A randomized and blinded single-center trial comparing the effect of intracranial pressure and intracranial pressure wave amplitude-guided intensive care management on early clinical state and 12-month outcome in patients with aneurysmal subarachnoid hemorrhage

Why Intracranial Compliance Is Not Utilized as a Common Practical Tool in Clinical Practice

Intracranial compliance (ICC) holds significant potential in neuromonitoring, serving as a diagnostic tool and contributing to the evaluation of treatment outcomes. Despite its comprehensive concept, which allows consideration of changes in both volume and intracranial pressure (ICP), ICC monitoring has not yet established itself as a standard component of medical care, unlike ICP monitoring. This review highlighted that the first challenge is the assessment of ICC values, because of the invasive nature of direct measurement, the time-consuming aspect of non-invasive calculation through computer simulations, and the inability to quantify ICC values in estimation methods. Addressing these challenges is crucial, and the development of a rapid, non-invasive computer simulation method could alleviate obstacles in quantifying ICC. Additionally, this review indicated the second challenge in the clinical application of ICC, which involves the dynamic and time-dependent nature of ICC. This was considered by introducing the concept of time elapsed (TE) in measuring the changes in volume or ICP in the ICC equation (volume change/ICP change). The choice of TE, whether short or long, directly influences the ICC values that must be considered in the clinical application of the ICC. Compensatory responses of the brain exhibit non-monotonic and variable changes in long TE assessments for certain disorders, contrasting with the mono-exponential pattern observed in short TE assessments. Furthermore, the recovery behavior of the brain undergoes changes during the treatment process of various brain disorders when exposed to short and long TE conditions. The review also highlighted differences in ICC values across brain disorders with various strain rates and loading durations on the brain, further emphasizing the dynamic nature of ICC for clinical application. The insight provided in this review may prove valuable to professionals in neurocritical care, neurology, and neurosurgery for standardizing ICC monitoring in practical application related to the diagnosis and evaluation of treatment outcomes in brain disorders.

Analysis of intracranial pressure pulse waveform in studies on cerebrospinal compliance: a narrative review

Continuous monitoring of mean intracranial pressure (ICP) has been an essential part of neurocritical care for more than half a century. Cerebrospinal pressure-volume compensation, i.e. the ability of the cerebrospinal system to buffer changes in volume without substantial increases in ICP, is considered an important factor in preventing adverse effects on the patient's condition that are associated with ICP elevation. However, existing assessment methods are poorly suited to the management of brain injured patients as they require external manipulation of intracranial volume. In the 1980s, studies suggested that spontaneous short-term variations in the ICP signal over a single cardiac cycle, called the ICP pulse waveform, may provide information on cerebrospinal compensatory reserve. In this review we discuss the approaches that have been proposed so far to derive this information, from pulse amplitude estimation and spectral techniques to most recent advances in morphological analysis based on artificial intelligence solutions. Each method is presented with focus on its clinical significance and the potential for application in standard clinical practice. Finally, we highlight the missing links that need to be addressed in future studies in order for ICP pulse waveform analysis to achieve widespread use in the neurocritical care setting.

Intracranial Pressure Monitoring for Acute Brain Injured Patients: When, How, What Should We Monitor

While there is no level I recommendation for intracranial pressure (ICP) monitoring, it is typically indicated for patients with severe traumatic brain injury (TBI) with a Glasgow Coma Scale (GCS) score of 3-8 (class II). Even for moderate TBI patients with GCS 9-12, ICP monitoring should be considered for risk of increased ICP. The impact of ICP monitoring on patient outcomes is still not well-established, but recent studies reported a reduction of early mortality (class III) in TBI patients. There is no standard protocol for the application of ICP monitoring. In cases where cerebrospinal fluid drainage is required, an external ventricular drain is commonly used. In other cases, parenchymal ICP monitoring devices are generally employed. Subdural or non-invasive forms are not suitable for ICP monitoring. The mean value of ICP is the parameter recommended for observation in many guidelines. In TBI, values above 22 mmHg are associated with increased mortality. However, recent studies proposed various parameters including cumulative time with ICP above 20 mmHg (pressure-time dose), pressure reactivity index, ICP waveform characteristics (pulse amplitude of ICP, mean ICP wave amplitude), and the compensatory reserve of the brain (reserve-amplitude-pressure), which are useful in predicting patient outcomes and guiding treatment. Further research is required for validation of these parameters compared to simple ICP monitoring.

Fiber-Optic Intracranial Pressure Monitoring System Using Wi-Fi-An In Vivo Study

BACKGROUND

Continuous invasive monitoring of intracranial pressure (ICP) is essential in neurocritical care for surveillance and management of raised ICP. Fluid-based systems and strain gauge microsensors remain the current standard. In the past few decades, several studies with wireless monitoring were developed aiming to reduce invasiveness and complications.

OBJECTIVE

To describe a novel Wi-Fi fiber-optic device for continuous ICP monitoring using smartphone in a swine model.

METHODS

Two ICP sensors (wireless prototype and wire-based reference) were implanted in the cerebral parenchyma of a swine model for a total of 120 minutes of continuous monitoring. Every 5 minutes, jugular veins compression was performed to evaluate ICP changes. The experimentation was divided in 3 phases for comparison and analysis.

RESULTS

Phase 1 showed agreement in ICP changes for both sensors during jugular compression and releasing, with a positive and strong Spearman correlation (r = 0.829, P < .001). Phase 2 started after inversion of the sensors in the burr holes; there was a positive and moderately weak Spearman correlation (r = 0.262, P < .001). For phase 3, the sensors were returned to the first burr holes; the prototype behaved similarly to the reference sensor, presenting a positive and moderately strong Spearman correlation (r = 0.669, P < .001).

CONCLUSION

A Wi-Fi ICP monitoring system was demonstrated in a comprehensive and feasible way. It was possible to observe, using smartphone, an adequate correlation regarding ICP variations. Further adaptations are already being developed.

