Methods Of Intracranial Pressure Monitoring Research Articles

Assessment of increased intracranial pressure in patients with brain injury

Background: Monitoring and managing elevated intracranial pressure (ICP) is one of the core topics in neurocritical care. Although invasive methods are regarded as standard means, the recent development of non-invasive monitoring devices help clinicians handle ICP issues without additional risks of device-related complications.Current Concepts: According to the Monro–Kellie hypothesis, any brain injury that can cause a mass effect will lead to ICP elevation. Therefore, an ICP surge beyond the capacity of a compensatory reserve will decrease cerebral blood flow and may end up causing secondary brain damage. Indications for invasive ICP monitoring may vary according to the underlying conditions or the severity of brain damage. Regardless, ICP monitoring is considered when there is a risk of ICP elevation. In addition to pressure monitoring, external ventricular drainage catheters are used therapeutically to drain cerebrospinal fluid to reduce ICP. Several ICP monitoring probes are available based on pressure measurement types. Recently, non-invasive ICP monitoring methods have been developed and are increasingly used in patients with severe brain injuries. Pulsatility index from transcranial Doppler ultrasonography, quantitative pupillary light reflex from an automated pupillometer, and optic nerve sheath diameter using ultrasonography are commonly used surrogates for ICP surges in neurointensive care units.Discussion and Conclusion: ICP monitoring is essential for managing patients with severe brain injuries. Understanding the differences among the ICP monitors and determining the appropriate methods for ICP monitoring is necessary for optimizing patients’ care in the neurocritical care unit.

Using near-infrared spectroscopy and a random forest regressor to estimate intracranial pressure.

.SignificanceIntracranial pressure (ICP) measurements are important for patient treatment but are invasive and prone to complications. Noninvasive ICP monitoring methods exist, but they suffer from poor accuracy, lack of generalizability, or high cost.AimWe previously showed that cerebral blood flow (CBF) cardiac waveforms measured with diffuse correlation spectroscopy can be used for noninvasive ICP monitoring. Here we extend the approach to cardiac waveforms measured with near-infrared spectroscopy (NIRS).ApproachChanges in hemoglobin concentrations were measured in eight nonhuman primates, in addition to invasive ICP, arterial blood pressure, and CBF changes. Features of average cardiac waveforms in hemoglobin and CBF signals were used to train a random forest (RF) regressor.ResultsThe RF regressor achieves a cross-validated ICP estimation of , mean squared error (MSE), and 95% confidence interval (CI) of on oxyhemoglobin concentration changes; , MSE, and 95% CI of on total hemoglobin concentration changes; and , MSE, and 95% CI of on CBF changes.ConclusionsThis study provides a proof of concept for the use of NIRS in noninvasive ICP estimation.

Assessment of Cerebral Autoregulation Using Invasive and Noninvasive Methods of Intracranial Pressure Monitoring.

Pulse amplitude index (PAx), a descriptor of cerebrovascular reactivity, correlates the changes of the pulse amplitude of theintracranial pressure (ICP) waveform (AMP) with changes in mean arterial pressure (MAP). AMP relies on cerebrovascular compliance, which is modulated by the state of the cerebrovascular reactivity. PAx can aid in prognostication after acute brain injuries as a tool for the assessment of cerebral autoregulation and could potentially tailor individual management; however, invasive measurements are required for its calculation. Our aim was to evaluate the relationship between noninvasive PAx (nPAx) derived from a novel noninvasive device for ICP monitoring and PAx derived from gold standard invasive methods. We retrospectively analyzed invasiveICP (external ventricular drain) and non-invasiveICP (nICP), viamechanical extensometer (Brain4Care Corp.). Invasive and non-invasive ICP waveform morphology data wascollected in adult patients with brain injury with arterial blood pressure monitoring. The time series from all signals were first treated to remove movement artifacts. PAx and nPAx were calculated as the moving correlation coefficients of 10-s averages of AMP or non-invasiveAMP(nAMP) andMAP. AMP/nAMP was determined by calculating the fundamental frequency amplitude of the ICP/nICP signal over a 10-s window, updated every 10-s. We then evaluated the relationship between invasive PAx and noninvasive nPAx using the methods of repeated-measures analysis to generate an estimate of the correlation coefficient and its 95% confidence interval (CI). The agreement between the two methods was assessed using the Bland-Altman test. Twenty-four patients were identified. The median age was 53.5years (interquartile range 40-70), and intracranial hemorrhage (84%) was the most common etiology. Twenty-one (87.5%) patients underwent mechanical ventilation, and 60% were sedated with a median Glasgow Coma Scale score of 8 (7-15). Mean PAx was 0.0296 ± 0.331, and nPAx was 0.0171 ± 0.332. The correlation between PAx and nPAx was strong (R = 0.70, p < 0.0005, 95% CI 0.687-0.717). Bland-Altman analysis showed excellent agreement, with a bias of - 0.018 (95% CI - 0.026 to - 0.01) and a localized regression trend line that did not deviate from 0. PAx can be calculated by conventionaland noninvasive ICP monitoring in a statistically significant evaluation with strong agreement. Further study of the applications of this clinical tool is warranted, with the goal of early therapeutic intervention to improve neurologic outcomes following acute brain injuries.

