, including most neurosurgical emergencies, and is not limited by closing and closed fontanelles Modern scanners with multiarray detectors image the patient rapidly (decreasing the need for sedation) and acquire volumetric data that may be reformatted in any plane CT, however, requires transporting the patient from the ICU (although some portable units are available) and uses ionizing radiation (x-rays) to produce digital computer-reconstructed images based on differences in tissue density (which affects x-ray attenuation) The choice of radiation parameters, slice thickness, postprocessing, and image viewing (window width and level) must be tailored to the particular clinical question to optimize the images For example, CT may be performed at a lower radiation dose when the clinical indication is to evaluate ventricular size However, this lower-dose CT may not be sensitive to parenchymal abnormalities Therefore, the ICU team and radiologist need to closely communicate in order to tailor the study appropriately With advancements in available computational power, newer CT scanners employ complex postprocessing algorithms, such as iterative reconstruction, which enable scanning with lower radiation doses while maintaining image quality New CT neuroimaging techniques—such as dual-energy CT, in which different energy x-ray sources are simultaneously used—allow improved differentiation of iodine, calcium, and hemorrhage; automated bone removal in CT angiography and CT venography; production of virtual nonenhanced CT images; and metal artifact reduction in the instrumented spine.7,8 CT uses differences in density to generate images Bone and other calcifications have the highest density Other components in decreasing density are soft tissue (e.g., brain), water (e.g., CSF), fat, and air On CT, increasing density is represented by an increase in brightness on the images However, the human visual system is not able to appreciate the entire range of image intensities that are necessary to represent the full range of density values measured by CT Therefore, the CT images have to be reviewed while adjusting window and level settings to interrogate ranges of density The difference in density between bone and brain is great, whereas the difference between brain and fat is smaller The density difference between gray and white matter is much smaller but is sufficient to be appreciated with the appropriate window and level Generally, as edema develops in nonfatty tissue, there is a decrease in density Acute blood (approximately between 12 and 72 hours old) is of higher density than brain, and CT is sensitive in the detection of acute (generally less than 7–10 days old) parenchymal, intraventricular, and extraaxial hemorrhage (epidural, subdural, and subarachnoid; Fig 61.3) CT is also useful in the evaluation of ventricular size, extraaxial collections, cerebral edema, mass effect, and cerebral herniation (secondary to spaceoccupying mass or diffuse cerebral edema) Iodinated intravenous (IV) contrast can be used with CT to evaluate the integrity of the blood-brain barrier (BBB) and differences in tissue perfusion With injection of IV contrast, vessels demonstrate a transient increase in density, with a variable rate of contrast leak into the tissues depending on the local pathophysiology The rate of equilibration of contrast concentration between vessels and parenchyma is much slower in the brain because of the intact BBB Contrast then is especially useful in the brain, where disruption of the normal BBB can reveal underlying pathology This increased density from contrast material is also used to image arteries and venous structures with CT angiography (CTA) and CT venography (Fig 61.3C) With the appropriate software, CHAPTER 61 Neuroimaging 737 B A C D F • Fig 61.2 Transcranial Doppler ultrasound images Color and spectral E Doppler waveforms from (A) normal right middle cerebral artery (MCA) and (B) right terminal internal carotid artery (ICA) Abnormal right middle cerebral (C) and terminal internal carotid (D) waveforms in another patient with sickle cell disease and prior history of stroke Magnetic resonance angiographic images (E and F) of this patient with abnormal transcranial Doppler demonstrate narrowed proximal MCAs and terminal ICA ... information about flow velocity and direction An advantage of TCD is that it can be performed through the thinner portions of the skull, primarily the temporal squamosa, including in older children and... suspected pathologies, complexity of the imaging examination, and the child’s clinical condition This chapter reviews available imaging modalities and the disease processes that are more commonly... differences in tissue density (which affects x-ray attenuation) The choice of radiation parameters, slice thickness, postprocessing, and image viewing (window width and level) must be tailored to the particular