Spindle wave in intracranial pressure signal analysis for patients with traumatic brain injury: A single-center prospective observational cohort study

Objective: Intracranial pressure (ICP) monitoring is an integral part of the multimodality monitoring system in the neural intensive care unit. The present study aimed to describe the morphology of the spindle wave (a shuttle shape with wide middle and narrow ends) during ICP signal monitoring in TBI patients and to investigate its clinical significance. Methods: Sixty patients who received ICP sensor placement and admitted to the neurosurgical intensive care unit between January 2021 and September 2021 were prospectively enrolled. The patient's Glasgow Coma Scale (GCS) score on admission and at discharge and length of stay in hospital were recorded. ICP monitoring data were monitored continuously. The primary endpoint was 6-month Glasgow Outcome Scale-Extended (GOSE) score. Patients with ICP spindle waves were assigned to the spindle wave group and those without were assigned to the control group. The correlation between the spindle wave and 6-month GOSE was analyzed. Meanwhile, the mean ICP and two ICP waveform-derived indices, ICP pulse amplitude (AMP) and correlation coefficient between AMP and ICP (RAP) were comparatively analyzed. Results: There were no statistically significant differences between groups in terms of age (p = 0.89), gender composition (p = 0.62), and GCS score on admission (p = 0.73). Patients with spindle waves tended to have a higher GCS score at discharge (12.75 vs. 10.90, p = 0.01), a higher increment in GCS score during hospitalization (ΔGCS, the difference between discharge GCS score and admission GCS score) (4.95 vs. 2.80, p = 0.01), and a better 6-month GOSE score (4.90 vs. 3.68, p = 0.04) compared with the control group. And the total duration of the spindle wave was positively correlated with 6-month GOSE (r = 0.62, p = 0.004). Furthermore, the parameters evaluated during spindle waves, including mean ICP, AMP, and RAP, demonstrated significant decreases compared with the parameters before the occurrence of the spindle wave (all p < 0.025). Conclusion: The ICP spindle wave was associated with a better prognosis in TBI patients. Physiological parameters such as ICP, AMP, and RAP were significantly improved when spindle waves occurred, which may explain the enhancement of clinical outcomes. Further studies are needed to investigate the pathophysiological mechanisms behind this wave.

Blood Pressure Management After Intracerebral and Subarachnoid Hemorrhage: The Knowns and Known Unknowns

Blood pressure (BP) elevations often complicate the management of intracerebral hemorrhage and aneurysmal subarachnoid hemorrhage, the most serious forms of acute stroke. Despite consensus on potential benefits of BP lowering in the acute phase of intracerebral hemorrhage, controversies persist over the timing, mechanisms, and approaches to treatment. BP control is even more complex for subarachnoid hemorrhage, where there are rationales for both BP lowering and elevation in reducing the risks of rebleeding and delayed cerebral ischemia, respectively. Efforts to disentangle the evidence has involved detailed exploration of individual patient data from clinical trials through meta-analysis to determine strength and direction of BP change in relation to key outcomes in intracerebral hemorrhage, and which likely also apply to subarachnoid hemorrhage. A wealth of hemodynamic data provides insights into pathophysiological interrelationships of BP and cerebral blood flow. This focused update provides an overview of current evidence, knowledge gaps, and emerging concepts on systemic hemodynamics, cerebral autoregulation and perfusion, to facilitate clinical practice recommendations and future research.

Waveform Morphology as a Surrogate for ICP Monitoring: A Comparison Between an Invasive and a Noninvasive Method

BACKGROUND

Although the placement of an intraventricular catheter remains the gold standard technique for measuring intracranial pressure (ICP), the method has several limitations. Therefore, noninvasive alternatives to ICP (ICPni) measurement are of great interest. The main objective of this study was to compare the correlation and agreement of wave morphology between ICP (standard intraventricular ICP monitoring) and a new ICPni monitor in patients admitted with stroke. The second objective was to estimate the discrimination of the noninvasive method to detect intracranial hypertension.

METHODS

We prospectively collected data of adults admitted to an intensive care unit with subarachnoid hemorrhage, intracerebral hemorrhage, or ischemic stroke in whom an invasive ICP monitor was placed. Measurements were simultaneously collected from two parameters [time-to-peak (TTP) and the ratio regarding the second and first peak of the ICP wave (P2/P1 ratio)] of ICP and ICPni wave morphology monitors (Brain4care). Intracranial hypertension was defined as an invasively measured sustained ICP > 20 mm Hg for at least 5 min.

RESULTS

We studied 18 patients (subarachnoid hemorrhage = 14; intracerebral hemorrhage = 3; ischemic stroke = 1) on 60 occasions with a median age of 52 ± 14.3 years. A total of 197,400 waves (2495 min) from both ICP (standard ICP monitoring) and the ICPni monitor were sliced into 1-min-long segments, and we determined TTP and the P2/P1 ratio from the mean pulse. The median invasively measured ICP was 13 (9.8-16.2) mm Hg, and intracranial hypertension was present on 18 occasions (30%). The correlation and agreement between invasive and noninvasive methods for wave morphology were strong for the P2/P1 ratio and moderate for TTP using categoric (κ agreement 88.1% and 71.3%, respectively) and continuous (intraclass correlation coefficient 0.831 and 0.584, respectively) measures. There was a moderate but significant correlation with the mean ICP value (P2/P1 ratio r = 0.427; TTP r = 0.353; p < 0.001 for all) between noninvasive and invasive techniques. The areas under the curve to estimate intracranial hypertension were 0.786 [95% confidence interval (CI) 0.72-0.93] for the P2/P1 ratio and 0.694 (95% CI 0.60-0.74) for TTP.

CONCLUSIONS

The new ICPni wave morphology monitor showed a good agreement with the standard invasive method and an acceptable discriminatory power to detect intracranial hypertension. Clinical trial registration Trial registration: NCT05121155.