Noninvasive detection of elevated ICP using spontaneous tympanic membrane pulsation

Neurological conditions such as traumatic brain injury (TBI) and hydrocephalus may lead to intracranial pressure (ICP) elevation. Current diagnosis methods rely on direct pressure measurement, while CT, MRI and other expensive imaging may be used. However, these invasive or expensive testing methods are often delayed because symptoms of elevated ICP are non-specific. Invasive methods, such as intraventricular catheter, subdural screw, epidural sensor, lumbar puncture, are associated with an increased risk of infection and hemorrhage. On the other hand, noninvasive, low-cost, accurate methods of ICP monitoring can help avoid risks and reduce costs while expediting diagnosis and treatment. The current study proposes and evaluates a novel method for noninvasive ICP monitoring using tympanic membrane pulsation (TMp). These signals are believed to be transmitted from ICP to the auditory system through the cochlear aqueduct. Fifteen healthy subjects were recruited and TMp signals were acquired noninvasively while the subjects performed maneuvers that are known to change ICP. A custom made system utilizing a stethoscope headset and a pressure transducer was used to perform these measurements. Maneuvers included head-up-tilt, head-down-tilt and hyperventilation. When elevated ICP was induced, significant TMp waveform morphological changes were observed in each subject (p < 0.01). These changes include certain waveform slopes and high frequency wave features. The observed changes were reversed by the maneuvers that decreased ICP (p < .01). The study results suggest that TMp waveform measurement and analysis may offer an inexpensive, noninvasive, accurate tool for detection and monitoring of ICP elevations. Further studies are warranted to validate this technique in patients with pathologically elevated ICP.

Cerebrospinal fluid dynamics in pediatric pseudotumor cerebri syndrome

PurposeThere is a growing body of evidence highlighting the importance of comprehensive intracranial pressure (ICP) values in pseudotumor cerebri syndrome (PTCS). Due to the highly dynamic nature of ICP, several methods of ICP monitoring have been established, including the CSF infusion study. We have performed a retrospective review of the CSF dynamics measurements for all pediatric patients investigated for PTCS in our center and examined their diagnostic value compared with clinical classification.MethodsWe retrospectively recruited 31 patients under 16 years of age investigated for PTCS by CSF infusion test. We used the clinically provided Friedman classification 13/31 patients with definite PTCS (group A), 13/31 with probable PTCS (group B), and 5/31 not PTCS (group C), to compare CSF dynamics in the 3 groups.ResultsCSF pressure (CSFp) was significantly increased in group A (29.18 ± 7.72 mmHg) compared with B (15.31 ± 3.47 mmHg; p = 1.644e-05) and C (17.51 ± 5.87; p = 0.01368). The amplitude (AMP) was higher in the definite (2.18 ± 2.06 mmHg) than in group B (0.68 ± 0.37; p = 0.01382). There was no in either CSFp or AMP between groups B and C. No lower breakpoint of the AMP-P line was observed in group A but was present in 2/13 and 2/5 patients in groups B and C. In group A, sagittal sinus pressure (SSp) and elasticity were the only parameters above threshold (p = 4.2e-06 and p = 0.001953, respectively), In group B, only the elasticity was significantly higher than the threshold (p = 004257). Group C did not have any of the parameters raised. The AUC of CSFp, elasticity, and SSp for the 3 groups was 93.8% (84.8–100% CI).ConclusionsMonitoring of CSFp and its dynamics, besides providing a more precise methodology for measuring CSFp, could yield information on the dynamic parameters of CSFp that cannot be derived from CSFp as a number, accurately differentiating between the clinically and radiologically derived entities of PTCS.

Interventional Radiology Percutaneous Liver Biopsy Pediatric Nursing Guidelines

Critically ill patients with brain injury often need intracranial pressure (ICP) monitoring. The two most common methods of ICP monitoring are via an external ventricular drain (EVD) catheter and via an intraparenchymal fiberoptic catheter. In addition to ICP monitoring, an EVD has the additional advantage of being able to treat hydrocephalus or lower elevated ICP by cerebrospinal fluid drainage. In addition to ICP monitoring, frequent radiographic imaging is also considered to be a fundamental component of neurological multimodal monitoring. As such, patients with EVDs often require intrahospital transport for advanced imaging. There are currently no national or international standards guiding intrahospital transport to and from the radiology suite. We use a fictional case to describe practice patterns and variations that may improve care of the patient with EVDs during transport to radiology. The fundamentals for ICP monitoring are highlighted, and an emphasis is placed on clear and concise communication.

Safeguarding Medication Administration in Radiology

Critically ill patients with brain injury often need intracranial pressure (ICP) monitoring. The two most common methods of ICP monitoring are via an external ventricular drain (EVD) catheter and via an intraparenchymal fiberoptic catheter. In addition to ICP monitoring, an EVD has the additional advantage of being able to treat hydrocephalus or lower elevated ICP by cerebrospinal fluid drainage. In addition to ICP monitoring, frequent radiographic imaging is also considered to be a fundamental component of neurological multimodal monitoring. As such, patients with EVDs often require intrahospital transport for advanced imaging. There are currently no national or international standards guiding intrahospital transport to and from the radiology suite. We use a fictional case to describe practice patterns and variations that may improve care of the patient with EVDs during transport to radiology. The fundamentals for ICP monitoring are highlighted, and an emphasis is placed on clear and concise communication.

Pelvic Congestion Syndrome

Critically ill patients with brain injury often need intracranial pressure (ICP) monitoring. The two most common methods of ICP monitoring are via an external ventricular drain (EVD) catheter and via an intraparenchymal fiberoptic catheter. In addition to ICP monitoring, an EVD has the additional advantage of being able to treat hydrocephalus or lower elevated ICP by cerebrospinal fluid drainage. In addition to ICP monitoring, frequent radiographic imaging is also considered to be a fundamental component of neurological multimodal monitoring. As such, patients with EVDs often require intrahospital transport for advanced imaging. There are currently no national or international standards guiding intrahospital transport to and from the radiology suite. We use a fictional case to describe practice patterns and variations that may improve care of the patient with EVDs during transport to radiology. The fundamentals for ICP monitoring are highlighted, and an emphasis is placed on clear and concise communication.

Validation of Noninvasive Absolute Intracranial Pressure Measurements in Traumatic Brain Injury and Intracranial Hemorrhage.

Increased intracranial pressure (ICP) causes secondary damage in traumatic brain injury (TBI), and intracranial hemorrhage (ICH). Current methods of ICP monitoring require surgery and carry risks of complications. To validate a new instrument for noninvasive ICP measurement by comparing values obtained from noninvasive measurements to those from commercial implantable devices through this pilot study. The ophthalmic artery (OA) served as a natural ICP sensor. ICP measurements obtained using noninvasive, self-calibrating device utilizing Doppler ultrasound to evaluate OA flow were compared to standard implantable ICP measurement probes. A total of 78 simultaneous, paired, invasive, and noninvasive ICP measurements were obtained in 11 ICU patients over a 17-mo period with the diagnosis of TBI, SAH, or ICH. A total of 24 paired data points were initially excluded because of questions about data independence. Analysis of variance was performed first on the 54 remaining data points and then on the entire set of 78 data points. There was no difference between the 2 groups nor was there any correlation between type of sensor and the patient (F[10, 43] = 1.516, P = .167), or the accuracy and precision of noninvasive ICP measurements (F[1, 43] = 0.511, P = .479). Accuracy was [-1.130; 0.539] mm Hg (CL = 95%). Patient-specific calibration was not needed. Standard deviation (precision) was [1.632; 2.396] mm Hg (CL = 95%). No adverse events were encountered. This pilot study revealed no significant differences between invasive and noninvasive ICP measurements (P < .05), suggesting that noninvasive ICP measurements obtained by this method are comparable and reliable.