The Use of Standardized Management Protocols for Critically Ill Patients with Non-traumatic Subarachnoid Hemorrhage: A Systematic Review

The use of standardized management protocols (SMPs) may improve patient outcomes for some critical care diseases. Whether SMPs improve outcomes after subarachnoid hemorrhage (SAH) is currently unknown. We aimed to study the effect of SMPs on 6-month mortality and neurologic outcomes following SAH. A systematic review of randomized control trials (RCTs) and observational studies was performed by searching multiple indexing databases from their inception through January 2019. Studies were limited to adult patients (age ≥ 18) with non-traumatic SAH reporting mortality, neurologic outcomes, delayed cerebral ischemia (DCI) and other important complications. Data on patient and SMP characteristics, outcomes and methodologic quality were extracted into a pre-piloted collection form. Methodologic quality of observational studies was assessed using the Newcastle-Ottawa scale, and RCT quality was reported as per the Cochrane risk of bias tool. A total of 11,260 studies were identified, of which 37 (34 full-length articles and 3 abstracts) met the criteria for inclusion. Two studies were RCTs and 35 were observational. SMPs were divided into four broad domains: management of acute SAH, early brain injury, DCI and general neurocritical care. The most common SMP design was control of DCI, with 22 studies assessing this domain of care. Overall, studies were of low quality; most described single-center case series with small patient sizes. Definitions of key terms and outcome reporting practices varied significantly between studies. DCI and neurologic outcomes in particular were defined inconsistently, leading to significant challenges in their interpretation. Given the substantial heterogeneity in reporting practices between studies, a meta-analysis for 6-month mortality and neurologic outcomes could not be performed, and the effect of SMPs on these measures thus remains inconclusive. Our systematic review highlights the need for large, rigorous RCTs to determine whether providing standardized, best-practice management through the use of a protocol impacts outcomes in critically ill patients with SAH.Trial registration Registration number: CRD42017069173.

Impact of smoking on course and outcome of aneurysmal subarachnoid hemorrhage

Background

While the smoking-related risk of experiencing an aneurysmal subarachnoid hemorrhage (aSAH) is well established, it remains unclear whether smoking has an unexpected “protective effect” in aSAH, or if smokers are more at risk for complications and poor outcomes.

Methods

Prospective, observational study investigating the course and outcome of aSAH in patients admitted during the years 2011 and 2012. Smoking status at admittance, demographic, medical, and radiological variables were registered along with management, complications, and outcome at 1 year in terms of mortality, modified Rankin score, and Glasgow outcome score extended. We compared current smokers with nonsmokers on group level and by paired analysis matched by aSAH severity, age, and severity of vasospasm.

Results

We included 237 patients, thereof 138 current smokers (58.2%). Seventy-four smoker/nonsmoker pairs were matched. Smokers presented more often in poor clinical grade, had less subarachnoid blood, and were younger than nonsmokers. Ruptured aneurysms were larger, and multiple aneurysms more common in smokers. Severe multi-vessel vasospasm was less frequent in smokers, whereas all other complications occurred at similar rates. Mortality at 30 days was lower in smokers and functional outcome was similar in smokers and nonsmokers. Poor clinical grade, age, cerebral infarction, and vertebrobasilar aneurysms were independent predictors of 1-year mortality and of poor functional outcome. Serious comorbidity was a predictor of 1-year mortality. Smoking did not predict mortality or poor functional outcome.

Conclusions

Notwithstanding clinically more severe aSAH, smokers developed less frequently severe vasospasm and had better outcome than expected. The risk for complications after aSAH is not increased in smokers.

Measuring intracranial pressure by invasive, less invasive or non-invasive means: limitations and avenues for improvement

Sixty years have passed since neurosurgeon Nils Lundberg presented his thesis about intracranial pressure (ICP) monitoring, which represents a milestone for its clinical introduction. Monitoring of ICP has since become a clinical routine worldwide, and today represents a cornerstone in surveillance of patients with acute brain injury or disease, and a diagnostic of individuals with chronic neurological disease. There is, however, controversy regarding indications, clinical usefulness and the clinical role of the various ICP scores. In this paper, we critically review limitations and weaknesses with the current ICP measurement approaches for invasive, less invasive and non-invasive ICP monitoring. While risk related to the invasiveness of ICP monitoring is extensively covered in the literature, we highlight other limitations in current ICP measurement technologies, including limited ICP source signal quality control, shifts and drifts in zero pressure reference level, affecting mean ICP scores and mean ICP-derived indices. Control of the quality of the ICP source signal is particularly important for non-invasive and less invasive ICP measurements. We conclude that we need more focus on mitigation of the current limitations of today's ICP modalities if we are to improve the clinical utility of ICP monitoring.

Non-invasive Estimation of the Intracranial Pressure Waveform from the Central Arterial Blood Pressure Waveform in Idiopathic Normal Pressure Hydrocephalus Patients

This study explored the hypothesis that the central aortic blood pressure (BP) waveform may be used for non-invasive estimation of the intracranial pressure (ICP) waveform. Simultaneous invasive ICP and radial artery BP waveforms were measured in 29 individuals with idiopathic normal pressure hydrocephalus (iNPH). The central aortic BP waveforms were estimated from the radial artery BP waveforms using the SphygmoCor system. For each individual, a transfer function estimate between the central aortic BP and the invasive ICP waveforms was found (Intra-patient approach). Thereafter, the transfer function estimate that gave the best fit was chosen and applied to the other individuals (Inter-patient approach). To validate the results, ICP waveform parameters were calculated for the estimates and the measured golden standard. For the Intra-patient approach, the mean absolute difference in invasive versus non-invasive mean ICP wave amplitude was 1.9 ± 1.0 mmHg among the 29 individuals. Correspondingly, the Inter-patient approach resulted in a mean absolute difference of 1.6 ± 1.0 mmHg for the 29 individuals. This method gave a fairly good estimate of the wave for about a third of the individuals, but the variability is quite large. This approach is therefore not a reliable method for use in clinical patient management.

The best marker for guiding the clinical management of patients with raised intracranial pressure-the RAP index or the mean pulse amplitude?

Raised intracranial pressure is a common problem in a variety of neurosurgical conditions including traumatic brain injury, hydrocephalus and intracranial haemorrhage. The clinical management of these patients is guided by a variety of haemodynamic, biochemical and clinical factors. However to date there is no single parameter that is used to guide clinical management of patients with raised intracranial pressure (ICP). However, the role of ICP indices, specifically the mean pulse amplitude (AMP) and RAP index [correlation coefficient (R) between AMP amplitude (A) and mean ICP pressure (P); index of compensatory reserve], as an indicator of true ICP has been investigated. Whilst the RAP index has been used both as a descriptor of neurological deterioration in TBI patients and as a way of characterising the compensatory reserve in hydrocephalus, more recent studies have highlighted the limitation of the RAP index due to the influence that baseline effect errors have on the mean ICP, which is used in the calculation of the RAP index. These studies have suggested that the ICP mean pulse amplitude may be a more accurate marker of true intracranial pressure due to the fact that it is uninfluenced by the mean ICP and, therefore, the AMP may be a more reliable marker than the RAP index for guiding the clinical management of patients with raised ICP. Although further investigation needs to be undertaken in order to fully assess the role of ICP indices in guiding the clinical management of patients with raised ICP, the studies undertaken to date provide an insight into the potential role of ICP indices to treat raised ICP proactively rather than reactively and therefore help prevent or minimise secondary brain injury.