Study of Intracranial Pressure Monitoring In Traumatic Brain Injury

Intracranial pressure monitoring is considered the standard of care for severe traumatic brain injury and is used frequently. However, the efficacy of treatment based on monitoring in improving the outcome has not been rigorously assessed. We conducted a trial in which we included 26 patients of all types of traumatic brain injury (TBI) and they were monitored for intracranial pressure by Conventional fluid filled system with a manometer (Group 1) and compared with the Fiber optic transducer-tipped intracranial pressure monitoring system (Group 2).The main aim of this study was to examine the relationship between Intracranial Pressure (ICP) monitoring and in-hospital mortality. The median length of stay in the ICU was similar in the two groups (12 days in the conventional pressure-monitoring group and 9 days in the new fiber optic group; P=0.25), the number of days of brain-specific treatments (e.g., administration of hyperosmolar fluids and the use of hyperventilation) in the ICU was similar in both groups. The distribution of serious adverse events was similar in the two groups. We concluded that ICP monitoring (as is any monitoring modality) is a useful guide for management. The outcomes are decided by the differences in management protocols that the knowledge of the said parameter brings about. ICP monitoring is recommended for the better management of traumatic brain injury and fiber optic ICP monitoring seems to be beneficial than using the conventional methods of ICP monitoring with manometer.Nepal Journal of Neuroscience, Volume 15, Number 2, 2018, page: 23-29

Noninvasive in-ear monitoring of intracranial pressure during microgravity in parabolic flights.

Among possible causes of visual impairment or headache experienced by astronauts in microgravity or postflight and that hamper their performance, elevated intracranial pressure (ICP) has been invoked but never measured for lack of noninvasive methods. The goal of this work was to test two noninvasive methods of ICP monitoring using in-ear detectors of ICP-dependent auditory responses, acoustic and electric, in acute microgravity afforded by parabolic flights. The devices detecting these responses were handheld tablets routinely used in otolaryngology for hearing diagnosis, which were customized for ICP extraction and serviceable by unskilled operators. These methods had been previously validated against invasive ICP measurements in neurosurgery patients. The two methods concurred in their estimation of ICP changes with microgravity, i.e., 11.0 ± 7.7 mmHg for the acoustic method ( n = 7 subjects with valid results out of 30, auditory responses being masked by excessive in-flight noise in 23 subjects) and 11.3 ± 10.6 mmHg for the electric method ( n = 10 subjects with valid results out of 10 tested despite the in-flight noise). These results agree with recent publications using invasive access to cerebrospinal fluid in parabolic flights and suggest that acute microgravity has a moderate average effect on ICP, similar to body tilt from upright to supine, yet with some subjects undergoing large effects whereas others seem immune. The electric in-ear method would be suitable for ICP monitoring in circumstances and with subjects such that invasive measurements are excluded. NEW & NOTEWORTHY In-ear detectors of intracranial pressure-dependent auditory responses allow intracranial pressure to be monitored noninvasively during acute microgravity. The average pressure increase during 20-s long sessions in microgravity is 11 mmHg, comparable with an effect of body tilt. However, intersubject variability is large, with subjects who repeatedly experience from nothing to twice the average effect. A systematic in-flight use would allow the relationship between space adaptation syndrome and ICP to be established or dismissed.

Intracranial Pressure Monitoring-Review and Avenues for Development.

Intracranial pressure (ICP) monitoring is a staple of neurocritical care. The most commonly used current methods of monitoring in the acute setting include fluid-based systems, implantable transducers and Doppler ultrasonography. It is well established that management of elevated ICP is critical for clinical outcomes. However, numerous studies show that current methods of ICP monitoring cannot reliably define the limit of the brain’s intrinsic compensatory capacity to manage increases in pressure, which would allow for proactive ICP management. Current work in the field hopes to address this gap by harnessing live-streaming ICP pressure-wave data and a multimodal integration with other physiologic measures. Additionally, there is continued development of non-invasive ICP monitoring methods for use in specific clinical scenarios.

Optic nerve sheath diameter: A novel way to monitor the brain

AbstractMeasurement and monitoring of intracranial pressure is pivotal in management of brain injured patients. As a rapid and easily done bed side measurement, ultrasonography of the optic nerve sheath diameter presents itself as a possible replacement of the conventional invasive methods of intracranial pressure management. In this review we go through the evolution of optic nerve sheath diameter measurement as a novel marker of predicting raised intracranial pressure, the modalities by which it can be measured as well as its correlation with the invasive methods of intracranial pressure monitoring.

Monitoring of Intracranial Pressure by CT-Defined Optic Nerve Sheath Diameter.

Intracranial pressure (ICP) can be monitored by the optic nerve sheath diameter (ONSD) technique. We hypothesized that diameter of the optic canal (OC) can be a limiting factor for this technique. In the prospective cohort study, we analyzed CT scans of 600 OCs of healthy adults and 54 canals of patients with ICP monitoring. The diameters were measured through its length and the narrowest one was chosen for further analysis. ONSD was measured at 3 and 10 mm from the anterior opening of the canal. The correlation analysis was performed between invasive and ONSD methods of ICP monitoring and OC diameters in pathological cases. The narrowest cross-sectional area of the normal OC was 13.85±2.89 mm² and varied from 25.5 to 6.6 mm². Apparently 9.17% OCs were narrow (˂10.9 mm²). Correlations exist between the optic nerve sheath area at the 3-mm distance from the anterior opening of the canal and the area of the anterior opening itself (P = .012), and the sheath area 10 mm from the anterior opening and the narrowest part of the canal (P = .015). Cases with narrow canals provided false-negative readings via ONSD method if compared with invasive monitoring. In its narrowest part, the average OC is 11 to 16.75 mm² wide. We suggest measuring this area simultaneously with the ONSD during ICP monitoring. If the area of the narrowest lumen of the canal is less than 10 mm², ONSD technique for ICP monitoring should not be used.

Advances in Intracranial Pressure Monitoring and Its Significance in Managing Traumatic Brain Injury.

Intracranial pressure (ICP) measurements are essential in evaluation and treatment of neurological disorders such as subarachnoid and intracerebral hemorrhage, ischemic stroke, hydrocephalus, meningitis/encephalitis, and traumatic brain injury (TBI). The techniques of ICP monitoring have evolved from invasive to non-invasive—with both limitations and advantages. Some limitations of the invasive methods include short-term monitoring, risk of infection, restricted mobility of the subject, etc. The invasiveness of a method limits the frequency of ICP evaluation in neurological conditions like hydrocephalus, thus hampering the long-term care of patients with compromised ICP. Thus, there has been substantial interest in developing noninvasive techniques for assessment of ICP. Several approaches were reported, although none seem to provide a complete solution due to inaccuracy. ICP measurements are fundamental for immediate care of TBI patients in the acute stages of severe TBI injury. In severe TBI, elevated ICP is associated with mortality or poor clinical outcome. ICP monitoring in conjunction with other neurological monitoring can aid in understanding the pathophysiology of brain damage. This review article presents: (a) the significance of ICP monitoring; (b) ICP monitoring methods (invasive and non-invasive); and (c) the role of ICP monitoring in the management of brain damage, especially TBI.

Intracranial pressure monitoring

AbstractBrain specific monitoring enables detection and prevention of secondary cerebral insults, especially in the injured brain, thereby preventing permanent neurological damage. Intracranial pressure (ICP) monitoring is widely used in various neurological, neurosurgical and even medical conditions, both intraoperatively and in critical care, to improve patient outcome. It is especially useful in patients with traumatic brain injury, as a robust predictor of cerebral perfusion, and can help to guide therapy and assess long-term prognosis. Intraventricular catheters remain the gold standard for ICP monitoring, as they are the most reliable, accurate and cost-effective, and allow therapeutic cerebrospinal fluid drainage. Newer fibreoptic catheter tip and microchip transducer techniques have revolutionised ICP monitoring, with their ease of insertion in patients with narrow ventricles, and reduced risk of infection and haemorrhage. Furthermore, non-invasive methods of ICP monitoring, such as transcranial Doppler, optic nerve sheath diameter, etc., have emerged as promising techniques for screening patients with raised ICP in settings where invasive techniques are either not feasible (patients with severe coagulopathy) or not available (setups without access to a neurosurgeon). Therefore, ICP monitoring, as a part of multi-modality neuromonitoring, is a useful tool in the armamentarium of the neuro-intensivist in decreasing morbidity and mortality of critically ill neurological patients.