Principles of cerebral hemodynamics when intracranial pressure is raised: lessons from the peripheral circulation

Background: The brain is highly vascular and richly perfused, and dependent on continuous flow for normal function. Although confined within the skull, pressure within the brain is usually less than 15 mmHg, and shows small pulsations related to arterial pulse under normal circumstances. Pulsatile arterial hemodynamics in the brain have been studied before, but are still inadequately understood, especially during changes of intracranial pressure (ICP) after head injury.

Method: In seeking cohesive explanations, we measured ICP and radial artery pressure (RAP) invasively with high-fidelity manometer systems, together with middle cerebral artery flow velocity (MCAFV) (transcranial Doppler) and central aortic pressure (CAP) generated from RAP, using a generalized transfer function technique, in eight young unconscious, ventilated adults following closed head trauma. We focused on vascular effects of spontaneous rises of ICP (‘plateau waves’).

Results: A rise in mean ICP from 29 to 53 mmHg caused no consistent change in pressure outside the cranium, or in heart rate, but ICP pulsations increased in amplitude from 8 to 20 mmHg, and ICP waveform came to resemble that in the aorta. Cerebral perfusion pressure (=central aortic pressure – ICP), which equates with transmural pressure, fell from 61 to 36 mmHg. Mean MCAFV fell from 53 to 40 cm/s, whereas pulsatile MCAFV increased from 77 to 98 cm/s. These significant changes (all P < 0.01) may be explained using the Monro–Kellie doctrine, because of compression of the brain, as occurs in a limb when external pressure is applied.

Conclusion: The findings emphasize importance of reducing ICP, when raised, and on the additional benefits of reducing wave reflection from the lower body.

The correlation between pulsatile intracranial pressure and indices of intracranial pressure-volume reserve capacity: results from ventricular infusion testing

OBJECTIVE The objective of this study was to examine how pulsatile and static intracranial pressure (ICP) scores correlate with indices of intracranial pressure-volume reserve capacity, i.e., intracranial elastance (ICE) and intracranial compliance (ICC), as determined during ventricular infusion testing. METHODS All patients undergoing ventricular infusion testing and overnight ICP monitoring during the 6-year period from 2007 to 2012 were included in the study. Clinical data were retrieved from a quality registry, and the ventricular infusion pressure data and ICP scores were retrieved from a pressure database. The ICE and ICC (= 1/ICE) were computed during the infusion phase of the infusion test. RESULTS During the period from 2007 to 2012, 82 patients with possible treatment-dependent hydrocephalus underwent ventricular infusion testing within the department of neurosurgery. The infusion tests revealed a highly significant positive correlation between ICE and the pulsatile ICP scores mean wave amplitude (MWA) and rise-time coefficient (RTC), and the static ICP score mean ICP. The ICE was negatively associated with linear measures of ventricular size. The overnight ICP recordings revealed significantly increased MWA (> 4 mm Hg) and RTC (> 20 mm Hg/sec) values in patients with impaired ICC (< 0.5 ml/mm Hg). CONCLUSIONS In this study cohort, there was a significant positive correlation between pulsatile ICP and ICE measured during ventricular infusion testing. In patients with impaired ICC during infusion testing (ICC < 0.5 ml/mm Hg), overnight ICP recordings showed increased pulsatile ICP (MWA > 4 mm Hg, RTC > 20 mm Hg/sec), but not increased mean ICP (< 10-15 mm Hg). The present data support the assumption that pulsatile ICP (MWA and RTC) may serve as substitute markers of pressure-volume reserve capacity, i.e., ICE and ICC.

Routine intracranial pressure monitoring in acute coma

BACKGROUND

We know that the brain damage resulting from traumatic and other insults is not due solely to the direct consequences of the primary injury. A significant and potentially preventable contribution to the overall morbidity arises from secondary hypoxic-ischaemic damage. Brain swelling accompanied by raised intracranial pressure (ICP) prevents adequate cerebral perfusion with well-oxygenated blood.Detection of raised ICP could be useful in alerting clinicians to the need to improve cerebral perfusion, with consequent reductions in brain injury.

OBJECTIVES

To determine whether routine ICP monitoring in severe coma of any cause reduces the risk of all-cause mortality or severe disability at final follow-up.

SEARCH METHODS

We searched the Cochrane Injuries Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OvidSP), EMBASE (OvidSP), CINAHL Plus, ISI Web of Science (SCI-EXPANDED & CPCI-S), clinical trials registries and reference lists. We ran the most recent search on 22 May 2015.

SELECTION CRITERIA

All randomised controlled studies of real-time ICP monitoring by invasive or semi-invasive means in acute coma (traumatic or non-traumatic aetiology) versus clinical care without ICP monitoring (that is, guided only by clinical or radiological inference of the presence of raised ICP).

DATA COLLECTION AND ANALYSIS

Two authors (ET and RF) worked independently to identify the one study that met inclusion criteria. JR and RF independently extracted data and assessed risk of bias. We contacted study authors for additional information, including details of methods and outcome data.

MAIN RESULTS

One randomized controlled trial (RCT) meeting the selection criteria has been identified to date.The included study had 324 participants. We judged risk of bias to be low for all categories except blinding of participants and personnel, which is not feasible for this intervention. There were few missing data, and we analysed all on an intention-to-treat basis.Participants could be 13 years of age or older (mean age of sample 29; range 22 to 44), and all had severe traumatic brain injury, mostly due to traffic incidents. All were receiving care within intensive care units (ICUs) at one of six hospitals in either Bolivia or Ecuador. Investigators followed up 92% of participants for six months or until death. The trial excluded patients with a Glasgow Coma Score (GCS) less than three and fixed dilated pupils on admission on the basis that they had sustained brain injury of an unsalvageable severity.The study compared people managed using either an intracranial monitor or non-invasive monitoring (imaging and clinical examination) to identify potentially harmful raised intracranial pressure. Both study groups used imaging and clinical examination measures.Mortality at six months was 56/144 (39%) in the ICP-monitored group and 67/153 (44%) in the non-invasive group.Unfavourable outcome (defined as death or moderate to severe disability at six months) as assessed by the extended Glasgow Outcome Scale (GOS-E) was 80/144 (56%) in the ICP-monitored group and 93/153 (61%) in the non-invasive group.Six percent of participants in the ICP monitoring group had complications related to the monitoring, none of which met criteria for being a serious adverse event. There were no complications relating to the non-invasive group.Other complications and adverse events were comparable between treatment groups, 70/157 (45%) in the ICP-monitored group and 76/167 (46%) in the non-invasive group.Late mortality in both the monitored and non-invasive groups was high, with 35% of deaths occurring > 14 days after injury. The authors comment that this high late mortality may reflect inadequacies in post-ICU services for disabled survivors requiring specialist rehabilitation care.