Telemetric Intracranial Pressure Measurement: A Graphical Approach to Data Analysis.

In recent years, radiofrequency identification has been used for the continuous measurement of intracranial pressure (ICP) in patients with a cerebrospinal fluid (CSF) shunt for hydrocephalus . Unlike ICP monitoring in an inpatient setting, measurements in mobile patients outside the hospital provide ICP data that take into account the everyday activities of each individual patient. Common methods of ICP monitoring and analysis cannot be used for those patients. In addition, ICP measurements in mobile patients require considerably longer observation times than in-hospital monitoring. For this reason, ICP measurements over a period of 7 to 10 days must be analyzed effectively and efficiently. A possible approach is to analyze ICP data graphically. Pathologic changes can be expected to be associated with specific patterns that can be detected graphically (e.g., Lundberg A waves). Patients without pathologic ICP values and without intracranial pathologies usually show an approximately normal distribution of ICP data. By contrast, patients with pathologic ICP values are likely to show major deviations from a normal distribution such as changes in minimum and maximum values and multimodal distributions. Against this background, we present a new graphical method for detecting pathologic conditions. This novel method is based on the distribution of ICP data that is assessed using GNU R, a free software package for statistical computing and graphics. A left-skewed distribution indicates CSF shunt overdrainage and a right-skewed distribution suggests CSF shunt underdrainage. In addition, an additive analysis of the number of physiologic ICP values can be helpful in detecting possible causes of CSF shunt overdrainage or underdrainage. The approach presented here shows that patients with hydrocephalus objectively benefited from ICP-guided adjustments of the opening pressure of a shunt valve or the insertion of a valve. This objective improvement was confirmed by the patients' subjective perception of well-being. Further investigations should be performed to examine the influence of multimodal ICP distributions and to assess how data analysis is affected by a drift that can occur when a sensor has been in place for an extended period of time.

Noninvasive assessment of intracranial pressure using otoacoustic emissions in pediatric patients with idiopathic intracranial hypertension (IIH)

The ability to follow response to treatment with elevated intracranial pressure (ICP) and papilledema are crucial factors in the preservation of visual function in IIH. Current methods of ICP monitoring are invasive. Distortion-product otoacoustic emissions (DPOAEs), measured non-invasively through the ear canal, appear to be sensitive to ICP changes in healthy subjects.1 We evaluated whether changes in DPOAEs correlate with changes in ICP in pediatric patients.

Measuring Elevated Intracranial Pressure through Noninvasive Methods

Elevated intracranial pressure (ICP) is an important cause of secondary brain injury, and a measurement of ICP is often of crucial value in neurosurgical and neurological patients. The gold standard for ICP monitoring is through an intraventricular catheter, but this invasive technique is associated with certain risks. Intraparenchymal ICP monitoring methods are considered to be a safer alternative but can, in certain conditions, be imprecise due to zero drift and still require an invasive procedure. An accurate noninvasive method to measure elevated ICP would therefore be desirable. This article is a review of the current literature on noninvasive methods for measuring and evaluating elevated ICP. The main focus is on studies that compare noninvasively measured ICP with invasively measured ICP. The aim is to provide an overview of the current state of the most common noninvasive techniques available. Several methods for noninvasive measuring of elevated ICP have been proposed: radiologic methods including computed tomography and magnetic resonance imaging, transcranial Doppler, electroencephalography power spectrum analysis, and the audiological and ophthalmological techniques. The noninvasive methods have many advantages, but remain less accurate compared with the invasive techniques. None of the noninvasive techniques available today are suitable for continuous monitoring, and they cannot be used as a substitute for invasive monitoring. They can, however, provide a reliable measurement of the ICP and be useful as screening methods in select patients, especially when invasive monitoring is contraindicated or unavailable.

783 Management of Severe Paediatric Trauma Brain Injury (PTBI) Guided by Intracranial Pressure (ICP) Monitoring in a Picu in Algeria

Background and AimsPTBI is the leading cause of death and long-term morbidity. Current recommendations for the management of severe PTBI (Glasgow Coma [GCS] score ≤8) indicate that ICP monitoring is...