AUTHORS' CONCLUSIONS

The data from the single RCT studying the role of routine ICP monitoring in acute traumatic coma fails to provide evidence to support the intervention.Research in this area is complicated by the fact that RCTs necessarily assess the combined impact of measurement of ICP with the clinical management decisions made in light of this data. Future studies will need to assess the added value of ICP data alongside other information from the multimodal monitoring typically performed in intensive care unit settings. Additionally, even within traumatically acquired brain injury (TBI), there is great heterogeneity in mechanisms, distribution, location and magnitude of injury, and studies within more homogeneous subgroups are likely to be more informative.

Outcome of Surgery for Idiopathic Normal Pressure Hydrocephalus: Role of Preoperative Static and Pulsatile Intracranial Pressure

OBJECTIVES

To examine the outcome of surgery for idiopathic normal-pressure hydrocephalus (iNPH) and how outcome relates to the preoperative static and pulsatile intracranial pressure (ICP).

METHODS

An observational cohort study included all patients with iNPH managed at our department during the years 2002-2012 in whom overnight ICP monitoring was part of the preoperative work-up. Clinical data were retrieved from a quality registry and ICP scores from a pressure database.

RESULTS

The study included 472 patients, 316 in the surgery group and 156 in the nonsurgery group. Among those treated surgically, 278 (90%) showed clinical improvement (Responders) whereas 32 (10%) had no improvement (Nonresponders). Among Responders, only about one third reached the best clinical scores; moreover, the difference in clinical score between Responders and Nonresponders declined with time after surgery, particularly after 3-4 years. The surgery was accompanied by acute intracranial hematomas in 11 patients (3.5%), of whom 4 (1.3%) died. Survival (age at death) was significantly greater among the Responders than in Nonresponders. Although the static ICP was normal in all patients, the pulsatile ICP was significantly greater in Responders than in Non-responders.

CONCLUSIONS

The pulsatile ICP was greater in shunt Responders than Nonresponders. Although the clinical improvement declined over time and the majority did not experience complete relief of symptoms, shunt Responders lived significantly longer than Nonresponders. The present observations suggest that the current surgical treatment regimens for iNPH (primarily shunt surgery) address only some aspects of the disease process, in particular the aspect of brain water disturbance.

Comparison of pulsatile and static pressures within the intracranial and lumbar compartments in patients with Chiari malformation type 1: a prospective observational study

BACKGROUND

In Chiari malformation type 1 (CMI), the obstruction of cerebrospinal fluid (CSF) flow through the foramen magnum is believed to cause alterations of intracranial pressure (ICP) pulsations. Foramen magnum decompression (FMD) is therefore considered a treatment of choice. However, the pathophysiology of CMI is poorly understood and it remains unknown how ICP alterations relate to symptoms and radiological findings. This study was undertaken to measure pulsatile pressure and its gradient between intracranial and lumbar compartments, and to determine its relationship to clinical and radiological findings.

METHOD

In patients with symptomatic CMI, we simultaneously measured ICP and lumbar CSF pressure, with particular focus on analysis of pulsatile pressure. Ventricular CSF volume (VV), intracranial volume (ICV) and posterior cranial fossa volume (PCFV) were calculated using volumetry software.

RESULTS

In 26 patients (median 35 years), we found clearly abnormal or borderline values of pulsatile ICP in 18/26 patients (69 %; median 4.5 mmHg) and abnormal pulsatile pressure gradient in 17/24 patients (71 %; median 2.6 mmHg). The correlation between pulsatile ICP and the pulsatile pressure gradient was significantly positive (p < 0.001). We found no significant correlation between pulsatile or static pressure and extent of tonsillar ectopy, VV, ICV or PCFV. The pulsatile pressure gradient was significantly higher in patients with syringomyelia (p = 0.02).

CONCLUSIONS

In this cohort, the pulsatile ICP was elevated in 69 %. The intracranial-lumbar pulsatile pressure gradient was abnormal in 71 % and significantly higher in patients with syringomyelia. The elevated pulsatile ICP significantly correlated with pulsatile pressure gradient; no similar correlation was found for static ICP. We interpret the results as providing evidence of impaired intracranial compliance as an important pathophysiological mechanism in CMI.

Characteristics of intracranial pressure (ICP) waves and ICP in children with treatment-responsive hydrocephalus

BACKGROUND

One important goal of modern treatment of pediatric hydrocephalus is to normalize the intracranial pressure (ICP) and ICP volume reserve capacity to optimize normal brain development. Better knowledge of the characteristics of ICP waves/ICP in pediatric hydrocephalus may provide new insight into the mechanisms behind modern hydrocephalus treatment. The aim of the present work was to characterize the ICP waves/ICP in children with either communicating or non-communicating hydrocephalus who improved clinically after surgery. The hydrocephalic children not treated surgically following ICP monitoring served as reference patients.

METHODS

The patient material includes all children with hydrocephalus and no previous surgical treatment who underwent diagnostic ICP wave/ICP monitoring during the period 2002-2011. We retrieved the information about the patients from the patient records and the digitally stored ICP waveforms. The ICP wave characteristics amplitude, rise time and rise time coefficient and the mean ICP were determined in the patients treated surgically for their hydrocephalus. The findings were compared with findings in children not treated surgically after ICP monitoring who served as reference patients.

RESULTS

The patient material includes 58 patients. Thirty-one (53%) were treated surgically after ICP monitoring, of whom all improved clinically. As compared to the reference patients, patients treated surgically presented with increased ICP wave amplitudes (MWA) and mean ICP. Alterations were comparable in communicating and non-communicating hydrocephalus. We found no apparent association between the ICP wave/ICP scores and presence of symptoms, indices of ventricular size or age.

CONCLUSIONS

Children with either communicating or non-communicating hydrocephalus improving clinically after surgery presented with elevated MWA and mean ICP. In particular, the levels of MWA were raised to a magnitude seen when intracranial compliance is impaired. Hence, the present observations may support the idea that improvement of intracranial compliance can be an important mechanism by which shunts work in pediatric hydrocephalus.

Intracranial pressure monitoring in pediatric and adult patients with hydrocephalus and tentative shunt failure: a single-center experience over 10 years in 146 patients

OBJECT In patients with hydrocephalus and shunts, lasting symptoms such as headache and dizziness may be indicative of shunt failure, which may necessitate shunt revision. In cases of doubt, the authors monitor intracranial pressure (ICP) to determine the presence of over- or underdrainage of CSF to tailor management. In this study, the authors reviewed their experience of ICP monitoring in shunt failure. The aims of the study were to identify the complications and impact of ICP monitoring, as well as to determine the mean ICP and characteristics of the cardiac-induced ICP waves in pediatric versus adult over- and underdrainage. METHODS The study population included all pediatric and adult patients with hydrocephalus and shunts undergoing diagnostic ICP monitoring for tentative shunt failure during the 10-year period from 2002 to 2011. The patients were allocated into 3 groups depending on how they were managed following ICP monitoring: no drainage failure, overdrainage, or underdrainage. While patients with no drainage failure were managed conservatively without further actions, over- or underdrainage cases were managed with shunt revision or shunt valve adjustment. The ICP and ICP wave scores were determined from the continuous ICP waveforms. RESULTS The study population included 71 pediatric and 75 adult patients. There were no major complications related to ICP monitoring, but 1 patient was treated for a postoperative superficial wound infection and another experienced a minor bleed at the tip of the ICP sensor. Following ICP monitoring, shunt revision was performed in 74 (51%) of 146 patients, while valve adjustment was conducted in 17 (12%) and conservative measures without any actions in 55 (38%). Overdrainage was characterized by a higher percentage of episodes with negative mean ICP less than -5 to -10 mm Hg. The ICP wave scores, in particular the mean ICP wave amplitude (MWA), best differentiated underdrainage. Neither mean ICP nor MWA levels showed any significant association with age. CONCLUSIONS In this cohort of pediatric and adult patients with hydrocephalus and tentative shunt failure, the risk of ICP monitoring was very low, and helped the authors avoid shunt revision in 49% of the patients. Mean ICP best differentiated overdrainage, which was characterized by a higher percentage of episodes with negative mean ICP less than -5 to -10 mm Hg. Underdrainage was best characterized by elevated MWA values, indicative of impaired intracranial compliance.

Predictors of shunt dependency after aneurysmal subarachnoid hemorrhage: results of a single-center clinical trial

BACKGROUND

Hydrocephalus (HC) after aneurysmal subarachnoid hemorrhage (aSAH) is a common sequel. Proper selection of patients in need of permanent cerebrospinal fluid (CSF) diversion is, however, not straightforward. The aim of this study was to identify predictors of CSF shunt dependency following aSAH.

METHODS

We re-analyzed data acquired from aSAH patients previously enrolled in a prospective, controlled single-center clinical trial in which shunt dependency was not one of the end points. In the present study patients were allocated into two groups: those receiving a shunt (here denoted as shunt dependent) and those not receiving a shunt, based on a clinical decision process. Predictors of shunt dependency were identified by applying uni- and multivariable analysis. We tested a set of predefined possible risk factors based on the results of the clinical trial, including the impact of CSF drainage volume exceeding 1,500 ml during the 1st week after ictus.

RESULTS

Ninety patients were included in the study. Significant predictors of shunt dependency were poor clinical grade at admission [odds ratio (OR) 4.7, 95% confidence interval (CI) 1.2-18.4], large amounts of subarachnoid blood (OR 3.8, 95% CI 1.0-14.0), large ventricular size on preoperative cerebral computer tomographic (CT) scans (OR 1.0, 95% CI 1.0-1.1), and CSF volume drainage exceeding 1,500 ml during the 1st week after the ictus (OR 16.3, 95% CI 4.0-67.1). Age ≥70 years, larger amounts of intraventricular blood, vertebrobasilar aneurysm, and endovascular treatment tended to increase the likelihood of receiving a shunt. Outcome was not significantly different between shunted and non-shunted patients.

CONCLUSIONS

In this cohort of patients with clinical grade aSAH at admission, larger amounts of subarachnoid blood and large ventricular size on preoperative cerebral CT, and CSF drainage in excess of 1,500 ml during the 1st week after the ictus were significant predictors of shunt dependency. Shunt dependency did not hamper outcome.

European Stroke Organisation (ESO) guidelines for the management of spontaneous intracerebral hemorrhage

BACKGROUND

Intracerebral hemorrhage (ICH) accounted for 9% to 27% of all strokes worldwide in the last decade, with high early case fatality and poor functional outcome. In view of recent randomized controlled trials (RCTs) of the management of ICH, the European Stroke Organisation (ESO) has updated its evidence-based guidelines for the management of ICH.

METHOD

A multidisciplinary writing committee of 24 researchers from 11 European countries identified 20 questions relating to ICH management and created recommendations based on the evidence in RCTs using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

RESULTS

We found moderate- to high-quality evidence to support strong recommendations for managing patients with acute ICH on an acute stroke unit, avoiding hemostatic therapy for acute ICH not associated with antithrombotic drug use, avoiding graduated compression stockings, using intermittent pneumatic compression in immobile patients, and using blood pressure lowering for secondary prevention. We found moderate-quality evidence to support weak recommendations for intensive lowering of systolic blood pressure to <140 mmHg within six-hours of ICH onset, early surgery for patients with a Glasgow Coma Scale score 9-12, and avoidance of corticosteroids.

CONCLUSION

These guidelines inform the management of ICH based on evidence for the effects of treatments in RCTs. Outcome after ICH remains poor, prioritizing further RCTs of interventions to improve outcome.

The effect of baseline pressure errors on an intracranial pressure-derived index: results of a prospective observational study

Background

In order to characterize the intracranial pressure-volume reserve capacity, the correlation coefficient (R) between the ICP wave amplitude (A) and the mean ICP level (P), the RAP index, has been used to improve the diagnostic value of ICP monitoring. Baseline pressure errors (BPEs), caused by spontaneous shifts or drifts in baseline pressure, cause erroneous readings of mean ICP. Consequently, BPEs could also affect ICP indices such as the RAP where in the mean ICP is incorporated.

Methods

A prospective, observational study was carried out on patients with aneurysmal subarachnoid hemorrhage (aSAH) undergoing ICP monitoring as part of their surveillance. Via the same burr hole in the scull, two separate ICP sensors were placed close to each other. For each consecutive 6-sec time window, the dynamic mean ICP wave amplitude (MWA; measure of the amplitude of the single pressure waves) and the static mean ICP, were computed. The RAP index was computed as the Pearson correlation coefficient between the MWA and the mean ICP for 40 6-sec time windows, i.e. every subsequent 4-min period (method 1). We compared this approach with a method of calculating RAP using a 4-min moving window updated every 6 seconds (method 2).

Results

The study included 16 aSAH patients. We compared 43,653 4-min RAP observations of signals 1 and 2 (method 1), and 1,727,000 6-sec RAP observations (method 2). The two methods of calculating RAP produced similar results. Differences in RAP ≥0.4 in at least 7% of observations were seen in 5/16 (31%) patients. Moreover, the combination of a RAP of ≥0.6 in one signal and <0.6 in the other was seen in ≥13% of RAP-observations in 4/16 (25%) patients, and in ≥8% in another 4/16 (25%) patients. The frequency of differences in RAP >0.2 was significantly associated with the frequency of BPEs (5 mmHg ≤ BPE <10 mmHg).

Conclusions

Simultaneous monitoring from two separate, close-by ICP sensors reveals significant differences in RAP that correspond to the occurrence of BPEs. As differences in RAP are of magnitudes that may alter patient management, we do not advocate the use of RAP in the management of neurosurgical patients.

Baseline pressure errors (BPEs) extensively influence intracranial pressure scores: results of a prospective observational study

Background

Monitoring of intracranial pressure (ICP) is a cornerstone in the surveillance of neurosurgical patients. The ICP is measured against a baseline pressure (i.e. zero - or reference pressure). We have previously reported that baseline pressure errors (BPEs), manifested as spontaneous shift or drifts in baseline pressure, cause erroneous readings of mean ICP in individual patients. The objective of this study was to monitor the frequency and severity of BPEs. To this end, we performed a prospective, observational study monitoring the ICP from two separate ICP sensors (Sensors 1 and 2) placed in close proximity in the brain. We characterized BPEs as differences in mean ICP despite near to identical ICP waveform in Sensors 1 and 2.

Methods

The study enrolled patients with aneurysmal subarachnoid hemorrhage in need of continuous ICP monitoring as part of their intensive care management. The two sensors were placed close to each other in the brain parenchyma via the same burr hole. The monitoring was performed as long as needed from a clinical perspective and the ICP recordings were stored digitally for analysis. For every patient the mean ICP as well as the various ICP wave parameters of the two sensors were compared.

Results

Sixteen patients were monitored median 164 hours (ranges 70 – 364 hours). Major BPEs, as defined by marked differences in mean ICP despite similar ICP waveform, were seen in 9 of them (56%). The BPEs were of magnitudes that had the potential to alter patient management.

Conclusions

Baseline Pressure Errors (BPEs) occur in a significant number of patients undergoing continuous ICP monitoring and they may alter patient management. The current practice of measuring ICP against a baseline pressure does not comply with the concept of State of the Art. Monitoring of the ICP waves ought to become the new State of the Art as they are not influenced by BPEs.

An intracranial pressure-derived index monitored simultaneously from two separate sensors in patients with cerebral bleeds: comparison of findings

Background

In an attempt to characterize the intracranial pressure-volume compensatory reserve capacity, the correlation coefficient (R) between the ICP wave amplitude (A) and the ICP (P) level (RAP) has been applied in the surveillance of neurosurgical patients. However, as the ICP level may become altered by electrostatic discharges, human factors, technical factors and technology issues related to the ICP sensors, erroneous ICP scores may become revealed to the physician, and also become incorporated into the calculated RAP index. To evaluate the problem with regard to the RAP, we compared simultaneous RAP values from two separate ICP signals in the same patient.

Materials and Methods

We retrieved our recordings in 20 patients with cerebral bleeds wherein the ICP had been recorded simultaneously from two different sensors. Sensor 1 was always a solid sensor while sensor 2 was a solid sensor (Category A), a fluid sensor (Category B), an air-pouch sensor (Category C), or a fibre-optic sensor (Category D). The simultaneous signals were analyzed with automatic identification of the cardiac induced ICP waves, with subsequent determination and comparison of the Pearson correlation coefficient between mean wave amplitude (MWA) and mean ICP (RAP) for 40 6-s time windows every 4-min period.

Results

A total of 23,056 4-min RAP observations were compared. A difference in RAP ≥0.4 between the two signals was seen in 4% of the observations in Category A-, in 44% of observations in Category B -, in 20% of observations in Category C -, and in 28% of observations in Category D patients, respectively. Moreover, the combination of a RAP of <0.6 in one signal and ≥0.6 in the other was seen in >20% of scores in 3/5 Category A -, in 3/5 Category B -, in 5/7 Category C - and 1/3 Category D patients.

Conclusions

Simultaneous monitoring of the ICP-derived index RAP from two separate ICP sensors reveals marked differences in the index values. These differences in RAP may be explained by erroneous scoring of the ICP level. This will hamper the usefulness of RAP as a guide in the management of neurosurgical patients.

Simultaneous monitoring of static and dynamic intracranial pressure parameters from two separate sensors in patients with cerebral bleeds: comparison of findings

BACKGROUND

We recently reported that in an experimental setting the zero pressure level of solid intracranial pressure (ICP) sensors can be altered by electrostatics discharges. Changes in the zero pressure level would alter the ICP level (mean ICP); whether spontaneous changes in mean ICP happen in clinical settings is not known. This can be addressed by comparing the ICP parameters level and waveform of simultaneous ICP signals. To this end, we retrieved our recordings in patients with cerebral bleeds wherein the ICP had been recorded simultaneously from two different sensors.

MATERIALS AND METHODS

During a time period of 10 years, 17 patients with cerebral bleeds were monitored with two ICP sensors simultaneously; sensor 1 was always a solid sensor while Sensor 2 was a solid -, a fluid - or an air-pouch sensor. The simultaneous signals were analyzed with automatic identification of the cardiac induced ICP waves. The output was determined in consecutive 6-s time windows, both with regard to the static parameter mean ICP and the dynamic parameters (mean wave amplitude, MWA, and mean wave rise time, MWRT). Differences in mean ICP, MWA and MWRT between the two sensors were determined. Transfer functions between the sensors were determined to evaluate how sensors reproduce the ICP waveform.

RESULTS

Comparing findings in two solid sensors disclosed major differences in mean ICP in 2 of 5 patients (40%), despite marginal differences in MWA, MWRT, and linear phase magnitude and phase. Qualitative assessment of trend plots of mean ICP and MWA revealed shifts and drifts of mean ICP in the clinical setting. The transfer function analysis comparing the solid sensor with either the fluid or air-pouch sensors revealed more variable transfer function magnitude and greater differences in the ICP waveform derived indices.

CONCLUSIONS

Simultaneous monitoring of ICP using two solid sensors may show marked differences in static ICP but close to identity in dynamic ICP waveforms. This indicates that shifts in ICP baseline pressure (sensor zero level) occur clinically; trend plots of the ICP parameters also confirm this. Solid sensors are superior to fluid - and air pouch sensors when evaluating the dynamic ICP parameters.

Pressure-derived versus pressure wave amplitude–derived indices of cerebrovascular pressure reactivity in relation to early clinical state and 12-month outcome following aneurysmal subarachnoid hemorrhage

Object

Indices of cerebrovascular pressure reactivity (CPR) represent surrogate markers of cerebral autoregulation. Given that intracranial pressure (ICP) wave amplitude–guided management, as compared with static ICP-guided management, improves outcome following aneurysmal subarachnoid hemorrhage (SAH), indices of CPR derived from pressure wave amplitudes should be further explored. This study was undertaken to investigate the value of CPR indices derived from static ICP–arterial blood pressure (ABP) values (pressure reactivity index [PRx]) versus ICP-ABP wave amplitudes (ICP-ABP wave amplitude correlation [IAAC]) in relation to the early clinical state and 12-month outcome in patients with aneurysmal SAH.

Methods

The authors conducted a single-center clinical trial enrolling patients with aneurysmal SAH. The CPR indices of PRx and IAAC of Week 1 after hemorrhage were related to the early clinical state (Glasgow Coma Scale [GCS] score) and 12-month outcome (modified Rankin Scale score).

Results

Ninety-four patients were included in the study. The IAAC, but not the PRx, increased with decreasing GCS score; that is, the higher the IAAC, the worse the clinical state. The PRx could differentiate between survivors and nonsurvivors only, whereas the IAAC clearly distinguished the groups “independent,” “dependent,” and “dead.” In patients with an average IAAC ≥ 0.2, mortality was approximately 3-fold higher than in those with an IAAC < 0.2.

Conclusions

The IAAC, which is based on single ICP-ABP wave identification, relates significantly to the early clinical state and 12-month outcome following aneurysmal SAH. Impaired cerebrovascular pressure regulation during the 1st week after a bleed relates to a worse outcome. Clinical trial registration no.: NCT00248690.

An evaluation of three measures of intracranial compliance in traumatic brain injury patients

PURPOSE

To compare intracranial pressure (ICP) amplitude, ICP slope, and the correlation of ICP amplitude and ICP mean (RAP index) as measures of compliance in a cohort of traumatic brain injury (TBI) patients.

METHODS

Mean values of the three measures were calculated in the 2-h periods before and after surgery (craniectomies and evacuations), and in the 12-h periods preceding and following thiopental treatment, and during periods of thiopental coma. The changes in the metrics were evaluated using the Wilcoxon test. The correlations of 10-day mean values for the three metrics with age, admission Glasgow Motor Score (GMS), and Extended Glasgow Outcome Score (GOSe) were evaluated. Patients under and over 60 years old were also compared using the Student t test. The correlation of ICP amplitude with systemic pulse amplitude was analyzed.

RESULTS

ICP amplitude was significantly correlated with GMS, and also with age for patients 35 years old and older. The correlations of ICP slope and the RAP index with GMS and with age were not significant. All three metrics indicated significant improvements in compliance following surgery and during thiopental coma. None of the metrics were significantly correlated with outcome, possibly due to confounding effects of treatment factors. The correlation of systemic pulse amplitude with ICP amplitude was low (R = 0.18), only explaining 3 % of the variance.

CONCLUSIONS

This study provides further validation for all three of these features of the ICP waveform as measures of compliance. ICP amplitude had the best performance in these tests.

Frequency dependent transmission characteristics between arterial blood pressure and intracranial pressure in rats

The pulsatile energy transmission between arterial blood pressure (BP) and intracranial pressure (ICP) is affected by cerebrospinal fluid (CSF) and brain tissue. Studies in dogs have shown that the transfer function (TF) between BP and ICP shows damping of pulsatile energy around heart rate frequency (1-3Hz) with notch filter characteristics, and the amount of damping is sensitive to cerebral compliance. This investigation aimed to assess whether this notch filter characteristic is an intrinsic property of the brain enclosed in a rigid skull and therefore applies across species with a large difference in body size. This was done by determining the TF between BP and ICP in rats with corresponding significantly smaller body size and higher heart rate (5-7 Hz) compared to dogs. Arterial BP and ICP waveforms were recorded in 8 anaesthetized (urethane) adult male Sprague-Dawley rats with solid state micro-sensor transducer catheters. The TF was computed as the ratio of ICP and arterial BP waveform amplitudes for the first 4 harmonics. Arterial BP and ICP signals were normalized for pulse amplitude such that attenuation or amplification is detected for any TF values significantly different to unity. Mean cardiac frequency was 5.72 Hz (range 4.6 - 7.11 Hz). Of the 4 harmonics only the heart rate frequency band showed a statistically significant attenuation of 17%, while the higher harmonics showed a progressive amplification. Findings show that the rat brain acts as a selective frequency pulsation absorber of energy centered at heart rate frequency. This similarity with larger animals indicates a possible allometric mechanism underlying this phenomenon, with notch filter characteristic frequency scaled to body size. This study suggests that the TF between arterial BP and ICP is an intrinsic property of the brain tissue and CSF enclosed in a rigid compartment and can be used to assess changes in cerebral compliance due to abnormal CSF pressure and flow as occur in hydrocephalus.